questions about flash brands and focusing

ladylaura

Hello all,

I have two questions:

I was taking pics in a dark bar last weekend with my Rebel XT and I noticed two things:

First, I was borrowing my dad's Canon Speedlite 420EX flash, and it was working fine, then all of a sudden the pictures were REALLY blown out! I was shooting manual and hadn't changed any settings, but all of a sudden it was really overexposed! Was this the flash acting up? I heard somewhere that other people have found Canon flashes to be inconsistent this way. Working fine then randomply giving too much power or underexposing. Has anyone else found this to be a problem? When I finally buy my own should I invest in a Nikon instead?

Secondly, the red laser-beam like sensors for focusing in the dark never engaged. Consequently, my pictures weren't very in focus. I can see the flash has this feature, but it never works. Is this because it's an old flash unit? It just doesn't work with my camera? It would greatly help these lighting situations, so I would like to research this too before buying my own.

Ok, sorry for being so long winded. Thanks for any info you can supply!
~Laura

Shay Stephens

My guess would be a malfunctioning flash. They don't last a long time.

pathfinder

If you would post the pics and the exif data from the shots that were properly exposed, and those that were overexposed, we might be better able to explain the situation.

I am aware of complaints about the EOS flash system, but my experience is that they work extremely well if they are understood and used properly. I shoot with a 580ex and a 430ex both on and off the camera without difficulty.

Was the flash in ETTL? Are you sure you did not change the FEC or the EC?

You say you did not make any changes to cause the exposure changes - the exif data will tell us if this is actually the fact. Then we can try to sort out what happened.

You never saw your AF light trigger and your shots were out of focus?? The flash depends on focus distance for exposure.

Did you accidentally switch off the AF switch on your lens barrel? That would casue the camera to fail to focus, and contribute to incorrect exposures as well. I have done this a few times, as the switch in on the lens barrel and is rather small and not noticed. Especially in a dim bar. What you see in the viewfinder is that the AF stops - check your lens barrel AF switch too.

Jekyll & Hyde

ladylaura wrote:

...Working fine then randomply giving too much power or underexposing. Has anyone else found this to be a problem?

J: Check that the flash foot is very secure on the shoe.

ladylaura wrote:

Secondly, the red laser-beam like sensors for focusing in the dark never engaged.

H: Do you have the "Custom Function" for AF-Assist enabled in your camera setup? Mode=2

Good luck,
J&H