Return of Interesting article on DxO about 5D III and D800...

Started Apr 10, 2013 | Discussions thread
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Just another Canon shooter
Just another Canon shooter Senior Member • Posts: 4,691
Re: Return of Interesting article on DxO about 5D III and D800...

cpkuntz wrote:

This isn't a half-bad introduction to the concept.

From Wikipedia:

http://en.wikipedia.org/wiki/Optical_resolution

Some optical sensors are designed to detect spatial differences in electromagnetic energy. These include photographic film, solid-state devices (CCD, CMOS detectors, and infrared detectors like PtSi and InSb), tube detectors (vidicon, plumbicon, and photomultiplier tubes used in night-vision devices), scanning detectors (mainly used for IR), pyroelectric detectors, and microbolometer detectors. The ability of such a detector to resolve those differences depends mostly on the size of the detecting elements.

Spatial resolution is typically expressed in line pairs per millimeter (lppmm), lines (of resolution, mostly for analog video), contrast vs. cycles/mm, or MTF (the modulus of OTF)). The MTF may be found by taking the two-dimensional Fourier transform of the spatial sampling function. Smaller pixels result in wider MTF curves and thus better detection of higher frequency energy.

I am not sure why my comment to this has disappeared.

This article explains how to measure resolution but not what it is. In an analog setting, things are clear - you measure the whole MTF curve, which determines the FT of the PSF, and then the PSF itself. Resolution is a function, not a number. On a sensor, this changes, which is the point John makes. You are pretending that you are measuring an analog signal but you are not. The discretization changes the nature of what you measure and even change of the angle of the slanted edge will change the result.

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