Understanding the Beauty Dish


The Beauty Dish (BD) is a favorite tool for many, and it's a unique lighting tool. But it doesn't seem like very many really understand it, what it does, and how that affects the look(s) it generates. And you will hear all sorts of information (or misinformation) on how to use it. Some will say it should be placed "as close as possible." Some will say "within 1x it's diameter" (for a 16" BD!!??). And yet others will say it should be used at longer distances, like "8-10ft."

So what *IS* the answer? Well, as with everything in photography there really isn't a "right" or "wrong." How you use a BD is dependent on what your goals are. However, "the purpose" of a BD is to "carve out features" in high contrast, that's what it was designed for. And that requires great facial features to start with, because although a beauty dish will emphasize and enhance good bone structure and good complexion, it will do exactly the same with imperfections too.
Distance, as illustrated and explained below, is an important variable. So too is the position of the beauty dish relative to the position of the subject. And as beauty dishes are often used to emphasize good bone structure, they are normally positioned directly in front of where the subject's face is pointing, and high so that the beauty dish creates the right shadows in the right places - the position of the shadows is a product of the light position, and the softness/hardness of the shadows is a product of the distance.

For this article I will have to be fairly generic because there are a lot of variables which include the design of the dish itself, the surface (silver or white), and the type of light used in it. In a perfect world, a beauty dish is a parabolic reflector that has its focus point in a pre-set and fixed distance, but even perfectly-designed parabolic reflectors produce imperfect results if the light source (the flash tube) is not of the same type/shape and positioned in exactly the same place that it was designed for. 
But the general idea of a BD is a metal reflector with a central deflector plate which creates "rings of light." Here is an image of my 22" silver BD and the rings it produces with a bare bulb flash (AD360). This BD, when used with a bare bulb flash produces rather even and crisp lighting, which is what you want.


But a poorly designed BD, or a well designed BD paired with the wrong type of light, can be very uneven. This is particularly common when paired with speedlights because most were not designed for a speedlight to begin with. But it may be possible to adjust things so that you get better light from it by adjusting the installation of the deflector plate, using a diffusion dome/wide angle screen, or some combination of all (the top right image is what you want to avoid). 

photo credit: Dave F


Whatever the (final) pattern of light your BD is putting out can't really be changed... if you put a sock (diffuser) or a honeycomb (grid) on the BD it will still be the pattern you are starting with. I.e. if you grid that strong ring of light, it will just become a harder/more defined strong ring of light. If you diffuse it, it will just be a diffused ring of light. And if you do put a sock or honeycomb on it, it will *not* focus.

A BD produces "rings of light" but it is not meant to be "a ring-light," it is meant to be a high contrast "even" light. For that to happen the rings have to merge into a unified light in the "focus zone." That happens at some distance away where the rings are focused together by the parabolic reflector. The basics of what happens are diagramed below.

Exactly where, and to what extent, these things happen has to be determined by testing (focus is typically at ~3-6ft). My results are different w/ the AD360 (bare vertical bulb) than it is with a studio strobe (bare circular tube), and different again with a speedlight (fresnel lens/reflector). But *my* BD reaches maximum focus at ~5-6ft when used with a bare bulb/tube.
Note that *nothing* in the diagram (left of the BD) happens if the light is modified with a sock or honeycomb!
(at least not in the same way or to the same extent)

Here is an image taken at 1ft... that is "as close as possible" and "within 1x diameter," but it's pretty ridiculous. I had to slant the light hard in order to not have the BD overwhelm the entire shot. You can see the slightly darker center at this short range (contrast edited to make it more apparent).
(the black bars in these images is the shutter due to using the D810 at 1/320 x-sync and wireless triggers... I was going to crop them out but decided against it) 


Here is the pattern at 3ft. This is reasonable for "as close as possible," but it is outside of the "1x diameter" distance. The dark center has been replaced with a brighter center... this is the beginning of the focus zone.


Here is the pattern at 5ft. The center is even smaller/brighter now and the light is near it's maximum focus.


And here is the pattern at 7ft. At this point the light is starting to go the other way. The center is larger and it is loosing it's focus. It is now acting more like a large bare "virtual light source" closer to the wall/subject. This "virtual light source" is the size, shape, and distance of the light at maximum focus. I.e. it's the pattern approximately 5ft in front of my BD.


And here are some dummy tests. For all of these images the light was kept at a 45* high camera position, and the front of the mannequin head is about 1.5ft from the white wall.

At one foot, it's about unusable... and having the ability to photograph around it means being very close with a wider angle lens which results in a weird perspective.
Make note of the double shadow under the chin due to the light not being "combined" yet. This result is what some call the "liquid wrap" effect, the face looks kind of monotone.


At 3ft the double shadow is going away and the contrast is increasing providing a touch more "sculpting." The cheeks, chin, eyes, and lips are coming out a bit more.


This is the sweet spot for this setup, the cheeks, chin, eyes and lips are coming out even farther. At 5ft the contrast is maximizing while also looking more "even" due to less falloff. Believe it or not, the exposure on the nose is the same as it is in all of the other images.


At 7ft the light is moving out of the focus zone. It is "flatter" and has lost most of it's "sculpting" characteristics. But note that the catchlights are slightly *larger* even though the BD is farther away.


And one at 9ft for the heck of it (the maximum I could do with 45* elevation due to ceiling height). It's not a big difference, a little less falloff and smaller catchlights.


There is no "right or wrong" here... if you want flatter and softer, go real close and use the sock/diffuser (or use a softbox, that's what they are designed for). If you want "sculpted" with higher contrast, use it w/in the focus zone as it was intended. But there's not much point to using it beyond the focus zone, other than the "virtual source" being larger/closer than the actual source.




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