5D3 and 24 1.4 II L Edit, and other Lenses, owners please read!

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Louis

Louis

Nov 13, 2011
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#1
Please can you check your camera, in AV Mode and Evaluative Metering, do not move, and switch the lens to manual and back again to Auto AF and please look at your metering value does it change?

It doesn't seem to change with a different lens :o

But does with the 24mm

Thanks for your time,


Louis
 
#3
Re: 5D3 and 24 1.4 II L owners please read!!!!!!!!!!!!

Louis said:
Please can you check your camera, in AV Mode and Evaluative Metering, do not move, and switch the lens to manual and back again to Auto AF and please look at your metering value does it change?

It doesn't seem to change with a different lens :o

But does with the 24mm

Thanks for your time,


Louis
Click to expand...

I have a 5DIII and 24LII (that exact combo happened to be sitting on my desk when I saw your post...), and can confirm the issue you noted - switching between AF and MF on the lens changed my metering value by 1/3rd of a stop (AF mode was giving me an exposure of 0.3" and MF gave me 1/5) - an odd little quirk, but I don't really consider it to be much of an issue. I'm running the latest firmware if that makes any difference.
 
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#5
Re: 5D3 and 24 1.4 II L owners please read!!!!!!!!!!!!

Same here, just read your post and checked.

Just put it down on a desk and tested what you described:

Can confirm your observation, for me it jumps between 1/30th and 1/40th for the same value of f/1.4 and ISO 1000 for the current light in the room.
 
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#6
Re: 5D3 and 24 1.4 II L owners please read!!!!!!!!!!!!

Just to confirm - everything else is the same with the physical setup? Remember that it's not just what's in front of the camera that matters - light entering through the VF also affects metering so if you're in a different position behind the camera, that can make a difference. Try covering the VF during testing (a lens cap hung over the eyecup does the trick).

Since Live View metering is done using the image sensor rather than the metering sensor, might be good to see if the same phenomenon occurs in live view.
 
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#7
Re: 5D3 and 24 1.4 II L owners please read!!!!!!!!!!!!

I have that same combination but am currently at work. I will check it out when I go home.

Thank you for bringing this to our attention. I am interested in knowing about any such things about the equipment I've purchased.
 
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#8
Re: 5D3 and 24 1.4 II L owners please read!!!!!!!!!!!!

I can report the same thing on a 5D2 and 24 1.4L II... strange and with caveats:
Consistently shifted (on tripod), from 1/60 1.4 to 1/50 1.4 or equivalent. As a silly test, I then changed my focus point selection and then did not see the shift, though when I changed it back to my center focus point the "issue" no longer appeared in this sitting, though I will keep an eye on it. Does not happen with other lenses.

Aren't the newer lenses smarter in terms of where you are focused and communicating that with the camera or am I making this up?

Edit:
I take it back. I was able to repeat the result with the focus point selection, and each time changing the focus point to all made the "issue" go away -- on a 5D Mark II.
 
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#9
Re: 5D3 and 24 1.4 II L owners please read!!!!!!!!!!!!

neuroanatomist said:
Just to confirm - everything else is the same with the physical setup? Remember that it's not just what's in front of the camera that matters - light entering through the VF also affects metering so if you're in a different position behind the camera, that can make a difference. Try covering the VF during testing (a lens cap hung over the eyecup does the trick).

Since Live View metering is done using the image sensor rather than the metering sensor, might be good to see if the same phenomenon occurs in live view.
Click to expand...

The change was directly related to physically moving the AF/MF switch on the lens - shutter speed on the secondary LCD updated instantly as I switched the AF/MF switch (I flipped the switch multiple times a second and shutter speed changed directly in time with each flip of the switch). Viewfinder covered, ISO100, f/2.8 - additionally, this issue does not replicate in LV mode or any other metering mode besides evaluative metering.
 
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#12
Re: 5D3 and 24 1.4 II L owners please read!!!!!!!!!!!!

neuroanatomist said:
Just to confirm - everything else is the same with the physical setup? Remember that it's not just what's in front of the camera that matters - light entering through the VF also affects metering so if you're in a different position behind the camera, that can make a difference. Try covering the VF during testing (a lens cap hung over the eyecup does the trick).
Click to expand...

I was really careful with this, holding it absolutely one place, keeping my head/eye/hands/everything exactly same position, and AF on I got 1/50-1/60, and 1/40 with MF. Everytime, and switching back and forth it was always 1/50 or 1/60 for AF, and 1/40 for MF. I didn't cover VF though.

And live-view it used 1/60 every time regardless of AF/MF.
 
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#13
Re: 5D3 and 24 1.4 II L owners please read!!!!!!!!!!!!

More testing, this is getting strange.

