Grain is a word used in film photography to describe the fineness of detail a film or paper is capable of capturing.

Landscape photographers typically want the finest detail possible, which comes from fine grained films. Documentary photographers and journalists may need faster speeds (higher ISOs) and will compromise detail for speedier films that have more grain.

In digital, noise is the compromise we make for shooting faster ISOs, and the latest cameras biggest improvement is usually related to the detail maintained even at very high speed ISOs.

So, if detail is the desired result, why would we want to add grain and reduce detail in an image? There are three reasons I might add grain.

1. Focus fixer

First, if I’ve fouled, up I might use grain to fix it. I liked this photograph of Jane and Cody in the desert, but the sharpest focus is actually on a rock behind the couple, leaving them just a little soft.

This kind of thing drives me nuts! Im a snob about where sharpness falls in a picture. So I used the Grain adjustments to remove just enough detail that the difference in sharpness is unnoticed.

Slide the Amount to the right and adjust the Size and Roughness. I think you’ll find that more Roughness is better than less; when Roughness approaches 0 it begins to look distinctly digital and distracting. Having altered Size and Roughness, go back up to Amount and see if you can get away with less.

Heres another image where focus was way off, but Erin’s expression made the image worthwhile, so adding grain made the image more artsy.

The sharp focus is no longer distractingly inaccurate, and there’s the added bonus of a vintage look, which is the next reason to add grain.

2. The filmic look

Lets face it, shooting film is hip. One of the big allures of film is the classic look of the grain. Simply adding a bit of grain to an image helps remove the focus on technical perfection and emphasizes the composition and color and tones. Add grain, then sculpt it to perfection.

Come back an hour later and look at the image again with fresh eyes to see if it’s too much. If you’re like me, you’ll do too much at first. But with time you’ll refine a style to your grain use.

3. Reduce noise reduction

The third reason I add grain to an image is to ease noise reduction.

Noise reduction is a great boon, but it may leave my photograph looking something from Barbie doll world, with skin that’s just too smooth and everything looking like molded plastic. Adding a little grain back in makes the image more believable.

In this case, I’d be very gentle. This portrait was shot at ISO 25,600 on my old Nikon D700. It’s got all kinds of grid-like noise and color noise from the high ISO. Here you can see the original, the noise reduced version and the grain added version.

Grain has been a part of photography from the beginning, and it’s such a wonderful luxury to get to choose to use it as an effect and a fixer. Dive in and slide those sliders around — Grain is one tool you need to be ready to use.

This article is adapted from our book, “Develop Great Images Adobe Photoshop Lightroom” available on iBooks.