Exposure off 2 stops using flash meter

mountainhouse

I've had a Minolta IVf meter quite a while. Today I tried to use it as a flash meter the first time (580ex about 4' out using 1/32 power). It is overexposing shots by about 2 stops (both with and without the cord attached). I just used the same meter to do an outside incident measurement, and it looks dead on. So I don't think it's a battery issue. The manual's pretty basic. Since I've not done this before, it's likely I'm missing something obvious. :scratch I set the ISO, speed and put it in the right mode. Then hold it directly in front of (and close to) the subject, as if I were taking an incident reading. Any ideas?

heatherfeather

One time that happened to me, and it was a simple problem of the flash not being seated properly on the contacts... It took me a frustrating 1/2 hour to figure it out... You might check that.

Scott_Quier

This is going to sound quite the stupid question, but I gotta ask. Are you sure the meter is reading the flash? Put another way, have you compared a reading of the ambient light with that of the flash? Are they different? If they are close, there's a chance your metering technique has issues.

To better help you, could you post a short step-by-step outline of the process you go through to meter your flash? Oh, and did you notice that I didn't ask you for an example photo (that's supposed to be funny)?

pathfinder

mountainhouse wrote:

I've had a Minolta IVf meter quite a while. Today I tried to use it as a flash meter the first time (580ex about 4' out using 1/32 power). It is overexposing shots by about 2 stops (both with and without the cord attached). I just used the same meter to do an outside incident measurement, and it looks dead on. So I don't think it's a battery issue. The manual's pretty basic. Since I've not done this before, it's likely I'm missing something obvious. I set the ISO, speed and put it in the right mode. Then hold it directly in front of (and close to) the subject, as if I were taking an incident reading. Any ideas?

What, precisely, were the settings for ISO 100 at 4 feet with a 580ex at 1/32nd power?

I can duplicate that lighting with my 580ex, and read what my Sekonic L-358 flashmeter measures and compare it to what you used for your picture if that will help.

This is a table of flash exposure settings for the 430ex at ISO 100 at various power settings. The 430ex is about 1 stop less bright than the 580ex, so from this table at 4 feet, witha 430 ex your aperture should be f2.2 - with a 580ex, that would be about f3 or so. Is that near what you used?

mountainhouse

Sorry for the slow reply.

I'm still puzzled. Guessing maybe the meter is not working on flash:

I set up another test. Flash on camera (avoid any cord issues), 5' from the subject at 1/16 power. At ISO 100, I'm getting good exposure at f/8.0 (used 1/200 sec). Flash meter is showing f/5.0. Following the instructions, I had the meter in non-cord mode. That seems like more difference than expected compared to the 430EX numbers.

Step by step: I set up the camera/flash measuring 5' from subject, using a tripod. I used our living room which has a high ceiling to minimize reflection. Ambient light is about 6 stops lower. Camera is set on manual, as is the flash. As far as metering:
1) Power up flash
2) Hold down ISO button and set to correct ISO using up/down buttons on the side of the meter.
3) Hit mode key until display shows "NON.C".
4) Use same up/down buttons to set shutter speed - used 1/180 sec.
5) Hit meter button and "NON.C" display indicator starts to blink. Gives about 10 second window for measurement.
6) Position immediately in front of subject and fire shutter.

I can photograph the setup if there's a chance I'm doing something wrong. Thank you all for input so far!

pathfinder

OK - I dragged out my 580ex, a pair of PWs, and my Sekonic L-358 incident flash meter that I have used previously to measure flash output strength.

I mounted the 580ex on a tripod stand about 5 feet high, set it to manual mode, zoom 50mm, and connected it to a PW, and pointed it directly at my Sekonic's light measuring dome.

I stepped back a measured amount - 3 feet, 4 feet, 5 feet, by a tape measure etc - and fired the flash pointing directly at my Sekonic 358 (with its built in PW transmitter) and got the results in the following table. These data should be very accurate. The ambient light in the room was nearly non-existent - just light enough to read the controls by. I did this with the flash at 1/32 power output and 1/4 power output as well. Do these results match what your meter was reading? If not, I think your meter is in error



At 1/32nd power, it looks like the 430ex is about 2 stops less intense than the 580 ex, but at 1/4 power there is exactly one stop difference - who knew?