CA, Vignetting, Distortion--- Questions?

Started Apr 9, 2010 | Discussions thread
Mike K Veteran Member • Posts: 5,525
Re: CA and Resolution/Sharpness

It is my subjective observation that the lenses with a reputation for sharpness always have very low CA. Whether it is lateral or longitudinal, I believe that low CA will lead to a sharper image, especially at wider f stops. Thus I think that CA is the parameter of the 3 mentioned which should be minimized in the design of the lens. For example the Zeiss 21 has long held a reputation as the "best" WA lens made, and it certainly has some waveform distortion and vignetting at f2.8-4.0. I find the waveform distortion can be readily corrected with PT lens, an inexpensive and easy to use software tool, without perceptible loss of detail. Vignetting is readily addressed with the same software as well as PS. However, to get another WA lens (say the 16-35 II) to look as sharp and dramatic as the Zeiss 21 using tools in PP is very difficult indeed.
Mike K

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