Using tiny apertures - Part 6, Not so tiny after all

 I enjoy giving practical advice about close-up/macro, especially to people who are starting out. It is nice to do in its own right, but sometimes there are incidental benefits: explaining things encourages me to think things through more carefully to try to ensure what I'm saying is true, and relevant, and preferably with an easy to digest presentation. Sometimes other people will respond to correct what I've said, which is always very welcome, or add extra information I didn't know about. Sometimes I'll spot errors myself as I think things through. And sometimes I ramble off and do some practical experiments which teach me things I might not otherwise have stumbled upon. That happened yesterday.

A question came up in this thread at dpreview.com about the effective aperture of the Laowa 100mm macro, a lens that I use a lot. I thought I would show a practical example but as I was preparing it I realised that things were not working out the way I expected. There was something going on that I didn't understand about the way the effective aperture changed as the magnification changed. 

See this post for an introduction to effective apertures. I have been using the simplified formula mentioned in that post

    effective f-number = nominal f-number * ( 1 + magnification )

So when I photograph a springtail using 7X magnification with the lens set to f/45, the effective aperture I'm using is:

    45 * ( 1 + 7 ) = around f/360

With my close-up lens setups I would use f-numbers equivalent to f/45 on the Sony full frame A7ii that I'm using at the moment. Since depth of field roughly doubles for each two stops decrease in aperture (which is a doubling of the f-number), using f/360 rather than f/45 gives me around 8 times greater depth of field than I could get previously.

Or so I thought.

Let's go back to that formula. That is the simplified version. The full version is this:

effective f-number = nominal f-number *
                                    ( 1 + magnification/pupil magnification )

Pupil magnification is the exit pupil divided by the entrance pupil. "The entrance pupil is the optical image of the physical aperture stop, as 'seen' through the front (the object side) of the lens system. The corresponding image of the aperture as seen through the back of the lens system is called the exit pupil." (Wikipedia).

That is all very well, but manufacturers don't state the size of the entrance and exit pupils for their lenses and they can be difficult to measure, so pretty much everyone uses the simpler formula, which assumes that the pupil magnification is 1. I've always found the results I have got from the simplified formula good enough for my purposes.

Until yesterday.

I'll miss out the bit about how and why I got confused and what I did to grope my way out of the darkness to some sort of understanding. If you are interested you can read about that in the sub-thread starting here at dpreview. The upshot was that I came to think that, when using teleconverters, the formula should be

effective f-number = nominal f-number * 

                 ( 1 + magnification/ (pupil magnification * teleconverter power )  )

where teleconverter power is 1.4 for a 1.4X teleconverter, 2 for a 2X teleconverter, 2.8 for a 1.4X and a 2X teleconverter used together, and 1 if no teleconverter is used.

Not knowing what the pupil magnification is, we may as well as usual assume that it is 1. This simplifies the formula to

effective f-number = nominal f-number * 

                                    ( 1 + magnification/ teleconverter power   )

I did an experiment to test this formula. I used a Canon MPE-65 lens on a Canon 70D dSLR, and captured five images with 1X, 2X, 3X, 4X and 5X magnification set on the MPE-65, with all five using the same settings of f/11, 1/10 sec, ISO 3200. I photographed a light area on my computer screen and held the lens against the screen so there would not be an issue with the brightness changing because of different working distances from shot to shot. (The fact it would be out of focus would not matter).

I then added a 1.4X teleconverter and captured another five images with the same magnifications set on the MPE-65 and the same settings for aperture, shutter speed and ISO. Then the same again with a 2X teleconverter and lastly with both of the teleconverters together. 

Before I did this, I did some calculations, to see what my proposed formula would predict I would see. To my surprise, as shown in last but one column of the following table, it predicted that with 1X magnification on the MPE-65 the four images using no teleconverter, 1.4X, 2X and 2.8X should all have the same effective aperture, so they should all be the same brightness. And it predicted the same would be the case for 2X, 3X, 4X and 5X magnification. 

Those predictions are very different from what the usual formula predicts, as shown in the last column in the table below. It predicted that the images with 1X set on the MPE-65 would have a larger effective f-number and so would get darker when I added the 1.4X teleconverter, darker again with 2X and darker still with 2.8X. And it predicted the same would be true with 2X, 3X, 4X and 5X magnification set on the MPE-65. (It also predicted some pairs of images, shown by the colours in the table, where the brightness would match between images that had a different magnification set on the MPE-65 but which had the same overall magnification once the teleconverters were taken into account.)

Here is the table.

Here are the 20 images.

They exactly match the predictions from the formula which takes the teleconverters into account.

Is this a fluke, a special case, something to do with the MPE-65 in particular? That looks unlikely to me given that I did a different experiment with a Laowa 100mm macro that came up with similar conclusions.

With the Laowa 100mm macro on a Sony A7ii I captured images at 1X, 2X and 4X magnification, once with one 2X teleconverter and again with two 2X teleconverters. This time the magnification was the actual, overall magnification, so for example for the 1X magnification shot I set the magnification on the lens to 1:2 when using the 2X teleconverter and 1:4 when using both teleconverters. And similarly for the 2X and 4X shots. 

Assuming once more that the pupil magnification is 1, using the usual formula so the effective aperture depends only on the magnification, then both 1X magnification shots should have the same effective aperture and therefore the same brightness, and the same for the pair of 2X magnification shots and the pair of 4X magnification shots. 

In contrast, these are the calculations using the revised formula that takes the teleconverters into account. As shown by the colours, it predicts that the effective f-number, and hence the brightness, should match between the 1X magnification using the 2X teleconverter and the 2X magnification using 4X teleconversion, and also between 2X magnification using the 2X teleconverter and 4X magnification using 4X teleconversion.

