"Soft" image on lens question

Started Feb 9, 2013 | Discussions thread
flint-hill Senior Member • Posts: 1,215
Re: "Soft" image on lens question

Questions like this one don't get many answers because they take a half-hour to summarize the answers that exist, and often the data isn't everything you'd like it to be.

Not sure if you're looking for images or numbers.  Numbers are good for this kind of analysis, so that's where I'll concentrate.

Here are some numbers on E-mount lenses.  Roger writes very briefly in this article, so you may have to go over it a couple of times if you're unfamiliar with the concepts.

http://www.lensrentals.com/blog/2012/04/nex-7-lens-imatest-resolution-comparison

Note that in this article the kit zoom is tested at 20mm rather than 24mm (which favors the Zeiss, because the zoom is sharper at 24mm than at 20mm) but you have to deal with the data that you can find.

You'll need to know what MTF-50 measures.  Here are a couple of articles:

Here are comparisons of the kit zoom vs the Zeiss 24mm at slrgear.com:

Kit zoom:

Zeiss 24mm:

The second bullet in each of these tests is the relative blur index simulator.  Set the kit zoom to 24mm and compare it to the Zeiss aperture for aperture.  Both tests were done on a NEX-5, so they're roughly comparable.

If you're new to all this, you'll just have to wade through the tests and expect that it will take some time to learn to interpret them.

The kit zoom is pretty good at 24mm at f/5.6 and f/8.  The Zeiss will beat it handily at wider apertures.  And of course the maximum aperture at 24mm is f/4 for the kit zoom and f/1.8 for the Zeiss.  If you need an aperture wider than f/4, the Zeiss wins by default.

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