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As the creep up in resolution continues for digi cameras. Will
moire become more or less of a problem? As chips show more and more
fine detail will the point of moire just shift to other finer
detail.
Is there a res we need to pass when moire will be no more? if so what.
Just curi0ous,
Kevin
To correctly sample something you need to sample at a frequency
that is a minimum of 2 time to frequency of what you want to
sample. In the real world it will depend on the lens you use. So
you will stop to have moire when your resolution (sampling rate) is
twice better then the lens res. Evidently if there is not detail in
the target that is producing any moire you wont have moire before
that. Now that is before any AA filter is used on the sampling
device.
--
Gaetan J.
'when you assume something you make an ass out of u and me' B.Hill
--To correctly sample something you need to sample at a frequency
that is a minimum of 2 time to frequency of what you want to
sample. In the real world it will depend on the lens you use. So
you will stop to have moire when your resolution (sampling rate) is
twice better then the lens res. Evidently if there is not detail in
the target that is producing any moire you wont have moire before
that. Now that is before any AA filter is used on the sampling
device.
--
Gaetan J.
'when you assume something you make an ass out of u and me' B.Hill
--To correctly sample something you need to sample at a frequency
that is a minimum of 2 time to frequency of what you want to
sample. In the real world it will depend on the lens you use. So
you will stop to have moire when your resolution (sampling rate) is
twice better then the lens res. Evidently if there is not detail in
the target that is producing any moire you wont have moire before
that. Now that is before any AA filter is used on the sampling
device.
--
Gaetan J.
'when you assume something you make an ass out of u and me' B.Hill
Gaetan J.
'when you assume something you make an ass out of u and me' B.Hill
As the creep up in resolution continues for digi cameras. Will
moire become more or less of a problem? As chips show more and more
fine detail will the point of moire just shift to other finer
detail.
Is there a res we need to pass when moire will be no more? if so what.
Just curi0ous,
Kevin
wrong, moire is not caused by the "bayer" pattern. It is cause by a frequency sampling another frequency. The foveon chip will eliminate some chroma problem but not all since some is caused by the lens.The new Foveon chips should greatly reduce (but not completely
eliminate) moire problems, since they don't use Bayer pattern color
filters.
--however, you'll still get moire patterns when something you're
photographing has a grid pattern on it which interacts with the
grid pattern on your CCD.
I'm eager to see Foveon based cameras hit the market, and see how
they do in the real world. I'm not about to buy the upcoming Sigma
camera to satisfy my curiosity though. I don't like the idea of a
camera that only takes one vendor's lenses (Sigma's)
Duncan C.
----------
As the creep up in resolution continues for digi cameras. Will
moire become more or less of a problem? As chips show more and more
fine detail will the point of moire just shift to other finer
detail.
Is there a res we need to pass when moire will be no more? if so what.
Just curi0ous,
Kevin
Ok, but doesn't the bayer color filter pattern introduce a courser sampling frequency for each color, and thus more tendency to moire patterns?wrong, moire is not caused by the "bayer" pattern. It is cause by aThe new Foveon chips should greatly reduce (but not completely
eliminate) moire problems, since they don't use Bayer pattern color
filters.
frequency sampling another frequency. The foveon chip will
eliminate some chroma problem but not all since some is caused by
the lens.
I do not understand what you mean by courser and it's implication....Ok, but doesn't the bayer color filter pattern introduce a courserwrong, moire is not caused by the "bayer" pattern. It is cause by aThe new Foveon chips should greatly reduce (but not completely
eliminate) moire problems, since they don't use Bayer pattern color
filters.
frequency sampling another frequency. The foveon chip will
eliminate some chroma problem but not all since some is caused by
the lens.
sampling frequency for each color, and thus more tendency to moire
patterns?
this is interresstingDuncan C
Thanks for the input guys.--To correctly sample something you need to sample at a frequency
that is a minimum of 2 time to frequency of what you want to
sample. In the real world it will depend on the lens you use. So
you will stop to have moire when your resolution (sampling rate) is
twice better then the lens res. Evidently if there is not detail in
the target that is producing any moire you wont have moire before
that. Now that is before any AA filter is used on the sampling
device.
--
Gaetan J.
'when you assume something you make an ass out of u and me' B.Hill
Gaetan J.
'when you assume something you make an ass out of u and me' B.Hill
Thanks for the input guys.--To correctly sample something you need to sample at a frequency
that is a minimum of 2 time to frequency of what you want to
sample. In the real world it will depend on the lens you use. So
you will stop to have moire when your resolution (sampling rate) is
twice better then the lens res. Evidently if there is not detail in
the target that is producing any moire you wont have moire before
that. Now that is before any AA filter is used on the sampling
device.
--
Gaetan J.
'when you assume something you make an ass out of u and me' B.Hill
Gaetan J.
'when you assume something you make an ass out of u and me' B.Hill
One other question. When I scan a neg with ccd's why do I not get
moire then?
Kevin
The "moire" effect is an aliasing error caused by the sensor resolution being too low to capture the data in question.As the creep up in resolution continues for digi cameras. Will
moire become more or less of a problem? As chips show more and more
fine detail will the point of moire just shift to other finer
detail.
Is there a res we need to pass when moire will be no more? if so what.