This is what the images looked like. They match as predicted by the revised formula that takes teleconverters into account.

Histograms from Raw Digger show that the two matches were in fact very, very close indeed. 

I am persuaded that when using teleconverters, effective f-number can best be calculated using the formula

effective f-number = nominal f-number * 

                 ( 1 + magnification/ (pupil magnification * teleconverter power )  )

with the usual simplification of pupil magnification = 1 if the pupil magnification is unknown.

This means that the tiny apertures I am using are not as small as I thought they were, which in turn has implications for depth of field, diffraction softening and flash power requirements. That said, I don't think it makes much difference in practical terms, because I'm choosing my aperture settings based on experiments and experience as to what works for what I'm doing, how I like to go about and what I find acceptable as results. Knowing that the correct numbers to describe the apertures I'm using are are smaller than I thought makes no difference to that. Which makes this discovery, assuming it is true, more interesting than useful. (And the same will be the case if it eventually turns out to be wrong.)

 There is a discussion about all this, with additional examples, in this thread at dpreview.com.

Using tiny apertures - Part 5, post processing and image display

Using tiny apertures produces images that I find unusable for my purposes out of the camera. 

For example, below on the right are out of the camera JPEGs of two tiny aperture captures. (These are taken from JPEG preview images embedded in raw files which were resized to my normal 1300 pixel high display size. We are looking at the central portion of the 1300 pixel high images.) For my purposes and visual tastes the right hand images are not usable.

On the left are the same images as they look after having some post processing. These do look usable to me, for my purposes of viewing on screen at 1300 pixels high.

Two questions come to mind:

• What post processing did I use?
• Are the results authentic, or are we looking at artificial intelligence /machine learning interpretations/inventions?
  
  

Post processing 

The post processing products and workflow I use change from time to time. I'll describe here my current approach as at April 2021.

My aim is to produce JPEG images in the sRGB colour space for viewing as a whole image (i.e. no zooming in) on my PC or online at 1300 pixels high on a calibrated monitor in subdued lighting.

I use three editors in sequence: DXO PhotoLab, Adobe Lightroom and Topaz DeNoise AI. I sometimes also use Adobe Photoshop and very occasionally Topaz Sharpen AI.

I use two passes of the raw files from a session. The first pass is to get all the images from the session into a state where I can tell which of them might turn out ok after being processed. (They are in such bad condition before having any processing that I can't tell whether they would be useful or not.)

There are typically in the order of 400 to 600 images from a session.

For the A7ii double teleconverter setup the first pass involves:

• In PhotoLab, selecting all of the raw files from the session and applying a preset to them all. It is the same preset for all the images, irrespective of ISO etc. (I have one version of the preset for the A7ii, and another version for my other cameras.) 
  
  The preset sets the white balance to a fixed Temp and Tint which I established using a test shot of the grey patch on a ColorChecker Passport using the KX800 flash with the diffusion setup I used in the session.
  
  The preset sets a colour rending profile based on the A7ii body (as known by PhotoLab)
  
  The preset applies a mild amount of PhotoLab's ClearView Plus and Smart Lighting, pulls the highlights down somewhat and pulls the shadows up somewhat.
  
  The preset applies the default level of PhotoLab's DeepPRIME noise reduction and also Chromatic aberration correction at the default level.
  
  The preset outputs full size uncompressed 16 bit TIFF files.
  
  
• I import the TIFF files manually into Lightroom and apply Auto Tone Control to them all and also a preset which adds a little Contrast, a fair amount of Texture, a little Clarity and even less Dehaze.
  
  I export to 1300 pixel high uncompressed 16 bit TIFF files
  
  
• I drag the 1300 pixel high TIFF files into DeNoise AI and apply the AI Clear method with Auto settings, with export to JPEG.
  
  

In Faststone Image viewer I go through the JPEG images and mark those that I will take into the second pass. I work very quickly. I don't try to make final decisions at this point. If in doubt, I include the image. I may end up with lots of very similar images. That doesn't matter.

I select the marked JPEGs and copy them into the folder containing the full size TIFF files exported from PhotoLab. In Lightroom I synchronise the folder, select the JPEGs and give them a colour mark. I then deselect the JPEGs so I'm seeing all the TIFFs and all the JPEGs, with the JPEGs standing out because of their colour marking. I go through and for each of the JPEGs I give a colour marking to the associated TIFF file. I then select the marked TIFF files and these are what I work on in the second pass. This time I am working on an image by image basis, doing a combination of adjustments and selection.

What follows is a simplification. The process is not as linear as described here. I may pick subsets of similar images and give them the same adjustments select from them into a smaller subset, re-adjust etc. I may go back to earlier stages and rework as necessary. I may change my mind this way and that depending on how things go.

• In Lightroom I do a combination of adjustment and selection.
  
  Adjustments are mainly from the Basics tab (most often Exposure, Highlights, Shadows, Whites, Blacks), and sometimes Graduated Filters and/or Radial Filters and/or Adjustment Brush. Also cropping.
  
  I occasionally do a round trip from Lightroom to PhotoShop and back to do cloning that is too difficult or tedious to do in Lightroom. 
  
  
• While working in Lightroom I mark images that I may want to use with a different colour label and end up with a subset of the selected images that have now been processed individually.
  
  I clear out the contents of the folders containing the 1300 pixel high TIFFS and JPEGs and export the selection subset of images from Lightroom to 1300 pixel high TIFFs and use DeNoise AI on them as in the first pass.
  
  

I then go through the reduced number of JPEGs doing a combination of putting them in an order that I think will display nicely, selecting from between near duplicates, going back and readjusting some images in Lightroom to correct issues I have noticed with individual images or make the look more consistent from image to image. In Lightroom I use colour markings and/or star markings to keep track of the selections and sub-selections I use along the way.

