How do you deal with reflections in glass, oven doors, car windows when filming video? Heck, sometimes you even see the camera? We’ll show you two main methods we use.
Discovering unforeseen issues on set is part of filmmaking and solving those problems can make or break your timeline and your shot. It makes sense when you think about it, we’re recording everything we see through the angle of our lens. And one problem, refections, can really compound it by showing us areas outside of that viewpoint.
A subscriber recently asked us how to deal with reflections in the glass window in their oven. They’re attempting to film a dish cooking and well, glass reflects.
Blocking Reflections
One way is to block the actual refection. We can do that with a flag or hanging some dark material which on a filmset is usually duvateen. Here I’ll hang the duve on a grip arm setup horizontally. I’ll twist the spring clamps back so they don’t reflect as well or paper tape them.
Hanging duvateen off a grip arm to block reflections in glass.
Now the trick is to figure where to place it. So that means, it's angle of incidence and angle of reflectance time.
It may sound complicated but it’s not. Basically, the direction a light hits a surface, it reflects off of it at the same angle. If you draw a line perpendicular to the surface at the point of the reflection, you’ll see how the angle stays the same.
Angle of Incidence equals Angle of Reflectance.
Now transfer that to a vertical reflective surface and see how that helps you determine what is causing the reflection or hot spot.
Now apply that to the reflection you're seeing in your shot to determine how to block it out.
So when you think about it, that’s pretty simple right. Yeah, if you and the reflecting surface are both vertical, at the same height and angle. But what if it’s tilted down or angled up? Well, all I can say now is good luck and welcome the wonderful world of filmmaking.
Sorry, there’s no easy answer. If you can figure out the angle in your head you can block it out. Otherwise, trial and error.
But what if there is no angle because you’re looking directly at the surface and you and the camera are reflected in it?
In that case, you need to black yourself out. Drape duvateen on either side of the camera or cut a hole in black showcard for just the lens to peep through.
Blacking out the camera when shooting straight into an oven door.
If the surface is shiny, and black is causing negative fill, use a white fabric or the white side of showcard. They do this in the still world all the time for closeups product shots.
Okay, these are great but a little bit of a pain. If only there was something a little easier? Well, there is, method #2. It’s magic, well science, but it doesn’t work in all situations and also comes with some trade-offs.
The Polarizing Filter
What does it do? I It blocks out polarized light? You see, light from the sun or a light source is unpolarized light, it’s a wave oscillating in a variety of directions. While polarized light is light vibrating in only one direction, on one plane. This can happen naturally when light is reflected off a non-metallic surface and can be more pronounced depending on the angle the light hits it.
Think of a polarizing filter as a series of very fine, parallel slits that only let in a wave of light oscillating in the direction of the slit. As you spin the polarizer, you spin the slit and therefore change which wave of light you’re letting in, or keeping out.
As you spin the polarizer filter on your lens, you spin the slit that allows in polarized light.
For even more detail, check out Eric Mickelsen’s video on polarized light, link below.
Just know that as you spin it, depending on the situation, it will block some light reflecting off a surface and therefore darken that surface.
Spinning the polarizer takes out most of the reflections on the picture frame glass but note how it affects the table top reflections in opposition to the picture frame glass.
Because a car windshield is curved, note how it doesn’t get all the reflections. I would need to choose which one to leave in, which is fine, as it’s part of the aesthetic of an angled car windshield.
Because of the curve of a car windshield, you probably won't get out all the reflections but that's okay, it's more realistic that way.
When we think of reflections we think glass and shiny surfaces. But pretty much everything reflects light, otherwise, we wouldn’t see it. This means using a polarizer can have an interesting effect on the contrast of your image.
Here’s blue sky, which is our atmosphere reflecting sunlight. Nice, but it’s also a bit bright. Twist the polarizer and I can use whatever level of darkening I want: a little or a lot.
Now the rule out there is a polarizer will only work on blue sky 90 degrees to the sun. Well, not really. Here I’m using it at 90 degrees to the sun, now 180. But I have to readjust the polarizer for each meaning panning the camera would not work. That’s one trade-off.
Using a Polarizer on Other Surfaces
Where else can we use it? Shiny green leaves reflect light. Get rid of the shine, we’ve now lowered the contrast of our shot by getting rid of those bright highlights.
This may sound crazy but asphalt also reflects light. Works as long as you’re at an angle to its surface. Sometimes, instead of getting rid of window reflections, it affects the contrast of what’s reflected in them.
Now the other trade-off, it eats up light, a stop or higher. Not much of a problem outside on a sunny day but inside.
So with an oven shot, we may need to shoot light into it through the glass door.
One other trick, not a reflection but a device that gives off polarized light, LED monitors. They have polarizing material in them to make them work.
Polarizers are not that expensive and a great tool to have in your kit but it can get costly if you have to buy one for every lens you have. At least get one to take it out and shoot tests. There’s really no right way to use them. It just gives you additional choices in how you manage what you see or don’t see in your shot.
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Eric Mickelsen Explains polarized light
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