How to Evaluate a Camera Lens for Performance

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SUMMARY

This discussion focuses on evaluating camera lens performance using digital imaging techniques, specifically with LCD displays. It highlights that modern testing can be conducted without expensive equipment, as LCDs allow for flicker-free photography. Key insights include the importance of stopping down lenses to achieve maximum sharpness and the variability of lens performance across different f-stop settings. The conversation also touches on the subjective nature of image quality assessment among photographers.

PREREQUISITES
  • Understanding of lens f-stop and aperture effects
  • Familiarity with digital imaging techniques
  • Basic knowledge of LCD technology and its advantages over CRT
  • Experience with photography and image evaluation
NEXT STEPS
  • Research techniques for testing lens sharpness at various f-stop settings
  • Learn about the impact of lens aberrations on image quality
  • Explore the differences between LCD and CRT displays in imaging
  • Investigate tools for digital image analysis and comparison
USEFUL FOR

Photographers, imaging technicians, and anyone interested in optimizing camera lens performance through practical testing methods.

Andy Resnick
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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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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.
 
Drakkith said:
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.
 

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