5D Mark III Question ISO 1000 vs 3200 f/4 vs f/6.3

Guys, I'm going to post pics, but wanted to type this question out.

I'm shooting my 5d mark iii with the 24-105 attached, indoors at night, low lighting conditions. I wanted to take a pic of my daughter while she was using her computer, etc. I took the shot at ISO 1000, f/4 in Av mode, Servo. I then decided to take another at f/6.3 to see if I could notice a difference. I did the same thing with the ISO bumped to 3200 with both respective apertures. When I went to the rear LCD screen to review the shot, the f/6.3 shot was brighter than the f.4 at both ISO 1000 & 3200. I thought the screen on the computer may have effected the light, etc. SO, I took a shot of my parrot, same thing, the f/6.3 looks brighter than the f/4 at. Did the same thing with less light with a shot of the paper towel holder and the same thing occurred, the 6.3 @ 1/13 was brighter looking than 4.0 @ 1/30 at ISO 1000, 6.3 @ 1/40 & 4.0 @ 1/100 at ISO 3200 same results.

I then covered the top LCD and no change in the results.

ISO3200: f/4 & f/6.3 ... Please don't comment on what crappy pics!!

ISO 1000, etc.

Most cameras meter wide-open and then stop-down right before taking a photo. The 5D is no different. Likely what is happening here is a lens aperture accuracy issue. The camera has to assume that when it tells the lens to shrink the aperture to f/6.3 that the lens will do it accurately. This appears to be tightening the aperture too far on the shorter exposures. Test another lens to rule out lens flaws.

Thanks. Going to right now.

Just did the same shot of the paper towel holder with the 24-70, same test at 1000 and 3200, etc. Barely noticeable vs the 24-105 shots.. If anything the only thing I immediately noticed was the silver in the tea pot changed slightly, but not the white parts e.g. cabinet, blinds, etc.

Looking at my posted pics, the difference isn't as great as on the LCD and mac..But it's def there.

coldcuts113 wrote in post #14301407
Just did the same shot of the paper towel holder with the 24-70, same test at 1000 and 3200, etc. Barely noticeable vs the 24-105 shots.. If anything the only thing I immediately noticed was the silver in the tea pot changed slightly, but not the white parts e.g. cabinet, blinds, etc.

Looking at my posted pics, the difference isn't as great as on the LCD and mac..But it's def there.

Wait, are you saying the 24-70L shots behave the same way or not?

Not. There is no difference on the white portions. Only the silver pot. I'll post in a min.

coldcuts113 wrote in post #14301418
Not. There is no difference on the white portions. Only the silver pot. I'll post in a min.

Oh ok. I'll wait.

ISO 3200 f/4, f/6.3 w/24-70

All shots posted here in jpeg, straight out of the camera, no editing at all.

ISO 1000: f/4, 6.3 w/24-70..

I'm surprised this thread isn't getting "lit up" as it has to do with the 5d mark iii, lol... At least you checked in AngryCorgi!!

coldcuts113 wrote in post #14301458
I'm surprised this thread isn't getting "lit up" as it has to do with the 5d mark iii, lol... At least you checked in AngryCorgi!!

Yeah. Well it looks to me a slight bug with your 24-105L aperture servo. Might want to get it looked at if it is under exposing too much for your liking.

Not sure if this is the issue, but ISO 1000 is not a native ISO to the 5D wheras 3200 likely is. That means some push/pull is done with ISO 1000, although I'm not sure which direction.