Thanks for your reply Gary. By 'digital filters' I mean it's a setting in the camera's menu that appears to add the chosen filter's colour to the image when it is proccesed, much like adding a stain. They aren't a physical filter of any sort so they wont modify the amount of each colour reaching the sensor as an optical filter does.

I think this means that selecting the red digital filter for example, just electronically adds the same amount of red to all the pixels whereas using a red optical filter in front of the lens would let a lot of red light from the scene through making red things in the mono conversion lighter but restrict the amount of blue making a blue sky appear darker. The 'digital' filter doesn't do that!

Must rip the plastic off this weeks AP and get reading, I've been looking forward to Angela's article (Haven't finished last week's mag yet though!)