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02-26-2015, 04:45 AM   #1
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Question on front and back focusing issues

Hello,
I was reading this excellent article..Fixing Front and Back Focus - Introduction - In-Depth Articles

And had a question some here can probably easily answer. I'm not currently having any issues that I know of with front and back focusing but like to know as much as I can.

According to the article dslrs like the k3 have 2 different autofocus mechanisms. One is called phase detect autofocus (used when viewing thru the eyepiece).The other is contrast detect auto focus(used when taking pictures in live view).

Problems with front and back focusing can occur with the phase detect auto focus and are often correctible in the camers. Live view's Contrast Detect Autofocus Is slower but does not suffer from back and front focusing issues.

The article goes on to explain much in testing and correction on the phase auto detect system. My question is if you mount your camera on a tripod, take a picture of a simple test sheet or object using both the phase auto detect system and the contrast detect system....could you use a comparison of the two images taken under identical conditions as a test if you think you might have a front or back focusing issue?

Is it unrealistic to assume that these 2 different autofocus mechanisms would yield roughly similar results if both systems are functioning as they should?

Apologies here if Its been suggested or discussed before...or if I am way off the mark here. Just trying to understand the technical aspects of the focusing systems better.
thanks,
Al

02-26-2015, 05:30 AM   #2
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QuoteOriginally posted by brewmaster15 Quote
.could you use a comparison of the two images taken under identical conditions as a test if you think you might have a front or back focusing issue?
Sure, Al, going into Live View is a way of checking the less accurate PD system.
02-27-2015, 08:12 AM   #3
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QuoteOriginally posted by clackers Quote
Sure, Al, going into Live View is a way of checking the less accurate PD system.
Thanks for the reply!
al
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