veroman Offline Upload & Sell: On
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Photonic wrote:
Steve,
I am happy that you are enjoying the investment you made in your camera to remove the AA filter. It is clear that you find the images it now produces to be very pleasing to your eye. Others may agree. My concern is that your posts seem to suggest that you believe you have created a "better", higher resolution camera in so doing. All I can tell you is that there is no getting around Nyquist. If you don't properly low pass filter the optical path in front of the sensor then you will produce aliasing which represents false detail.
This said, not all low pass (AA) filters are created equally. It is impossible to make a perfect LPF and as with most engineering challenges you can trade performance for cost. I can imagine that the original filter on your camera was of the less expensive variety and perhaps used a lower cut off frequency to compensate for other non-ideal attributes. If that is the case it might make more sense to replace the AA filter with a better one rather than removing it completely.
Your post has motivated a good and useful conversation. I think that many will find the article linked by snapsy to be very informative on the entire subject of aliasing.
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I really don't think I've created a "better" t1i. What I've done is make the camera more applicable to my needs, i.e. it's closer to what I see in my larger, full frame cameras and can therefore substitute for them when I travel. The real acid test is when I actually use it on a long trip and see how it's done when I arrive back home. So far, the issue of false detail has yet to be seen as any kind of a serious problem, and moire has not shown up at all as far as I can see.
The snapsy article, I think, is overall a good one, but full of caveats and contradictions, particularly when the author qualifies his stance on the subject of false detail by saying things like, "Rarely will you see such obvious image contamination as on a resolution chart. In a real-world image, it may be much harder to spot what's 'real' and what's aliased 'fake' detail. To an untrained eye, a heavily aliased image might even look good." I mean, come one ... either he believes false detail in a still image makes for a poor image or he doesn't. It seems to me he hasn't made up his mind or is too insecure in his observations to stand firm on false detail.
Anyway, I will post images from time to time with my filter-free t1i, including those where the filter removal hurt an otherwise good shot.
Best,
Steve
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