Luminous Landscape Forum
Raw & Post Processing, Printing => Digital Image Processing => Topic started by: paulbk on February 12, 2007, 07:48:08 pm
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Can someone explain (or point me to) how anti aliasing filter works? I know what it does (see fyi below). I don’t know HOW it does it (physically). Is it some type of lens that defuses the light across multiple pixels to soften contrast transitions?
It seems that AA filtering should be done in software processing, not at the capture phase.
fyi, this is the function of an AA filter..... An AA filter is an optical assembly that fits in front of the sensor and behind the camera lens. It eliminates aliasing by lowering the high-frequency/high-contrast areas in an image that would normally exceed the sampling capability of the sensor and thereby reduces/limits the effect of moiré patterns, contrast jaggies (stair step), etc.
p
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Can someone explain (or point me to) how anti aliasing filter works? I know what it does (see fyi below). I don’t know HOW it does it (physically). Is it some type of lens that defuses the light across multiple pixels to soften contrast transitions?
It seems that AA filtering should be done in software processing, not at the capture phase.
fyi, this is the function of an AA filter..... An AA filter is an optical assembly that fits in front of the sensor and behind the camera lens. It eliminates aliasing by lowering the high-frequency/high-contrast areas in an image that would normally exceed the sampling capability of the sensor and thereby reduces/limits the effect of moiré patterns, contrast jaggies (stair step), etc.
p
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=100573\")
[a href=\"http://en.wikipedia.org/wiki/Anti-aliasing_filter]http://en.wikipedia.org/wiki/Anti-aliasing_filter[/url]
AA filtering cannot be done in software processing since it's impossible to seperate aliased features of the image from real features. About the only exception is color moire which because it forms a characteristic pattern can be removed or attenuated semi-automatically in many cases by some raw processors. However there are types of aliasing including maze patterns, luminance moire, and non-moire false color artifacts that either cannot be fixed or can be fixed only to a degree with time consuming manual procedures in PP.
George Deliz
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It seems that AA filtering should be done in software processing, not at the capture phase.[a href=\"index.php?act=findpost&pid=100573\"][{POST_SNAPBACK}][/a]
It can't be done in software. Software can not distinguish signals at frequencies below the nyquist from those above. They become indistinguishable in the capture.
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FYI I had the AA filter removed from my 5D by maxmax and am happy with the modification, sharper images better color. I had the 5D HR mod done which replaces the AA/bandpass filter with just a bandpass filter.
Marc