Check out this math-free visual explanation of light falloff
Sep 25, 2020
Dunja Djudjic
Dunja Djudjic is a multi-talented artist based in Novi Sad, Serbia. With 15 years of experience as a photographer, she specializes in capturing the beauty of nature, travel, and fine art. In addition to her photography, Dunja also expresses her creativity through writing, embroidery, and jewelry making.
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Light has many properties that we need to learn if we want to control it and improve our photography. One of them is light falloff: the property of light to become less and less bright the further it travels from its source. Most of us know this feature as the Inverse Square Law, and it involves quite a lot of math. Well, at least too much for my taste.
If like me you also don’t really like math, you’ll love this video from Adorama. Photographer Gavin Hoey will show you what light fall off looks like in the real world, and his demonstration is visual rather than mathematical.
So, how can you incorporate your knowledge of light falloff into your photography? Well, knowing how it works can help you set up a zone with very even lighting, or with very contrasty light. I love Gavin’s thought that “photography isn’t about formulas; it’s about actually seeing what’s happening.” So, he starts off with some visual tests to show you what light falloff looks like on his studio wall at different stops. Observe how the lighting changes as his model Fern moves closer to the light source.
After visually demonstrating the light falloff, Gavin moves to actually apply it to a shot. He sets up a large black and white umbrella with a speedlight inside of it, bouncing off the white surface. The knowledge of the light falloff lets him expose the model just the way he wants: her face is properly exposed, whereas her feet and the floor of his studio remain darker, creating a high-contrast, moody shot.
Make sure to check out Gavin’s video for the visual demonstration of light falloff, as well as for some lovely shots that he made using his knowledge of this concept. And I hope that it will help you connect an image with a mathematical formula.
[What Is Light Fall Off? | Take and Make Great Photography with Gavin Hoey | Adorama]
Dunja Djudjic
Dunja Djudjic is a multi-talented artist based in Novi Sad, Serbia. With 15 years of experience as a photographer, she specializes in capturing the beauty of nature, travel, and fine art. In addition to her photography, Dunja also expresses her creativity through writing, embroidery, and jewelry making.
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3 responses to “Check out this math-free visual explanation of light falloff”
Inverse square law (for light) = the farther you are from a light, the faster it gets dark
The inverse square law is the a constant, regardless of whether you’re talking about light, gravity or anything else that obeys it. There isn’t one specifically “for light”. :)
And, actually, the further away you get, the slower it gets darker. It falls off more quickly the closer you are to the source. You lose 2 stops going from 2ft to 4ft away (a difference of 2ft), but if you’re starting 20ft away from it, you need to be 40ft away to lose another 2 stops (a difference of 20ft).
As with any generalization, mine has limitations and shortcomings. I use the caveat (for light) because other point sources don’t emit light. Photographically, other applications of the inverse square law aren’t as useful. Yes, my simplification falls apart as distances become great. However, supplemental light sources are typically used within distances where the graph of 1/x^2 falls precipitously