Available Light

In an earlier article, I advised that if you needed to use a flash, there were no good pictures to be taken anyway. I realize now that anyone who has spent time reading the wankier photo forums, especially those related to Leica cameras could have taken this the wrong way. To clarify, my statement was not meant as a dig against flash or an attempt to uphold the ideals of “available light photography”. If people want to gain a sense of nobility by shooting in crappy low light, that’s not my problem.

The point that I wanted to make was that using the flash well is hard, and you should know some things before you try. Used well, flash can provide you with that “natural light” look anywhere you can plug a light into a wall. Used poorly, artificial light will turn that $10,000 full frame 16 megapixel digital body you just bought into something that may as well be a point and shoot. The light you want in most photographs, especially photographs of people, usually has two basic characteristics:

1. It is relatively diffuse and low contrast.

2. It usually comes from the one side of the subject.

The first characteristic is desirable because it ensures that there will not be splotches of dark shadow or blown out highlights to distract you from the details of the picture. Everything will fit into the dynamic range of your film or digital capture. The second characteristic is desirable because light at an angle provides modeling and gives the subject a 3-d look, rather than the paper flat look you get with front lighting.

If you want to get an idea of what this kind of light looks like, sit your best friend down in front of a window on a bright cloudy day and take some pictures and take note of what the light is like. That is what you are after.

Alternatively, the next time you go to a movie or watch a well produced television show, pay attention to the lighting, especially in indoor scenes. Movies and television are almost always shot completely with artificial lights. But, motion picture photographers really know their lighting, so the characters always look as if they are lit by virtual windows strewn all over the set, even if there are no windows to be found.

At this point, we should be clear about one thing. Your fancy digital camera with its single dedicated flash is generally not going to get you this look. Without a handy window, the only way to get this look is to use multiple lights (to get the directional lighting) and a large array of devices like reflectors and bed sheets (to get the diffusion). This is too much for even the most dedicated amateur to carry around.

However, there are situations where your single flash can be useful, if you are careful.

If you are only carrying one flash, your dream situation is to be taking pictures in a small room with white walls and a short white ceiling. When you see this, you should jump for joy because it means you can bounce the flash into the walls and ceiling. What this means is that you pivot the flash to point either at the ceiling or a wall, rather than straight ahead at the subject. The result is that you get a nice diffuse light source (light coming off of the ceiling) rather than a tiny little point source flash. With most modern SLR cameras, bouncing the flash is easy because the exposure system of the camera will control the light for you. You just have to pivot the flash head to point up and shoot away. The difference between bounced and direct flash is immediately evident. Instead of flat white faces and lots of hard shadows, you get a nice flat overall light with diffuse shadows that go in the right direction.

You can also buy gadgets that attach to your flash that will try and bounce and redirect light in various ways. These can be helpful for those situations where the ceiling is a bit too high, but since they are in general not much larger than the flash, things like the Omnibounce or the various Lumiquest widgets can’t really add enough diffusion to get nice lighting. So, if you walk into that stadium, or ballroom with high ceilings and all you have is your one pathetic light, don’t even bother.

With some newer cameras, you can easily bounce the flash and bring it off the camera using the new-fangled wireless flash modes. Nikon and Canon both support this mode of use. What’s nice about this is that you are gaining diffusion by using the bounce, and also getting the light at a better angle by taking it off the camera. My personal camera, the Nikon D70, has a delicious mode where the built-in flash on the camera can wirelessly control one or more compatible flashguns. So if you were ambitious, you could even do some multi- light setups. I generally use the wireless mode just to bounce my one flash all over the place at weird angles.

Finally, no discussion of working with a single flash would be complete without talking about fill flash. FIll flash refers to blending flash with ambient light to lower the contrast on the subject when you are taking pictures in harsh and contrasty lighting conditions. Basically what this means is that rather than using the flash as the main light in your picture, you can program it to throw just a bit of extra light into the scene to open up shadows that would otherwise go to black. It turns out that with modern flashes, you can tell the flash to calculate how much light it would put out to light the subject, and then put out one or two stops less than that amount. You do this by setting the flash exposure compensation on the flash to (say) -2 stops.

Flash exposure compensation works just like the normal exposure compensation dial on the camera itself. If you dial it up, the flash puts out more light and tones in the picture get lighter. If you dial it down the camera puts out less light, and the tones get darker. The difference is that modern cameras and modern flashes can meter light from the flash separately from the ambient light from the scene. It is this magical technology that allows you to effortlessly mix flash and natural light. Dialing the flash compensation to -2 tells the flash to put out 2 stops less light than whatever the ambient light exposure is. The result will be just enough light to fill in the shadows of the picture without making the use of flash obvious.

For example, suppose you are taking pictures of your girlfriend at the beach. The sun is right overhead and she has a huge hat on, so her face is in shadow. If you just take the shot, you will take a great picture of the beach and the hat and a dark splotch where her face is supposed to be. Ideally you’d like to get a bit of light into that area under the hat so you can actually see her luminous face. If you were resourceful and had a big bag, you’d be carrying a reflector that you could use for this purpose. You’d just have to grab some beer guzzling beach guy to hold it for you. Of course, all you have is your puny flash. So, you get out your flash, set the flash exposure compensation to -2 and shoot a picture. Here is what happens:

1. The camera picks an exposure for the main subject based on the ambient light. This will expose the beach and the hat in a way that is pleasing.

2. The camera fires the flash. The flash bounces off your girlfriend and back to the camera. The camera computes how long the flash must be on in order for the light bouncing off your girlfriend and her hat to be two stops less than the exposure that it picked for the rest of the scene. Again, this is what the exposure compensation setting does for you. The -2 setting is telling the flash to make all the tones in the picture darker than it would normally. This is perfect, because all you want is for the flash to light up the shadows a bit, which are dark.

3. The combined light from the scene and the flash hits the film/ccd in the camera. The effect will be that the beach and the hat are well exposed, and your girlfriend’s face has just enough light on it to bring it into the dynamic range that the film can hold. But, since we told the flash to underexpose, it won’t look look like you have put a light on her face at all. In the picture, the shadow on your girlfriend will look like a normal shadow in real life: darker than the sunlit areas, but with detail. What you’ve done is use the flash to balance the contrast in the scene. This is something your eyes do automatically for you, but which the film or CCD in your camera does not know how to do.

To sum up, the trick to using a single flash wisely is to try and manipulate the situation so that the flash will look natural. Direct flash on a large group of people in a small room is not a great situation. Bounced flash in a small room with a small subject is a good situation. You will get pleasing light and no one looking at the picture will suspect a thing. Using the flash for fill is another perfect situation. Modern cameras and flashes are particularly good at automatic fill flash. In fact, that’s all the built-in flash in most cameras is really good for.

So, next time you find yourself with no available light except your puny flash, you’ll know what to try before giving up altogether.