Originally posted by devouges I did some reading about how a lens can limit the amount of pixels used in a sensor. Does any kind of information exist regarding pentax lenses and at how many pixels they will be optimal ?
Be aware that a lens' resolving power depends upon the f-number: The larger the f-number (the more the lens is stopped down), the lower the resolution.
For ideal, diffraction-limited lenses the relationship will be:
Resolution on sensor = 2.44 * (wavelength of light) * (f-number).
For example, the wavelength of yellow-green light is some 0,000555 milimeters and any lens at f/2 (f-number = 2) will at best be able just and barely to separate two points of an image formed on the sensor that are separated by 0.0027 mm. At f/4 the points will have to be separated by 0.0054 mm - which is just a bit above the pixel pitches that we see on APS-C sensors today.
Now, as said, this assumes ideal lenses, and no real lenses are only diffraction limited. Further, the two points must have an adequate difference in contrast for the sensor to detect that there is actually a difference. So, indirectly the sensor characteristics come into play as well. And there are more complications involved as well......
Although the following article in Luminous Landscape is nearly 6 years old, I believe (I am NOT an expert) that this is still an accurate description of the situation:
Do Sensors “Outresolve” Lenses?