80mm, PP in Photoshop, Crop

[Des]

Nice unusual pose, Gunnar!

Did you really take this at f28 or is this a typographical error?

If it was taken at f28, you would have lost a lot of sharpness. All lenses have a peak aperture which provides maximum sharpness (in the centre of the image). The peak is usually about one or two stops narrower than the widest aperture. (Sharpness in the corners might peak at a different point, often stopped down further.) With any lens it is rarely worth going more than a couple of stops beyond the peak. For example, if the peak is f8, it would rarely be worth going beyond f11 or so. After the peak, sharpness tapers off because of an effect known at diffraction.

Reviews such as those at Photozone will show where the best performance is for your particular lens:
http://www.photozone.de/pentax/138-pentax-smc-da-50-200mm-f4-56-ed-review--test-report
This review suggests that f11 might be the best point at each focal length for this lens.

[Gunnar]

Thank you for the post, and suggestions. Here is the fact. It is actually f29, as my Pentax display shows, but here I could not choose f29, only similar value. That is why I wrote f28. I apologise I did not mention precize info about it.

So again, I aplogize to all the members here

Gunnar

[FozzFoster]

80mm, PP in Photoshop, Crop

cute cat! nice one!