When shooting for monochrome, (greyscale or black & white) output using a digital camera, I recommended that you shoot in colour and convert the image in your imaging application.Before we explore this topic in detail, let’s have a look at how colour is interpreted as shades of grey.
As you can see, the picture no 2 taken in B/W mode on a Nikon D1 camera is more or less identical to picture no 3 which was converted to Greyscale in Photoshop. The B/W shot, taken with the camera has more depth to it, look how the Red crayon has a deeper tone and the Yellow crayon has more sparkle.
The real surprise for me was in picture no 4. I had always thought the Desaturate command was nothing more than desaturating the colours, but it has also altered the grey values, compare it to the Greyscale picture, particularly on the Yellow and Blue crayons. In most day to day work you might not be aware of a change in tone by using the Desaturate command, for extra precision I recommend you experiment with the Channel Mixer and master it.
Glass filters designed for use on film cameras will give identical results on a digital camera. Don’t worry if you forget to set the camera to B/W mode, you can always convert the image to greyscale and the grey tones will be identical.