Quote Originally Posted by HDNitehawk View Post
Another concept I have been mulling over, how many pixels are required to accurately read a line pair in any situation.
I am off looking for some a source talking about the lack of benefit of actual light hitting a digital sensor at wider than f/2 (don't know why, I really do have better things to do). But, I stumbled upon this article. I thought you might be interested in the following quote:

"lens sharpness (rather than sensor resolution) is often the weakest link when it comes to achievable resolution. 60 line pairs per millimeter is considered an exceptionally good lens resolution. D-SLR sensors have a typical pixel pitch of 4-6 µm, corresponding to 125-90 line pairs per millimeter."

This was taken under the header of "Having too many MPixels Really doesn't help"

But, in checking his math, it is an interesting and potentially simple way to go about the problem.

If I am following him correctly, if we assume 1:1 image transfer onto the sensor, so a macro lens, then 6 um * 90 = 540 um. Double this to get "line pairs" and you are at 1.08 mm. Working backwards, dividing 1 mm (or 1,000 um) by 12 um (pixel pair) = 83 pixel pairs per mm on the sensor. Go with the 4.1 um pixel pitch for the 7D II, you would get 1,000 um / 8.2 = 122 pixel pairs per mm.

So, if we assume 1:1 image transfer, lenses aren't coming close to sensors. But most lenses are ~0.2x. If I am thinking about that correctly, at the MFD, every 5 mm is projected onto 1 mm of the sensor. So, that 122 pixel pairs on the 7DII sensor could resolve 24.4 line pairs per mm with a 0.2 to 1 projection. From here, I think we also need to consider the whole Bayer filter issue, etc.

So with macro lenses, even current sensors are overkill (at MFD), but with standard lenses, there is benefit to higher MP. This is counter to what luminous landscapes' statement, but it seems right to me.