Virtual Pathfinder video "How Much Oversampling is Acceptable?", produced 9 February 2020. Music by The Infinite Wave. This video is a calculation how much an image can be magnified for a telescope with a certain aperture, without apparent deterioration. The telescope resolution angle is calculated using Dawes' limit - this can also be calculated using the more conservative and more mathematically formal Rayleigh criterion, but the difference is small.
Using the angle of resolution, it is possible to determine the size of the smallest resolvable detail in the focal plane, which is where the sensor is. The optimal sampling is when the sensor pixel pitch is half the size of the smallest resolvable detail - which is where the optics and the sensor is matched.
If the focal length, or magnification, is increased from the optimal sampling focal length, then the image will be oversampled. The same data will be repeated over multiple pixels. That is no problem, until the repetition becomes large enough to be resolved by the human eye, from a certain viewing distance for a given image size. The eye cannot resolve more than 2 Megapixels for an image of the size 9 x 15 cm at about 30cm from the eyes.
At the optimal sampling, almost all pixels contain unique information, which is too small for the human eye to distinguish (unless zooming in).
0 Comments