When I have got the point of having a set of images that I am content to use I go back to Lightroom and use the Spot Removal brush with Visualise Spots turned on to deal with dust spots. Having done that I re-export to JPEG and reapply DeNoise AI. At this stage, or earlier, I may be using settings different from the defaults in DeNoise AI, or I may be using the DeNoise method rather than the AI Clear method, or in extreme cases I may (very rarely) use Sharpen AI instead of or as well as DeNoise AI to deal with locally blurred or out of focus issues. With DeNoise AI or Sharpen AI I sometimes use their inbuilt mask function.

I then do administrative tasks to do with numbering/naming the JPEGs, assembling a folder containing both the JPEGs and the associated raw files, updating a couple of administrative spreadsheets, making a local backup copy and a cloud backup copy of the assembled folder and spreadsheets, and uploading the JPEGs into a Flickr album.

Image authenticity

I see two aspects of authenticity: whether the particular images processed this way look authentic; how far photographic images of invertebrates in general are authentic.

As far as these particular images are concerned, when I compare an out of the camera image with a post processed image I think I can see where most or all of the "extra" detail has come from. (Actually it's not so much "detail" - that seems to me to be about small-scale structures towards the limit of what I can make out. It's more a case of areas of varying sizes that are more clearly distinguished from one another in the processed images, plus some things like hairs that look thinner with more clearly defined edges in the processed version.) 

What I'm not noticing in the processed images is something I have seen with upsizing software, GigaPixel AI for example, where the upsized images have some "details" that are obviously artificial.

So from the point of view of "invented" detail, I'm fairly comfortable with the processed images. Some of the edges look too sharp, too well defined, for example some things in the background of the upper of the two examples at the start of this post. But that is more like ordinary over-sharpening and to do with visual preferences, and if I put more time and attention into the processing, for example using the masking in DeNoise AI more and more carefully, then I think that is in my own hands to deal with.

As to the general issue of photographic authenticity, particularly as it relates to small invertebrates, I think this gets tricky. The thing is, especially with smaller subjects, I have no way of knowing what they "really" look like because I can't make them out with my own eyes in anything like the detail I can see in photographic images, nor can I resolve the subtleties of colour and texture. 

That said, my feeling is that my invertebrate images are not authentic. Nature, to the extent I can make it out, looks much softer in its edges and colours than my images of it. That is fine by me, because my aim with my photography is generally to make what I think of as "pretty pictures" not authentic records of reality. For those whose viewpoint has more to do with reality and authenticity, I can see that my images could be problematic, over the top, unappealing or even distasteful. 

I see other forms in inauthenticity in some images of invertebrates. One has to do with focus stacked images, where depending on the scene there can be a sudden and to my eye very unnatural-looking  and visually disturbing break between the in-focus and out of focus areas. This can happen too with other subjects, for example in my flower stacks, where I try hard to avoid it.

And then there are dead animals put on to a machine to be photographed, or animals that have been cooled in a refrigerator to stop them moving, or baited to take them away from their natural activity so they are conveniently placed to be photographed. How natural/authentic is any of that? 

And then there is the wider issue of how authentic are photographs in any case? For example, I never see the world, or people, as a thin in-focus slice with an out of focus background like you get especially when using large apertures. 

I can enjoy all sorts of images of animals, as long as I don't get the impression of some sort of cruelty being involved. As to arguments about authenticity though, I wouldn't want to come down too hard on that one way or another, it is too slippery a concept for that. If I find an image pleasing to view, and/or informative, that is enough for me.

Using tiny apertures - Part 4, my preferred setup

By early November it had started getting cold and I wasn't finding any invertebrates in our garden. However, I had another piece of good fortune.  Opposite our house there is a church, and it has some fairly unkempt woodland around it. 

I had never been in there but I had read that springtails can be found in cold conditions and since the leaf litter wasn't cleared out of the wood I wondered if there might be springtails to be found there. I sought and received permission to go into the wood.

It turned out to be a bit of a goldmine. I did find springtails, and some other things too, some almost as small and some larger. Not huge numbers of anything, and it took time to find things that were there, but I found enough to keep me interested and let me carry on experimenting. Here are some of the things I found in November and December, all the way through to 25 December. (Yes, I went over there on Christmas Day. We were having a lockdown "unchristmas"; no family gathering for the first time I can remember.)

By then I had firmed up on what I would use, at least to begin with, in 2021: the A7ii with two 2X teleconverters and a Laowa 100mm 2:1 macro lens, and a Venus Optics KX800 twin flash, which I have been using for several years.

Yes, it's big, it's heavy, but consider this: the spider (?spiderling) below was small, perhaps around a couple of millimetres long. Perhaps it was a bit bigger, I don't know. What I do know is that it was scampering around almost continuously, and fairly fast. Over the course of around 16 minutes I captured around 155 images and 27 of them were to my way of thinking usable, a success rate of approaching 20%. For my visual tastes, for my hands that show a fair bit of hand-shake at 6:1 or whatever magnification I used, and with my definitely not lightning-fast reactions, I count that as a success. And it is something I am confident I could not do with any of my close-up lens setups.

So yes, the image quality isn't of the highest order. Here is one of them as an example. But close-up macro, especially out in the field, especially with smaller subjects, especially with moving subjects, is a game of trade-offs, and I'll obviously try and improve, but for now  at least I'm feeling that I've got a mix of trade-offs that I can live with.

So what is it like to use this big, heavy beast, out in the field?

Well, not too bad actually.

I get from infinity focus to 8:1 magnification with a turn of around 120 degrees of the focus/magnification ring on the Laowa 100. I'm using from 1:1 to 8:1 for these sorts of subjects. At 8:1 the scene size is 4.5mm x 3mm. That is about as small as I can handle, working hand-held as I do. I can get from 1:1 to 8:1 with a turn of around 90 degrees of the focus/magnification ring.

