550EX under/over-exposure

[karusel]

I don't use my flashes much, since I prefer natural light, but today I've been shooting indoor hip-hop training and the majority of shots are correctly exposed, some were overexposed by about 2 stops and some (7 in a row!!) underexposed by about 2 stops, I can see shadows so flash obviously did fire. My settings were M, flash on ETTL, ISO 400, f/4.5, 1/90s @ 28mm, the camera is 10D, the batteries were always fresh as I replaced them before their performance would go down. Oh, and I didn't recompose the shot after half depressing the shutter, which would AFAIK mess with auto exposure. I would not weep much if those shots were not crucial, but they are... now I process them with heavy EC, and you can imagine the noise... A crappy 4 megapixel point and shoot with a popup flash would deliver better photos than I will... I'm a bit down now... and pi$$ed off... for not chimping!!

So hey, anyone experienced similar problems, is this a serviceable problem with the flash or is it something like, a well-known problem? I've been searching the forums but I couldn't find this specific problem, although some professional photographer I talked with once mentioned that he got more consistent results with the Sigma's flash than with Canon's. When I was home putting my gear together I was thinking about just that and I almost took the Sigma, but I thought I'd need all the power I could get, and Canon's a bit more powerful, so Canon it was. Next time I'm taking the Sigma. :mad:

[tim]

Did the flash fully charge between those 7 shots? Were there reflective surfaces in the shot? Flash photography's quite difficult, it takes practice and experience to get good at it.

[karusel]

Oh man, I think I know what happened with those bunch of shots, (I'm putting a sample photo below - processed with default settings) 3 guys in white shirts...

[CyberDyneSystems]

Arrgh! White shirts! Was it partial metering too?

[Huckaback Photo]

Hello Karusel.
sorry to hear of your problems.
Firstly to try and sort your images that have lots of noise, if you dont already own a noisware program can i suggest a free bit of software which i've been real impressed with.

visit http://www.imagenomic.com/

then download noiseware comunity edition. yes there are other versions which you pay for but this works for free.
first with flash do some tests set up to take some shots say auto & ettl , but before you shoot fire a test flash with the ready button on back of flash unit.
used to get similar probs with my D60 and 550 ex flash on speaking to a camera mechanic (repairer) he said it was a common thing and could be overcome by preflash the unit prior to actual pictures being taken.
as Tim mentioned above if it had not recycled fully between shots ujnder exposure could happen,
hope this is of some use.

Martin (Huckaback Photo)

My Galleries. http://www.pbase.com/huckaback_photo

[Huckaback Photo]

Karusel
just saw your posted image ,
dont have a problem with this for adjustment into PS some levels plus a bit of USM
so check this out.
with compliments

Martin