Sensor sweet spot
In theory, a lens is sharpest wide open, but we know that isn't true. That is because we don't have "perfect" lenses.
In practice, stopping down two stops often gives best results, but modern zooms can actually keep on improving right down to f16. The better the lens, the more likely it will be that the "two stops down" rule-of-thumb will be close to accurate.
Photodo, EPZ and PU all have lots of lens tests and charts that show us what we might expect from any given lens.
We've never seen one.
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283
Is it possible that those that experience the best sharpness with the lens only slightly stopped down are misinterpreting their results?
......
Therefore, it seems likely to me that those reporting the best sharpness with lenses only slightly stopped down, are probably getting the benefit of the first stop or so of improvement that you get when the lens is no longer wide open, coupled with the least amount of camera shake, that you get with wide apertures and hence short exposures.
Did all my tests on a tripod. Why would anyone test their lenses handheld. It doesn't make sense as you're introducing obvious and significant variables.
Anyway for me photography isn't about an obsession with sharpness, i'ts a about the vibe the image portrays and I love F/1.2 - F/1.4 type apertures with the depth of a shallow DOF and nice Bokeh.
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283
Did all my tests on a tripod. Why would anyone test their lenses handheld. It doesn't make sense as you're introducing obvious and significant veriables.
Fair enough... interesting results then.
Pentax K-3, DA18-135, DA35 F2.4, DA17-70, DA55-300, FA28-200, A50 F1.7, A100 F4 Macro, A400 F5.6, Sigma 10-20 EXDC, 50-500 F4.5-6.3 APO DG OS Samsung flash SEF-54PZF(x2)
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Derek
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24265 posts
22 years
Tyldesley,
Manchester
In practice, stopping down two stops often gives best results, but modern zooms can actually keep on improving right down to f16. The better the lens, the more likely it will be that the "two stops down" rule-of-thumb will be close to accurate.
Photodo, EPZ and PU all have lots of lens tests and charts that show us what we might expect from any given lens.