Checking sharpness

Blasted

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Hi there,

How do I go about checking the sharpness of a lens? I have been sent a few jpegs unaltered from a Canon 17-55mm that I'm interested in. Is there anything specific I should be looking for?

Thanks.
 
Make sure you have turned off all in camera sharpening and put the cam on a tripod. Use something with text like a newspaper page or even a test chart (you can download & print them). Shooting at f/2.8 will probably not give as much sharpness as f/8.

Remember that sharpness is not the only consideration - there is falloff, distortion and bokeh quality to consider. I'd imagine that a zoom will be less sharp at the ends of the focal length range than the middle as well.
 
boliston said:
Make sure you have turned off all in camera sharpening and put the cam on a tripod. Use something with text like a newspaper page or even a test chart (you can download & print them). Shooting at f/2.8 will probably not give as much sharpness as f/8.

Remember that sharpness is not the only consideration - there is falloff, distortion and bokeh quality to consider. I'd imagine that a zoom will be less sharp at the ends of the focal length range than the middle as well.
Click to expand...

I don't think that the OP has got the lens yet, just some JPEGS from it that can be checked.
 
Blasted said:
Hi there,

How do I go about checking the sharpness of a lens? I have been sent a few jpegs unaltered from a Canon 17-55mm that I'm interested in. Is there anything specific I should be looking for?

Thanks.
Click to expand...

Look to see if there's any significant increase in softening from the centre to the edges.

If the images have been done properly in the first place, they'll be of flat subjects taken parallel to the 'film' plane with the camera bolted down to a tripod. As mentioned by boliston above...

If not, they're really not much use as too many variables creep in. PM the seller and ask for better images if they're not as described above.

Any lens working at its 'sweet-spot' of f/8 or thereabouts in good light will look good to the naked eye, it's at the extremes of aperture that any potential problems manifest.
 
If you want to check that it's a good copy, then you won't be able to tell anything meaningful without shooting specific tests, preferably against another good lens for comparison.

Basically, you need to get hold of the lens and do it yourself.

TBH, whatever it is you are trying to do, doing it by remote control like that seems completely pointless. Sorry ;)
 
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