Some dumb questions I have been wondering about

Started Mar 28, 2013 | Discussions thread
Tom Axford Veteran Member • Posts: 4,157
Re: Some dumb questions I have been wondering about

Wellington100 wrote:

3) Why do most cameras have IQ reducing AA filters when the few cameras that don't have them jump in IQ and moire is nowhere to be seen in 99.99% of the images?

This is a big subject and there is no simple answer, but you can make a start by looking at the Wikipedia article on "aliasing".

A rather oversimplified answer is that if you omit the anti-aliasing (AA) filter from a camera, some of the extra resolution you obtain is illusory. Apart from the obvious problems of moire patterns (which are mathematically impossible to completely remove in post-processing), in any image taken without an AA filter, some of the finest detail will be false detail.

A simple example of this is than almost any straight line will show jaggies which were not there in the image produced by the lens - they are an artefact of the pixel array used both in the sensor and the resultant digital image.

For these reasons, most cameras still use AA filters. The non-AA cameras are really for those who put resolution as their very top priority and don't mind if the images are sometimes a slightly less accurate representation of reality.

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