Aperture + Sharpness Question

[hudub]

The smaller the aperture the sharper the image. Is there any cutoff for this? The reason I ask is that I shot this landscape at f32 and it seemed really soft and blurry.

[DrPablo]

Yes, for small format (APS-C and 35mm) cameras the limit is around f/8 to f/11, depending on the lens. The only reason to stop down beyond that is 1) for DOF, or 2) for exposure issues (say you want a very long exposure). Better lenses have fewer aberrations and will tend to become diffraction-limited at wider apertures.

Lens flaws tend to get better as you stop down, which is why stopping down makes the image sharper.

But light diffracts as it passes through the aperture pupil, and diffraction becomes more of a problem as you make the aperture narrower.

The "diffraction limit" is usually reached at f/8, f/11, etc, and this means that diffraction becomes the primary limit to lens sharpness beyond this point.

Larger formats are much less affected by diffraction because of enlargement factors, and that's why with LF you can stop down to f/64, f/90, or even f/128 on some LF lenses without significantly affecting image quality, though even in these cases you still have the best performance around f/8 or f/11.

[kevin_c]

What he just said^^^ :-) Out of interest, to get that f/32 aperture what shutter speed did you use and did you use a tripod? (possible camera shake?)

[Jon, The Elder]

Looking at your gear list, I assume you used your Tamron (right?). You might check their specs to get an idea. Generally a good lens will give you some nice results between f16 and f22 on a shot like this.

[hudub]

What he just said^^^ :-) Out of interest, to get that f/32 aperture what shutter speed did you use and did you use a tripod? (possible camera shake?)
Here are the image specs 17mm f32 1/25sec iso 100. With the crop factor I should have been shooting at 1/27sec or faster for handheld but I'm pretty sure I was still using a tripod at this point.

Looking at your gear list, I assume you used your Tamron (right?). You might check their specs to get an idea. Generally a good lens will give you some nice results between f16 and f22 on a shot like this.

Yes this was the Tamron 17-50 I just got it in on Friday and I went out to get a few shots and see how it performed before the weekend. I got some really sharp images and this was the only one that suprised me. I'm pretty happy with its sharpness wide open (http://photography-on-the.net/forum/showthread.php?t=321609) and here is image at f8. I'm really glad I got a good replacement for my kit lens.

[PhotosGuy]

Generally, a lens was considered sharpest at 2.5-3 stops down from the maximum aperture. Now with the "crop-sensors", we're using mainly the center (sharpest) portion of the lens & I'm not sure where the dividing line is.
As I see it, you could (1) not worry about it 'till you get to f/16+, or (2) join "Measurebaters Unanimous" & ask Curtis for a membership card? :D

What you do need to think about at small apertures is the amount of dust on your sensor: Some personal views on Sensor cleaning. (http://photography-on-the.net/forum/showthread.php?t=184448)