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Forum: Pentax SLR Lens Discussion
11-03-2015, 05:11 PM
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I take many of my shots at a range of apertures whenever I can. I like something like 2.8. 5.6, 8, 16 and sometimes all six in that range. I've so many times had my favourite one of a series be an odd focal length i wouldn't have expected, I wouldn't get comfortable thinking you know something. At this point I'd say, the specific alignment of the elements of the photo are completely changed by the aperture used. Unless you are willing to start including the distance of the subject from the lens, the distance of the subject from the background, placements of other objects in the frame in relation to the subject, a simple calculation based on the need for more light or whatever is not likely to give you the best shot very often. IN fact really only useful when you have time constraints and may only get one chance. Then best guess will have to two. The rest of the time, shoot as many f-stops as you have time for.
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Forum: Pentax SLR Lens Discussion
11-03-2015, 07:08 AM
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And over-saturation leads to loss of detail.
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Forum: Pentax SLR Lens Discussion
11-02-2015, 08:03 PM
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Almost all Pentax lenses are sharpest at ƒ5.6. The three amigos are sharpest at ƒ4. Diffraction starts to set in both on FF and APS-c at ƒ8 but the drop-off at ƒ8 is not so bad. By ƒ11 it's more noticeable, but it's not until ƒ32 you start to see the coke bottle lens effect. You might want to look over the photozone charts, they are presented in an understandable format, unfortunately they haven't done any Pentax testing on anything newer than a K-5. But you get a nice feel for how a lens produces with good distortion and CA numbers.
Pentax K Lens Tests
Click through the list of K mount lenses, by the time you're done you will have seen some very different philosophies in lens design, from the centre sharp 77, which excels at the centre but not so much on the edges, to the 70 2.4 sharp across the frame, and not much difference from ƒ2.4 to ƒ 11.I default to ƒ5.6 on most lenses, unless I know I want a lot of depth of field when I go to ƒ8 or ƒ11 or 16. If I want a nice creamy background I use a faster lens and a wider aperture. I've never found a lens where the basic approach is much different.
Some ƒ4 lenses are very good wide pen ut are still better at ƒ5.6. I would never hesitate to use my DA*605250 wide open if I needed a faster shutter, Same with he DA* 300 ƒ4. The DA*200 is almost identical MTF, from ƒ4 to ƒ8. the numbers are engaging and different lenses can have quite different characteristics.
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