The focus/magnification ring moves very smoothly and easily. Together with the small amount of turning required, this means I can use a technique for finding the subject very similar to what I use with my close-up lens setups. 

Finding small subjects can be infuriatingly difficult. You can see it, you know exactly where it is, but can you get it into the frame so you can see it? Sometimes not, or only after a fair bit of searching. The problem is that you may be pointing straight at it but if the focus plane isn't quite close to the subject it may be invisible, especially at higher magnifications.

What I do is to pull back and reduce the magnification, a lot. This makes it much easier to see the broader picture and locate the subject within it. Having found the subject I turn the focus/magnification ring to increase the magnification, while simultaneously moving the camera to keep the scene somewhat in focus. It doesn't have to be fully, or even much, in focus, just enough so you can keep track of where the subject is. Then I may turn the focus/magnification ring a little to fine tune the framing and then move the camera to fine tune the focusing. 

I don't use any magnification of the image on the screen; I find that too disruptive, and slow. I don't want to be stopping to push buttons at that point. My subject may be momentarily about to move, or it may be in motion, as that little spider was for a number of those shots. How then do I get the focus plane in the right place, especially when just looking at that little screen, and quite possibly not having a particularly clear view to look at? After all, it matters hugely where the focus plane is placed in terms of exactly what ends up in focus.

Well, that is true normally, but bear in mind that depth of field roughly doubles with every two stops reduction in effective aperture. With the apertures I'm using I have a (relatively) large depth of field. I think that what is going on is that because of that much larger than usual depth of field I can get away with not being so accurate about placing the focus plane. 

So what apertures am I using? 

[Note: The effective f-numbers mentioned below might not be right. Please see the next post, here, for more on that.]

I experimented with various f-numbers, and it can get rather complicated because of the variation of effective f-number with magnification. For quite a while I tried to keep up with the mental arithmetic needed to keep the effective f-number constant as magnification changed. Then I had a session with all the wasps and flies on the pigeon carcass where I left the f-number the same, and didn't alter it as I changed magnification. To my surprise, it worked ok.

I then tried doing this in more sessions. I ended up leaving the f-number somewhere around f/45. The effective aperture would then vary from around f/90 at 1:1 to around f/400 at 8:1. It worked. Why would that be? I suspect that as subjects get smaller they need a smaller effective aperture to get enough depth of field to cover the same proportion of their body etc as I like to have with larger subjects (for example, for a winged insect, the head, body, near side legs and preferably near side wing in focus). By leaving the f-number set on the camera to a constant value the effective f-number increases as the magnification increases, and perhaps this is just what is needed to keep the depth of field coverage fairly constant in relation to the subject and its size in the frame. Anyway, for whatever reason, it appears to work. I need to firm up on this, or make alternative arrangements if it turns out not to be so satisfactory after all. But for now, I'm regarding it as a very helpful simplification.  

And what does using f/45 mean in terms of depth of field, compared to what I get with my close-up lens setups?

Well, with my close-up lens setups I use apertures that give the same depth of field as f/45 on full frame like the a7ii. With f/45 set on the A7ii/lens, at 1:1 the effective f-number is f/90, which means that it will have twice the depth of field as a close-up lens image of the same scene. At 2:1 the effective f-number is around f/132 and by 3:1 the effective f-number has reached f/180, which means that it will have four times the depth of field as a close-up lens image of the same scene. By 7:1 the effective f-number has reached f/360, which means that it will have eight times the depth of field as a close-up lens image of the same scene, and a bit more than that at the setup's maximum magnification of 8:1. These are rather significant increases in depth of field, and I like that a lot.

There are of course other factors, both positive and negative.

It is great to be able to be able to cover all the scene sizes I want to work with without having to make any changes to the kit. That for example, makes it practical, irrespective of subject size, to do one of my favourite manoeuvres, which is to move frequently back and forth between whole body, environmental and closer-in shots, including when I'm tracking a moving subject. This sort of thing (only more so sometimes, especially at the environmental end of the spectrum).

Flash can be a bit of a problem. With close-up lens setups the working distance remains fairly constant irrespective of magnification as long as you don't change to a different close-up lens, and even if I change between a Raynox 150 and a Raynox 250 the working distance is not affected enough to disrupt flash usage. 

With the double teleconverter setup the working distance gets very large out towards 1:1 with the result that the flash heads are distant from the subject and also pointing in the wrong direction. The KX800 has flexible arms, but I don't like moving them around too much. They are a bit fragile. I have broken one of the arms on one of my KX800s several times and have had to superglue the broken joints together, which reduces their flexibility. Also, having to move the flash heads breaks the flow of the capture routine and also slows me down. The kit is also a bit heavy to hold one-handed while adjusting the bendy arms of the KX800 with the other hand, and those adjustments work better, with less danger of causing damage,  using both hands, which would mean putting the kit down. That can be problematic in wet conditions and/or with brambles etc all over the place. And of course it puts paid to any thought of moving smoothly closer in and further out. 

To some extent I can compensate for the increased distance by increasing the ISO rather than making a big adjustment to the bendy arms, but that doesn't solve the problem of the flash heads pointing in the wrong direction, which does require physical manipulation of the arms. I may have some fine tuning to do on this front.

Very small apertures require a lot of illumination. I don't like running the flash at more than 1/4 power because of the impact on recycle times. That in turn means that it isn't possible to use base ISO. In fact I'm typically using ISO 1600 and 3200. I'm not too bothered about this as ISO 3200 gives about the same amount of noise as base ISO with my bridge cameras, and I can live with that. Of course, higher ISOs also lose details. However, the diffraction effects are so strong that the details that would be lost through higher ISOs may have already gone anyway, and with modern noise reduction things seem to work out ok for my purposes.

