Lens sharpness and distance from subject

[insanitybeard]

It does. Use a lens at 1m, then at infinity - it is a different lens really. I have noticed this with my 17-55 - much better at 2-3m than at infinity.

Many people test lenses at close distances and make far reaching conclusions; and this is wrong.

This is a very good point, and not one I've seen covered in any depth on most review sites I've come across- anybody know any review sites where this is considered with more than a passing comment?

 

[Pi]

This is a very good point, and not one I've seen covered in any depth on most review sites I've come across- anybody know any review sites where this is considered with more than a passing comment?

I have not seen any. Maybe the reason is that every such site has one (expensive) chart only and this pretty much determines the distance. I believe that you can still test at different distances even with the same chart, in the center at least; but they do not do that.

 

[East Wind Photography]

That's because the test chart is designed to reveal the limits of the lens at the test distance. Doesnt matter if you move the chart further away. Likely the test chart wont show anything. In order for the distance test to work you would need a chart that is proportionately larger to show the same pattern but larger scale.

For example moving the same chart out to twice the distance will double the number of lines shown per mm...so you are effectively trying to test the lens at an even finer resolution which most sensors would likely not be able to resolve.

This is a very good point, and not one I've seen covered in any depth on most review sites I've come across- anybody know any review sites where this is considered with more than a passing comment?

I have not seen any. Maybe the reason is that every such site has one (expensive) chart only and this pretty much determines the distance. I believe that you can still test at different distances even with the same chart, in the center at least; but they do not do that.

 

[Pi]

That's because the test chart is designed to reveal the limits of the lens at the test distance. Doesnt matter if you move the chart further away. Likely the test chart wont show anything.

It would but you need software which would still analyze it. The slanted edge test allows you to vary the distance to some degree. An edge is an edge at any distance but you do not want the whole chart to be viewed at an extremely narrow AOV, so there is some practical limit how far you can get. This requires a curious tester, not the typical businesses type.

 

[East Wind Photography]

And likely a test of the lens OFF of a camera body since the limiting factor of most decent lenses is the chip.

That's because the test chart is designed to reveal the limits of the lens at the test distance. Doesnt matter if you move the chart further away. Likely the test chart wont show anything.

It would but you need software which would still analyze it. The slanted edge test allows you to vary the distance to some degree. An edge is an edge at any distance but you do not want the whole chart to be viewed at an extremely narrow AOV, so there is some practical limit how far you can get. This requires a curious tester, not the typical businesses type.