I was taking pictures of some mushrooms when a fly walked up, giving me the chance to look at diffraction effects on a D800 as I varied the f stop. I was pleasantly surprised at the usability up to f16 or even f22. This was on a tripod. The lens is a favorite, although not one o the sharpest- the Series E 75-150 f3.5 MF lens on an extension tube for close focus. Approximately 135 mm. The f22 shot is a little darker, but the hairs on the fly are only somewhat lost. The depth of field is much greater, which would be the reason to use such a small aperture. There is a larger version of this on my photo.net page in the contributions section. The larger image is the f22 version.