Reading resolution charts comparing MFT lenses to FX lenses

Started Mar 29, 2013 | Questions thread
KenBalbari Regular Member • Posts: 276
Re: I wonder

RoelHendrickx wrote:

Which makes me wonder (just a theoretical spiel) :

* If one wanted to test the quality of lenses across systems (just the lenses, not the sensors), would it not be conceivable to mount all lenses from all systems in front of the same sensor (through a specific set of adapters, used only for that purpose), in order to level to playing field for the lenses?

* If this was (theoretically) conceivable, would it then be best to use a BIG sensor (in size or in pixel count), or a smaller one, as that level playing field.

Yes, this is done, and it's refferred to as an optical testing bench.  Instead of a typical image sensor, an expensive sensor is used which can resolve at a higher level than any current camera sensor.  And any lens can be mounted on the bench.

This has become less common though in professional tests only because of the increasing effectiveness of computer software analysis like DxO Analyzer and Imatest.

"So why does everyone use image analsyis MTF? Because it’s accurate within its limitations and it’s reasonably priced. A good Imatest setup costs around $10,000 and gives reproducible numeric results that are more accurate than shooting a test chart. A good optical bench capable of measuring MTF across the entire lens costs 10 times as much.

An optical bench, though, has several advantages: it’s testing the lens at infinity, the variables of the camera are eliminated, and it provides greater accuracy.  On the other hand, most can only measure the lens at infinity. Sometimes you want to know how a lens does at 20 feet rather than at 250 feet."

I believe Popular Photography used to test all lense on a sophisticated optical bench, but maybe that equipment has become a little outdated by now, as I can't seem to find anywhere on their site where they brag about it anymore.

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