Another problem is dust spots. Using tiny apertures makes any dust etc on the sensor show up very clearly, especially with the rather strong post processing that the images need (see next post), and the more so as the aperture gets smaller. And it is not just dust on the sensor. There are another eight surfaces on which dust etc can settle: the front and back of each of the teleconverters, the front and back of the macro lens, and the front and back of a UV filter which is permanently attached to the front of the macro lens. The effect on the image of dust on any of those surfaces becomes  larger and more diffuse the further away the surface is from the sensor. That can make the spots more difficult to handle during post processing. 

I have tried very hard to get the A7ii sensor completely clean so that no spots show up. Despite many efforts, and despite deploying an air purifier to remove dust in the air of the room I use for sensor cleaning, I have yet to get the sensor so clean that it shows no spots at the effective apertures I am using.

Despite the problems, overall I'm getting fairly comfortable with the capture workflow with the A7ii double teleconverter setup.

Being able to capture images is one thing. Being able to make something presentable out of them can be quite another. Next up, post processing and image display.

Using tiny apertures - Part 3, Experiments

 

Now invigorated by unexpected success, I tried various combinations of the following, some of which I had already and some of which I purchased as the exercise went on:

• A Sigma 105mm macro lens, autofocus, infinity focus to 1:1
• A Canon 65mm MPE-65 macro lens, manual focus, 1:1 to 5:1 only
• A Laowa 25mm macro lens, manual focus, 2.5:1 to 5:1 only
• A Meike 85mm macro lens, manual focus, infinity focus to 1.5:1
• A Laowa 100mm macro lens, manual focus, infinity focus to 2:1
• A Canon EF-S mount 14-45 kit lens, used reversed with a simple reversing ring and with a Meike wired reverser (allows aperture control and autofocus)
• A Kenko 1.4X teleconverter
• A Kenko 2X teleconverter, and later a second one
• Kenko 12, 20 and 36mm extension tubes

Apart from the 14-45, these were all Canon EF mount. Also, a hybrid setup using:

• An Olympus 60mm micro four thirds macro lens, infinity focus to 1:1
• Meike 10 and 16mm micro four thirds extension tubes.
• Raynox close-up lenses

Since I had adapters for EF mount to Sony E mount and for EF mount to micro four thirds, I could test any of the EF mount kit on my Sony A7ii and various Panasonic G series micro four thirds cameras, in addition to mounting them directly on my Canon 70D dSLR.

With various of the EF mount combinations I got more results of a type I hadn't achieved with my close-up lenses. This included some other (not quite so) small subjects that I had previously had difficulty with, such as this small spider, captured here with a Sigma 105mm macro and a 2X teleconverter on the A7ii.

I had started out with very small subjects in mind, but it turned out that these setups could give me results I liked with larger subjects, both for whole body shots of the sort I use so much. 

(The yellows look a bit OTT to me in this one, but that of course is a separate, and curable, issue, like with the previous one looking a bit on the dark side. These were quickly processed as part of large volume test sessions. That's my excuse anyway.) 

I was also getting some results I liked the look of with closer-in shots of larger subjects, which I had never done much of previously, but began to find more appealing to try. This one, like the previous one, was captured with a Laowa 100mm macro and 2X teleconverter on the A7ii.

 Three months in to these experiments, at the end of August, I had a great piece of luck. Something, presumably a cat, killed a pigeon and left it on the grass in our garden. It quickly attracted a large number of wasps and flies.

This gave me several days in which I had a target-rich scene I could use to test various setups and compare both the resulting images and the operational characteristics of the setups. As well as using several of the E-mount setups, I also used a close-up lens setup to check whether the E-mount setups with their greater depth of field really did produce results I preferred. Strictly like for like comparisons were obviously impossible as there was continuous movement in the scene. But I captured so many images that it was possible to pick pairs that were similar enough to draw conclusions from. (Results obviously varied from image to image, but I concluded that overall the E-mount setups did produce results that I preferred compared to the close-up lens results.) 

Another very useful comparison was between the handling characteristics of A7ii, 70D and G9 setups. That led me to the conclusion that I preferred using the A7ii. I could see more clearly what was going on, which let me react faster and focus more reliably, which was helped some of the time with focus peaking signals from the A7ii. They were quite weak, and absent quite a lot of the time, but when they were there they were helpful. I didn't get any focus peaking signal from the G9 and the 70D didn't have focus peaking.

These were the sort of images I was comparing between setups.

Using tiny apertures - Part 2, Frustration, and then an unlikely discovery

Mid summer 2020. We've been in lockdown/shielding for several months now. The tiny flies have turned up as usual on our minuscule excuse for a pond. As usual I try to photograph them. As usual I fail. 

These tiny flies are hyper-active. They usually don't stay in one place for more than a very few seconds. They land in different places on the lily pads so I can't simply set up the focus for one place and wait for one to turn up. 

I need to be quick to frame them, gain focus and shoot before they fly off. But at higher magnifications it is difficult to point the camera in exactly the right direction so a tiny subject is in the frame. You can sometimes spend a long time just trying to get subject to show up in the frame. It can be very frustrating. Also, with the strong close-up lenses you need to get enough magnification for these tiny subjects, the working distance has to be just right, within very few millimetres, otherwise autofocus won't engage.  

It is difficult doing all this fast - working distance, frame, focus, shoot - and in this case needing the camera low to get a nice angle on them, with the camera almost touching the water, fingers dipping into the water sometimes. The bright light doesn't help either, even though I'm using an LCD hood (couldn't use the viewfinder for these even if I wanted to because of the angles involved). 

