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06-08-2011, 06:04 PM   #1
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Pixel pitch and lens resolution

I'm curious about the relationship between pixel size and the required resolving power of a lens to fully exploit a digital sensors resolution. For example, what is the resolution required (in LP/MM) to take full advantage of the sensor in the 645D, which I believe has a pixel pitch of approximately 6 microns?

Calling the resident physicist... are you there Leping?

06-09-2011, 09:29 AM   #2
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In order for the system MTF to equal the sensor MTF, you would need a resolving power of an infinite number of lines per mm (if the only two factors in your system are the optics and pixel pitch). Your question has no real answer. What problem are you trying to solve?
06-09-2011, 11:34 AM   #3
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Not a problem really, just trying to ascertain if there's a relatively simple way to pre-determine how well a lens will perform on a particular sensor.
The consensus seems to be that as the size of the pixels shrink, it places more demand on the lens, ie, a lens with greater resolving power is required to meet the potential of the sensor. If this is true, is there not a way to quantify the lp/mm performance of a lens on different sensors? For example, a sensor with a pixel pitch of 5 microns is more demanding than one with a pixel pitch of 8 microns is it not?
If I have a lens that resolves 70lp/mm is there an optimal pixel pitch?
06-09-2011, 12:01 PM   #5
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Unfortunately, it is not as simple as a lines per mm number. You would really need to have the MTF on the lens and then figure out the systemic MTF from there. Then the problem is not simply a pixel-pitch problem. The size of the sensor is a factor in that as well--a compact with a small sensor with a 5.9 micron pitch will need a much high-resolution lens than the 645D as the image is very much smaller. The good news is I wouldn't really worry about it. (You can't get resolving power data for lenses anyway.) I have found enough image samples on the web to figure out if the lens is good. But be careful, pixel peeping is not a good reference for the 645D as you are viewing the image in a condition that is far stricter then any it will be displayed in, either on the web or in print.

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