Film grain and its uses

I describe a simple technique for applying film grain in my article on Digital Black and White. All you have to do is apply a layer of scanned film grain onto your image in Overlay mode. I still haven't discovered a better way to simulate film grain in digital processing; however, I have tweaked the technique slightly. The film grain layers I use nowadays have been adjusted to average out at 50% gray, which means they will not affect the tonality of the underlying image. I also use a few different versions for different uses; coarser for a grainy high-ISO look, and superfine for on-screen display only.

See below for samples of the grain fields I use nowadays. Feel free to download and do whatever you like with them.

Pastoral in Black and White. Minolta Dimage 7i, with Tri-X recipe applied in the channel mixer, and hit with a coarse grain field. I thought it made the distance look more interesting.

Adding grain to an image may seem like an affectation more than a serious photo processing tool. It can be that, although it is an affectation that can work quite well with the right kind of picture. However, grain also has some "legitimate" uses -- that is, situations in which adding grain will improve the overall look of the picture whether you actually like a grainy look or not.

The first such situation is using grain as a dither. When you do tone curve manipulations, smooth gradients such as the sky tend to develop posterization -- visible banding in the gradient from light to dark. An effective way to combat posterization is to add noise to the gradient you're manipulating. Grain is just a special kind of noise -- it's just somewhat more attractive than random or Gaussian noise you can add with Photoshop filters. So, if you have a banding problem, you might want to drop in a grain field in Overlay mode, and see if it makes things any better.

Faces. Sony DSC-V3 at ISO800, pushed a stop in post-processing and hit with the Portraesque curve, grain used to mask digital noise.

The second such situation is masking digital noise. Grain may be noise, but it's a nicer kind of noise than the chromatic stuff you get off a digital sensor. Simply overlaying a grain field on a high-ISO digital photo will usually make it look better. If you do the following procedure to reduce chromatic (color) noise on the picture first, the results are even better -- I get quite usable ISO800-1600 photos from my point-and-shoots this way, and have experimentally gone up to ISO12800 with my digital SLR:

1. Duplicate background layer.
2. Apply Smart Blur to the top layer, radius 25, threshold 25 (adjust these so that noise gets completely smoothed out, but outlines are preserved, more or less).
3. Set blend mode to Color on the top layer.

Grain fields, normalized to average out at 50% gray, at four different degrees of coarseness. To make your own, just clone enough of the grain field to cover your photo. I've saved the big grain fields in their own files to save time.