Gain or ISO are integral parts of the exposure triangle. Learn what they do, and how they affect your video.
Gain or ISO is a crucial point in the exposure triangle. Light travels into your lens, through your aperture, and your shutter controls how long each frame of video is exposed to the incoming light. Gain or ISO boosts your sensors sensitivity to light. This can help you attain proper exposure when there’s not enough light hitting your sensor. The main drawback to increasing gain or iso is that it introduces unwanted noise and grain into your image. You will always get cleaner footage by having gain off, or iso at it’s lowest setting. Here’s our test shots using a 5D Mark III in a low light scenario. You can see that as we increase our ISO, the noise in the image also increases. Here’s a second test using the JVC hm600u. The smaller sensor does contribute to a noiser image, as yiou can see when we increase the gain. Okay, you know what gain and iso do, so let’s talk about the physical controls to manipulate them. Traditional camcorders will typically have a 3 position gain switch labeled L, M, and H. Accessing your menu system will allow you to choose how much gain each switch applies. The best practice is to set L to the lowest setting possible. This may be zero, or even a negative number. This will allow you to shoot without applying gain whenever possible. The M and H switch can be set to your preference. 6db of gain will effectively give you one full extra stop of exposure. However, many camcorders with smaller sensors will produce enough unwanted noise in the image to make it objectionable, even with a boost of just 3db. DSLRs use ISO to change the sensitivity of the sensor. The setting is typically accessed by pressing a dedicated ISO button on your camera, and using the dial to adjust it. doubling your iso will effectively increase your exposure by one full fstop. Unlike many camcorders, DSLR’s may produce acceptable results at a wide range of ISO settings. Each camera is different. in order to find out what iso or gain settings produce acceptable results, it’s important to real-world test footage with your camera, and examine the results to see what works. Using gain and ISO can help make a dimly lit scene manageable, but remember, adding more light to the scene can help minimize the use of it, and keep your footage relatively noise free, so don’t use it when you don’t have to.