Five Ways To Avoid Overexposing Your ShotsMonday, November 27, 2017
You've just had a great day of shooting. The actors were great, and you had some great setups. Then you get back home to review the footage and everything is shrouded in a white glow--your green trees look like they're covered in snow, and there's an empty white spot where your actor's ear was.
You've overexposed your shots!
An overexposed shot means that too much light has hit the camera sensor, making your image very washed out. To properly expose an image, your camera's sensor needs to view it with the right amount of light, at the right amount of sensitivity, for the right amount of time. Push any one of these three things in the wrong direction and you risk overexposing the image.
While there are some means to recover a slightly overexposed digital image in post-production, they're not ideal, and many don't end up looking very natural. And if the image is more than slightly overexposed, most digital camera sensors interpret that as pure white. So too much light on your actor's ear will result in the sensor recording that as a white blob, and no amount of post-production magic will ever be able to fix it.
There are very few cameras that do well with overexposed images, so it's almost always better to get it right during the shoot itself. There are a multitude of ways to go about avoiding overexposure--we've given you five ways to get you started, along with some basic scenarios in which you might use them.
1. Lower your camera's ISO
The ISO is your camera's sensitivity to light. ISO ranges vary from camera to camera, but generally run from about ISO 200 up to ISO 12800. The higher the number, the more sensitive your camera will be to the light. In low light situations, you'll want to have a higher ISO to make your camera's sensor more sensitive to the light, whereas outdoors in direct sunlight you'll want to be shooting at a lower ISO.
If your whole image is overexposed, this is may be the easiest and most practical fix. However, if this particular scene isn't evenly lit, you may need a different solution. For example, if you're using window light to shoot a scene and the light is brighter on one side of the actor's face, lowering the ISO may help fix the overexposed portion, but make the rest of the scene too dark. In this case, you may need to also bring in some additional fill lights (see #4 below).
2. Stop down your lens
If you look at your camera lens like the a human eye, the the lens aperture would be the pupil. Similar to the way your pupil dilates larger and smaller to let in more or less light, the aperture's blades make the opening of the lens larger or smaller to do the same thing. The size of your lens aperture is measured in f-numbers, or "stops." The smaller the number, the more open the aperture is, allowing more light to come in. To "stop down" means to adjust the aperture to a larger f-stop setting, letting less light come in. For example, if your aperture is set to an f-2.8 and the shot is overexposed, you could try "stopping down" to an f-5.6 to allow less light to enter the camera lens.
Like changing the ISO, this is a relatively simple adjustment to make within your camera. However, this method could also have some unintended consequences. In addition to controlling how much light comes in to the lens, the aperture also controls the depth of field (DOF) of your camera. DOF is a measure of how much of your shot will be in focus. A lower f-stop will give you a much shallow depth of field where only a portion of the shot is in focus, while the higher f-stops will keep your whole background in crisp focus.
Cinematographers often use a shallow DOF to make sure the focus of a shot is kept in one area. Shallow DOF also produces that beautiful "cinematic" blurred background that you may be looking for in a particular shot. You may lose that shallow DOF if you need to stop down your aperture to correct overexposure, so you'll want to carefully consider that before choosing this method.
3. Use an ND filter
Sometimes you may need a shallow DOF, but you're already shooting a low ISO and the shot is still overexposed. In this case, a neutral density filter, or ND filter, may be exactly what you need. An ND filter reduces the intensity of all wavelengths of light equally, resulting in less light entering the lens without changing the hue of the colors. It's the equivalent of "stopping down" several f-stops but you're able to keep the shallow DOF that you need for the shot.
ND filters typically screw right on to the camera lens. A basic ND filter is very inexpensive, and should be a part of every cinematographer's camera bag. The only real downside to using an ND filter is that it will also darken the image seen in your camera's viewfinder. This may not be an issue for you, and if you're using an external video monitor when you shoot, you can easily adjust the monitor to compensate for the darker image.
4. Add more light
Shooting with uneven lighting (such as our window light example above) can cause a special set of problems. The same thing goes if you're using practical lights mixed in with your film lights--for example, if you're shooting a dinner scene with candles and floor lamps in the shot. It can be tricky to keep the right balance of exposures for all of these multiple light sources--you usually need enough ambient light to keep the detail in the darker portions, but this often means overexposing the brighter light sources.
The solution is to actually add more lights. You need to add enough fill light to bring the darker portions of your scene up to an exposure that works for you, without having to change the ISO and overexpose the other light sources.
The easiest way to do this--start with the light sources that you can't change, like your practical lights. Set your ISO at a level that properly exposes these lights first. In our example photos, the top image is exposed solely for the candles. The other parts of your scene may be too dark but this is OK--use your fill lights to bring up the ambient light level of those dark parts to a level that works for the rest of your scene. In the bottom example photo, they've used fill lights to bring up the ambient light level to a good exposure, while still keeping the nice glow of the candles at their proper exposure level.
Professional DPs use this technique every day to get scenes with multiple light sources to look natural. This is where it comes in handy to have a great light kit. Even if you can't pony up for pro-level lights, there are many DIY options out there that will at the very least give you a more natural and properly exposed look.
5. Take away the light
Can't add more lights? Try taking some light away. Oftentimes outdoor scenes are partially overexposed due to direct sunlight hitting parts of the scene and not others. If possible, try to move your scene to somewhere where you won't be in direct sunlight. Or (if your shooting schedule allows it) shoot on a cloudy day, where there's plenty of light, but not the hard, harsh light of direct sunlight.
Other options involve flagging, filtering, or softening the light. If you have a hot spot of overexposed light, use a black fabric flag off camera to block that light from hitting that spot in your scene. If you're shooting something like our window light scene above where you can't flag the light source off completely (in this case we want the window light coming in, but need it to be less intense), then you have a couple of other options. You can use a neutral density gel, or ND gel, on the window. An ND gel is a thin sheet of plastic that works similar to an ND filter. You can cut your ND gel to cover the outside of the window, which gives you the same effect of "stopping down" a few f-stops to cut down on the light coming in through the window. Another option is to use "rip stop" fabric to soften and dampen the light. Rip stop is the same sort of fabric used in professional light softboxes. It not only lowers the level of the light, but also creates a very soft, diffused look. Rip stop should be available at most fabric or craft stores, but an opaque shower curtain could give a similar effect if you can't find the rip stop.
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