As many of you may know, RGB printers such as modern inkjet printers do not have a white ink and therefore cannot print a pure white. If you have an image that has pure white values (such as a blown out highlight), most printers will not lay down ink at that location and you will instead have just the paper white – which is likely not white at all. Depending on the image, this can result in prints that have a distracting transition from areas with ink and those without. So what to do when you have an image with the problem (and assuming you can’t go back to your Raw file to save those highlights)?
The answer is actually pretty straightforward. If you are using Photoshop, you can simply make a curve that slightly turns white into light gray. Here’s a sample one I used today:
Basically, you need to lock down the bulk of the curve and then just slightly pull down the white point. The curve will start out at a value of 255 and you may have to experiment to see what you need for your print. Usually pulling down the 255 value to somewhere between 245 and 250 will add just enough gray to your pure whites to differentiate those areas from the unprinted parts of the paper without making the whites appear muddy. I often run a test print or two to make sure I get to the right balance.
Brooks Jensen of Lenswork posted today about dealing with this issue in the offset printing realm and how they deal with the issue using Lightroom when preparing images to be printed in Lenswork.
If you have an images that has blown highlights, this simple technique can result in a subtle, but noticeable, improvement in print quality.
