Автор: langel
Дата: 14-04-10 16:28
Serious studies on Foveon sensor capabilities report, that , even though their Spatial Sampling Frequency ( Pixel Spacing) is 127.53 pixels / mm , their EFFECTIVE resolution reaches 132 pixels PER MM , that is far above its Nyquist frequency (1/2*pixel spacing) , with no limiting Moire.
It is clear that for sensors with pixels smaller than 4 µm ,( High Spatial Sampling Frequency ),final image resolution is limited by lens quality more than by any other factor , excepting noise.
If a lens is "too good" ,having an extended MTF response beyond the sensor's Nyquist frequency , "aliasing" could be a problem , and the lens's sharpness might not be useable. Most DSLR with conventional Bayer sensors, have anti-aliasing filters for this purpose . But the reduced aliasing comes at the expense of resolution.
The Foveon sensor in the Sigma SDxx cameras has an unusually high MTF ( Contrast ) at its Nyquist frequency, yet it has no anti-aliasing filter. Any aliasing , if it happens , is usually unnoticeable , because it is monochrome, not color.
The clear conclusion is that If the lens is not good enough, it won't be able to take advantage of the potential resolution of the sensor.
NOTE :This point is very important . High spatial frequencies correspond to fine image detail. The more extended the response,the finer the detail ,the sharper the image.
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