How to Evaluate a Camera Lens for Performance

[Andy Resnick]

I’ve done plenty of imaging performance testing on a variety of systems, from millimeter wave to UV. Until very recently, such testing required expensive and specialized equipment. Now, with digital imaging (at least in the visible), you can perform the same type of characterization on your camera for free.
All you need is an LCD.
LCDs work differently from old CRT displays- they are not raster-scanned, for example. So, you can take photos of the display without fear of flicker (which happens if the shutter speed is not a multiple or fraction of 1/30s).
Why evaluate lens performance? There are at least two reasons.
First, lenses do not deliver constant performance over the full range of f-stop. Trained photographers have a saying “Always use the lens stopped down at least 1 stop from maximum”. The reasoning behind this bit of lore is that almost all aberrations get worse with a larger aperture (smaller f-stop). Maximum sharpness will be obtained for a limited range of...

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[Drakkith]

Nice job, Andy. Though I admit it is a bit difficult to tell the difference between the pictures to my untrained eye. They look almost identical for the most part.

 

[Andy Resnick]

Nice job, Andy. Though I admit it is a bit difficult to tell the difference between the pictures to my untrained eye. They look almost identical for the most part.

Thanks!

Which images? The 15/3.5 images are clearly different, the others less so.