View Full Version : Canon DSLR Flash Tips

11-23-2004, 02:22 PM
OK, this may be obvious to many of you out there (and if so you have my permission to send back a Duh), but I just discovered a tip this weekend that saved me $1600.

I have started shooting weddings as part of my weekend photo business, and have been extremely frustrated with the flash performance of the DReb. It tends to vastly underexpose shots, especially when there is a lot of white in the scene - and there's a lot of white at weddings! So I decided to take advantage of my local Best Buy's 2 year no interest financing this week, and upgrade to a 20D, with it's newer fancier ETTL-II flash metering. Before taking the plunge, however, I decided to check some of the pro boards to see if the flash metering is improved on the 20D, the most common answer being "no".

But buried in one post was this tip:

Canon's ETTL metering system is weighted by the focus point that is active, and operates independently of the exposure metering. In other words if you, like me, compose with the center focus point only (half pressing the shutter button to lock in camera exposure, then recomposing your image), the flash meter takes a reading off of the center focus point at the moment you take the shot.

Here's an example: The bride is walking down the aisle with her father. You set up the shot, focusing on her face with the center focus point, half depressing the shutter button to lock focus and exposure, then recompose so that the center focus point is bullseyed on her white bodice, the camera meters camera exposure and focus for her face, but meters the flash off of her white dress, since that is where the center focus point is resting when you trip the shutter. The result - a very unerexposed image and a lot of time in photoshop trying to rescue the once-in-a-lifetime moment (which I have been thankfully able to pull off). In frustration, I switched everyting to manual to combat this...

The solution: Compose and shoot with a focus point that will rest on the skin throughout the entire shot.

Simple and effective. I immediatly wrapped my wife in a white sheet and tested the theory, and sure enough it worked. Whenever I composed on the face with the center point, then recomposed so that the center point was on the "dress" - underexposure. Whenever I composed with a focus point that rested on her face the entire time - perfect exposure.

Hope this helps a few of you out there who are feeling a little frustrated with your Canon flash exposure...


So how did that save me $1600. Well now I don't need a 20D...just yet!

11-24-2004, 06:33 AM
I don't generally shoot weddings, at least not lately since I got the Rebel. I did a few years ago with my film cameras. I shot a Karate Demo last Friday--guess what, just about everyone wears white uniforms and a number of the close shots were a bit hot--I'll try the trick you describe. I think it's a canon thing, my G2 did the same thing until I set flash exposure down a half stop which fixed the problem on that camera. Unfortunately the Rebel doesn't let you set flash exposure separately so that one won't fix my problem here. At first I thought the issue might be my 380EX speedlight but the same thing happens with my new 550EX. Do any of the digital EOS bodies give you separate exposure control for the flash like my G2 does?

I'm also having a problem with dark backgrounds in flash pictures, the subject seems to be exposed ok but in anything but full auto mode the backgrounds are always way too dark and need to be photoshopped to fix em up. With lots of action you really need to shoot in Tv mode with high speed sync or sport mode (while stuck with iso400 only) if you want good pictures of this kind of thing. I'd like to try to figure out what the dark background problem is since it doesn't happen near as much in full auto (maybe because the camera is kicking the iso up?????). I'm thinking I might to add a couple of slave flashes to really fix it right