Thursday, February 10, 2011

A flash meter is a flash meter

This picture has nothing to do with today's post, except that it was taken with a Metz 45 CT1. I think around 1982. I used the Metz Tele Attachment 45-33 while taking the picture with the 50mm lens. That is why the flash illuminates only a part of the picture like a spotlight. The Tele Attachment illuminates an 135mm lens angle for FX format. There will be a separate blog with some experiments for the Tele Attachment. I just used this picture today, because I do not want to post a blog without at least one picture, and a series of pictures regarding today's topics would have been less entertaining.

The user poppy left a comment at the blog Batteries or Rechargeable he or she had an issue with the flash metering. In short the flash was used in full manual half and quarter, but the flash meter showed the same reading. Unfortunately poppy did not write what type of flash meter was used. The assumption from poppy was that flash meters are generally built for studio flash and that they have inconsistencies when used with on camera flashes.

Hmmmm, I thought that should be tried in practice.

I own only one external meter the Gossen Mastersix. You have seen it in the Batteries or Rechargeable blog. Today I took a number of 45ers and the Gossen to see if it meters consistently.

First I tried the 45 CT4 with M 1/2 and 1/4. The meter worked fine. For each setting I fired a number of flashes and the meter showed the same result for each. As expected it also showed f32 for full power f22 for 1/2 and f16 for 1/4. So the meter works?

Well then I used a Metz 45 CT5 with Mecamat 45-30 That allows manual settings from full power to 1/64 as described here. I got fine results up to 1/16 power. Then the Gossen showed me that It could not measure properly by displaying its error code "uuuu" instead of an aperture. I guess that the flash needs a minimum duration to be measured. 1/16 has the duration of 1/8000s that still worked. 1/32 has the duration of 1/16000s and that no longer worked.

After all Gossen is a German make, so something like that should be in the manual?
I looked it up and it amazingly says Flash duration 1/1000s to 2s.

Hmmmmm, 1/1000s is not very generous and would indeed limit flash metering to studio units. It seems to work to 1/10000. Either there in a typo in the manual or the careful German engineers did not want to commit to the full specification and left one zero off to be on the safe side.

Poppy has been on to something.

If you want to buy a new or used flash meter, you should find out how short the flash can be to be measured. I know now that 1/16 for my 45ers and 1/8 for the SB800 and SB900 is the minimum manual power I need to be able to measure it with my flash meter.

That is good to know.

Thanks Poppy.

1 comment:

  1. Just checked with my Mastersix, Metz 45 CT1 with mecamat 45-20.
    It measures down to 1/64 (16000th of a second) just fine...