Q I like to scan in painted colour charts, to help me choose colours for my paintings. However I have noticed that the colours in scans are not particularly accurate when compared with the originals. How can I improve them?

A You can create a colour profile for a scanner, which OS X and its applications can then use to correct colours shown in scans.

However you will need to purchase scannable colour standards such as an IT 8.7 ‘target’ and profiling software, and even then scanning different paint surfaces may result in inaccuracies. Some third-party scanner software packages, such as SilverFast and VueScan, support profiling and application of generated profiles.

You may find it more useful to measure the colours in your charts using a handy spectrophotometer, such as X-Rite’s ColorMunki Design, as detailed here.

This allows you to get accurate RGB and L*a*b* estimates for paint patches, and to assemble them into patch libraries. You can use these figures to compare paints from different manufacturers, and even analyse the most common colours in images in your Photos or iPhoto library. ColorMunki can be used to calibrate your monitor and printer too, essential steps in handling colour accurately.

Updated from the original, which was first published in MacUser volume 30 issue 12, 2014.