modern macro ring flash with a view camera?

Hi all,

I was wondering how I can use a modern Canon ETTL macro flash (the MT-24 EX Twinlight) with a macro lens (I have a Nikon 135mm macro lens for my view camera).

This is a very versatile flash that can be easily positioned to illuminate a 4x5" subject for 1:1 shots. The ring flash will fit on the 4x5 lens. I also have a cord that will allow this kind of lens to trigger the flash.

The problem is that I haven't a bloody clue how to estimate or calculate exposure with an ETTL flash, and unlike my DSLR my view camera isn't going to tell the flash what to do.

Any ideas?

Got an incident flash meter?

An incident flash meter would work.. but remember to calculate for bellows-extention.
Essentially with the lens racked out to 1:1, there is less light falling on the film than would normally.
There should be some pretty good calculators around if you google it.

At 1:1 you about double the length of the bellows. Light at the film plane would be quartered. F/5.6 becomes F/11. Etc. A tape measure (metric) helps.

Peter Gomena

If your digi allows you to fix the flash at full power, you use it work out a ball park exposure. Or even work backwards to get a usable guide number.

Big hint: educate yourself about Spiratone's MacroDapter. Ask Google what it can find for you.

Bigger hint: buy copies of A. A. Blaker's book Field Photography, which guide number arithmetic very well, and Lester Lefkowitz' book The Manual of Closeup Photography, which will take you the rest of the way. If you know the flash's GN, calculating the aperture to set given flash-to-subject distance and magnification or flash-to-subject distance given GN and desired effective aperture is easy.

Nice that you want to use gear you already have, but it probably isn't the best solution to the problem. Two reasons: ring lights give flat lighting, controlling output (hint: ND gels) is harder with a ring light than with a couple of tiny flashes.

You don't need TTL autoflash. You need to understand what you're doing. If the mental arithmetic is too much for you, shoot calibration shots and keep the notes.

As Dan alludes to, the GN should help out a lot. Or a flash meter. I'll note that with the very small apertures required for DoF in LF Macro shooting, and the bellows loss, you are likely going to require quite a few pops from that wee ring flash to get enough light.