A hair light is a fantastic tool in portrait photography. But how do you know what it is, or when to use it? These are great questions that I'll address in this article, so read on!
What is a hair light and where do I put it?
A hair light is simply a light that is used to do exactly what it sounds like: light up the hair. A hair light is generally placed behind the model and about 3 feet above the head, with the light angled down and slightly forward to strike the top of the head and shoulders. It is common to see the light placed off to one side, but it can also be placed directly behind your model. Each placement will give a slightly different look to the photo.
Be aware that when using a hair light, because it is pointed in the general direction of the camera, the light from your hair light can travel to the lens and cause lens flare. To avoid this, you can simply block the extra light by taping a piece of cardboard to the top of the light to block it from reaching the lens. (You can buy a “snoot” or “barn doors” to attach to your hair light, but a piece of cardboard will work just as well and of course will cost a whole lot less!)
Another thing to watch out for is an overpowering hair light. The goal is to light the hair, not blow it out. You want to add interest and texture to your image. But if the hair light is too bright, you will succeed only in blowing out the area of the photo where the hair light is shining. This is particularly a problem for a blonde-haired model, as blonde hair is already very light-colored to begin with. Start by setting the power of your hair light to roughly the same power as your key light, and adjust as necessary. You want to create interest but not draw attention to the light.
Who should use a hair light and when should they use it?
Hair lights are great for studio portrait photographers. (Landscape photographers won't find any use for a hair light.) This doesn't mean you can ONLY use a hair light in a studio, but that is the most common place to see one. Any time you are photographing a person (even outdoors), a hair light can be a great addition to the photo.
A hair light is really important if you are shooting a model with dark hair against a dark background. It's very easy to lose the model in the background without a hair light. But even if you don't have a dark-haired model on a dark background, hair lights still make a big difference in the photo by adding interest and highlights to the model's hair.
However, when you add a hair light to the shot, you get a bit of a glow around the head that serves to separate the model from the backdrop. Additionally, you can see that Dustin's hair has a lot more definition, interest, and color now that we're using a hair light. And instead of being sucked in to the backdrop, Dustin is very clearly separated from it.
Try using a hair light next time you're taking some portraits. Experiment with the placement, source, and power of the light, and see what different results you get.