Canon 7D Metering/Flash Question

07/25/2010 05:02:38 PM · #1

I'm not really sure where to start with this question, so I'll post a couple photos to start:

Shot with Canon EOS 30D - ISO 400, 1/50", f/8, 550EX Flash w/ FEC @ 1 2/3 +

Shot with Canon EOS 7D - ISO 400, 1/50", f/8, 550EX Flash w/ FEC @ 1 2/3 +

I use these photos in a blog and I shoot them all at the same settings in the same environment so they will all look relatively close in exposure. When I upgraded to the 7D recently, this is what happened. The following photo is shot with the 7D again and at all the same settings but I reduced the FEC to zero.

Is there something different in the flash metering on the 7D that understands on its own when the background or prominent area of the image is brighter than 18% gray?

Message edited by author 2010-07-25 17:05:49.

Canon EF 24-105mm f/4.0L IS

07/25/2010 10:02:48 PM · #2

Anyone? Bueller?

scalvert

Canon EOS-5D Mark III

07/25/2010 10:25:28 PM · #3

Are you using the flash wirelessly on the 7D?

Canon EF 24-105mm f/4.0L IS

07/25/2010 10:34:47 PM · #4

No.. it's on camera... turned up and bounced off the ceiling...

scalvert

Canon EOS-5D Mark III

07/25/2010 11:18:49 PM · #5

Well it's hard to say for sure, but the metering system in the 7D is very different from that of the 30D. It has 63 zones (vs. 35 on the 30D) and meters in color where the 30D only recognizes luminosity. If both cameras are set to evaluative metering and you haven't cropped off a ton of image area, it looks like the 7D is more accurate with that much FEC. My guess is that fewer zones on the 30D lead to that camera's E-TTL system reading a specular highlight off the glass as a larger area, and underexposing as a result. If that hunch is correct, then trying both cameras with a non-reflective subject should provide a better match.