kndreyn wrote:
I bought a 1D MkII and the 580EX flash unit a couple of weeks ago. I'm having a little problem with exposures using the flash. Everything is coming out underexposed unless I press the FE L button. Pressing that fixes the exposure. So while experimenting with it, I bumped the flash up 1 full stop and that gave me a good exposure, but if I press the FE L button with the flash increased, the pictures are overexposed. I took the camera back to the shop where I bought it, and they were puzzled too. They said the latest firmware was supposed to have corrected these problems. Has anyone else been seeing this with your 1D MkII? BTW - it does the same thing with my 550 EX flash.
I just tried the same thing on mine and my results for the most part were opposite to yours. In other words, when using FEL, my images were underexposing compared to the normal flash. But neither your camera nor mine have anything wrong with them. When shooting in normal flash mode, ie ETTL-II mode, the flash exposure is computed by measuring the pre-flash output over the entire frame and then applying ETTL-II logic. Unlike ETTL, AF point is not really taken into account in ETTL-II mode.
However, when using FEL, it seems as if the pre-flash reading is taken only from the area within the spot metering circle of the frame. So, depending on the refectivity of the area used as the target for FEL, you may get the exposre just right, under or over.
As for the general consensus that flash expsure with ETTL-II on the 1DmkII always leads to underexposure, that was my initial assessment, too. However, after taking several test shots, I've come to the conclusion that ETTL-II is working as advertised. What I did to get around what seems like extreme underexposure when viewing the LCD display is the increase my LCD brightness to 4 (from the default 3). The histogram also seems to show that the exposure is not as far right as it could be but again, when I analyzed the image in PS, I found there there were very tiny hot spots that would have come out blown had I increase the the flash compensation.
But, of course, this is just my personal view. I, for one, like to have my flash pictures coming out as natural as possible to the setting I was shooting in.