Going back to the darkroom

This article was written by Rob Griffith and has been taken from the latest edition of the book 'Practical Colour Management' - available as an e-book or hardcopy from the Native Digital website.

Just when you thought it was safe to come into the light this article is going to suggest that as photographers you go back into the dark to do your processing. I’m going to suggest some basic guidelines for ambient lighting around a computer workstation used for image editing and also to suggest how you can take things further and create ideal colour viewing conditions.

Monitor Viewing

Computer monitors are of course a light source. Our visual system adapts to any light source by essentially doing an automatic white balance. What happens when you take a photograph of a scene with multiple colour temperature light sources? The camera tries to balance the scene as a whole or perhaps the dominant light source and this can result in some parts of the scene looking correct and others having a cast. The same can be true if you face your visual system with multiple light sources, for example a monitor, desk lamp and window. So a simple rule if you want to view images on your monitor is to make it the dominant light source and keep the ambient lighting to a minimum. It doesn’t have to be completely dark, but just a lot dimmer than a normal office environment. There are a couple of ISO standards that deal with viewing images on monitors ISO 3664 and ISO 12646 both recommend a light level of around 32 lux or lower, typical office lighting can be around 750 lux.

So, pull those blinds, turn off the over head lights and your desk lamp. As well as the level of the light you should think about the colour temperature of the light. If you are calibrating your monitor to 6500K it makes sense to have any ambient light you do have to approximately the same colour temperature, a cheap option may be to just have a daylight balance bulb, or you can get florescent tubes that conform to a lighting standards called D50 or D65 that conform to daylight conditions.

Also think about your wall colours. One reason to have dim ambient lighting is to minimize reflection from walls. If you do have lighting that conforms to a standard then keep in mind that as light bounces off a coloured wall it’s wavelengths change. You can go to the extreme of buying special neutral paint.

Lastly, if you can’t create a totally dim environment then a good monitor hood will lessen light falling directly on a monitor.

Print Viewing

One of the most common support calls I get is from customers who have bought a monitor or monitor calibration solution from us, and maybe used our custom profiling service to profile their inkjet but still when they put the print next to the monitor they see a difference. There are good biological and physical reasons for this. Firstly, as I said above your eye adapts to light sources so as you flick your eye from the print that’s lit by the ambient lighting to the image on screen lit by the monitor back light your eye is trying to adjust but not being given the time to do so. Secondly a monitor is an emissive light source and a print a reflective one so the qualities of light from each differ widely.

The only real way to get a good monitor to print match that has both images in your field of view at once is to buy a specialist viewing booth that has a known colour temperature and probably the ability to vary in intensity. That way monitor and viewing booth can both be adjusted and calibrated to match. Such systems will cost several hundred pounds. For most users a better option is to view print and monitor independently.

Daylight is the best viewing light for most customers. It’s free and is always spectrally even (i.e it contains a good spread of wavelengths). The best way to evaluate a print to monitor match is to view the print under daylight for several minutes. Then go and look at the monitor for several minutes. Letting your visual system adjust to each light source should mean you see a closer match than if you flicked your eyes from monitor to print.