Canon 7D focus issue-new observation

Started Mar 31, 2013 | Discussions thread
rndman
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Re: Canon 7D focus issue-new observation
In reply to ldgehman, Apr 1, 2013

ldgehman wrote:

I realize there has been much discussion about the Canon 7D focusing issue, whether real or perceived  but I have purchased a 7D in December last year, and I have been battling "real" focus problems since I received it The biggest problem is that the focus/sharpness issue is intermittent. At first I thought it was just the learning curve with a new camera, but finally I started to run tests from a tripod to stationary objects, and I discovered that one day I could take ten shots in sequence and get ten absolutely tack sharp images. The next day I could take the same ten shots and possibly get one or two good ones with the rest having varying degrees of softness.I got the same results whether using AF or MF. The problem seemed worse with the longer focal length lenses. Here is the interesting part--I used my 400mm lens from a tripod to a stationary object and switched the camera to "Live View" mode, using the 5X and 10X magnification feature to manually focus as precisely as possible. What I observed on the screen I believe is a clue to the inconsistent sharpness. When the problem is present the screen (in "Live View") is constantly jittering with focus rapidly fluctuating in and out. Remember, this is all with manual focus. Whenever I observed the jittery screen and then took regular test shots (out of "Live View") as stated before, I would get about 10% sharp images. When the problem cleared (no image jitter in "Live View") then the test shoot yielded 100% good images. Bottom line is the quantity of good images coincided directly with the image/focus jitter observed in "Live View". I certainly don't claim to be knowledgeable about the inner workings of the image sensor or focus sensor on this camera or any camera, but I suspect there is something going on with one of these sensors or supporting hardware or software. It's completely hit or miss depending on the state of the sensor image at the instant the shutter is released.

The big question is--what is causing the image/focus jitter or fluctuation? And can I get someone to listen to my observations without automatically attributing my frustration to operator error? That is basically the response I have gotten so far from Canon technicians. I wonder if others with "real" focus problems with this camera may have or could have observed a similar phenomenon in "Live View" mode. I have not seen a description of such in any forum. If anyone else is experiencing similar symptoms switch to  "Live View" with magnification, focus manually, and look for jittery focus.

OK. I have seen that "jitter". But I guess it is more like waving or fluid so to speak. Like an image in the water. I have seen this happen only when the subject is outside. If you are inside a room (hoping you have long enough distance) it does not happen. I could test only within 25-30 feet inside.

Now I am not sure if this is due to the air density or weather or whatever.

Now is that the factor I am not sure. You mention that you don't see that always. I need to check that. However as you have mentioned, I too have the inconsistent focus behavior even on a tripod with shutter speed much high (> 1200) , MLU engaged and 10 sec timer. I am yet to determine if I should send mine to Canon (it is ut of warranty so I have ample time to ponder)

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