Canon 20D and SpeedLite 580 problem==> Help

Hello all Canon users,
I'm so glad that I've found this forum which I can always post my questions here. I love Canon cameras since I first learn photography. Here comes my problem I just bought the 20D and a SpeedLite 580EX I don't know why I always get at least 1stop under when I shoot it at P mode (camera) Flash set E-TTL. I tried it on with my Mezt 54-MZ3 SCA 3102 ( flash set at Auto) pix came right expose If I set the 580 flash 1stop over pix came out OK I wonder is it just me or any one else has same problem??? Thanks for reading!!!

Welcome to POTN mr lite

It's best if you post a sample picture or two, so we can give you specific advice. ETTL flash photography's not quite as simple as Canon makes it out to be. The best thing to do to start with is read The EOS flash bible, it's huge but you'll understand your flash much better.

In short, the camera assumes every scene is about 18% grey, and it sets the flash output so that it is. If you have a very dark scene the flash will overexpose it (blacks look grey), if you have a very light scene it will under expose it (whites look grey). The solution is to use FEC (flash exposure compensation). For dark scenes set it to between -2 and -1, for light scenes set it to between +1 and +2 - experiment and see how it goes. Your histogram is your best tool for this.

Hope that helps.

speed2lite wrote:
Hello all Canon users,
I'm so glad that I've found this forum which I can always post my questions here. I love Canon cameras since I first learn photography. Here comes my problem I just bought the 20D and a SpeedLite 580EX I don't know why I always get at least 1stop under when I shoot it at P mode (camera) Flash set E-TTL. I tried it on with my Mezt 54-MZ3 SCA 3102 ( flash set at Auto) pix came right expose If I set the 580 flash 1stop over pix came out OK I wonder is it just me or any one else has same problem??? Thanks for reading!!!

Using my 420EX I typically have to dial in +2/3 stop FEC. If you do a search on most of the forums, this is pretty common for Canon DSLR's. I contacted Canon about this and was told that the camera has been designed to underexpose a bit to prevent blowing out the highlights when using flash.

I use anywhere from +1/3 to +1 1/3 FEC. You need to get used to checking your histogram after taking a shot and adjusting as necessary.

tim wrote:
Welcome to POTN mr lite

It's best if you post a sample picture or two, so we can give you specific advice. ETTL flash photography's not quite as simple as Canon makes it out to be. The best thing to do to start with is read The EOS flash bible, it's huge but you'll understand your flash much better.

In short, the camera assumes every scene is about 18% grey, and it sets the flash output so that it is. If you have a very dark scene the flash will overexpose it (blacks look grey), if you have a very light scene it will under expose it (whites look grey). The solution is to use FEC (flash exposure compensation). For dark scenes set it to between -2 and -1, for light scenes set it to between +1 and +2 - experiment and see how it goes. Your histogram is your best tool for this.

Hope that helps.

This is the best reply about flash help in the forum that I have read so far...thank you.

I have allways known about the camera seeing 18% grey and when there is more black parts in the piture the camera overexposes and when there is more white it underexposes ( thats why snow looks grey), but I never thought that this goes also for flash photography...

Thanks...

No problem, hope it helps you make better photos

Oh and I am sorry...Welcome to POTN, speed2lite.

Regards,

tim wrote:
No problem, hope it helps you make better photos

I am sure it will...with knowledge comes creativity...hehe

...or was it with great power comes great responsibility...hmmm

Cheers,

Either way, something's great

In addition to what others have said, you may want to check Custom Function 14. I found switching from Evaluative to Average yielded better results.