aperture sweet spots test

[roy_rogers]

Ive just done a test with my stock lens on my d50 and found on 20mm the sharpest

images were around f8 to f11 with f11 being the sharpest. So I thought Id do a

test where Im zoomed in at 55mm, so on that test its from f16 to f22 with f19

being sharpest. I am wondering if this seems right or if zooming in makes no

difference? I guess it does surely? The optimal sharpest must change with

different zooms?

[Peter_in_PA]

"The optimal sharpest must change with different zooms?"

 

I don't know how critical your test was, but yes, that sounds likely. I've found in my very

unscientific testing that my 18-200 is great at f5.6, but zoomed to 200 I really need to get to

f8 or f11 for great sharpness.

 

Be careful past f16 with most lenses as you reach the diffraction point. I'm surprised that you

get best sharpness at f19.

[tommyinca]

The optimal sharpest also changes depends on distant of subjects and position of light source for some lens. Thats why in many cases, it is better to just start taking pictures and forget about the test.

[roy_rogers]

Well it was very similar from f16 to f19, but very bad at f22 at 55mm, Im just looking for general best, its a bit hard to judge in the field but doing these simple tests I can then bracket the aperture around these values I guess

[elliot1]

I have found f8 works well for me overall with my consumer lenses but I have not done the testing to the extent you have. I am sure each lens has its sweet spot (the 'experts' say it is two stops down from wide open).

 

Many here on Photo.net suggest that shots above f11 tend to loose a little of their sharpness.

 

Why not post your test shots?

[bjørn rørslett]

If a zoom lens has a "sweet spot" around f/8-11 at the wide end where it goes to f/3.5, it does not follow that f/16-f/19 is the "sweet spot" at the other end where the same lens starts at f/5.6. On the contrary, I think it is highly unlikely the result is for real, and that f/8-f/11 or thereabouts is the peak @200mm too (at least, this is the situation for the 18-200 lenses I've tested). With careful setups it's easy to see the decline in sharpness that occurs much earlier than f/19. Very few lenses for today's DX cameras can appear critically sharp at f/16 and even fewer at f/22.

 

If all lenses had a peak in performance two stops down from the wide open setting, the task of reviewing lenses would have been much easier than it really is. Such blanket statements miss the real performance peak more often than they apply. What is certain, however, that the "sweet spot" is somewhere along the aperture range of the lens and is unlikely to be at the minimum aperture(s).

 

Sharpness is not an inherent property of the optics so subject contrast and lightening also play an important role in determining how sharp an image is perceived.