AUTOFOCUS ACCURACY, BACK & FRONT FOCUSING PROBLEMS
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I personally never had any auto-focusing problem with any lens or camera I ever owned. It seems that these days, members of every blog and forum sites are talking about checking and adjusting the auto-focus on their lenses or DSLR. I think there is a perception that many lenses or DSLR cameras are having front or rear focus problems. In reality, I am inclined to think that novice photographers, “Pixels Peepers”, and inquisitive hobbyists, influenced by the available internet information, are finding problems where there is none. If a particular lens consistently gives out-of-focus results, when all other lenses used with the same DSLR are okay, you might have a focusing problem with that particular lens. If most of the pictures taken with the same DSLR, but with various lenses, are out-of-focus, you might have a DSLR camera-focusing problem.
If you think there is a focusing problem, several auto-focus testing charts are available from forums, blogsites and websites. I probably downloaded most of them and found inaccuracies with all of them. They are either too small, or too cluttered, or have measurements that are not to scale, etc. One thing charts seem to have in common is that no one is ever sure of which exact point of the chart the camera is actually focusing on.
Back or front focusing problems are more notorious with subjects that are within a short depth of field, such as macro pictures or selective focusing pictures, and with the lens used at its widest aperture.
Most newer cameras have the capability of adjusting the front and back focusing. Using my charts, you can test and adjust your lenses just as accurately as factory rechnicians. If your camera does not have the adjustment feature, you can still check all your lenses and send them to the manufacturer for calibration.
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Posted by Aundre on 7th Sep 2011
And to think I was going to talk to someone in prseon about this.
Posted by Torkel on 28th May 2011
Thanks for these charts, they saved my day!
On my 50/F1.4 I had to go all the way to -10, no wonder I couldn't get any sharp pictures at 1.4 before! But now I can! :)
Also the 16-45 needed -10 but my 55-300 was best at -7.
It seems as if my camera was badly adjusted camera from the factory, I'm happy it could be adjusted this easy.
Posted by Donald on 28th May 2011
Thanks for the charts, you've helped to diagnose focus problems with both AF and manual focus lenses! Sheesh, who knew that was even possible :-)
Posted by Tanny on 28th May 2011
This must be the most comprehensive and easy to understand explanation of auto focusing adjustment on the K20D that I have come across. Do keep up the great work