APC-S SENSOR VS FULL FRAME SENSOR IN TESTING PART II

Started Mar 5, 2013 | Discussions thread
qianp2k
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Re: that's a little too simple
In reply to Gearóid Ó Laoi, Garry Lee, Mar 8, 2013

Gearóid Ó Laoi, Garry Lee wrote:

carlk wrote:

You misunderstood it. The way DxO or other test sites phrased it does make it a little confusion. Lens intrinsic optical resolution CANNOT be changed when mounted on different cameras. It's just simple physics. What the difference you see on the final output comes from factors outside the lens. You might not get what the lens resolution coulc offer if the sensor can not resolve that much at the output size but the optics up to just before reaching the sensor will never change.

If it's resolution / mm then that's true. However, if you've a bigger sensor and the lens can cover that, even though the resolution /mm does not change, you may be able to see more detail.. as the number of mm is bigger..

http://forums.dpreview.com/forums/thread/3396841

Let me point to another thread above that is related to this discussion. There is no so-called sensor resolution. There is no so-called lens resolution. Neither one can take photos alone. DXOMark and all creditable test sites all test sensor+lens resolution. Yes the same sensor with different lenses or the same lens on different sensors (either different crop formats or different MP amount) result to different resolution.

The key part for one camp is to ignore crop factor or crop magnification (or enlargement). The reason why 60D/7D can use 100mm lens instead of a 160mm on 5D to shoot the same scene (the same AOV) is thru 1.6x more magnification that is equivalent to digital zooming. So all pixels are enlarged 1.6x bigger that inevitably will result to resolution loss and other penalties.  Although DXOMark didn’t use explicitly the term ‘crop factor’ in its article but that explains why 12.8mp 5D outresolves 18mp 7D with as good as lenses such as Sigma 35/1.4 and 100L.

DXOMark P-MPix is just another easier way to explain but comply to the same result as from its previous method by measuring into MTF data that converted to P-MPix by a secret formula that DXOMark will not reveal of cause but certainly not based on their subjective guess.

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