So, lots of "missed it, again". 

But a few work. That's good. Apparently. But when I come to look at them on the PC it is the usual story. Nothing I'd really want to use.

One of the things I have learnt over the years is that some techniques seem impossible to me when I first try them, but as I practice it can get easier, eventually becoming sufficiently routine for me to wonder what the problem was.

So, lack of practice, lack of appropriate muscle memory, perhaps that was the problem. Having to think explicitly about sequencing the actions, hesitating while thinking what to do next, rather than going through the sequence of actions smoothly from one to the next, fitting it all together into a confident, smooth, seamless, fast and accurate performance.

So I decided to get serious about it. Rather than moaning about how difficult it all was I would practice, practice, practice. I would achieve that smooth performance, I would succeed with this. I could do it.

I spent several days on it, not worrying that it wasn't working yet. I would get that breakthrough moment when it all fell into place. Then it would be ok.

It eventually dawned on me that I was kidding myself. The images  simply didn't have enough depth of field for me to want to use them. It wasn't just that it was difficult to get the plane of focus in the right place, I could live with that. Have lots of attempts and pick out the few that work. I've done that before. However, as I looked through the best of my attempts it became clear that even when the focus plane was ideally placed there simply wasn't enough depth of field. And nothing I could do by way of better execution was going to alter that.

I had to admit it to myself; I had failed. I wasn't going to succeed with these tiny flies.

And then a little thought in the back of my mind - "not with this kit you're not going to succeed". Hmmmm.....

So if close-up lenses were not going to work, was there something else that might? Something in the macro lens, extension tube etc area? Given my prior experience I couldn't see why anything like that would work. But it would be nice to get a bit of hands-on practice with some of the kit I had accumulated and never really used. Even if it wasn't going to work for these tiny flies I might learn something of interest. And the flies would probably be there for a few more days to give me some small subjects to practice on.

I first tried a Laowa 25mm macro lens on my Sony A7ii. To my surprise I quite quickly got some results that were better than I had ever achieved with my close-up lens setups. This was the image that sticks in my mind as making me think it would be worth pursing these alternative approaches. 

And there were others Here are two from the same day, one of a slightly larger subject just two minutes after the one above, the other of a much larger subject later in the day, but in both cases closer in on the subject with the subject filling more of the frame with greater depth of field than I think I had ever previously achieved.

I didn't like the way the setup handled, but that was beside the point. These images showed that with this sort of setup I could get results that I liked which I couldn't get with my close-up lens setups. 

My motivation skyrocketed. 

That was at the beginning of June 2020. It was the start of 7 months of fairly intensive experimentation and testing.

Using tiny apertures - Part 1, Background

 I re-started photography in 2007 after a gap of more than 30 years and started photographing insects, spiders, snails etc using a close-up lens on a small (1/2.3") sensor bridge camera. Since then I have continued using close-up lenses for invertebrates, both on newer small sensor bridge cameras and also micro four thirds cameras (with a 45-175mm camera lens) and an APS-C dSLR (with a 55-250mm camera lens). I have moved back and forth between these setups for years, mainly between bridge and micro four thirds, unable to decide which was best; each has its own merits and problems for what I want to do. (I'll talk about flowers etc another time, which have taken me on a different path.)

In order to get as much depth of field as I could for insects etc I used minimum apertures; f/8 on the bridge cameras and f/22 on the micro four thirds cameras. On the dSLR minimum aperture varied from f/22 at 55mm focal length to f/32 at 250mm focal length.

Used with a close-up lens, these apertures gave me very similar depth of field on all three types of camera, which was enough to get images like this with single shots (i.e. not focus stacking). 

From time to time I experimented with other approaches, including various combinations of macro lenses, extension tubes, teleconverters and reversed lenses, some of which let me get greater depth of field than I could with my close-up lens setups by using smaller effective apertures than I could with my close-up lens setups.

None of it worked to my satisfaction. For example, for the kit I tested I found that:

• Macro lenses either didn't let me use autofocus, or if they did it got so slow and unreliable as the magnification increased that it wasn't worth using. With my close-up lens setups I had autofocus that was responsive and accurate, and which especially with the bridge and micro four thirds setups let me use a very small focus area which allowed me to place the plane of focus pretty much exactly where I wanted it. Manual focus was in contrast very hit and miss, especially with subjects that were moving around.
• Macro lenses gave softer images at minimum aperture than close-up lenses
• A setup that let me use a tiny aperture (I tested an effective f-number of around f/132) gave images that were so soft as to be not usable.
• Using extension tubes would mean opening up the camera out in the field to change between them depending on scene/subject size. This would risk getting dust etc on the sensor. When using small apertures this matters greatly as dust shows up very clearly, especially with the fairly strong post processing I used.
• Teleconverters were promising as they provided greater magnification at the same minimum working distance or the same magnification as without them but with a greater working distance. However, a 1.4X teleconverter softened images a bit and a 2X teleconverter softened them more.
• When reversing lenses that didn't have a manual aperture control, I could only control the aperture with a procedure that was slow, fiddly and opened up the camera to dust etc. Alternatively, I could use a device that let me change the aperture in the normal way, but this caused very bad flare. Or I could use a legacy lens with manual aperture control, but none of the ones I tried worked well in my hands.
• Most of these setups were big, heavy and awkward to use.
• None of these setups gave me noticeably better image quality  than my close-up lens setups for the single-capture large depth of field shots that I typically go for. (This may seem surprising. Why wouldn't proper, very sharp, macro lenses give me better results? I think because of softness and loss of detail caused by diffraction. With the apertures I was using the excellent sharpness of the high quality lenses got blurred away by the large amount of diffraction softening.)

So, I kept coming back to my close-up lens setups. 

