NOTE: Like many of the the other posts in this blog, this one makes use of the concepts and terms discussed in the Luminosity Masks tutorial on my website.
Part 2 of this series looked at image sharpening using luminosity masks. Specifically, it discussed how a Darks-series mask can help eliminate light halos that result from enhanced edge contrast that occurs during the sharpening process. The Darks-series mask also allows the “dark halos” from the sharpening process to remain and thereby impart an appropriate amount of sharpness to the image.
The concept of selecting the image’s darker tones for sharpening can also be applied to improving detail in an image before sharpening. There are several ways this can be done in Photoshop, but the method below uses adjustment layers (instead of pixel-containing layers), so that the overall increase in file size is kept to a minimum. It’s also somewhat paradoxical in that it uses blur to increase sharpness.
Here’s are the steps:
- Create a Dark Darks luminosity selection.
- With the selection active, create an unadjusted adjustment layer (Curves, for example), with the selection in place as the layer mask on the adjustment layer.
- Duplicate the adjustment layer so that there are now two identical adjustment layers with the Dark Darks mask as the layer mask.
- Set the blending mode of the bottom adjustment layer to Multiply. This will darken the image.
- Set the blending mode of the top adjustment layer to Screen. This will reverse the darkening in Step 4.
- Click on the layer mask of the top adjustment layer (the one set to Screen blending mode) so that the framing brackets are around it.
- Invoke the menu command Filter > Blur > Gaussian Blur… and set the blur radius to 15.
- Put the two new adjustment layers into their own group.
- Adjust the opacity of the group to dial in the amount of detail enhancement desired for the image.
A Photoshop action to do these steps can be downloaded here.
This is it what it looks on the Layers panel when it’s finished.
Below is an image where the Detailed Darks group was employed and set at 50% opacity. Rolling the mouse over the image shows how it would look without the Detailed Darks group being used to enhance detail in the darker tones. (It may take a few seconds for the rollover image to appear.) Although this is a small jpeg, the improved detail is already apparent at this size. It’s subtle, with the luminosity masks blending the effect so well that it’s hard to say exactly what is producing it. And even though the effect is concentrated primarily in the darker tones because of the Dark Darks mask that was used, the entire image, including the lighter tones, seems to have benefited.
What’s happening here is that the two adjustment layers are working together to create sharpening edges throughout and around the darker tones in the image. The Multiply blending mode layer essentially creates a dark halo throughout the Dark Darks selection. The blurred mask on the Screen blending mode layer lightens the dark halo from the Multiply blending mode layer considerably (but not entirely), AND it also lightens the pixels now included in the mask’s selection because of the blur that was applied to the mask. These newly included pixels are on the opposite or lighter side of the Dark Darks selection edges, and Screen blending mode layer lightens these pixels. This creates a situation where pixel-darkening from the un-blurred mask layer is adjacent to pixel-lightening from the blurred mask layer, and this is essentially a working definition of how Photoshop sharpens an image by increasing contrast at the edges. The combination of blurred and un-blurred luminosity masks provides a nicely feathered and graduated sharpening-like effect that is restricted to the tones selected by the layer masks. In an image, this is perceived as improved detail. For a “normal” image it will look like a very sharp lens was used to take the picture. In an image with with slightly blurry areas caused by lack of depth-of-field or imprecise focus, it can actually help reduce the blurriness to some degree.
There are potentially many variations on the ways this technique could be applied to an image: different opacity settings for the group layer, different luminosity masks for the adjustment layers, and restricted application using a mask on the group layer are some possibilities. Interestingly, substituting a Light-series mask (Light Lights instead of Dark Darks, for example), does not sharpen the light tones; it blurs them. This leads to some thoughts on ways to enhance the light tones, and the final installment in this series will provide an example of using luminosity masks to give special attention to the lighter end of the tonal spectrum.