A big difference between film and video is their ability to handle overexposure and underexposure. Film shooters tend to overexpose images as you can always pull the exposure down in post and make it look the way you want.
Video shooters are just the opposite. The rule is “protect your highlights”. And that’s where shooting video with a DSLR can make a huge difference.
One of the benefits of a DSLR is the low light capabilities. If you’re having to close the f-stop on the camera to handle a bright area in the frame a regular camcorder will likely lose all resolution in the darker areas. Things will just go black.
Open up the exposure to so you can see the detail in the low light areas and you blow out the white areas that are over lit.
Yes, you may want to work on your lighting to reduce this problem. And, if you’re working outside you’ll need good ND filters to cut the light hitting the lens to a manageable level.
The question is… how far down can you take it before you lose the shot?
Here’s a link to a set of tests showing the results of over and under exposing a standard test chart. The camera is a Panasonic DVX-100, a mid-level HD camcorder introduced a few years ago.
http://www.dancoplan.com/articles/exposing_video.html
The chart was shot with fairly even lighting and exposure was set using a waveform monitor to ensure the blacks and whites were at spec. Then the exposure was opened up 2 stops and closed down 2 stops. The results are easy to see and confirm the street wisdom – better to be under exposed than over.
While the test above shows still captured from a video and uses a Panasonic HD camcorder, this test shows actual video from a Canon 5D Mark II shooting a similar test chart.
Canon 5D Mark II – Over and Under Exposure Tests from Ben Cain / Negative Spaces on Vimeo.
While you can see most of the results here, I suggest going to Vimeo and downloading the video to view in full resolution on your computer to really see what’s going on.
The results are similar. At +2 stops the gray scale is totally blown out at the white end. At -2 stops the scale is pretty well gone at the black end. In other words, both the 5D and the DVX-100 give about 5 stops of exposure in the real world before the image is unusable.
To my eye the 5D held up better on overexposure than the DVX-100 so the street wisdom is not perfectly true. I’d still rather be on the low side if I have to choose one or the other.
Neither of these test are perfect – we don’t know how the cameras were setup and other technical details. The blog with information about the 5D test says that he dropped the saturation and contrast. Some people prefer taking it even further to a super flat setup. That would certainly affect the outcome of this test.
Ultimately, the only test that really matters is what happens with your camera, your lighting and your production. Hopefully, you’ll take some time to run a few tests for yourself to see what works for you. Here’s a simple test showing a Canon 7D working pretty well at -4 stops. Impressive.
Canon 7D latitude/exposure test from Seth Johnson on Vimeo.
