Sharpness/detail and anti-aliasing filter - why not get rid of all AA filters?

Armanius,

Antialiasing is somewhat complex, so I'll try to give you the simple version.

Basically, a sensor is trying to record an image with both low and high frequency spatial information. What I mean by high frequency is that the information has really fine detail, for example. If the sensor is recording part of an image that has higher detail than the sensor can really resolve, nasty things start to creap into that part of the image. That part of the image is undersampled. An AA filter is a low-pass filter for resolution. The stronger the AA filter, finer detail gets smoothly blurred out at the cost of losing maxiumum resolution. On the other hand, the weaker the AA filter, the greater the resolution, but the higher chance that artifacts such as Moire will creep in.

For example, weak AA filter:

Olympus E-PL1 Review: 7. Resolution Test: Digital Photography Review

Stronger AA filter:

Olympus E-P1 Review: 17. Photographic tests (RAW): Digital Photography Review

As you can see, the E-PL1 starts to show moire artifacts at around 2400 lph, but it has overall greater absolute resolution vs the E-P1. Looking at the E-P1, which has less overall absolute resolution, doesn't have the nasty moire as resolution increases. Instead, the lines smoothly blurr together.

 

Djarum, thanks for that explanation. I think it was the first time I really understand the advantages and tradeoffs of an anti-aliasing filter.

 

There are cameras that exclude the AA filter entirely. Leica X1 comes to mind.

 

Then there's the film option.... 

 

I haven't seen images from that camera specifically, but I wouldn't take pictures of anyone wearing certain ties or shirts that would give a moire effect. It's all about balance. I think the E-PL1, for example, gives a good balance.

 

Well, then we can get into under sampling because of the lenses. But yes, if the lens is up to it, removing the AA on higher megapixel cameras would be the way to go.