Adventures in Lighting: Reflecting On Reflections: Keeping Your Shot Free of Unwanted Light Sources
I was reprising my “Lighting from Home Depot” lecture (on which I based my book A Shot in the Dark: A Creative DIY Guide to Digital Video Lighting on (Almost) No Budget) last week for Hollywood Shorts and one of the attendees asked me how to deal with reflections on set.
Direct reflection - problem
The diagram shows the camera placement relative to the glass
cabinet doors where the unwanted reflection of the lamp is seen.
Note that the angle of incidence of the lamp to the glass is 69
degrees, exactly the same as the angle of reflection, which is 69
degrees bouncing the reflection into the camera’s lens.
I floundered for a minute, trying to find the best way to answer her, but the variables involved in “reflections on set” are just too numerous to address generally. After a few questions back and forth, I understood what she was getting at and was able to give an effective response.
This month’s column is inspired by her question. I’ve I thought up a few tips to help shooters understand how best to deal with unwanted reflections—mostly from light sources—in their shot.
It’s part of the camera operator’s job to keep an eye out for “bogeys”—unwanted elements—in the shot, be they a crew member’s water bottle, an abandoned apple box or electrical cord, a roll of gaff tape, someone’s script pages (production crews are notoriously messy) or the silent—and often missed—shot-killer, a reflection of a light, equipment or even crew in the shot.
I’ve seen many inexperienced crew members scramble to solve a reflection problem, but, in truth, they aren’t hard to track down. Luckily, light follows a few set rules of physics. For instance, The angle of incidence is equal to the angle of reflectance.
Let’s use that law of physics to track down the source of the offending reflection. In order to do this, stand at the lens of the camera (if it’s a particularly stealthy reflecting offender, put your head right in front of the lens so that your eyes are level with it) and note the angle of your vision toward the reflection. If you walk in a straight line from the lens toward the reflective surface, the angle at which you arrive at the reflecting surface is the same angle as the source of the offending reflection, but in the opposite direction.
This process is sometimes easier if you have a laser pointer. From the lens position, point the laser at the reflection and wiggle it around a little. If your surface is reflective enough (or your laser is bright enough), you’ll find the laser point dancing on the offending source of the reflection like a red-faced tattletale. The laser method may not work well if you’re dealing with glass or reflective surfaces, where most of the light will pass through the surface instead of reflecting.
Definitely something to watch out for are compound reflections, when a light source is reflected from multiple surfaces. This can easily happen if you are shooting toward a corner and there are reflected surfaces on both sides of the corner—the light can actually be reflecting off of one surface into the other and then toward the camera. Keep in mind that the same laws of physics apply. Trace the path of the reflection based on the angle of incidence being equal to the angle of reflectance.
We’ve found the offender!
Now to solve the reflection.
Direct reflection - fix
In this case I moved the camera a mere 7.5” to the left,
which changed the camera’s angle relative to the glass door.
The lamp remains at at a 69 degree angle of incidence, but with
the camera in its new position, its angle to the glass is now 60
degrees and the reflection of the lamp misses the lens,
so it is not seen in the shot.
Sometimes this reflection comes from a light leak around the sides of a lighting fixture, either out of the ventilation holes or between the lens and the barndoors. This can generally be resolved by wrapping that side of the light source with a piece of black wrap, preventing the light spill from traveling toward the reflective surface. Be careful not to wrap the lamp too tightly. Nor do you want to wrap the whole lamp, especially if it’s an incandescent source—you may trap dangerous heat and damage the fixture or start a fire. Just use enough black wrap to cover the one side and the offending light leak. An alternative is to place a flag alongside the lamp to stop the light from hitting the reflective surface.
The reflection may come from the face of the light itself, in which case you can’t necessarily cover or flag the offending reflection because you’ll cut the light off of whatever it is lighting. If you can move the lighting fixture, that’s one of the best solutions; move it to a new location where the angle of incidence to the reflective surface does not end in an angle of reflectance to the lens. Sometimes this means moving the fixture as little as a couple of inches to one side.
Another alternative is to change the angle of reflectance by changing the angle of the reflective surface to the camera. If it’s a glass door that’s reflecting the light, for example, opening or closing the door slightly can eliminate the reflection, and you don’t have to move a single light.
I encountered this problem a few days ago while working on a small feature called Lot Lizard. The director wanted to shoot the front of a cafe with two actresses sitting on either side of the glass door. We had a direct reflection of the camera in the glass door and not enough grip hardware to black out the camera from view. I simply placed a block in the door to hold it open slightly—not enough to really be noticeable, just enough to keep the reflection of the camera out of the glass.
If the reflection is in the glass of a picture frame on the wall, sometimes wadding up a little ball of paper or gaff tape and placing it between the wall and a lower corner of the frame will tip the frame enough to eliminate the reflection but not enough to be noticeable to the camera.
The final and least desirable solution is to alter the reflective property of the surface with the offending reflection. You’re generally doing this by making the surface more diffuse, often with dulling spray or hair spray that “gunks up” the reflective surface and eliminates the specular nature of the reflection. This can make the reflective surface look odd, unnatural and unrealistic, however, so do this only as a last resort.