How to adjust focus

Workingdog · 12-28-2009, 02:18 PM

So, I've read a few posts on how to adjust the focus on the K7 / K20/etc. and all seemed to involve a printed chart graduated in cm that one had to set at a 45 degree angle, blah, blah.
I used that method but decided to try another, maybe easier method and see if it gave the same results. Using Scrabble tiles, I used the letters A thru G with A closest and G furthest away. D is in the middle and is the focus point.
The photos below are with the pentax 55-300. 1st taken at 135mm and second at 300mm. You can see that the lens goes from slight backfocus at 135 (compare B & F) to slight front focus at 300 ( compare C & E). So, I'm not going to adjust.
This is the same result I got using the chart.

Last edited by Workingdog; 02-02-2011 at 04:57 PM.

Marc Sabatella · 12-28-2009, 08:39 PM

It's normal for the in focus range to extend further behind the target than in front. It's only backfocus if the target itself is out of focus, or *way* offcenter in focus zone.

12-28-2009, 02:18 PM	#1
Workingdog Veteran Member Join Date: Dec 2007 Location: York, PA Photos: Gallery Posts: 736	How to adjust focus So, I've read a few posts on how to adjust the focus on the K7 / K20/etc. and all seemed to involve a printed chart graduated in cm that one had to set at a 45 degree angle, blah, blah. I used that method but decided to try another, maybe easier method and see if it gave the same results. Using Scrabble tiles, I used the letters A thru G with A closest and G furthest away. D is in the middle and is the focus point. The photos below are with the pentax 55-300. 1st taken at 135mm and second at 300mm. You can see that the lens goes from slight backfocus at 135 (compare B & F) to slight front focus at 300 ( compare C & E). So, I'm not going to adjust. This is the same result I got using the chart. Last edited by Workingdog; 02-02-2011 at 04:57 PM.

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12-28-2009, 08:39 PM	#2
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	It's normal for the in focus range to extend further behind the target than in front. It's only backfocus if the target itself is out of focus, or way offcenter in focus zone.