Video production – Using a Neutral Density filter for outdoor shooting on bright days
With dSLR video you typically use a shutter speed of 1/50 or 1/60 second when recording. And if you are outside on a really bright and sunny day, you’ll have to use a low ISO and a small f-stop so that you don’t overexpose your video.
A small f-stop is one that is small in diameter, like f16 from the graphic below.
A large f-stop is large in diameter, like f2 or 2.8.
But here’s the problem: You want shallow depth of field!
Shallow depth of field is when the background of your shot is super out of focus, and many people like that effect because it looks kind of artsy. You see this effect a lot in TV shows and movies. Plus, if you use shallow depth of field, you can get cool bokeh effects. To get shallow depth of field you need to use a big wide open f-stop.
If you’re using a slow shutter speed like 1/60s on a bright sunny day, sometimes it’s impossible to use a wide open f-stop like f2.8 because there is just TOO much light around. So you need some way to get rid of the excess light.
Here’s a little background:
Hopefully you remember from your photography course that E = I x T.
Oh man, not math! Well this is really simple math and this formula will help you understand the relationship between f-stops and shutter speed.
Exposure = Intensity x Time
- Exposure is the total amount of light
- Intensity is f-stops, which is physical size of the lens opening
- Time is the shutter speed value, so how LONG the shutter stays open, and it’s measured in seconds or fractions of a second in most cases
So when the f-stop is big like f 2.8 your shutter speed in bright sun is usually pretty high, like 1/500 second or even faster! This is not a problem with still photos, but if you use a fast shutter speed in your videos they can get jumpy looking especially if your subject is moving.
Neutral Density filter to the rescue!
To use a video recommended shutter speed in combination with a wide open aperture (f-stop) you need to block out some of the light, and a neutral density filter will do that.
Watch this live demonstration of a variable neutral density (ND) in action. In the video I show you how the depth of field changes when you rotate the ND filter. It’s pretty cool to see so be sure to watch it right to the end.