In some of the questions I have asked here, some of the terms frequently used to describe the difference in image quality between the cheaper lenses and the premium ones have been increased contrast, better sharpness, better colour saturation, colour rendering among others. I have also seen similar terms used on sites that do lens reviews, and they mostly cover CA, distortion and resolution.
To this end, I was wondering whether there are any standard tests available to quantify these parameters:
- Colour rendering/saturation (see related question)
- Contrast
- Sharpness (many sites seem to use MTF resolution charts for this)
Also, are there any sites that evaluate lenses based on the same, as it may not be practically possible for the average user to perform these tests?
Note: LensRental has a comprehensive "how-to", but that did not make use of too many standard tests (got it from this question that is somewhat related).
Answer
I use DxOMark to compare technical lens data. They use a standard test process to measure and compare the following lens parameters:
- Resolution
- Transmission
- Distortion
- Vignetting
- Chromatic aberration
These data points are taken at different focal lengths (for zoom lenses), at different apertures and are tested on a variety of camera bodies.
Honestly, I don't understand what to make out of half of the graphs and numbers they list, but their lens comparison feature makes it easy to find serious anomalies between lenses with similar technical specifications.
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