Tuesday, 31 January 2017

Vertagopus arboreus

Vertagopus arboreus

This is the first usable field image I have managed to produce with the Canon MP-E 65mm macro lens. The Fotodiox Pro converter works very well on this manual lens, no need for the expensive Metabones. (Hmm, there's a bit of a cheapskate theme developing here...) Some thoughts:

The problem with this lens is twofold. As with all macro lenses it has a very shallow depth of field. No seriously, very shallow. At 5x magnification and f2.8 (wide open), the d.o.f. is approximately 0.2mm. So obviously, you stop down to f16. And that's when the problem starts. You can just about get away with f16 at 1x magnification, but at 5x by the time the light hits the sensor, you've magnified the diffraction to the point where the image is unusable. Workable combinations are something like:

1x: f11-16
2x: f8-11
3x: f6.3-8
4x: f5.6-6.3
5x: f4-5.6

That means that at higher magnifications, you're working with tiny d.o.f. No problem - focus stacking! Yes, for dead specimens in a studio - good luck with that for live springtails in the field. "Oh, he's just complaining again. Whack it on f5.6, no problem." F5.6 is a fine aperture, one of my personal favourites. A nice landscape shot, half the frame filled with sky, no problem. But there's no point in pointing the MP-E 65mm at the sky - the furthest it can focus is a few inches away from the front element. And with macro, we're not pointing at the sky anyway, but grubbing around in hedge bottoms, pointing the lens downwards. Even without all this the MP-E 65mm seems to be a rather light-hungry lens, i.e. compared with the results from the same aperture on a wide angle lens. So we need a lot of light. Direct sunlight would do the trick, but when you're only an inch away from a frisky insect, you'll be blocking ambient light most of the time. So my next step is to build a lighting rig for this lens in the field. I'm too tight to shell out £800 for the Canon MT-24EX Macro Twin Lite Flash and I don't know if it would work on the Sony anyway. So it's DIY - the parts are on order from eBay.

Vertagopus arboreus, ~1.7mm long.
Sony ILCE-6000
Conon MP-E 65mm F2.8 G SSM
f2.8 1/100 ISO 3200