Following on from my previous blog post Enlightenment and after spending a bit of time this weekend reading Adobe Photoshop for Photographers by Martin Evening, a book so big that I seldom find the courage to pick it up let alone read, I discovered that Photoshop can automate the RGB levels procedure that I described in my previous post. Essentially by using the Auto Option feature in a levels panel, any scan can be colour corrected by 'Enhance per Channel Contrast' in effect aligning the dark and light point of the red, green and blue channels to the scans histogram. The start point is set by default very low to the first 0.10% of each of the channels colour clipping but can set to whatever tolerance you prefer. Thereafter the scan only requires mid grey identification, you can do this yourself or use Photoshop by checking Snap Neutral Midtones it can find the most neutral tone or mid grey and allow for it. In addition, the Auto Colour Correction Options panel offers an alternative automated method 'Find Dark and Light Colours' using this method Photoshop will find blackest and whitest points on any scan, again set to 0.10% but adjustable if you prefer. From there simply identify mid grey by checking Snap Neutral Midtones. Both methods work well and it's very quick and easy to see which is the most suitable starting point for any given scan. Below is a short screen video that shows the process.
