Sensor misalignment

If one or more lenses exhibit softness on the same side of a frame, does that indicate misalignment on the sensor? I have never shot walls or charts before but after getting my camera and lenses calibrated recently by Canon, I wanted to give it a try. What I see is all my tele lenses have softness on the left side of the frame and mostly on the bottom left corner. These lenses are 70-200 IS II, 135L, 200L (F2), and 300 F2.8 II. Some of my other lenses are fine such as 35L, 85L, 24-70 II, etc. It may be that tele lenses magnify the problem or all those lenses have some sort of a problem on the left side which is very unlikely or there is a problem with my sensor.

My testing is pretty accurate in that it is as good as it's going to get. I use an RRS TVC-34L tripod with a BH-55 ballhead and a PCLR clamp. I use remote control, mirror lockup, flash, and high shutter to eliminate or reduce the impact of shake.

Would it be a decent test if I were to rotate my camera and keep the lens same level and see if the same corner is soft which would indicate there is a problem with the camera?

Humble Photographer wrote in post #16259872
What I see is all my tele lenses have softness on the left side of the frame and mostly on the bottom left corner. These lenses are 70-200 IS II, 135L, 200L (F2), and 300 F2.8 II. Some of my other lenses are fine such as 35L, 85L, 24-70 II, etc.

I think this essentially answers your question.


You might also want to read through this http://www.dpreview.co​m …ation-facts-and-fallacies

The sensor itself is planar, and therefore not able to be out of position at one specific corner only. Prove it to yourself with a piece of framing glasss...lift one corner of the glass by distance N, and half way to the two opposite diagonal corners have to be lifted by a distance of N*(1/2), as well...and so does the exact center of the framing glass, as only one corner would be resting against the wood of the frame!
Or if one end of the framing glass is lifted by distance N, the other two corners can be in correct position against the wood frame, but the exact center of the glass still ends up lifted by N*(1/2) as well.

So you have to see something else in the frame out of focus, unless it happened to be masked by the Depth of Focus (analogous to Depth of Field, but at the focal plane side of the lens).

Humble Photographer wrote in post #16259872
Would it be a decent test if I were to rotate my camera and keep the lens same level and see if the same corner is soft which would indicate there is a problem with the camera?

I'd say so - mount the 300mm on it's foot on a tripod, manually focus & rotate camera around the tripod ring & see if there's any difference t'other way up. You're not moving the tripod position any so should be a valid test.

If it helps any, most sensor units I've seen have 3 mounting points to the camera body - 2 at the top, & one at the bottom, all are shimmed for alignment so that the distance from the lens mount is correct. They look pretty robust & I imagine it would take quite a lot of force to knock one out of alignment once assembled.

(10D sensor)

I have noticed that if I use 9 center points for AF instead of 1, all my tele lenses are fine except 70-200. The zoom is bad and in fact its terrible regardless of what AF point I use. I'm glad that the problem is not my expensive primes or the camera but the zoom. I need to figure out what to do now.

Humble Photographer wrote in post #16260953
I have noticed that if I use 9 center points for AF instead of 1, all my tele lenses are fine except 70-200. The zoom is bad and in fact its terrible regardless of what AF point I use. I'm glad that the problem is not my expensive primes or the camera but the zoom. I need to figure out what to do now.

Might the camera be still under warranty? If so, such an alighnment issue would seem to fall into 'manufacturing defect'. Contact Canon service and inquire, even if out of warranty...it might be a product design induced issue, just as the 5D mirror coming loose was the subject of a recall repair.

Wilt wrote in post #16261364
Might the camera be still under warranty? If so, such an alighnment issue would seem to fall into 'manufacturing defect'. Contact Canon service and inquire, even if out of warranty...it might be a product design induced issue, just as the 5D mirror coming loose was the subject of a recall repair.

Camera is still under warranty but how is this related to camera? I was actually implying that the softness on one side in majority of the tele lenses (in fact all except 70-200) correcting itself with a different AF point selection proves that both the camera and the lenses are fine. As I'm right on MFD so close to the target, tele lenses are probably very sensitive to slight contrast differences so that picking 9 instead of 1 AF point gives a more accurate focus capture.

Either the lens mount is not perfectly aligned, or the sensor assembly is not perfectly aligned, and it shows up with tele lenses is an indicator. Tele FL are more sensitive to alignment flaws for the same reason that wide angle FL have deeper DOF. It does seem strange that selection of AF point makes the problem better or worse...maybe the AF sensor itself has alignment issues, causing it to sometimes make missed focus worse, sometimes better?!

Humble Photographer wrote in post #16259872
If one or more lenses exhibit softness on the same side of a frame, does that indicate misalignment on the sensor? I have never shot walls or charts before but after getting my camera and lenses calibrated recently by Canon, I wanted to give it a try. What I see is all my tele lenses have softness on the left side of the frame and mostly on the bottom left corner. These lenses are 70-200 IS II, 135L, 200L (F2), and 300 F2.8 II. Some of my other lenses are fine such as 35L, 85L, 24-70 II, etc. It may be that tele lenses magnify the problem or all those lenses have some sort of a problem on the left side which is very unlikely or there is a problem with my sensor.

My testing is pretty accurate in that it is as good as it's going to get. I use an RRS TVC-34L tripod with a BH-55 ballhead and a PCLR clamp. I use remote control, mirror lockup, flash, and high shutter to eliminate or reduce the impact of shake.

Would it be a decent test if I were to rotate my camera and keep the lens same level and see if the same corner is soft which would indicate there is a problem with the camera?

How long have you had the 135 and 300? I heard a few things about Canon having some returns from decentering issues on those from fairly recent batches.