I took a lens-cap to cover VF, and it didn't change between AF/MF. Then I removed the lens cap, and still no change. And I'm sure it happened before.

So I turned my camera slightly to take different picture (with different exposure), and the problem came back. I put the lens cap back on VF, and still the problem stayed.

I changed different apertures (1.4....4.5), and the problem stayed. I turned the camera around for different directions, the problem stayed.

I took pictures with AF and MF (1/125 and 1/100), and the histograms for each were as expected, so MF 1/100 had more on the right.

The shutter speed indicator will jump the instant you flick the switch, you don't need to half-press the shutter. So take exposure with AF for 1/125, switch to MF and it changes immediately to 1/100, back to AF and it's 1/125, MF and it's 1/100.

And now no matter what I did, I cannot get it back to "no problem", which I got briefly few minutes ago.

Really strange.

Also no (bright) light shining at the top screen, and my model is anyway newer with the fix.
 
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#15
Re: 5D3 and 24 1.4 II L owners please read!!!!!!!!!!!!

Ok, I did plenty more testing, and now I have theory!

It seems I can find "spots" where it doesn't happen, and then other spots it does (see my post below telling it changed when I moved the camera).

I was able to find spot where the difference was full 1/1 stop. And I was able to find spot where it's exactly same. The "same" happened when the lighting of the area was quite uniform, and the 1/1 stop happened when there were big light differences (shade and sunny spot) in the frame.

Also, I was able to find spots where AF SS was slower, and where MF SS was slower.

So my theory: some reason it uses different spot/area for the evaluation when AF/MF is selected. Let's call them AFS and MFS to help explain. So if AFS hits bright area while MFS hits shaded, it will give MF longer shutter speed. If AFS is on the shade, it'll give longer shutter for AF.

If AFS and MFS areas are similarly illuminated, you don't get difference.
 
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#16
Re: 5D3 and 24 1.4 II L owners please read!!!!!!!!!!!!

Also, I can confirm it happens also with my 70-200. I'm guessing the OP just happened to use 24L so that the AFS and MFS were hitting suitable spots to see the problem.

So it's camera body problem, not lens problem. Something changes on the evaluation based on AF/MF. That is strange indeed. I wonder if Canon knows about that.

Maybe I should conduct more tests...
 
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#18
Re: 5D3 and 24 1.4 II L owners please read!!!!!!!!!!!!

Theory!

Flipping the switch triggers metering. Since evaluative metering invokes code that looks at multiple metering points and tries to intelligently guess what to do, it's somewhat reasonable to assume that it might a different decision on what to do each time it's invoked if the light entering the lens in non-uniform across the image.

A way to test if this is happening is to point the camera so the image is completely uniform in brightness across the image — at the sky, or a flatly coloured wall, etc.

Please bear in mind that I don't own this lens or camera, but I do have experience in programming. In algorithms like this, it's often the case that there's some guesswork involved — hell, I once implemented an algorithm that would just randomly choose one of tho values if it couldn't determine one value over another with any degree of certainty, and it worked just fine.

Since I doubt the camera saves the reasoning behind its metering decisions between each metering, I can easily see this sort of thing happening in something that's supposed to be "smart" like evaluative metering. If you require absolutely consistent metering, I guess evaluative isn't the right mode to choose.
 
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#19
Re: 5D3 and 24 1.4 II L owners please read!!!!!!!!!!!!

iKenndac said:
Theory!

Flipping the switch triggers metering. Since evaluative metering invokes code that looks at multiple metering points and tries to intelligently guess what to do, it's somewhat reasonable to assume that it might a different decision on what to do each time it's invoked if the light entering the lens in non-uniform across the image.

A way to test if this is happening is to point the camera so the image is completely uniform in brightness across the image — at the sky, or a flatly coloured wall, etc.
Click to expand...

This makes perfect sense. Evaluative metering is linked to the selected AF point. Switching to MF deactivates all of the AF points, which means evaluative metering can no longer be weighted toward a selected point. The fact that you're seeing this only with a wide angle lens is not unreasonable. With such a wide FLV, there's more in the scene to affect the metering when it is no longer weighted toward the selected point.

One way to test this would be simply to change the metering mode to center weighted average, spot, or partial. Doing any of those should eliminate the change with the switch in focusing mode.
 
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#20
Re: 5D3 and 24 1.4 II L owners please read!!!!!!!!!!!!

Louis said:
Thank You for at least replying, sometimes I get the feeling this Forum doesn't want to listen to any problems but to talk mainly about what's new coming out, or how well a Canon did compared to a Nikon vs dropping it

/sad
Click to expand...

I'm sure some people have that exact combo, but not a majority. so if we can't test out out, what benefit would it be for us to post?
 
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