Generally speaking, losing detail in your image is a bad thing. However, there is a creative way to do so that is most commonly employed in cinematography, known as "crushing the blacks." I alluded to this technique in my recent article on creating your first Photoshop actions and I received a number of queries about this technique. This article will give you a brief overview of what the effect is used for, why you would use it, and how.
What Is It and Why Would I Use It?
There are only really a few constants in elucidating this technique, and that is you're making the image flatter and you're altering the shadows. There's variations in how this process is performed and to what extent, but you will always lose detail in your shadows. This has many drawbacks and it certainly doesn't fit every image, but it can overcome obstacles and has worth in other areas too. For example, in cinematography it is often used to remove unwanted noise in the shadows; this applies to photography too. By removing the contrast in the shadows you're reducing the noise as well as the detail. This is a consideration of mine, but my primary motivation for using it when I choose to is that it can help your subject "pop" from the background. It is also part of, if not the entirety of, a look that has been popularized by Instagram, old film, and VSCO to name a few. Many of the filters and action sets that mimic any sort of film will crush the blacks to some degree or another. Let's get to some examples and how to use the technique in Photoshop (though this is achievable in Lightroom and other editing software). It is particularly effective in low-key images or images with a large dynamic range or high contrast.
How Do I Use It?
Although it depends on the image, I tend to crush the blacks in two different ways. The first, I create a curves adjustment layer, I click the shadow point in the bottom left and I change the values of the input and output to 15 each. This is the lighter and less invasive method. The alternative is a little more heavy-handed and I almost never leave the opacity at 100% when I employ it. You raise the shadows to whatever output value suits you; I tend to find 15 again to be in the right region. You then create a new point along the curve in the slightly brighter shadows and lower it, again until you find the look you're after. This is almost always then followed by raising the midtones back to their original state or marginally darker. It may be to some people's tastes as it is darker and moodier, but it rare fits my editing aims. Let's use a quick headshot I took of actor Joe Hughes as an example. Here's before any curves adjustment layers have been applied:
Here are the two different methods I use for crushing the blacks, side by side.
In this case I would (and did) opt for the lighter method and then almost always mask out the subject of the image. Whether I'm working on products or people, a loss of detail and contrast is unwanted. Here is a larger resolution version of before crushing the blacks and after.
The shadows in this image were not at all problematic because the original straight-out-of-camera file was well-lit, but even here you can see it removes some of the ugliness that hides in the darkest parts of images:
Crushing the blacks could be used for noise reduction in the shadows, stylistic purposes, or even to lower the detail of the shadows in horror films, but for me its greatest application is the separation it can offer between your subject and the background. Huge amounts of my work features this technique followed by the careful masking out of the subject and if performed correctly, it can add subtle pop to your images. This is prevalent in my product imagery in particular and below are some real-world examples, so to speak.
If you have any uses for this technique, or any additional comments, please leave them below.