On 3/17/2010 9:44 AM, Adam Maas wrote:
On Wed, Mar 17, 2010 at 12:31 PM, Mark Roberts<[email protected]> wrote:
Larry Colen wrote:
The luminous landscape article on the 645D touched on something that
I've been wondering about. Since it's always possible to throw away
information digitally, but not recover it, why isn't anti-aliasing done
in post processing if and when it's needed?
Anti-alias filtering, *by definition*, has to be done before sampling
takes place (which in the case of digital imaging is at the sensor).
Duh! Low pass filter. It's easy for me to understand in audio, but for
some reason in optical it's less intuitive.
One reason why you don't see AA on MF sensors is that you can do very
good moire reduction in a RAW converter (CaptureOne in particular is
excellent at this) while it's a lot more difficult to do on an ASIC
without the sheer horsepower of a PC.
I keep forgetting that "most" people use their camera as a computer and
process files in it, rather than using their camera as a camera and
their computer as a computer. Even so, I wouldn't think it would take a
lot of numerical horsepower to, when needed, smear the data from one
pixel into the surrounding ones as part of the Bayer conversion.
Also if you have enough pixels,
moire is less of an issue as it's related to the frequency of the
detail matching the sensor's pixel pitch, that's increasingly unlikely
with high-MP sensors.
I suspect that it has to do with the ratio of resolution of the lens
versus the resolution of the sensor. As such, with sensors that reach,
or exceed theoretical limits of the glass, the lenses probably act as
their own AA filters. In other words, I suspect that they are needed
less on a 1MP K20 than on a 6MP K100.
Another post processing question that's been niggling at me. Is there
any reason that a program like lightroom couldn't do binning, and turn
14MP K20 files into 7MP files with twice the dynamic range?
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