Greyscale or RGB?

There is a mis-conception that, because black & white images contain no 'colour' that they should be saved as a Greyscale image, but there is nothing gained by doing so: what you're doing is effectively throwing away 2/3rds of the information in the image: changing it from red, green, blue to just grey. Most printers are designed to work with RGB - desktop printers use a number of coloured inks to produce black & white and our print lasers are RGB as well. A greyscale version of your digital image will often results in a poorer quality image with loss in subtle detail.

Black & White prints often include a hint of colour and the photographic masters such as Ansel Adams, used traditional photographic papers with characteristics that lent colour to the print. Classic papers such Kodak Royal Bromesko and Agfa Rapid Record were designed to enhance the colour of the print, rather than present a neutral hue.

full colour original

desaturated image

Full colour original

Desaturated image

To illustrate how a greyscale image reacts differently to a monochrome image in RGB we took an original full colour image and simply desaturated it, so retaining all the RGB information and file size.

screen shot

We adjusted the image using "Curves" to brighten the highlights and lift some shadow detail and then saved the action for reference.

greyscale

rgb with curve applied

Greyscale with curve adjustment applied

RGB with same curve applied

The original image was then converted to greyscale and the same tone curve adjustments were applied. You can see that the greyscale image now looks a little washed out by comparison: bear in mind your browser and monitor may affect how these subtle differences appear! OK, it might be possible to further adjust the greyscale to match the RGB version but when you send your file to be printed you might well get the same effect in your prints.

Once you've finished working on a print what are your print options? Printed on gloss or semi-matt photographic paper retains the same sparkle of traditional prints made through the enlarger. A giclee print offers you a wider range of papers in terms of Cotton Rag or Baryta art papers and the choice is more subjective. Some images look great on a flat cotton paper and we recently used this for a series of monochrome prints for one of our featured artists Glynn Griffiths. Harman's Baryta is a wonderful paper that gives prints are real glow and works equally well for monochrome or colour images: it's worth spending a little extra for the impact it brings. If budgets are tight and prints are to be framed behind glass, then a photographic-style paper may be your choice. Glass always adds and extra depth to the tones of a print: it's not just there to keep the dust off!

Alistair Baird

The Darkroom UK Ltd