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Forum: Lens Clubs
04-11-2010, 09:52 AM
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Forum: Monthly Photo Contests
03-03-2010, 10:24 AM
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Rusting and decaying waterwheel
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Forum: Monthly Photo Contests
01-21-2010, 09:09 AM
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Forum: Pentax DSLR Discussion
01-03-2009, 11:39 AM
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I tried this with a 16-50 when I found that I could not see to manually focus on infinity whether in poor light or sunlight. Of course it didn't work;the point of sharpest focus varied from 16mm to 50mm . At 16 mm the cursor had to be set between the lemniscus and the 7m mark to obtain sharp focus whist at the other end it was set on the second lobe of the lemniscus. Other settings were: 20mm,first lobe,28mm and 35mm dead centre.Departures from these settings produced noticeable degradation in focus . And so any point of focus towards the wider end can be a little hit- or- miss. But then those of us who have come to know (and love) the foibles of our 16-50's,know this already.
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Forum: Lens Clubs
11-12-2008, 09:29 AM
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Hi Georgweb,
I have one too,and like you,never used it(it was left to me).Veijo Vilva's images very interesting-almost "impressionistic".
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Forum: Pentax SLR Lens Discussion
05-15-2008, 09:53 AM
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9011592 from Digital Depot.
Once I'd mastered autofocus ( which was new to me coming as I did from an OM1) and accepted its limitations I found this 16-50 to be excellent.
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Forum: Pentax DSLR Discussion
03-17-2008, 09:12 AM
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Like a few others with the K10D and *16-50 combination,I have had a few problems with the AF in the 16mm-20mm,and f2.8 sometimes f4 areas when focussing at infinity. I decided to determine where the points of sharpest focus lay for a particular object at ∞ (about 70/80m) for the range of focal lengths.I used manual focus and by trial and error discovered that at 16mm(and all f-stops ) sharpest focus lay with the cursor on the lens barrel just to the right of the lemniscate;at 20mm and 28 mm the cursor pointed to the middle;at 35 and 50 the cursor pointed to the middle of the second oval on the loop of the lemniscate.
On testing the AF with the different focal lengths and f-stops I found it to be accurate in that it adjusted the lens barrel to the same points I had discovered manually except in the cases of 16mm and 20mm and at f2.8 and f4,where the lens barrel seemed to have travelled too far.
This confirmed the problem that I'd already experienced so the solutions seemed to be:
a.return the camera for adjustment.
b.manually focus in the areas indicated as 'iffy'.
c.focus at 5.6 or above and then stop back up when focus is obtained
But this led me to a conundrum. If AF is carried out with the lens fully open,why should stopping down lead to accurate focus ?If my aperture is set to 2.8,there is some blurring,if its set to 5.6 or above ,it's sharp. It can't be a dof thing since the AF adjusted the barrel,time after time,to the same points of sharp focus that I had determined manually.So what have f-stops to do with autofocussing?
Do any of you who understand the mechanics of the AF system have any explanations as to what is going on ?
Incidentally ,I'm not a compulsive tester but now I feel more comfortable knowing when I can rely on the AF system and when I must work around it and can then concentrate on the photography.
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Forum: Photographic Technique
03-08-2008, 05:18 AM
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I think you might have cracked it for me J. since I've never bothered re-formatting after downloading.This would accord with what others have indicated that the problem was the card - as well as my ignorance. I'll re-format in future. Thanks again.
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Forum: Photographic Technique
03-06-2008, 05:45 AM
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Thanks for suggestions.Certainly the card seems a likely suspect though I'm still puzzled why I can still preview in camera. So I'll try different cards.No error messages in the mac.,though.Thanks again
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Forum: Photographic Technique
03-05-2008, 07:15 AM
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I'm unsure whether this is a Pentax k10 or a Mac 10.4.11 problem. Sometimes when I've downloaded a batch of photos,2 or 3 0f them,out of,say 50 ,will be black thumbnails. The images can be previewed in the camera but not downloaded.
I'd appreciate any suggestions.
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