Many cameras and external monitors have built in tools to help you achieve proper exposure, and identify what is over or underexposed. Waveform displays, spotmeters, zebras, and false color are four of the most common.
All of these tools rely on IRE, which is a unit used to measure the luminance or brightness video. Using an IRE scale, 0 represents pure black, 100 represents pure white.
Let’s start with a waveform monitor. It’s easy to see how it works by using a greyscale ramp. The monitor measure the luminance of your pixels and displays the resulting ire from left to right.
The 0 at bottom of the scope represents full shadow or black, and the shadows and darker portions of your shot will hover around this area. Any underexposed areas of your shot that are below this line will be represented as black, without any detail.
The 100 at the top of the scope represents full brightness or white. Highlights in your clip will hover in this area, and any overexposed areas will typically become a flat line at the top. Any areas in your shot beyond 100 will be represented as pure white, without any detail.
The middle portion of the scope represents the mid-tones, ranging from black, to grey to white as the percentage increases.
Let’s take a look at an example shot using the waveform monitor as our guide
As we open up our iris, we can see that the waveform monitor shows us that the brightest areas are becoming overexposed. As we close our iris, we can see the blacks that begin getting crushed
Next we have a spotmeter. A spotmenter will measure the ire value of a given point in your shot.
You may be able to move the spotmeter around, or have to move the camera itself to get a reading. Placing the spotmeter over any area will tell you exactly how bright it is, as well as confirming over or underexposure if the value is 100 or 0.
Zebras have been a common function on professional camcorders for a long time, and are starting to make their way into some dslr cameras aimed at videographers.
Zebras will overlay stripes over areas of your shot that fall within a user specified ire range.
For example, if we set our zebras to display 100 ire and above, then we’ll know that
any areas in our shot that have the striped overlay is overexposed. Of course, the zebras are not recorded to your final output.
False color can assign different colors to different ire values. This allows you to see underexposure, overexposure, and even midtones all in one view.
in our example red is over 100 ire and overexposed resulting in pure white. The orange color is just below 100 ire and retains detail. Fuchsia is below 0, and any area displaying this color is underexposed and pure black, while the blues are just above it, and will still retain some detail. It’s a clear indication of what’s over and underexposed.
Using an exposure assist control can also help you get skin tones to look good. Many shooters use a value around 70% to get good exposure on caucasian skin tones.
It’s important to remember that our eyes are constantly trying to make our images look good to our brain. LCD monitors shouldn’t be relied upon for critical judgement of your exposure. So use whatever exposure assist tools you can, to ensure your footage looks exactly the way you want it.