Crop vs FF question - why am I seeing such a difference

I hope this is the right section of the site to ask such a question.

Ok - so after 2 crop bodies I took the plunge and got a Full frame to see what I was missing.

Tonight for some test shots (to sell myself on the new 5D mkII) I compared it with my 7D at its current setting.

These comparisons are done with the same flash (430EX) and as close to same zoom as possible (wide). Both at f4.0 iso 100 and shutter speed of 1/60 I am finding the 7D image to be brighter. Neither image has been retouched other than converted from RAW and watermarked.

I shot many pics with both cameras and at no time could you confuse the output from one camera with the other. These two shots were the closest to being the same shot (no tripod so nothing precise as a comparison).

Could this have been part of the reason?
Exposure Mode Auto exposure
White Balance Auto white balance

The crackers are more in focus on the bottom picture. was it metering the color of the high chair?

No idea really, just taking a simple guess from what I know which isn't a whole lot.

Since the shot speed, ISO and aperature are the same for each shot, it could be that spot metering resulted in different measurements and flash levels. Maybe using a larger area for metering will provide a similar result between the two camera bodies.

is it possible that the ever so slight difference in the distance between you and the subject could affect how much flash hit the subject. judging the style of the room im assume the ceiling is flat and normal height (approximately 9ft) and is smooth rather than having blotched paint which can bounce the light different in places.

also im still new as far as glass and optics go but the 2 different lenses will render subjects slightly different and have different contrast but i dont think that would explain that actual exposure itself being darker for one lens rather than the other

These are different:

Focal Length 17.0 mm
Focal Length 10.0 mm

Subject Distance 0.61 metres
Subject Distance 0.49 metres

Using it in auto might also make a difference, try using in manual.

I hope "auto" white balance doesn't matter too much I use use mine in that setting, its just too hard to change from shade to sun to shade to cloudy to sunny to cloudy with every click.

Also i think this is a horrible comparison.

You should use a tripod and focus something that DOESN"T move and won't throw off the metering.

I think the comparisons here are fair. You should sell your 5D MKII to me for a fair price considering how bad it is.

I'm hoping the 7D wins so I wont be tempted to spend more money on camera bodies.

But, I think snapshots with a flash and different lenses may not give you an apple vs. apple comparison. How about a shot with constant lighting, using the same L lens at different focal lengths, on a tripod, and with a subject that has a lot of variation to compare (smooth tonal ranges, ultra fine details, wide range of light intensites, etc.).

davtackett wrote in post #13380624
These are different:

Focal Length 17.0 mm
Focal Length 10.0 mm

Subject Distance 0.61 metres
Subject Distance 0.49 metres

Focal length of 17mm on Full Frame vs 10mm on a 1.6 crop (so in essence 16mm). Was thinking it would be as close to 1:1 as I could get.

Indeed it is a moving subject but in no shot is the 5D brighter - if anything it was very dark. Both cameras were set to centerpoint focus and aimed at the little guys head.

True I should probably use a tripod and fixed subject - just that seeing so many variations between the two cameras used in the same real world lighting by the same photographer with the same settings at the same time made me ponder the question as to what I was missing.

I am able to rework all the images to make them usable (as snapshots at least) but the reason for the difference was what got me.

thanks for the comments

Was the flash set to ettl?

it was. I initially used my 580 MkII and found those pictures to be even worse. Switched to the 430 which has been more consistent for me over the years.

Out of curiosity, what differences were you hoping for with the 5D?

ImageMogul wrote in post #13381998
Out of curiosity, what differences were you hoping for with the 5D?

I was expecting to see the two being a little more similar. I just shot a hand full more pics of a static display with tripod and hands down the 7D is coming through brighter and richer.

As far as differences between the 5D and 7D. I was (am) expecting to see some improvement in image quality etc. Not that I have had complaints about the 7D. 7D continues to impress me. So far everything about the 5D MkII feels old and less thought out than the 7D. Be it the card door (7D is sprung), enabling video (not that I use it often), and layout. I have to say I double checked the front of the body to be sure I was seeing what I was seeing from the 5D.

I have heard (and maybe brought into) all the hype about how superior a FF body is and how lenses come to life with it. How it rocks as a portrait body etc. I have only used 2 lenses at this stage and nothing outdoors (weather) but if the trend of disappointment continues then the 5D will be looking for a new home. The deal I negotiated with the wife would mean the sale of a lot of other hobby items - at this rate I could do more with the $$ (but I continue to try and be impressed by it ).

I say next time, do a more simple comparison. don't involve flash at first. get a baseline with basic exposure settings and then can you only involve external flash.

White Balance. Put it in manual (and sample identically) for at least one side by side. The color tone seems very different between the pics posted. Are there filter differences between the lenses? The zooms you own have the range to allow comparisons with the same lens, probably the 70-200 is the best, stay away from either range extreme if possible. Shooting in manual would also help get more consistent comparison.
If you just want the 5dII to be brighter, try adjusting the exposure compensation. The histograms might be helpful to look at as well. It's probably also be worth taking comparison shots without flash and in a variety of settings.