CFC1
Distinguished Member
I had problems a couple of years ago with AF on my nifty fifty on my Canon 7d. It was hardly ever sharp, with the focus point fluctuating between back and front focussing. I did the usual chart tests and microadjusted accordingly, but I could never get any consistency either way. I noticed that if I acquired focus and then pressed the shutter again repeatedly, the lens would judder like it was trying to find focus again. This would happen 19 times out of 20. I would assume that if it was locked on correctly, then it wouldn't judder (try to refocus) again!. On the odd time that it didn't judder, if I then took the shot, it would be perfectly sharp. I gave the lens up as a bad job and a couple of weeks ago replaced it with the 50mm STM version.
I took a couple of shots for the first time last week, but again, wasn't that happy with the sharpness. So, I did a quick AF test on a chart this evening and am still having problems. This new lens is still doing the judder thing again when I press the shutter after focus has been confirmed, although not nearly as often as the old lens ... maybe 8 times in every 20. But still, the AF chart shows a variation in focus. It looks like it's back focussing in the main, with the odd shot about right.
The test was wide open at f1.8 on a tripod. I know that there is this rule that says that 1/3 in front and 2/3 behind the focus point should be in focus. Is this true in a test at close quarters like this?
Finally, is the "juddering" that I mention above when the shutter is pressed after focus has been achieved normal? Unfortunately I haven't got another body to test it on. I'm beginning to wonder if the problem is actually with the 7d body as opposed to the lenses.
Here are 4 consecutive test shots, each refocused after defocussing with my hand at a closer distance. Number 2 looks about right to me, but the other 3 seem backfocussed. Are these within tolerences or not?
Any advice/info would be greatly appreciated.
Cheers, Calvin
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I took a couple of shots for the first time last week, but again, wasn't that happy with the sharpness. So, I did a quick AF test on a chart this evening and am still having problems. This new lens is still doing the judder thing again when I press the shutter after focus has been confirmed, although not nearly as often as the old lens ... maybe 8 times in every 20. But still, the AF chart shows a variation in focus. It looks like it's back focussing in the main, with the odd shot about right.
The test was wide open at f1.8 on a tripod. I know that there is this rule that says that 1/3 in front and 2/3 behind the focus point should be in focus. Is this true in a test at close quarters like this?
Finally, is the "juddering" that I mention above when the shutter is pressed after focus has been achieved normal? Unfortunately I haven't got another body to test it on. I'm beginning to wonder if the problem is actually with the 7d body as opposed to the lenses.
Here are 4 consecutive test shots, each refocused after defocussing with my hand at a closer distance. Number 2 looks about right to me, but the other 3 seem backfocussed. Are these within tolerences or not?
Any advice/info would be greatly appreciated.
Cheers, Calvin
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