05-20-2011, 05:13 PM
[quote name='popo' timestamp='1305909208' post='8692']
In the case of bayer sensor, wouldn't the "strength" of AA filter be some two photosites of blur to allow for the sparse "chroma" detectors to work effectively. Foveon would need about one photosite strength. And before you go there, I know you can still extract some RGB info from all photosites, but let's say the "non-native" colour data is limited in value.
[/quote]
The AA-filter has NOTHING to do with what colour light is being captured right under it.
All the AA-filter ideally does, is make sure that the image is blurred enough, so that the resulting image does not have frequencies exceeding the sample frequency. In case of the sensors, the sampling frequency is related to the pixel pitch.
And that then is EXACTLY the same, for a foveon style sensor and a Bayer CFA style sensor.
Again, detail is in the luminance, not in the chrominance, There are no "gaps" in the luminance capturing with a Bayer CFA sensor.
Detail wise, no real difference, between foveon and Bayer CFA. But you can't compare them, because foveon doesn't put an AA-filter on it.
[quote name='popo' timestamp='1305909208' post='8692']
I'd consider moire in this case a manifestation of aliasing, so I wouldn't consider that a separate category, but more a subset.
[/quote]
Aliasing is you seeing edges where there are no edges, usually identified by "stair case" lines/edges. Moire patterns are the patterns that appear when sampling a higher frequency than the sensor can handle.
Both have to do with the arbitrary edges of each pixel, which do not necessarily correspond with the scene/projected image, but you can't call moire a kind of aliasing. Better is to say that it is CAUSED by aliasing.
[quote name='popo' timestamp='1305909208' post='8692']
Side note: when I converted the 300D to IR by removing the existing filter assembly, I didn't realise at the time I also removed the AA filter which was in the same module. I thought it looked sharper afterwards. Very rarely do I see something resembling moire or aliasing on it, although the longer wavelengths of IR do cause more diffraction blurring so may offset that itself.
I agree there, but that is the way of marketing.
[/quote]
Of course it looked sharper, sharp edges always look sharper. But the edges shown by the square pixels do not necessarily correspond to the edges in the scene... pixels only can have one value per pixel, no matter what gradations actually happen in the scene below that pixel. So... you feel you see more detail, but it is (almost always) false detail.
Preference is entirely personal.
In the case of bayer sensor, wouldn't the "strength" of AA filter be some two photosites of blur to allow for the sparse "chroma" detectors to work effectively. Foveon would need about one photosite strength. And before you go there, I know you can still extract some RGB info from all photosites, but let's say the "non-native" colour data is limited in value.
[/quote]
The AA-filter has NOTHING to do with what colour light is being captured right under it.
All the AA-filter ideally does, is make sure that the image is blurred enough, so that the resulting image does not have frequencies exceeding the sample frequency. In case of the sensors, the sampling frequency is related to the pixel pitch.
And that then is EXACTLY the same, for a foveon style sensor and a Bayer CFA style sensor.
Again, detail is in the luminance, not in the chrominance, There are no "gaps" in the luminance capturing with a Bayer CFA sensor.
Detail wise, no real difference, between foveon and Bayer CFA. But you can't compare them, because foveon doesn't put an AA-filter on it.
[quote name='popo' timestamp='1305909208' post='8692']
I'd consider moire in this case a manifestation of aliasing, so I wouldn't consider that a separate category, but more a subset.
[/quote]
Aliasing is you seeing edges where there are no edges, usually identified by "stair case" lines/edges. Moire patterns are the patterns that appear when sampling a higher frequency than the sensor can handle.
Both have to do with the arbitrary edges of each pixel, which do not necessarily correspond with the scene/projected image, but you can't call moire a kind of aliasing. Better is to say that it is CAUSED by aliasing.
[quote name='popo' timestamp='1305909208' post='8692']
Side note: when I converted the 300D to IR by removing the existing filter assembly, I didn't realise at the time I also removed the AA filter which was in the same module. I thought it looked sharper afterwards. Very rarely do I see something resembling moire or aliasing on it, although the longer wavelengths of IR do cause more diffraction blurring so may offset that itself.
I agree there, but that is the way of marketing.
[/quote]
Of course it looked sharper, sharp edges always look sharper. But the edges shown by the square pixels do not necessarily correspond to the edges in the scene... pixels only can have one value per pixel, no matter what gradations actually happen in the scene below that pixel. So... you feel you see more detail, but it is (almost always) false detail.
Preference is entirely personal.