Moire Issues

[David Fairbanks]

I know some of the first images were very raw, that might include no LPf.

[Johan Lindgren]

http://www.dvxuser.com/V6/showpost.p...6&postcount=33

Jarred saidd they were testing with IR and lo pass filters back in the dvxuser forum

Johlan

[Brook Willard]

Good find.

[Anders Holck]

BTW. here is a great example of Moiré vs Low pass filter
http://www.dpreview.com/reviews/kodakslrc/page22.asp
The Kodak on the left clearly resolves more detail (note that it also has a 2.5 MP advantage) but that moiré is pretty annoying.

[createra]

There is some issues with the hair in the Bubblegirl clip. But it's also mentioned that it's shot without a low pass filter.

[Stephen Williams]

Hi,

If you can turn off any sharpening (Red does not have any) you should not have big issues.

Remember the project is 'work in progress', I have not seen any problems with images so far.

Stephen

[Nick Shaw]

BTW. here is a great example of Moiré vs Low pass filter
http://www.dpreview.com/reviews/kodakslrc/page22.asp
The Kodak on the left clearly resolves more detail (note that it also has a 2.5 MP advantage) but that moiré is pretty annoying.

Is the colour artifacting you can see on the Kodak images moiré or bad de-Bayering artifacts? Moiré should not affect the colour, should it?

Nick

[David Fairbanks]

My experience is that it has nothing to do with sharpening. It's just the interference of the two patterns.

The images they have produced have been amazing, and it is a work in progress, so time will tell.

[Graeme Nattress]

Moire is visible aliassing. Being a sampled system, the sensor will exhibit aliassing on images if it is asked to record detail smaller than 1 pixel in dimension.

The above, is applicable to all sensors, including 3 chip systems, RGB silicon filter sensors etc. That's why all sampled systems need an anti-alias filter, which in a camera is called an OLPF or optical low-pass filter. The name tells you what it does. It passes though, or leave un-effected low frequencies, and attenuates high frequencies. We want to make sure than the sensor isn't asked to sample any frequencies or details so high that they would introduce aliassing.

With a bayer pattern CFA, this is even more important because moire on a bayer pattern sensor shows up as colour moire as well as luma moire. Colour moire, as shown above is quite nasty.

Now when we did our first mysterium shots, our OLPF had not arrived, so we just shot things as it, and I used a demosaic that was designed to be gentle on the eyes and remove some of the moire that could occur. It can't get everything, but was a good solution.

Now we have an OLPF in place, and we can be more free with our choice of demosaic. We don't get nasty colour moire on edges, and the slight softening makes for a very smooth, continous image, with no visible pixels or aliassing.

Aliassing makes it harder to suspend disbelief as we don't see aliassing in the real world. (we do see moire when two fine patterns are overlayed though). We don't see fine detail having steppy edges or being made of discrete pixels.

Excessive edge sharpness is know to cause judder in slow fps recording - think 24p.

Because in motion, aliassing changes on each frame, it's more noticible than on a still as it's almost as if the pixels are waving at you saying "look at me". On a still image, if there's a bit of moire, you can paint it out. On a movie, that would be terrible!

Graeme

[GlennChan]

Aliassing makes it harder to suspend disbelief as we don't see aliassing in the real world.
We do see aliasing on stuff that moves (although motion blur tends to act as a low pass filter). But other than that, for stationary stuff, we see incredibly low/no aliasing.

We also seem to get less aliasing in dim conditions. You can test this out by printing out a zone plate test pattern and holding it in your hands and moving it around. You can get one off here: (scroll down)
http://www.ecinemasys.com/products/e...lcd_vs_crt.htm

Or
http://www.worldserver.com/turk/opensource/#ZonePlate