7D unwanted exposure adjustment

T

thodani

New member
I have a Canon 7D and I noticed that with two of my lenses (the basic Canon zooms EFS18-55 and EFS55-250) the exposure adjusts during zooming, even though I'm in full manual mode. I went through every possible menu setting and everything that could potentially be an issue is disabled. I set each lens at its appropriate f-stop that it can maintain through the entire zoom range, so it's not stopping down at the long end of the zoom. But when I zoom in or out it seems to automatically adjust the shot. It is definitely not in auto iris, and if I just pan from bright to dark or reverse the exposure is maintained. This doesn't happen with the Tokina 11-16 lens, e.g., so I'm guessing that somehow Canon lenses communicate with the camera and override the manual setting?
Has anybody else seen this happen ?

Thanks,

Thomas
 
Thanks, Richard

The strange thing is that there is no auto adjustment going from bright to dark, only for different focal lengths. In fact, the lens doesn't fully correct, it only adjusts to a small degree. That means, I can purposely over- or underexpose, and when I change focal lengths it make a small adjustment (not a full correction!), and then holds that exposure steady until I change the focal length again.

Thomas
 
Just to add one more thing, I can hear a clicking sound from the lens when it adjusts, and it does the same thing in "Live view" still mode, but not in the regular still mode. Could it have something to do with being in "Live view" mode? I checked playback and it's definitely being recorded that way, so it's not just an LCD adjustment.

Thomas
 
thodani said:
I set each lens at its appropriate f-stop that it can maintain through the entire zoom range, so it's not stopping down at the long end of the zoom. But when I zoom in or out it seems to automatically adjust the shot.
Click to expand...

So just to be clear, you're saying that even if the lens is set at f5.6 or f8 and you zoom in (or out) the exposure is adjusting?
That is strange.

If you have a short clip showing that it might help to upload it so we can see what you're seeing.
 
Luis,

That's right, even at 5.6 or 8, so it's not stopping down due to lens limitations at the long end of the zoom. Also, there is no change in the readout of the settings (f-stop, shutter, ISO) while this happens. The fact that it's happening with both of the two cheap Canon zooms, but not the Tokina, makes me think that it's 1. not the camera, and 2. not a broken lens (chances of it happening to two lenses would be pretty slim) but rather a fault by design. Since so many people probably got the stock zoom lens with their camera I'm hoping that other people could check this out and see if it happens, too.

Thanks,

Thomas
 
That is interesting - and your guesses sound like you might be right.
There are similar issues with the GH1 when using the stock lens as well (not exposure specifically, but color rendition), so it's not out of the realm of possibility.

If you get the chance try shoot a short clip showing this off with both lenses.
With all the users here we should be able to figure out pretty quickly if this can be replicated or not.
 
I am in exposure simulation, which as far as I understand you want to be in when shooting video. It only affects the LCD and is supposed to have the LCD image reflect your wanted exposure level (i.e. WYSIWYG) instead of trying to give you the brightest image for easier focus and framing. When you switch exposure simulation off, the LCD constantly adjusts to maintain a balanced image. Just for fun, I turned it off, and the exposure corrections when zooming are still being recorded.
I checked with Canon's tech support but other than sending in the lenses they didn't have an answer. I still think that it's very unlikely that two new lenses would be broken and still wonder about some other solution.

Thomas
 
Well then it's easy to say with 100% accuracy that we found your problem. You are NEVER supposed to be in Exposure Simulation mode when recording video! That mode will run video in full auto REGARDLESS of whether the mode dial is set to manual. Exp Sim = auto exposure.

You need to read the new user manual pages that were released with the first firmware upgrade that came out with the full manual controls. You can then reqd it in Canon's own words. That explains everything, I knew it was going to be something simple like that...
 
Here is the quote from the manual:

"Exposure simulation displays and simulates how the brightness of the actual image will look. The Enable and Disable settings are explained below:
Enable
The image brightness displayed will be close to the actual brightness of the resulting image. If you set exposure compensation, the image brightness will change accordingly.
Disable
The image is displayed at the standard brightness to make the Live View image easy to see."
( I underlined those parts)

Exposure simulation, whether on or off, does not affect the recorded image.
It only affects the LCD image. (You might be thinking of exposure compensation).