Just curi0ous,
Kevin
This is not true. The moire effect is not caused by the Bayer pattern. The Bayer pattern does influence the exact appearance of the effect, but it doesn't cause it.Moire is mostly due to using the Bayer pattern in the ccd and the
drive to get the max resolving power (or sharpness). It will be
around as long as the Bayer pattern is used.
No, they're not. Increasing sensor resolution will make moire patterns go away, not get worse.Camera makers who
strive to get better resolving power are ultimately restricted by
moire and similar problems.
A lot of "consumer" cameras implement a significant "sharpening" phase in their post-processing, but this is independent of whatever anti-aliasing filter may be used.This is a common issue with consumer
cameras. The pro cameras go a different direction. Some use
anti-aliasing filters to reduce the effects. These filters
basically "fuzz" the image slightly to reduce the problem. Pro
cameras tend to go a bit softer in their images than consumer
cameras and assume the user will do what he wants in software (most
modern cameras now give the user some control in camera of the
sharpness, contrast, saturation, etc). Reducing moire means
slightly softer pictures.
The "moire" effect is an aliasing error caused by the sensorAs the creep up in resolution continues for digi cameras. Will
moire become more or less of a problem? As chips show more and more
fine detail will the point of moire just shift to other finer
detail.
Is there a res we need to pass when moire will be no more? if so what.
Just curi0ous,
Kevin
resolution being too low to capture the data in question.
As sensor resolution increases, it requires finer and finer detail
to produce a moire effect. So it will become less of a problem
with higher resolution cameras.
It doesn't go away completely until you reach the point that the
sensor resolution is higher than the image being resolved by your
lens. At that point, the lens will never produce enough detail to
generate the effect.
Other than increasing sensor resolution, the other solution is to
filter the image to reduce these aliasing errors, and in fact most
digital cameras do implement some kind of filter.
Mike Fulton
The "moire" effect is an aliasing error caused by the sensor
resolution being too low to capture the data in question.
As sensor resolution increases, it requires finer and finer detail
to produce a moire effect. So it will become less of a problem
with higher resolution cameras.
It doesn't go away completely until you reach the point that the
sensor resolution is higher than the image being resolved by your
lens. At that point, the lens will never produce enough detail to
generate the effect.
Other than increasing sensor resolution, the other solution is to
filter the image to reduce these aliasing errors, and in fact most
digital cameras do implement some kind of filter.
Mike Fulton
I agree in that the aliasing will kick in eventually whether the Bayer pattern is there or not but the Bayer pattern effectively decreases the color resolving power of the red and blue by a factor of two and the resolving power of the green by a square root of two. Thus the aliasing problems kick in much quicker due to the Bayer pattern than if there were an independent RGB measurement in each pixel. The unequal resolution of the colors also adds to the difficulty.This is not true. The moire effect is not caused by the BayerMoire is mostly due to using the Bayer pattern in the ccd and the
drive to get the max resolving power (or sharpness). It will be
around as long as the Bayer pattern is used.
pattern. The Bayer pattern does influence the exact appearance of
the effect, but it doesn't cause it.
A misunderstanding. The moire will always be and issue as long as there is detail in the image on the order of the size or smaller than the resolving power.Moire is what's known as an "aliasing" error. Basically, it means
that the signal being captured contained high frequency content
that could not be accurately be captured using the sample rate in
question. The difference between what COULD be captured, and what
should have been, produces this effect.
In an optical system, it means there was fine detail in the image
generated at the focal plane which could not be properly resolved
by the image sensor.
This is completely a question of sensor resolution. Is is NOT
dependent on what kind of image sensor is used. However, the exact
appearance of the error does depend on the type of sensor being
used. Bayer pattern sensors arguably produce the most
objectionable results because they generate false colors in
addition to creating wacky "random" patterns in the image.
Strictly speaking, the "correct" way to make this error go away is
to increase the sensor resolution. The more detail that the image
sensor captures, the higher the threshold for where the aliasing
errors occur.
Alternately, you can also tackle the problem by filtering the
image. Because the problem is that there is high frequency content
that cannot be recorded, the solution is to use a low-pass filter
to remove this portion of the signal before it's captured.
This is typically known as an "anti-aliasing" filter. In a digital
camera system, it is a mild optical diffusion filter that's
actually placed over the image sensor. This diffuses ultra-fine
detail before it reaches the sensor, removing the high frequency
content from the signal.
This works fairly well, but some people don't like this solution
because it can sometimes soften the image a little too much.
No, they're not. Increasing sensor resolution will make moireCamera makers who
strive to get better resolving power are ultimately restricted by
moire and similar problems.
patterns go away, not get worse.
A lot of "consumer" cameras implement a significant "sharpening"This is a common issue with consumer
cameras. The pro cameras go a different direction. Some use
anti-aliasing filters to reduce the effects. These filters
basically "fuzz" the image slightly to reduce the problem. Pro
cameras tend to go a bit softer in their images than consumer
cameras and assume the user will do what he wants in software (most
modern cameras now give the user some control in camera of the
sharpness, contrast, saturation, etc). Reducing moire means
slightly softer pictures.
phase in their post-processing, but this is independent of whatever
anti-aliasing filter may be used.
I agree that the anti-aliasing filters on some cameras are probably
a little too strong. However, if you use no filter, you greatly
increase the number of images where some aliasing error will be
visible.
Mike Fulton
