Re: Creating notans from photos using photoshop
@Norma46 Possible alternative tool:
Depending on how the photos are saved and available: color, grayscale, stored in a digital image, a handy tool is the Firefox add-on called Foxfiltre. It can process local files and is primarilly designed for use with color. It can separate continuous colors into 8 or 64 colors, convert to shades of gray, add, delete or exchange colors. My Photoshop version is old but newer versions should be able to select tone ranges like in Gimp cutoff settings.