cgardner
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 p.2 #8 · Could you folks post your Beauty Dish shots? | |
The unique qualities of dish lit shots are related to the design and the inverse-square law.
Moving a light very close to the face creates very rapid fall off and "steep" contrast gradients from nose to ears on the face. Centered above the slim symmetrical face of a model in a full face pose the combined effect is very dramatic because it frames the front "mask" of the face with shadows on the sides creating a "spotlight" effect on the front of the face.
But inverse-square fall-off and the placement of the light centered and overhead (a boom is needed for ideal placement) creates an exposure problem because the forehead winds up physically closer to the light and it's physically impossible to get the same exposure on forehead, eyes, moutn and chin at extreme close distances. Moved further away the relative distances of those body parts are more similar and the exposure more even.
If you tried that close-in centered strategy with a softbox you'd either get a blown out forehead or under exposed eyes. The physical design of a dish with a flat plate over the flash head solves that exposure dilemma by creating a dead spot in the middle of the light footprint. By aiming and feathering that darker center of the pattern on the closer forehead the overall exposure on the face by the lower half of the pattern is made even.
Because the design puts the flash unit behind and most of the output gets bounced back down into the dish before exiting forward it allows closer placement than a light with an umbrella would and produces more even lighting with a speedlioght's enclosed flash tube than just blasting it through the front of a sofbox.
But the "hole in the donut" lighting pattern disappears as the dish is moved further back. You can see this by aiming it at a wall starting from about a foot and then moving backwards. From around 8' it becomes a very diffuse source when used in a small space with reflective walls because so much "spill fill" gets bounced around the room a wide shot of the room will look like and overcast day.
I use that "spill fill" cause and effect to advantage by using my 22" Buff dish as my fill light back near the camera 8-9' from the subjects. I discovered the dish was a great fill source by accident. When I got mine I did a direct comparison between it and a SB with a 20" circle mask. Being lazy I just swapped the two as key and fill and noticed how much better the fill was from the disk, because so much more of the footrprint hit the ceiling and walls in my small space. That of course will vary with the space, height of ceiling, color of walls, etc.
I also noticed that because it was so small from 8' near the camera lens it created just a pin-dot of a second catchlight dead center in the pupil. That solved the problem of the distracting secondary catchlight that occurs when a large modifier is used as fill. They are impossible to retouch out of the eyes which is why fill gets move to the side. With the dish it just takes 2 seconds with a brush sampled from the black part of the pupil to removed the fill catchlight.
So I've been using my dish with diffusion sock primarily as my fill light, not for it's intended use. That's because I don't have occasion to shoot many models with slim, symmetrical faces in full face poses with a key light centered a foot or so from their face on a boom. But I'm ready if one shows up, rings the doorbell and the wife lets her in 
Like a ring light it was designed for a specific task but can be used for many other ones. From a distance it's footprint is larger than any other source the same size, such as a 22" umbrella or SB. As mentioned that can be an important factor in the overall holistic character of the light when used in a small reflective room. It's similar to the "wrap around fill" effect if skylight or boucing fill lights off the back wall of the studio, a strategy some portait shooters used in the 60's to get the flill lights out of the wall. Joe Zeltsman, photographer of that era who taught my mentor Zucker mounted his fill lights (a bank of flash heads with standard reflectors) on the studio ceiling that way to both get them out of the way and make the fill part of the exposure a constant that never changed.
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