This left me with an unresolved problem; small subjects. I had only very limited success with small subjects such as fruit flies, springtails, barkflies and barkfly nymphs, mites and tics, which were often around 2 to 3mm long and sometimes 1mm or less. 

 

This problem had been nagging away at me for a long time. Most of my invertebrate subjects are what I think of as middle sized, or occasionally large, and over the years I slowly progressed, for example as my post processing improved. What I had never been satisfied with, and seemed unable to make meaningful progress with, was small subjects like this springtail, which was probably around  two millimetres long. 

Very occasionally I would get an image like this, but the capture failure rate was huge and when one did work the processing effort could be disproportionate. (I had repeated attempts over several years trying to get something usable out of this one.) It was extremely difficult to enough depth of field for my taste, and I had to keep the subject smaller in the frame than I would have liked. It was all pretty disheartening and for the most part I ignored small subjects like this.

So how did I end up using a big, heavy, manual focus setup which used a macro lens and not just one but two teleconverters, both of the 2X variety, using effective apertures even smaller than the f/132 that I had shown was unusable, and using this setup to photograph subjects as small as 2mm or so long as they moved around quite fast, with a fairly high success rate?

That is what the next few posts will be about.

New kit? Too soon to say

 My reasons for considering the three options for new kit that I mentioned in this post are as follows:

• Sony A7rii. This should be just as good as my A7ii for the tiny aperture approach that I'm exploring for invertebrates. However, with its almost twice as many pixels it might be better than the A7ii for use with deep cropping using normal apertures, which might be better than using tiny apertures which destroy fine detail.
• Olympus E-M1 III. This has facilities for focus bracketing and stacking that work well for invertebrates. It might let me get both good detail and the deep depth of field I like, which I can't with the tiny, detail-destroying apertures that I currently use.
• Panasonic Leica 50-200 lens. This is a top of the line lens which might be better for flowers etc than the 60mm macro or 45-175mm lenses that I currently use.    

I'm thinking that there are some things I need to get sorted out before doing a full options analysis on any of these.

Is this tiny aperture approach with the A7ii really going to work for most of my invertebrate subjects? If not, I think this would call the A7rii option into question. If it does work well and gives me really good depth of field for my mid-sized subjects, I think that would undercut the case for an E-M1.

My invertebrates subjects are mostly mid-sized, often rather active, and often on foliage that is moving around in a breeze. I have only tested the tiny aperture approach on tiny subjects like springtails on the ground (for which it is definitely advantageous and practical) and for mid-sized insects that were numerous, often remained in one place for  a long time and were on something that wasn't moving around (a pigeon carcass). Yesterday I tried to photograph medium and small sized insects on foliage that was moving in a breeze and had absolutely no success with the A7ii. 

For invertebrates, I need to do some practical comparisons in contexts that are more typical than I've tested before, switching between the A7ii and one of my close-up lens setups. If the success rate with the A7ii turns out to be extremely low for my typical subject matter compared to the close-up lens setups then it doesn't matter how much better the images are; potentially nice images that you can't actually capture are not much use!

As to the 50-200, for flowers etc I have used both a macro lens and a tele-zoom lens with/without closeup lenses quite a lot. However, I realised a couple of days ago that I really don't have much of a feel for the differences between these two approaches in terms of how easy or difficult it is to capture images with them and also in terms of image quality/visual appeal of what I can produce using them. It is also unclear to me how much difference it would make, for stills and focus stacks, that I can always use f/2.8 with the macro lens but would almost always have to use a slightly smaller aperture with the 50-200 (although not as much smaller as with the 45-175). 

For flowers etc I need to do some practical comparisons between the 60mm macro and the 45-175.

I will come back to all this later.

Several rules of thumb

There are a couple of terms that are going to be important in some upcoming posts about photographing insects and other invertebrates: equivalent f-number and effective f-number. This can get very complicated, especially equivalence, but I'm just going to use a couple of rules of thumb relevant to the particular options I'm considering.

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I am considering setups involving cameras with three sensor sizes: 

• 1/2.3", around the size of sensor used by many smartphone cameras
• micro four thirds
• full frame

For insects etc I use f/8 (minimum aperture) almost all the time with my 1/2.3" sensor cameras. In order to get around the same depth of field with a micro four thirds setup I have to use f/22, and with a full frame camera I have to use f/45. These are the equivalent f-numbers that matter most to me. 

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Effective f-number needs a bit more explanation. (This explanation does not apply to Nikon kit, but I don't use any Nikon kit.)

When you photograph a small scene using a macro lens, extension tubes and/or a reversed lens or bellows, the f-number you are actually using (known as the "effective f-number") is smaller than the one you set on the camera (known as the "nominal f-number"). 

The effective f-number can be calculated using the following formula. (This formula is an approximation, but it works pretty well in my experience).

    effective f-number = nominal f-number * ( 1 + magnification )

So for example if I set the camera/lens to f/11 and I shoot at 1:2 (so the magnification is 1/2), the effective f-number is 

    f/ (11 * ( 1 + 0.5) ), which is around f/16.

If I set the camera/lens to f/32 and shoot at 3:1, the effective f-number is

    f/ ( 32 * ( 1 + 3 ) ), which is around f/128  

When it comes to depth of field, it is the effective f-number that matters.

I often use setups which have a close-up lens mounted on a telezoom lens. These include the zoom lens on a bridge camera and a 45-175mm lens on micro four thirds. 

The above calculations do not apply when using close-up lenses on telezoom lenses. In that case the effective f-number remains unchanged, irrespective of the magnification.

