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08-14-2014, 11:06 AM   #16
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This is very perplexing - if it's just this lens on the K5, and others work fine, and the lens works fine on the Kr then I don't think any of those circles meet in our little Venn diagram.

08-14-2014, 11:36 AM   #17
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Enough great shots missed ! I feel like throwing in the towel and selling the K5. A great camera and the quiet shutter was one of the selling points but alas it willnot perform asit should.
08-14-2014, 05:07 PM   #18
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QuoteOriginally posted by Robert Barnett Flash Quote
Ok I have had the camera tested and focus adjusted and calibrated by Pentax....and it has made no difference ! Still focusing in front I do not understand how to use the focus adjust in camera so any help would be appreciated before it goes on Ebay !
Have you carried out a proper test with focusing? (Tripod, centre spot focus, inclined plane, to accurately determine front or back focus?) Can you post some examples of your images with focus issues?
08-15-2014, 09:55 AM   #19
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Here are two examples the first at 400mm and the second at 500mm. Both were spot focused on the stone, yet the grass in front is in focus !

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08-17-2014, 08:24 PM   #20
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QuoteOriginally posted by Robert Barnett Flash Quote
Here are two examples the first at 400mm and the second at 500mm. Both were spot focused on the stone, yet the grass in front is in focus !
I think the grass is only fractionally more in focus than the stone, on the one photo. On the other, the edges of the stone seems pretty well in focus at this resolution. Maybe it's my eyes!
08-18-2014, 01:26 AM   #21
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The focus point is about a foot in front of the stone.
08-18-2014, 04:06 AM   #22
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QuoteOriginally posted by Robert Barnett Flash Quote
The focus point is about a foot in front of the stone.
At this resolution, the sides of the stone appear too sharp for that to be the case. Obviously, you have the benefit of looking at the full resolution images, but in these smaller images, that's not evident. Have you tried any tests?
There are many versions, (Feel free to google) but see, for instance, this one: http://www.kscameraclub.org/docs/pdfs/focus_test_chart_edited.pdf
08-18-2014, 04:29 AM   #23
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Not tried any tests but will have a look. The stone is way out of focus despite the focus point being right on it ! Plain to see at this resolution to my eyes.

08-18-2014, 08:01 AM   #24
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QuoteOriginally posted by Robert Barnett Flash Quote
Here are two examples the first at 400mm and the second at 500mm. Both were spot focused on the stone, yet the grass in front is in focus !
Yep, that is what happens. The camera AF system will lock focus when phase peaks align. If there are competing foreground objects they may win. You may think "That is just plain STUPID!" and you would be correct. The camera is stupid. It does not know whether you want the grass or the stone to be in focus. What is more, the camera does not do a good job of letting you know how much of the frame is being evaluated.

As noted above, a controlled test may be in order. Field tests are nice, but hard to control. Here are the bullet points:
  • Tripod
  • Drive mode set to 2s delay
  • Lens at maximum aperture
  • Detailed high contrast target (classified ads from the newspaper work great)
  • Target on wall parallel* to focal plane (sensor) of the camera
  • Best of 5 testing at various focal lengths, distance about 20x the focal length
  • Best of 5 testing using manual focus and magnified live view (rules out faulty optics)
If the camera fails to accurately lock focus under these conditions it is time to send the it back the Pentax. They did not do a good job. Seeking assistance from an online forum may be useful, but if the camera is still on warranty, Ricoh/Pentax is your best resource. A fine focus adjustment may also do the job. I would give you detailed instructions, but am not familiar with the K-5.


Steve

* Yes, I wrote parallel. An angled target may be useful for visualizing front/back focus, but creates an element of uncertainty for the AF system as to what constitutes the subject to lock focus on. As noted above the AF system is STUPID. We already know that.

Last edited by stevebrot; 08-18-2014 at 08:08 AM.
12-07-2014, 03:15 PM   #25
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Seems to have sorted itself out ! Thanks for all replies
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