In my last post, I described a basic workflow for using Lightroom to produce black and white images from color originals. In general, the process is simple and problem-free, but there are two specific areas where problems have arisen and suggest some strategies for working with them.
The first problem is easy enough to explain, if you have a smooth gradient from one hue to another, such as the pink-to-purple-to-blue transition of an earth shadow, you may need to exercise restraint and caution with the Grayscale Mix controls. It’s fairly easy, particularly if you use large or very differing adjustment values for the different hues in the gradient, to end up with unnatural looking results. In most cases, this is easy to fix, once you actually notice it, by careful adjustment of the sliders, but occasionally it won’t be, and you’ll have to resort to other techniques (perhaps the gradient filter tool, or working the image with other tools in Photoshop) to realize your vision.
The second problem is noise. Sometimes strong adjustments to the Grayscale Mix sliders will really bring out noise in an image, I often run into this when darkening skies. Noise reduction can help here, but, there’s a catch…
A third problem is trickier, a longstanding issue in black and white conversions in Lightroom, as well as Adobe Camera Raw, is a set of artifacts that often crop up along edges of images you’d applied strong Grayscale Mix adjustment effects. Below, I’ve included a 100% crop of a detail along the top of the mountain from the example in my previous post.
If you look carefully along the horizon, you’ll notice a stairstep like artifact of whitish areas moving into the dark sky. These are not, as they might first appear, JPEG compression artifacts. Instead I’ve come to believe that they’re an artifact of the numerous image processing steps Lightroom is undertaking in an image, in this case, perhaps a combination not only of the Grayscale conversion but also noise reduction and perhaps sharpening. I’ve encountered these artifacts most often in working with images like this one, where I’ve made strong Grayscale mix adjustments, along the boundary between a darkened sky and ground.
The core culprit, unfortunately, appears to be color noise reduction. When I turn off color noise reduction on the same crop of the same image, and leave all the other settings intact,
As you can see, there are two significant differences between the images, first, the stairsteps are gone, second, we’ve picked up a noticeable amount of noise in the sky. There isn’t much red/green data in the blue sky, and once we’ve eliminated the blue component, we end up with a lot of noise. The use of strong Grayscale Mix adjustments makes that even worse. Add to that a need to eliminate color noise reduction, and even in an ISO 100 image from a modern DSLR like the Canon EOS 1Ds Mark III, and you get some tolerable but surprisingly large noise.
None of this is the end of the world, save for larger prints many of this artifacts are going to be minimal once they’ve “hit the paper.” Still, It’s my hope that future versions of Adobe’s raw processing engine will be better able to handle this situation.
In the meantime, keep an eye out for artifacts like this near strong edges, and when any artifacts make themselves appear, look at reducing the amount of noise reduction you use in the image (while keeping an eye on grain), it’s almost always possible to get a good result this way.