Testing sharpness of adapted 24x36 SLR lenses

Started Sep 20, 2017 | Discussions thread
brightcolours Forum Pro • Posts: 15,566
Re: Testing sharpness of adapted 24x36 SLR lenses

ProfHankD wrote:

Belgarchi wrote:

First off, "sharpness" isn't really a thing. People often quote MTF50, but there's a good argument that MTF90 is closer to what people really see as sharpness, and one can also argue for MTF30 or lower because sensors are linear (not log), so postprocessing can relatively harmlessly doctor the contrast....

What camera to use? Here is my point of view on 5 typical mirrorless cameras, covering 90+% of the market.

DxO actually says quite a lot about how there is no such thing as "typical" and resolution measurements are not preserved across different body models in some cases despite using the exact same sensor chip.

If only DXO actually tested the lenses on the different bodies they claim they do. But there is strong evidence that they do not.

Anyway, I test on the highest-quality, highest pixel density, sensors that can adapt the lenses I care about. That generally means 24MP APS-C and 42MP FF, both from Sony. I also test APS-C both with plain adapter and with focal reducer... and where possible, I also test designed-for-APS-C lenses on FF and on FF using a 1.4x teleconverter (as a format converter). I don't bother with MFT. or smaller sensors.

Incidentally, the primary thing I test is not MTF, but OOF PSF (out-of-focus point spread function), which reveals a lot more than an MTF measurement does and also has the happy property that I can generally test it on just one sensor and have the results apply generally.

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