Reflector Primer - The Photographer's Best DIYed Friend
do you really need one? The short answer is yes. The long answer is....
A reflector, as the name implies, is something that reflects light. In photography, is it usually a big sheet of something white, silver or gold, that bounces light at your subject (or at anything you want light on for that matter).
If you are not to particular about having your reflector look all nice and nifty are plenty of DIY options here, and basically any flat surface will do. Foam boards, bed sheets, aluminum covered plywood, did I say any big surface yet?
What Can I do With a Reflector?
While a reflector does not solve all the problems known to mankind, it is a versatile tool that can assist both in the studio and on location. At occasions it is easier to deal with a reflector than with an additional light source, especially if you wanna go guerrilla.
Reflectors are great as they "travel light" and need no power.
Dueling With The Sun
In this picture, we had harsh sun backlight. A golden reflector came in to the rescue for filling face shadows. This is a scenario where adding an extra light source can be kind of tricky, and a situation where a reflector shines (no pan intended).
The light coming from a reflector usually relates to the light source it reflects. This means that you usually have enough "power" bouncing off of it. No power tweaking is needed.
Reducing Shadows In A One-Light-Source Scenario
If you only have one light, a reflector can serve as a fill. And it takes on some of the qualities of an additional light source. By bouncing the flash back at your subject. In this case the light source is a big square softbox, and the reflector is a 5 in one disc with the white cover. This creates a nice diffused fill.
When we were doing the lighting modifiers cheat sheet we actually took each image twice, with a single light source and then with a huge foam board reflector. Here is a little comparison chart.
Size: As with any light source the size of the reflector in relations to the subject will be a significant contributor to the light quality. As a generalization, you can say, that the bigger the reflector, the softer the light it produces.
Color: The color of the reflector will impact two light attributes: light color and light softness. Lets starts with color, since it is the more trivial one. A white reflector will have almost no impact on the light. What goes in, bounces off and comes out. A gold reflector will warm up your tones, while a silver reflector will cool them down. There is a cheat sheet that shows all that stuff here.
Surprisingly the color will also have an impact on how hard or soft the light is. Light bouncing of a white reflector will behave as if the reflector is a second light source the size of the reflector (let's say it is a very shiny white for the sake of simplicity). This is because the light bounces in a very diffused way.
It may seem counter intuitive, but light bouncing of silver or golden reflectors will be harder. This is because the light behaves more like it is reflecting in a mirror. There is a very good explanation for this in Light: Science and Magic (a must read for any light oriented photographer).
Shape: this is the last of the factors that contributes to the quality of the light. some of the reflectors can be bent to focus or diffuse the light. This can help if you want to narrow or widen the light coming off the reflector. While this is possible with some of the reflectors, it is impossible to do with a foam board.
When Reflectors Are Not The Optimal Solution
This may sound trivial, but I thought it is worth mentioning, reflectors can only reflect, they are useless as a single light source.
Reflectors are also not very good when it comes to controlling spill. You can not mount a snoot or a grid on a reflector. and while you can opt for smaller and smaller reflectors, it is really easier to use a flash or strobe covered with snoot or grid.
Where Can I Get One And How Much Do They Cost?
The good news is that you probably already own a reflector. A white T can serve as a reflector, and so will a pillow cover or a white bed sheet, assuming you have a way to stretch and stabilize them. Cost here (assuming you have one of those items @home) is 0.
Next in line is the foam board. A foam board is basically a sheet of foam trapped between two sheets of paper. That gives the foam some sturdiness, and it feels kinda like plywood only weighs very little. You can get those pretty much any size you want. and they are very cheap. On the negative side is that they don't bend or roll for storage and travel.
Foam boards can also be coated with aluminum foil to create a 2-in-1 silver/white reflector.
If you have a car, you are probably familiar with the Sun shield. They come in both foldable and collapsible forms and are usually silver reflective. If you take the foldable type, make sure you get the bubbly kind. it will help reflect the light in a more diffused pattern.
For the "store bought"-unmodded equipment there is the standard 5-in-1 reflector (which along with foam boards is my favorite reflector). It is a collapsible disc with a coat. The coat has 5 colors: white, black, silver, translucent (which is more a diffuser) and gold. Those will cover any reflecting need and can easily be carried in a bag. This is one of my favorite items in the bag and I use it a lot on sunny days.
At the high end there is the California sun bounce line of products. Those are used by pros and "high end amateurs". They cost a nice arm and a leg but are very sturdy and fold really nice. I have never used one of those before. So I can only tell from the experience of others. If the price tag is too high for you, you can try a DIY version instead.