A random walk to a new flash setup, possibly

 My experiments tend to be a bit haphazard. One consequence of this is that it can take me much longer to realise something than it would have had I been more methodical. I know that, but it's just not my style to be buttoned down methodical, carefully pre-planned, thorough records etc. It's the same with my style of shooting. Persistent, yes. Very persistent. But methodical, no. I try to be methodical sometimes, but I get bored with it, and wander off, lose track of the plan, can't be bothered to keep records, forget what happened, don't see the patterns. Bumbling along. Rather inefficient.

There can be an upside to this though Sometimes I wander along from one thing to another, and suddenly realise that I've ended up somewhere rather unexpected, but rather promising. Somewhere that had I been methodical, logical, rational, I probably wouldn't have reached. 

So it was yesterday.

I intended to go over the road to the church grounds to do some aperture variation tests as mentioned at the end of the previous post.  However, it kept raining on and off, which put me off. So I decided to do some indoor testing. That way I could be more, yes, methodical, and should be able to home in quickly on good apertures for different magnifications. I did need a suitable subject though. None of the man-made things I tried had the appropriate type and level of detail. But I searched the window sills and found a dead wasp, about 10mm long. That would do nicely, it's eyes in particular.

Until it's head fell off.

But even headless it was useful. Until it fell apart even more. But I did do some comparisons. I couldn't do enough to be sure about it, but to my surprise the comparisons I did manage to do seemed to support the continued use of the constant f/45 that I had happened upon by .... by accident? Out of laziness? Through some sort of unconscious evaluation? Who knows. Anyway, I should look at this more thoroughly when I can find another suitable subject. Should. Will? Maybe. We'll see.

Anyway, With the very small apertures I'm using I'm finding it difficult to get enough light on to the subject, especially when testing even smaller apertures than the f/45 I've been using recently. One thing that can lead to over-optimistic results is putting the subject on a somewhat reflective surface that can bounce light on to the subject, especially its underside. To try to avoid this I'll sometimes put the subject right on the edge of the table, bookshelf or whatever. A related problem can arise when the subject's surrounding are much lighter than they might be out in the field. To try to avoid dropping into that trap I put subjects on to dark (and not very reflective) doormats. I have several of these spread around in my study to try to protect the light coloured carpet from the muck that I bring in from the garden on my shoes. 

The doormat I used for the dark surroundings tests was in a position where it wasn't getting much light. That made it impossible to see enough to focus properly. The obvious solution would have been to move the mat into the light. But (fortunately) that never entered my mind. Instead the obvious thing seemed to be to turn on the KX800's focusing light. I realised that the KX800 I was using (I have three) was the one with a faulty focusing light which only comes on for a moment every second or so. It is unusable. (The flash itself is fine. It is the one I have been using for a while now. Just not the focusing light.)

One of the other two KX800s has a faulty arm. The KX800s have loc-line (or similar) arms. One of the arms on this one has broken several times, in different places, and each time I have superglued the broken ball and socket joint together. It is now rather inflexible and I wasn't keen on trying to bend the arms into the shape needed for the very long lens setup I'm using on the A7ii. So, I used the third KX800.

The focusing light started acting up. Not as bad as the first one, probably still usable, but I didn't like the way it was going. I decided to try a different direction.

I have a Yongnuo YN24EX twin flash. Like the Canon twin flashes, it can be mounted on the front of the lens, which gets the flash heads near to the subject. That had been sitting on the shelf for many months because although the power of the flash was fine given its front mounting, despite numerous attempts I couldn't arrange diffusion for it which got me illumination I liked. This was despite help from John Kimbler (@dalantech), who uses this type of flash setup to very good effect. However, I could live with not so good illumination for this exercise; it was how detail came out at different apertures that I was concerned with, and the YN24EX has focusing LEDs built in to each flash head. 

The simple, quick and straightforward thing would have been to mount the YN24EX flash heads on the front of the lens as I had done previously. But I looked at the pathetic little two-polystyrene-layer diffusers that were still on the flash heads as the last thing I had tried before giving up on the YN24EX, and I decided on a whim to try something else.

I remembered that I had bought a flash bracket with bendy arms like this one. 

The arms on the one I bought are very stiff indeed. Also, the configuration of the base and the arms made it uncomfortable to use hand-held. It was not an appealing piece of kit. I had not found a use for it. For some reason I decided to try using it with the YN24EX. 

I reused the diffusers from the KX800, and after an hour or so of testing and adjustments, the setup ended up looking like this.

The piglets illustrate the working distances. From 8:1 down to 2:1 or so the working distances are similar enough that it is easy to arrange the flash heads so they can provide satisfactory illumination without needing to adjust the position of the heads. However, as you approach 1:1 the working distance gets bigger faster, getting to around 350mm by 1:1, at which point the working distance is increasing very fast indeed. This makes flash illumination difficult for low magnifications, partly because the flash heads are pointing in the wrong direction (or if they are pointing in the right direction they are pointing in the wrong direction for higher magnifications). And even if they are pointing in the right direction the illumination level decreases with distance according to the inverse square law, and 1:1 is a lot further away than 2:1. Given that I am using very small apertures, this makes it difficult to provide enough light at lower magnifications. This is a general problem with this double teleconverter setup, not specific to the YN24EX.

What surprised me was that it seemed, at least from indoor testing, that this setup could actually provide (just) enough illumination out at 1:1, and enough light to aid focusing too. In dark scene tests I had to let the ISO go up beyond the ISO 3200 that is equivalent to what I have been using with close-up lenses for years, but not by much, and only right out at 1:1. It only needed a quite small increase in magnification to get it back to ISO 3200.

There were also a couple of hints that the quality of illumination might be slightly better than with the KX800. This seems unlikely, given that I was re-using the KX800 diffusion arrangement. However, more by accident than design, the outer diffuser was mounted further away from the flash head boxes than with the KX800, and previous tests indicated that greater inter-layer distances increase the diffusion effect. 

Here is what it looks like from the subject's perspective.

Desktop tests are one thing. How things work in the field can be quite another, so earlier today I went across to the church grounds to see if I could find anything to give the setup a reality test. It did ok.

• The flash bracket was not as uncomfortable to use as I thought it might be. I think that is because of the length of the lens setup and the fact that I keep my left hand at the front of the barrel, on the focus/magnification ring. With the left hand bendy arm running up close to the lens barrel, and my hand out at the front, the bendy arm didn't get in the way.
• The flash provided enough illumination for me to run the flash at 1/4 power as usual to keep recycle times fast enough for my shooting rate without having to raise the ISO so far as to be troublesome.
• The quality of the illumination was no worse than with the KX800, and might possibly have been just a little better with reflective surfaces. 
• The way the outer diffuser was mounted, a bit higher than with the KX800, left just enough of a gap underneath which I could look through to help with lining up subjects.
• I didn't need to use them, but it was nice to know I had focusing lights available should I need them.
• If I really wanted to, I could alter the direction the flash heads were pointing because there are flexible connectors at the ends of the bendy arms. This is not possible with the KX800 because the flash heads are in a fixed position at the end of its bendy arms. In order to rotate the flash heads you have to manipulate the arms, which moves the flash head to a different location. It can be tricky to get the flash head back to the right place but pointing in a different direction.  

I captured 285 shots during the test session and ended up keeping 60 of them, a keeper rate of 21%. Given that it was distinctly breezy, and that the majority of the subjects were fairly small, that seemed very satisfactory. 

Here are some of the images from the session. The rest are in this album at Flickr.