I can't really use an Elinchrom, it has to be vey very portable and fit inside the same backpack I'm carrying the rest of my equipment so it has to be a small speedlite-type flash unit. Most of those ring lights aren't really an option, their opening is much too narrow for big lenses and I want to avoid that lighting type.
Hi,
I agree on the type of lighting, I prefer to not use ring-lighting. However, a lot depends on you working space between subject and lens. On my Canon lenses I use a dedicated 2 flashhead unit with added diffusers, but on a large diameter lens that wouldn't fit. At very high magnification factors, it will become hard to get some semi-frontal light on your subject, and ring-lights may be unavoidable.
For the sake of portability, you could think of 2 very compact modest (depends on magnification factor and aperture used) power flashes on penlight batteries, mounted on a bracket of sorts (e.g.
Manfrotto 330B macro flash bracket). It's compact to store and transport, and the whole ensemble can be used handheld if needed, which is useful e.g. if you need to chase insects in the field (BTW 35mm equipment would be more suited for that than Medium format). The 330B is a bit on the flimsy side, IMHO.
If you really want to do this a lot, RRS has several more sturdy yet lightweight solutions, e.g. the
WPF-QR2 which is compact when transporting, or the
FR-91-QR of which they also have a smaller version if that still fits the lens position/diameter. The benefit of the Ring-bracket solution is that the lights can be moved more to the front of the lens, instead of the camera position. The more to the rear the flash is, the harder it is to avoid the lens from casting shadows on the subject.
You need the flashes in a position that allows to avoid a shadow from the lens barrel/hood getting cast on the subject. Also more distant flashes create harsher light, with lots of specular reflections, so you should aim to add something like diffusers to gain as much from the size of the light emitting surface and/or reflections from the subject's surroundings. Diffusers cost power, so make sure your flashes are powerful enough but not too powerful. Macro magnification costs a lot of light, exposure increases with magnification as (M+1)^2 (so at 1:1 magnification you need 4x as much light compared to infinity focus).
I in general find working with the RRS
system, a joy, which also helps the photography by being less of an obstacle to construct a solid solution with components that are already present.
Cheers,
Bart