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In the upcoming posts about invertebrates I will be comparing close-up lens kit on bridge and micro four thirds cameras with macro lens kit on full frame. There is a nice simplification for these comparisons:

• For the close-up lens setups I only need to consider equivalent f-numbers, because the effective f-numbers don't change with magnification.
• For the full frame macro setups I only need to consider effective f-numbers. This is because I will be using full frame equivalent in the comparisons, so the full frame options don't need any equivalence adjustment.

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Here are a couple of other rules of thumb that I'll be using.

• Depth of field roughly doubles with each two stops reduction in aperture.
  
  
  
• ISO 100 with my bridge cameras has roughly the same amount of noise as ISO 800 with my micro four thirds cameras and ISO 3200 with my full frame camera. 

A big hole and a travel camera

 I went out into the garden yesterday to grab a photo of some garden work I've been doing in the past few days. I took my travel camera as this is what I use for odd photos that I imagine most people capture with their smartphones (as probably I would if I had one).  This is what the area I was working on looked like a couple of years ago. 

The tree stump is the remains of a big cherry tree that, much to our disappointment, we had to have taken down because it was rotting and had the potential to do a lot of damage if it fell over. Along with the loss soon after, to our great surprise, of a big apple tree (which we never suspected had a problem, but which turned out to be rotten too), that was the end of our little woodland garden area. (By a stroke of good fortune it fell in to our garden and just crushed our old garden shed which needed replacing anyway, rather than falling where the prevailing westerly winds would have sent it, crashing down on our neighbours' cars, and possibly of course also our neighbours. It doesn't bear thinking about.)

Anyway, the stump of the cherry tree developed a nasty bracket fungus that was spreading in a way my wife didn't like at all (She is the Gardener. I am the Gardener's Assistant.) Her decision was that it would have to go. We will get a man with a stump grinder to get rid of it, but we want to limit the damage so we have cleared the plants out of the area the Gardener is prepared to sacrifice. My job was then to expose the roots and remove the earth so we could see what was going on. This would allow some of the roots to be cut out, with less collateral damage than with grinding, which can leave a difficult to repair mixture of subsoil and top soil depending on how far the grinding goes down and how far the subsoil comes up. It's lucky I did remove a lot of earth because it turns out that around the tree the subsoil came very close to the surface. As I removed it I kept the worst of the subsoil separate from the better soil and so I'll be able to refill it putting the subsoil back at the bottom.

So, here is what that area looks like now. I suppose I shouldn't be surprised the roots were substantial. It was a large tree. 

Here is the earth I removed. 120 or so bags, partly filled; no point doing my back in. A couple of tons? More perhaps.

Job finished. All wrapped up to keep it from getting wet and claggy.

And that might have been that for the day in the garden. But as I walked away I noticed the light on a couple of wallflowers. I had a camera in hand, so I photographed them. 

Then I noticed more light. And ... well, I carried on photographing. Perhaps I should have gone back indoors and got a more suitable camera. I generally use a Panasonic G9 micro four thirds camera with an Olympus 60mm macro lens for flowers and other botanical subjects. This gives me two excellent tools for working with flowers etc: 

• "Post focus" 6K video which makes it very quick and simple to capture videos, hand-held, that are easy to use for focus stacking
• Aperture bracketing, which lets me capture a sequence of seven images from f/2.8 to f/22 from which I can, later on my PC, select which I like best in terms of the balance between focus coverage of the subject and the look of the background; one (to my eye) improves as the other (to my eye) gets worse as the aperture changes.

The G9 has some other nice features too like: 

• A fully articulated screen which lets me capture at odd angles I couldn't achieve using the viewfinder, and makes it easy to work in portrait mode, which I do a lot with flowers, using the LCD screen (I almost never use a viewfinder). 
• A very flat Cinelike D profile that helps expand the available dynamic range which makes up a bit for the fact that video delivers JPEGs rather than giving the flexibility of raw that I get with stills.
• A joystick to move the focus area

In contrast, my (fit into a pocket) travel camera is a Panasonic TZ90 with a very small, 1/2.3" sensor that has 20 megapixels stuffed on to it, and a little lens that delivers a huge range of focal length from 24mm to 720mm full frame equivalent, which obviously is not going to be of the best optical quality. It doesn't have an articulated screen, so working at odd angles, and working in portrait mode are at best difficult, and because of the way the screen is hinged I can't use a lens hood like I can with the G9, and this makes it much more difficult to see what is on the screen on a sunny day, which it was in this case. 

The TZ90 doesn't have a joystick or Cinelike D. It doesn't have aperture bracketing. It does have post focus but it is 4K rather than 6K and so only uses 8 million of its 20 million small pixels. And in any case the choice of apertures is very limited at the longish focal lengths I was using meaning that I was mainly using f/5.6 through just one stop to f/8. These are equivalent to f/ 32 and f/45 on full frame so you have very little control over the depth of field, which is always rather large. And for focus stacking these small apertures are not as good as larger apertures, which will give better detail and softer backgrounds.

And you can't photograph the small scene sizes that you can with a macro lens like I use on the G9.

All in all, the TZ90 is, to say the least, not ideal for photographing flowers etc.

But I find it interesting, instructive and fun to use different setups from time to time, even though (and perhaps because) they can be slow, difficult, awkward etc to use and limited in what they can achieve even in the best of circumstances.

And sometimes a bit of ingenuity can extend their capabilities. There were subjects that looked promising that were too small for the TZ90. So I went back indoors for a kit change, but rather than taking out a G9 I put a Canon 500D mild close-up lens on the TZ90 using a simple adaptor which I cobbled together as an experiment three years ago. The last three photos below used this arrangement.

Below there are some more photos from that session. They were all shot raw and processed with, in this order, DXO PhotoLab, Lightroom and Topaz DeNoise AI. Three of them had a round trip from Lightroom to Photoshop and back for some stretching and squashing of edges of the images to produce a better balanced composition.