[wim]

Hi Frank,

[quote name='Frank' timestamp='1323171399' post='13479']

Hi Wim and Serkan:



Thank you very much for your very detailed interpretation. I understand that for any f-value greater than 11 the diffration becomes serious, but I find that for landscape in many cases f8 (at around 20mm）does not give enough DoF, f11 maybe marginally, so I often stop down to f16 or f13 at least, in occasional cases I stop down to f22. I also read that many (or just some?) professional landscape photographers shoot landscape with f16, f18, f20, and sometimes even f22 (35mm camera). From an aricle I read that something like "beyond f11 the diffration will cause the sharpness of objects in the focus plane to decrease due to diffraction, but the overall sharpness of the image will increase due to the increase in the DoF， untill the diffraction limit of f22 is reached". Did I misunderstand something?



Perhaps I need more tests to see the effect of f11, 13, 16 and beyond. But for the following scenery my past experince tells me that f8 will not give enough DoF (I focused on the foreground stone then the background trees and mountains would be blurry), f11 or 13 maybe marginally OK, to ensure a large enough DoF I stoped down to f16 (Nikon 16-35mm f4 lens at 22mm):

[/quote]

Nice picture, actually, and well composed.



I woudl like to remark something about DoF and sharpness here, especially when using (U)WA lenses.



The problem really is that DoF doesn't matter a lot, not as much as people may think. In the background there is not enough resolution on the sensor very quickly, especially with a WA or UWA lens, to resolve any detail anymore. There aren't enough pixels per detail item effectively. This was also the case with film, but no one ever saw this, because we didn't do pixelpeeping. Now with digital this is very easy of course.



To come to smaller apertures, what really happens is that diffraction makes details go to mush completely. If you look at the above photograph, you'll find that detail in the background is completely lost in some places, as in some places it has gone to mush essentially. By using F/8 or F/11 you will avoid that, to a degree where even areas slightly OOF will look sharper than mush at F/22. Granted the D700 is itself diffraction limited at about F/27 due to its relatively low pixel count (based on a study Serkan and I did in conjunction <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='' />), but that means effectively you shouldn't use anything below F/19, and when the lens shows aberrations, which almost any WA or UWA will do towards the periphery, subtract another 1 to 2 f-stops. If diffraction gets a little too large, and aberrations muddy things too, things just do turn into mush, especially there where you need it most or want it most.



I would think that with landscapes you may often be better off with using focus very selectively, and in PP use edge sharpening techniques to up the edge contrasts, in order to show the widest DoF possible.



F.e., the following image was shot at F/3.5 (even though by accident) on a Canon 5D classic (similar pixel density to D700), and it was sharpened with an edge sharpening:technique:







I've shown this as a 30 cm X 45 cm to professionals, and asked their opinion of the aperture used. They invariably said F/8 or F/11. There isn't really all that much detail in the background, but it looks crisp, and that is the secret. Focus was, as far as I can remember, somewhere at the bush to the left, IOW, rather much towards the front of the image, in order to get most of the road in focus.



Your picture is excellent, because the entire group of stones is sharp in focus, as our eyes would expect. Having used a similar technique as above, I am sure it would have looked incredibly sharp from front to back, at an aperture of about F/8, or F/11 at most.



I hope you don't mind, but I processed part of your picture, the upper part, and scaled it down to about 35% to make it not too big, and on one piece I used some edge sharpening, the other I left as it was, saved at jpeg quality 8.



First straight from your image:





Note that some of the trees in the background show no real detail, also check the fence and people in the picture (on the right).



And now with some edge sharpening (took less time than resizing and cropping the image):







There is some improvement visible, and it is much stronger even when looking at 100%, and the difference at 100% is even bigger. Even th erocks, which aren;t shown here, show more detail than those in the original image. However, I am 100% sure that if taken at F/8 or F/11, more relevant detail would have been preserved, and that detail would have come out even better using the above technique (as a start).



What this also proves, IMO, is that this lens is not as bad as one may think - it just requires a bit of careful processing to get the most out of it.



BTW, I hope you don't mind me doing this to your picture, if you do, say so and I will remove them.



HTH, kind regards, Wim