Friday, May 7, 2010

Camera returned from Canon, Repaired?

If you've been following along with my Canon 7D Auto focus woes you'll know that I recently had to send it in to Canon for that autofocus that was *say* off base, in my opinion, along with a bit of vertical noise banding even at iso 100.

Posted located here: Canon 7D Focus Issues?

I received the camera back a few days ago and have been running tests to see if there was improvement. The Canon facility wrote that they cleaned the CMOS sensor and calibrated the autofocus. With high hopes I ran it through a gamut of tests that I could imagine.


Well, the focus is DEFINITELY better. I can hit accurate focus over 90% of the time based on my tests (100 shots, only 7 out of focus). For that series I was using an envelope, printed with text, at 4to 5 yards of distance, using all three of my lenses. my 50mm, my 50-250mm, and my 28-132mm.

With all three, even at the lowest zoom (50mm for the 50-250m and 28mm for the 28-132mm) I hit consistent focus, 33 shots with each lens to make a full 100 shots.

It was broad daylight, and an aperature of 5.6 which is perfect for most of these lenses due to the lower f-stop breaking point of the Canon 7D (5.6 or so, versus the usual 8).

I have to test the noise banding I was seeing before, but I have to wait for a bright day with blue skies to really get a good test shot, no luck so far.

I would report that IF you have a camera that is consistently missing its autofocus mark by just a hair, try a few things:

1). Try a different lens. That lens may be uncalibrated or may have USM issues, it is worth ruling out the possibility that the lens is at fault.

2). If it is the focus on 2 or 3 different lenses then I suggest you try to remove the batteries (Note, I said batterieS... there are two in the unit, the true battery and the clock/time/settings battery). There have been reports online that removing both for 30 minutes at least would reset the camera and for some units seems to have fixed the focus issue.

3). Make sure it is not user error. I'm going to assume that if you are buying a Canon 7D, you are passed the point of learning what your camera can and cannot do and how it works. But, regardless, make sure you have a shutterspeed that is appropiate, make sure you have the right focus points selected (Point, is my recommendation, always Point, never Zone AF unless its a sports event or a fast moving object). The diffraction limit is also important, most lenses only allow 6-11 fstops for sharp pictures, after that you will actually lose quality. It is better explained on page 2 of this posting: Sharp images Canon 7D - Diffraction.
You can also use the lens MTF charts/graphs to decide where your particular lens is the sharpest, those can be found here: Photozone Lens List.

4). If you have checked the above, done your tests on tripods or hand held (at acceptable settings, mind you) and consistently seem to get missed shots, I would send it in. It'll cost you 30$ or so to ship it due to placing the insurance on the unit, but... well worth it, for a working camera.

An important additional note: Make sure you are NOT confusing out of focus with soft. The Canon 7D produces images that are considerably "softer" due to the high pixel count. These images, although apparently unsharp, respond well to post sharpening. If you run sharpening in post, and the image improves and is "now in focus" then auto-focus is NOT your issue. What you are seeing are soft images, due to the high pixel count of the Canon 7D. There is really no good way to change that, aside from setting the camera to only shoot at 15Megapixels in order to test the theory. So I would highly recommend you sharpen in post, to see if your images improve significantly. You can also set the camera to shoot both Raw + Jpeg and ensure that the incamera sharpening for jpegs is set to standard or higher. Then compare the jpegs to the raws. If you find the jpegs to be consistently "sharp and infocus" but raw files are not, then it is NOT a focus issue, but the softness exhibited by the pixel density.

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