EF 40mm f/2.8 issue

[pitchers]

I use the EF 40mm f/2.8 Canon "pancake" lens on a 6D and have an issue. The lens will appear to "focus" on whatever I select in the focus point in the viewfinder but when I press the shutter, it seems to "prefer" whatever is closest in the viewfinder and focuses on that. I've had the lens for a while but just had the oppportunity to use it for a solid week in a very photogenic environment and this drove me nuts!

The exposure also seems very erratic -- many photos are a stop or two underexposed -- with a very sharp cutoff, omitting about a third of the histogram in Lightroom.  The photos that are properly exposed and focused (about half) are lovely but it's so erratic.  It appears to be a communication issue between the lens and the camera.  I've removed and re-seated the lens a few times but no change. For comparison, my 24-105mm f/4 focuses and exposes perfectly, so this seems to be a lens-specific phenomenon.

Any thoughts...?

[TTMartin]

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@pitcherswrote:

But to answer the questions, I use the center focus point and the half-shutter-depress for focusing.  I'm set to spot-meter but it doesn't matter which meter mode I use. It happens if I'm in program [P] mode, or aperture- or shutter-priority.  I don't use the back focus but I use the back exposure-lock button. And I'm pretty much always on "one-shot."

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In my opinion the only time you should use 'Spot Metering' is when using full manual M and Manual ISO. Otherwise, you will get eratic exposure like you described. 

Use Evlauative Metering. Evaluative Metering is weighted to the focus point in use.

'All EOS models (to date) automatically lock exposure when you’re using Evaluative metering and One-Shot AF mode. Press the shutter button half-way down, and the exposure settings will be locked in-place with no further effort on the photographer’s part. If you keep partial pressure on the shutter button, you’ll see as you move the camera side-to-side that the shutter speed/aperture numbers don’t change. Pull your finger off the button, and the camera immediately begins to update exposure settings as the camera is moved.'

Using Auto Exposure (AE) Lock

[pitchers]

These have all been good photography tips. But does anyone have insight into this particular issue?  It is only with this lens.

"Thanks.  My point is that it is only this lens. If I sit in my chair and shoot through an open interior door (with the door frame still in the field of view), I can focus on a point in the next room but the resultant photo is focused for the doorframe.  If, while sitting in the same chair, I swap on my 24-105 zoom, set it at 40mm(ish), take the exact same photo, I get nice crisp distant focus as intended."

So it's not related to the mode, or any lens-independent user-adjustable camera setting. And no, the lens is not set to MF.

Oh well, was worth a shot.  Thanks, all!

[Waddizzle]

I agree that you should use Evaluative Metering for just about all handheld shooting.  

Are you using any lens filters on your lenses?  You suspect that you probably have a bad lens, though. 

[Waddizzle]

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@pitcherswrote:

These have all been good photography tips. But does anyone have insight into this particular issue?  It is only with this lens.

"Thanks.  My point is that it is only this lens. If I sit in my chair and shoot through an open interior door (with the door frame still in the field of view), I can focus on a point in the next room but the resultant photo is focused for the doorframe.  If, while sitting in the same chair, I swap on my 24-105 zoom, set it at 40mm(ish), take the exact same photo, I get nice crisp distant focus as intended."

So it's not related to the mode, or any lens-independent user-adjustable camera setting. And no, the lens is not set to MF.

Oh well, was worth a shot.  Thanks, all!

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Try your tests outdoors.  The 6D does not have the smarts to compensate for the flicker of artificial lighting.

[pitchers]

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@Waddizzlewrote:

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@pitchers

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Try your tests outdoors.  The 6D does not have the smarts to compensate for the flicker of artificial lighting.

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It's focus.  Focus problem. Problem with the focus. And just this lens. And the 6D is evidently smart enough with my other lenses, as noted.

Now I know how women must feel!  

I feel like I'm in Ghost.

Did a search and there is a firmware issue from 2012 for this lens but I suspect that this has been long resolved. Mine is < 3 years old. OK, I'll assume it's a bad lens. Thanks; over and out.

[ebiggs1]

"The exposure also seems very erratic -- many photos are a stop or two underexposed ..."

Whenever things don't go as expected, you should always start by resetting the camera.  Menu, Tools, clear all settings.  Start from square one.  Under good lighting conditions and the mode set to P, try it.  If all is well you know there is nothing wrong with the camera/lens combo.  You must do this first. Otherwise you are just guessing. And, so are Bob and me.

[ebiggs1]

Oh, and BTW, if you call Canon support they will make you do this too.