Removing Moiré Effectively - Page 7
For the purposes of this demo, I’ve shown the copy of the original file on the left and the working file (now containing only luminance moiré) on the right. If you have a look at the “a” and “b” channels of the copy, you should see very obvious moiré. The "copy" is the duplicate you made in step four. Here are those two channels:
Examine both channels carefully. Which one contains a better representation of the moiré that you are seeing in the right hand window? (The right hand window contains the file with only luminance moiré.) In this particular example, the better choice is the “b” channel.
The “a” channel contains magenta/green color information. Since the Bayer pattern on our digital camera's sensor samples twice as many green pixels as blue or red, in my experience thus far, the “b” channel often contains superior moiré information since the channel represents the yellow/blue information. I wouldn’t doubt that different colored subjects will require a close analysis to determine the best channel. Having used this technique for nearly three years, I use the b channel probably 90% to 95% of the time, however have used other channels when the "b" channel was not sufficient.