Reading resolution charts comparing MFT lenses to FX lenses

Started Mar 29, 2013 | Questions thread
Anders W Forum Pro • Posts: 21,468
Re: I did not express clearly, I think

RoelHendrickx wrote:

Anders W wrote:

RoelHendrickx wrote:

Great Bustard wrote:

Prairie Pal wrote:

I'm at photozone review website browsing through lenses for both FX and MFT.  I see that the highest resolving FX lenses can be near the 4000 lw/ph range.  The better MFT lenses rarely even get to 2300.  Is the difference between the 2 types of lenses relative?  Surely even the best MFT glass isn't inferior to FX.  I admit I can't technically explain what lw/ph is measureing, but to a certain extent I look at those graphs as a means of measuring one lens against another ie, when comparing the Sigma 35 1.4 to Nikon 35, or the various MFT primes between each other.

...and Anders will hopefully chime in so you can watch us argue about it. 

First of all, the resolution in the final photo, which is what PZ measures, is a function of many different factors:

  • Lens sharpness
  • Pixel count
  • Sensor size
  • AA filter
  • RAW conversion
  • Additional processing

In other words, you aren't looking at lens tests, you are looking at system tests (this is true for all other testing sites as well).

I thought the explanation by Chatokun was pretty clear (at least that made ME understand it).

And of course your opinion that lenses are not tested "in the void" but in front of a system's sensor, is also valid.

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?

This would "level the field" only if the sensor in question had near-infinite resolution so that the lenses using a smaller part of it wouldn't be disadvantaged compared to those using a larger part of it. Consider for example an FF-size sensor with 20 MP. An MFT lens would use only a quarter of it and thus 5 MP rather than 20. That would hardly help "levelling the field".

Another difficulty here is that you wouldn't only need the sensor and the adapters but the also be able to emulate the hardware/software of every body type out there. Pany and Oly MFT lenses can't focus, can't change the aperture, and can't keep the OIS lens group in place without electric/electronic support from the body.

* 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.

It should obviously be sufficiently big to accomodate the biggest image circle of any lens to be tested.

* More practical : don't all systems have roughly the same resolution sensors by now (and I mean SOMEWHERE in their lineup : for some systems that may be the top resolution sensor, while other systems may have such a sensor and others with higher MP count above it).  In other words : could we not all test all lenses from all systems on let's say a 12MP or a 14MP sensor?

Not really. For MFT, the top is 16 MP right now. Several recent APS-C cameras have 24 MP. And the highest-resolution FF camera has 36.

Yes, I know.

But what I was suggesting, was:

* use the current 16MP sensor for µFT

* use also a 16MP sensor (if need be, in an older camera model or in a "consumer" camera) for other brands.

It is at least possible to approximately "level the field" in that manner yes.

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