7D Unwanted Exposure Shift in Full Manual Mode - Can anyone help?

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davidmoss1595

New member
Hi everyone,

Have searched around to find the answer to an issue I am having with my new 7D. Even in full manual mode, exposure can shift when moving from areas of differing light levels. Youtube link here of a sample video:

http://www.youtube.com/watch?v=NFG3kax5_c4

As you can see, when I zoom out on the kit 18-135 lens the exposure changes. The aperture is set at 5.6, as I know that this lens is not fixed aperture, however the display tells me the aperture has not changed over the zoom range from wide to tele.

This appears to be an exposure/ISO shift of some kind, but everything is on Manual, and Auto Lighting Optimiser is off. What is happening?

I am using the 7D for micro budget shorts and features, but this issue prevents me from moving my camera in high contrast scenes. Another guy had the same issue with a daytime dolly shot to a far subtler extent:

http://www.dvinfo.net/forum/canon-eos-7d-hd/482007-exposure-shift-even-full-manual.html

Firmware is up to date, nothing changes on the display as I zoom out and it happens even when I am not zooming, merely moving the camera from areas of differing light levels.

HELP!
 
saneproductions said:
If your aperture is set to 5.6, shutter is 1/60 and you are in manual mode, I bet your iso is set to auto.
Click to expand...

I would bet this is what's happening.

The same thing happened to me when I started shooting with my 7D. I didn't realize I had taken the ISO down another tick from 100 to A (or from 200 to A - I might have already been shooting with Highlight Tone Priority on).
 
Wow! Thanks for the instant response!

ISO is manual and remains at 320, or whichever level I set it at. Highlight Tone Priority is disabled.

I think that the aperture of the lens is not changing, as you can see in the video the change occurs once the lens has finished zooming out and is still, it must be an issue that is separate from the glass, surely?
 
Make sure you are stopped down to the highest aperture of the lens. If it is 4-5.6 typically it will be 4 at the wide end and 5.6 at the long end. Set the aperture manually to 5.6 (or whatever) when the lens is in it's widest position. What could be happening is you set the lens to f4 on the wide end and are zooming in. This forces the lens to stop down to 5.6. You could also try stopping down to f8 and see if you still get the exposure variation.
 
Thanks Mike, I tried those suggestions, and I get the same results when beginning at the telephoto end on 5.6, then zooming out the aperture remains at 5.6. I tried it at f18 and the same results.

In the video you may notice that the image changes after I have stopped zooming, which would suggest to me that it is a sensor/in-camera behaviour rather than a mechanical attribute of the lens and the way its aperture reacts. I assume that if the aperture was changing the shift would happen during the zoom incrementally, and therefore not be very noticable.

I have tried zooming out very fast and once I am back at the wide end of the lens, at the same aperture value, the image slowly darkens after half a second. This would suggest that the camera is changing either the ISO or the exposure slightly, or something else? that is the camera itself adjusting rather than the lens.

I have tried it without zooming at all, and sometimes the same results are achieved when moving from a dark place to a light one...

Any thoughts?
 
I noticed this also, despite constant full manual setting and being stopped down. I assumed it was just the cheaper construction of the lens. Would be interesting if someone could actually explain why it does that, or even better how to fix it.
 
That's not the lens, the exposure stops down differently when it is, more of a 'click'. A better lit example would help but that looks like some sort of camera setting issue to me.
 
Just a guess: what Live View mode are you on?

If it's Exposure Simulation, change it to Movie Display (or something).
 
It really is the lens, When I try the USM lenses attached, this does not happen.
 
I use the 7D with a 50mm canon lens and it does the same things in full manual mode, with no camera movements going on or focus changes. I can attest to this happening. If does not happen with my manual Nikon lenses.
 
I believe there was a firmware update that addressed this a number of months back for the 7D, so you may want to make sure you have the newest firmware and see if that helps.
 
This is because you are using a non constant aperture lens. That's why they make the constant aperture lenses. The kit lens you have is a not a constant aperture lens.

Go to the store and try putting on a 17-55 2.8 IS Canon constant aperture and test it out.
 
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