What are the standard tests available to quantify lens parameters?

Question

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 1

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.

Answer 2

I think your first stop should be at Imatest, which offers many different suites of tests widely used by large commercial & industrial customers. That said they also cater for the individual, check out in particular the Imatest Master. The downside is the purchase price (although there seems to be trial version available) and you may need extra test charts to carry out some/most of the test. To be honest there is a lot of very useful info on their site and in their guides. I suspect you'll find them useful even if you don't decide to purchase the software.

I hope this helps.

Answer 3

Take a look at a sample test on photozone.de. They have standardized test results available for distortion, vignetting & CA and MTF charts. (Although these might be generated by imatest.com test suite)