Using less teleconversion

 Using the A7ii and subsequently the A7sii with the Laowa 100mm 2X macro and a pair of 2X teleconverters opened up new possibilities for me. Previously I had occasionally managed to get a half decent image of small subjects such as globular springtails and aphids, but it was difficult and had a very high failure rate, so for the most part I avoided subjects that small. Now I found I was able to capture better images of these small subjects, and to do so with a much higher success rate. My photographic opportunities had widened significantly.

However, there turned out to be a downside at the other end of the spectrum; photographing larger subjects had become problematic, especially more "environmental" shots of larger subjects from further out. The problem was working distance. The problem is usually having not enough of it. Now the problem was having too large a working distance. At 1:1 the working distance was around 380mm and was increasing fast as the magnification decreased any further. This large working distance made it difficult to throw enough light on to the scene (and I need to throw a lot of light on to the scene because of the very small apertures I'm now using).

There were two problems. One was simply the distance. Illumination decreases with the square of the distance between the light source and the subject, and by 1:1 the illumination had become very diluted. And that was if the flash heads were pointing at the subject. But at lower magnifications they were not, and that was the second problem. If the flash heads were pointing so as to illuminate small, close subjects then they were far away from pointing at distant, larger subjects and not providing them with much light, necessitating uncomfortably high ISOs. And if the flash heads were adjusted for larger subjects the smallest subjects got no illumination at all. It is true that adjusting the direction the flash heads were pointing had become much more feasible with the Yongnuo YN24EX than it had been with the Venus Optics KX800, but making any adjustments to the physical flash setup was very unattractive; it would be very disruptive for some of the sequences I like to capture, where I move freely between a wide range of magnifications, sometimes taking shots as frequently as every two seconds or so while change magnification from shot to shot.

I went back to my close-up lens setups and did some measurements to give me some context. I used my FZ330 small sensor bridge camera with Raynox 150 and Raynox 250 close-up lenses, as this was my most used setup, and the one with the widest range of magnifications.

The Raynox 150 was by far my most used setup with the FZ330 (sometimes I would have sessions with the FZ330 where I only used the Raynox 150 and didn't use the Raynox 250 at all). This let me photograph scenes from around 75mm wide down to 13mm wide. Using the Raynox 250 instead of the Raynox 150 gave me scene widths from 43mm down to 8mm. So by changing between the two close-up lenses I could photograph scenes from 75mm wide down to 8mm wide.

In contrast with the A7ii, the 100mm 2X macro and a pair to 2X teleconverters:

• I could go down to a scene width of 4.5mm, much smaller than with the Raynox setups. (I had more powerful Raynox close-up lenses, and I could stack Raynoxes for example a Raynox 150 and a 250, or two 250s. However, I had found it difficult to get good results with these setups.) 
• But I was limited for larger scenes to around 36mm scene width, which was very restrictive compared to the 75mm scene width I could get with my much used Raynox 150.

I did some measurements on the A7sii with 100mm 2X macro with one 2X and one 1.4X teleconverter. This would give me a minimum scene width of 6.4mm, which was still slightly smaller than I could get with the FZ330 and Raynox 250. At the maximum feasible working distance of around 380mm it gave me a scene width of around 53mm. That was not as good as the 75mm scene width I could get with the Raynox 150 on the FZ330, but it seemed like swapping out one of the 2X teleconverters and using a 1.4X in stead would give me a closer fit to what I needed.

So I experimented. It turned out that there was an adjustment I could make to the bendy arms holding the Yongnuo flash heads that brought them down a bit and let them point a bit more forwards and a bit less downwards and that was enough to let me use a slightly longer working distance, and that was all I needed to get to the sort of scene width I could get with the FZ330 and Raynox 150. So with the 2X plus 1.4X teleconverter setup I could cover the full range of scene sizes that I could with the FZ330 and Raynox 150 and 250, and could do so seamlessly, unlike with the Raynoxes which required changing close-up lenses to go between magnification ranges.

The other question was whether the 2X plus 1.4X teleconverter setup would give me enough magnification for what I wanted to do.  Although the double 2X teleconverter setup gave me up to 8X magnification, I had been feeling for a while (without doing any careful measurements) that I was rarely using much beyond 6X or so. It turned out in practice with the 2X plus 1.4X setup that I didn't often feel I was missing the extra 5.6X to 8X magnification range that the double 2X setup gave me.

So I decided to transition to a 2X plus 1.4X setup. So far it has worked well. Indeed, for reasons I don't understand, it turns out that I am using lower ISOs with this setup than the double 2X setup. I think that may be down to the adjustments I made to the position and direction of the flash heads. I'm sometimes using ISOs as low as 400, which gives me a three stop noise advantage over the FZ330 setup,  for which base ISO 100 is similar to ISO 3200 on full frame. And I'm rarely using ISOs as high as 3200, so there is at least a little noise advantage over the FZ330 setup for almost every shot, and sometimes a rather larger noise advantage.