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Forum: Pentax News and Rumors 04-18-2015, 04:30 PM  
HD PENTAX-D FA ★ 70-200mm F2.8 at 5th February?
Posted By Winder
Replies: 1,414
Views: 199,998
The thread is about lenses and their technical qualities. Sharpness. Using pictures that have been over sharpened in post tells you nothing about the lens. It make the bokeh look bad and adds white halos to the image. If your goal is to duplicate the look of over sharpened Canon OOC JPEGs, then they would great, but if the goal is to show the sharpness of the lens, then they are not great. Lot's of people like the look of over sharpened Canon JPEGs. Its very popular, so I won't argue the esthetics of it. Nobody is ganging up on Norm. It wouldn't matter who posted those. The reaction would be the same.
Forum: Pentax K-5 & K-5 II 03-17-2011, 10:32 PM  
K-5 1.03 versus K20D AF tests
Posted By Ray Pulley
Replies: 207
Views: 40,020
f2.8 sensors would not be closer to the center. They would be closer to the edges of the lens, which would be necessary for use in an f2.8 lens because it has a larger diameter than an f5.6 lens (focal length being equal). They may or may not be more sensitive, but they would have a larger base distance to use in computing the focus solution, which would make for a more accurate calculation.

Pentax positions the AF sensors at a diameter near the size that corresponds to f5.6 so that slower lenses will AF. Otherwise, if the sensors were positioned at a diamater that equated to f2.8 they would simply be blocked when a lens slower than f2.8 is used because there would be no glass out there on a f5.6 lens to gather any light from.



You mentioned sharpening. No sharpening was applied other than whatever default the camera applied.




Nope. No such gate.




In that case, Pentax need not calibrate them either ;)







QuoteQuote:

Seriously though, I agree that in your particular case the firmware effect seems to be big enough that minor alignment issues may not play a role. However, in general "AF fine adjustments" are done to get the last bit of performance out of the AF system. If the adjustment values are found by reading out the FF/BF on a ruler whose "0" mark is not exactly in the same plane as the focus target then one doesn't get optimal results.



I find that in many cases an adjustment of 1 either way at f1.4 will not get a perfectly centered focus adjust. This is irrelevant in real world use.




The model is embossed into the pics above.




I would start with the fact that focusing on a point at an angle is a basic flaw in this method. The paper methods I have seen (and used) are also far too close to the target. There are other issues with your method, but you are happy, so that is fine.






Sorry, you are going to have a hard time convincing me that something you taped to your kitchen table has a high degree of accuracy..



You talk like you would only be happy with a true optical bench test setup, but then are perfectly happy taping a piece of paper to some (maybe) flat surface and pointing your camera at it on a tripod. I find the disconnect rather odd.

Ray
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