Underexpose using 580EX

[Adriyan]

HI GUys

I'm new to this forum :D and I'm also pretty new with this current setup: 300D + 580EX. The problem is when i'm doing an indoor shoot using Ettl, i'm not getting a consistent exposure with my flash. Some times the pic comes out perfect other times it's just pretty underexpose.

FYI, i'm using autofocus and it's aim at the person's face most of the time.

Is there something wrong with what i'm doing or something's not right.

Pls help me here.

Thanks a million

[Rokkorfan]

Can you please post some shots where you have had underexposure and I may be able to assist you with your issue.

Cheers, Antony

[Adriyan]

Hi Anthony

Below are the photos that i'm referring to .. hope the pic actual appears

[HKFEVER]

It happens when the flash is not fully charged.

[tim]

Welcome to POTN :)

HKFever, flash charge has nothing to do with it in this case.

Your first image isn't underexposed, it's properly exposed. If it were any brighter the light parts of the picture would be blown out. If you don't care about that and want the image brighter you need to use FEC (flash exposure compensation) - read you manual for that, and look in the sticky thread in the lighting forum to find the link to the EOS flash bible.

The second image is underexposed from your point of view, but the camera's done exactly what i'd expect it to do. The reason is you have a large light source in the frame, and Canon cameras always expose the frame so the brightest part of the image isn't overexposed. The solutions in this case would be:
1) Zoom in on the girl if you're using a zoom lens, hit the exposure lock button (the flash will go), then frame the picture as you like and take it.
2) If you're using a prime lens (ie no zoom) point the camera down so the light's not in the frame, FEL again, the recompose and take the picture.
3) Increase your FEC (flash exposure compensation) to +1 or +1.5.
4) Change your position so the light's not in the frame.

ETTL2 is meant to discount small, bright light sources, though in practice it doesn't always do it properly. Mirrors and reflective surfaces often cause problems, there are solutions but I won't go into them right now. The light source is large in that 2nd picture, so even if ETTL2 works properly it would still do what it's done.

Read this thread (http://photography-on-the.net/forum/showthread.php?t=80413) for some more details.

Flash photography is a black art, and the only way to learn is to take photos, make mistakes, work out why they happened, and remember it for next time. Good luck!

[Adriyan]

Hi Tim

Yup the 1st pic exposure is good actually. Was tryin to show the difference in the exposure between the good (left pic) and bad (right pic).

Thanks for the advice. Will definitely look out for that in future. Meanwhile i'll keep on shooting. Hopefully this is the cause of the underexpose cause i hardly use the external flash so not really good with it.

[tim]

It takes practice... possibly months of practice... it's not easy, but you can get the hang of it if you u understand the principles.

Have a read of this (http://photonotes.org/articles/eos-flash/) and this (http://photography-on-the.net/forum/showthread.php?t=46599) to start with.