Fixing dark prints with a Darks-1 luminosity mask

I recently acquired a new Epson SureColor P800 printer. My old printer had started to leak from the print head. I primarily use Moab Lasal paper with a luster finish, so I went to the Moab website to find a color profile for the new printer/paper combination, and was pleased to find that one existed. I loaded it on my computer and did a test print. The color match to my monitor looked great. There was a problem, however. The print seemed dark and heavy overall because the shadows were blocked when viewed in ambient room light. Looking at the print under a brighter light source, I could still see the shadow separation that was apparent on my monitor, so it hadn’t been lost entirely. It just wasn’t printing well. I don’t normally view my prints under strong “gallery” lighting and want them to look good even in ordinary room light. So based on this initial test, I would need to find a consistent way to lighten them. The fact that there was NO color shift in the print meant that the profile I installed was doing a decent job in that important category. Brightness was the only thing that required adjustment.

I experimented with a few more prints that had Curves and Levels adjustments added to the sharpened image, but these ended up with obvious shifts in contrast and color saturation. I then decided to see if a luminosity mask could help. Since the image’s dark values were blocked, a Darks-series mask would be a good place to start. But how to use it? Curves and Levels adjustments hadn’t worked, so I needed an alternative for that also. In the end, I decided to still use an adjustment layer, but instead of adjusting the properties for the layer, I simply changed the layer’s blend mode to Screen, which lightens the image, except for pixels that are completely black.

Bingo! This approach worked well and next print looked much better. Here’s the steps I used:

1. Create a Darks-1 luminosity mask of the unsharpened image. (See NOTE at the end of this blog for methods to make a Darks-1 mask.)
2. Sharpen the image using the normal sharpening method.
3. Create a Levels (or Curves) adjustment layer at the top of the layer stack above the sharpening layer(s).
4. Set the adjustment layer’s blend mode to Screen.
5. Apply the Darks-1 luminosity mask created in Step 1 as a layer mask to the adjustment layer.
6. Lower the layer’s opacity to between 25 and 50 percent.

The image below shows the final layer stack with the print adjustment layer on top.

Not hard at all, and my image now matched my monitor in color, contrast, saturation, and brightness. In retrospect, this is sort of an obvious solution. The darks were blocked and Darks-series masks specifically targets these dark values. Screen blend mode is also a somewhat obvious choice since it provides an automatic, consistent lightening adjustment that keeps 100% black pixels 100% black, so there is a bit of a black anchor for the blackest blacks in the image. Screen blend mode also seems to lighten with less contrast and/or saturation shift that sometimes accompany adjustments to Curves and Levels using the Properties panel. So the overall effect was to create an automatic lightening effect restricted to just the dark, blocked tones in the image.

Subsequent tests showed that the optimal opacity of the added adjustment layer ranged from zero to 50 percent. It turns out that the value is easy to predict based on image’s histogram.

For images with prominent areas that are very dark or completely black, an opacity setting of 50% is needed.

For images where there is plenty of dark colors, but still excellent detail in these dark colors, an opacity of 25% works well. This histogram shape is common with many of my images, so an opacity setting of 25% is frequently my starting point when making test prints.

For images that are composed almost entirely of midtones and/or highlights with very few dark values, no adjustment is needed. There are essentially no dark values that are getting blocked in this situation, so the adjustment isn’t necessary.

While a custom profile might have been an alternative to consider, the fact that the colors were matching so well with the paper manufacturer’s profile meant that I wanted to continue to use it if I could. So far I’ve made prints of about a dozen different images using this method, and opacity settings of either 50% or 25%, depending on the histogram, have worked every time.

I’m not sure how widespread this problem might be. A member of the local camera club mentioned he had the same issue, so I’m sure I’m not the only one. It’s certainly an easy fix to try if your prints are looking too dark.

NOTE: A Darks-1 mask can be made and applied with either the TKActions V6 RapidMask2 module or the free Basic V6 panel. You can also make a Darks-1 layer mask using Photoshop’s Image > Apply Image… menu command using the settings shown below. Be sure to check the “Invert” checkbox in the dialog window to get a Darks-1 mask instead of a Lights-1 mask.