Again, I tried it both ways anyway, and it doesn't make a difference in the recorded image.
And, it doesn't happen with other lenses.

Thomas
 
same problems

same problems

Hi!

I have the same problems - exposure changes when changing the focal length. i guess this happens due to the lens i used (it doesn't have constant aperture)...

At the time i have no zoom lens with fixed aperture over the whole focal range, so i can't try it out at the moment, but i will do next week.

edit:

i just also recognized this issue, with an ef-s 60mm 2.8 as well when changing focus fastly.
anyone? ;-)
 
Just purchased my 7D (refurbished) and having same problem with both lenses that I have access to: a Canon and a Tamron. I've checked "exposure simulation," as suggested, and seems in video mode that it won't even allow that option (everything in that menu option is gray) to be enabled/edited. It only seems to happen in live mode and Yes, I have enabled/disabled "exposure sim" in photo mode, no difference.

Could it be that each of us having the problem need a firmware update?

I'm totally new to this type of camera (previously owned an XL-2), so I very much appreciate any help. I'll see if I can post some video.

Update: Scratch that, looks like my camera has the newest firmware per the Canon USA site.
 
Last edited:
Figured It Out!

Figured It Out!

I have resolved the issue with the help of two friends and lots of tests.

The problem seems to stem from the lenses I was using. Both were older or inexpensive models.

One was from an older Canon Digital Rebel -- the standard cheap EF lens that came with it and the other was a Tamron AF 18-200mm f/3.5-6.3 macro. With both lenses, as I zoomed in or out (didn't matter the direction) the "brightness" changes occurred as the the lens turn hit a new marked focal (mm) length.

With the help of friends, I tried a newer more expensive Canon EF and a newer Tamron AF 17-50 f/2.8, both performed perfectly with no aperture noises or variance in brightness of the images when zooming.

I don't know technically why the first two lenses are causing the problem, but I know without a doubt that it is the lenses. The "bad" lenses performed the same on my friend's 7D when tested.

What proved it beyond a shadow of a doubt for me? I used another friend's Tamron AF 18-200mm f/3.5-6.3 macro and it "caused" the same "exposure/clicking" problem on the cameras.

Still, I have zero idea as to what the technical/engineering issue with the lenses are that cause this performance issue. I did return my last email with Canon Support giving them what I just posted. Hopefully, they'll put it to their engineers and post somewhere online what the deal is.

It definitely had me completely freaked that I had just bought a lemon. Hope this helps!
 
I wouldn't call it a bad lens... maybe it's because of the constant aperture vs the variable aperture thing like Richard mentioned on the 2nd post?

Flixkid said:
I have resolved the issue with the help of two friends and lots of tests.

The problem seems to stem from the lenses I was using. Both were older or inexpensive models.

One was from an older Canon Digital Rebel -- the standard cheap EF lens that came with it and the other was a Tamron AF 18-200mm f/3.5-6.3 macro. With both lenses, as I zoomed in or out (didn't matter the direction) the "brightness" changes occurred as the the lens turn hit a new marked focal (mm) length.

With the help of friends, I tried a newer more expensive Canon EF and a newer Tamron AF 17-50 f/2.8, both performed perfectly with no aperture noises or variance in brightness of the images when zooming.

I don't know technically why the first two lenses are causing the problem, but I know without a doubt that it is the lenses. The "bad" lenses performed the same on my friend's 7D when tested.

What proved it beyond a shadow of a doubt for me? I used another friend's Tamron AF 18-200mm f/3.5-6.3 macro and it "caused" the same "exposure/clicking" problem on the cameras.

Still, I have zero idea as to what the technical/engineering issue with the lenses are that cause this performance issue. I did return my last email with Canon Support giving them what I just posted. Hopefully, they'll put it to their engineers and post somewhere online what the deal is.

It definitely had me completely freaked that I had just bought a lemon. Hope this helps!
Click to expand...
 
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