SEL20F28 impresses and puzzles at the same time

Started Apr 10, 2013 | Discussions thread
verybiglebowski Veteran Member • Posts: 3,897
Re: I appologize

Hanry I am so sorry, I was in a hurry and wrote harsh remark about useless tests. What I meant to say, is that they are useless in terms of lens comparisons. But they are great for you to see which lens works better on your camera, with your capturing and pp routine.

I believe, that many users might find valuable informations from your tests and user experience, but without strict and careful methodlogy, excluding all variables that you can and clearly state which one remains, such a test doesn't say anything relevant to the lens performance and thus can't be considered as useful in regard to lens comparisons.

Let me give you just one example - you are writing about front or back focusing, but that can be related to the lens, body, focus algorythm, change of lighting conditions etc. Such a result can't be used when discussing lens sharpness. (BTW, I think that because FOV is different between 20 and 19, the part of the image used to evaluate contrast for AF can be different too and cause differences in resulting focus. But that is only my guess)

Field of curvature - you are using AF (CV in MF) but it doesn't seem that you calculate for a DOF and use it to focus properly. If I understand, you focused to the background, probably at infinity. Thus, lenses with pronounced field curvature, might have blurred corners at certain distances, because of improper focus, not because the lens is bad.

Different exposure speed, no matter if camera is on tripod or not, can have significant impact on the final resolution.

There are many more things, that makes such a test irrelevant in terms of lens comparison, but they might give an idea to avarage user, what he/she might expect from the combination of camera and lens (system) in similar condition and using similar capturing routine.

So please, accept my appologize for saying something that I didn't meant to, and keep your tests comming. Maybe just consider to emphesize, what you tried to find out in such a test, so that inexperienced members, are not missleaded by comparing lenses.

All the best and keep testing.


 verybiglebowski's gear list:verybiglebowski's gear list
Sony Alpha a7R III Sony FE 16-35mm F2.8
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