The Beauty Dish Deflector Conundrum ...

I can't stand it anymore! I need to hear a cogent explanation of why curved beauty dish deflectors always have their concave side facing the light source. Like this:

HI Dave,

Are you using the 120J or have you tried this with studio strobes?

If not then I would be curious to see the same experiment done with one of those.

this interests me as well so I will be keeping an eye on this thread.

Ahh I see now that you're using a Speedlight.

interesting... I made a DIY beauty dish... and it more or less works and the results are not much different in appearance than what you in the lower left photo... and mine does have the truck mirror

Once the light is spread to the edges of the dish more, the dead-spot in the centre becomes more pronounced. I've tried what you've done in these pics before - I found that the results looked nice on a plain wall but I tried it on real subjects and soon switched back. Completely counter-intuitive like you say.

Interesting Dave,
I have been wondering the same thing.
I had a similar BD delivered Friday. It looks almost the same on my manequan model with the disk in each of the four option positions. Also with the included defusion fabric.

I'll do some tests agains a wall as well.

One question, wht zoom do you have the Speedlite set for?

I used 28 Degrees.

dmward wrote in post #10103088
Interesting Dave,
I have been wondering the same thing.
I had a similar BD delivered Friday. It looks almost the same on my manequan model with the disk in each of the four option positions. Also with the included defusion fabric.

I'll do some tests agains a wall as well.

One question, wht zoom do you have the Speedlite set for?

I used 28 Degrees.

With my 580EX II or SB-800s I've settled on the 24 degree setting. I have to redo this experiment with one of my bare bulb Sunpak 120Js.

What I find to be the *really* interesting takeaway from this is how little (if any) difference deflector orientation made when the "subject" was anything other than a blank wall. For that matter, substituting a flat deflector worked just as well as a convex or concave deflector. So, where's the science in all of this? Is there any? What tests were performed by Elinca, for example, that led them to conclude that a dish-shaped deflector with the concave side facing the flash tube was the optimal solution for Elinchrom BDs? Why would Profoto reach a different conclusion?

In my limited experiments, deflector distance from the flash tube and deflector diameter had a much greater effect on the BDs pattern than the deflector's shape.

We could expand the line of questioning to include the contouring of the dish itself. Will Mola/Speedotron/Hensel​/Profoto/Norman/Bowens​/generic/etc. BDs produce noticeably different results when used under similar circumstances? Are any of them any "better" than a DIY made out of a 16 or 20 quart stainless steel mixing bowl? I'd like to hear Hermes' thoughts on this subject.

I'm enough of a cynic to believe that much (if not all) of the variation we see in BD design can be attributed more to concerns over cosmetics and product differentiation than to physics.

Dave F.

tetrode wrote in post #10103250
With my 580EX II or SB-800s I've settled on the 24 degree setting. I have to redo this experiment with one of my bare bulb Sunpak 120Js.

What I find to be the *really* interesting takeaway from this is how little (if any) difference deflector orientation made when the "subject" was anything other than a blank wall. For that matter, substituting a flat deflector worked just as well as a convex or concave deflector. So, where's the science in all of this? Is there any? What tests were performed by Elinca, for example, that led them to conclude that a dish-shaped deflector with the concave side facing the flash tube was the optimal solution for Elinchrom BDs? Why would Profoto reach a different conclusion?

In my limited experiments, deflector distance from the flash tube and deflector diameter had a much greater effect on the BDs pattern than the deflector's shape.

We could expand the line of questioning to include the contouring of the dish itself. Will Mola/Speedotron/Hensel​/Profoto/Norman/Bowens​/generic/etc. BDs produce noticeably different results when used under similar circumstances? Are any of them any "better" than a DIY made out of a 16 or 20 quart stainless steel mixing bowl? I'd like to hear Hermes' thoughts on this subject.

I'm enough of a cynic to believe that much (if not all) of the variation we see in BD design can be attributed more to concerns over cosmetics and product differentiation than to physics.

Dave F.

Yes is the honest answer, although I don't have all the explanations as to why.

If you've ever used a Mola for example, you'll see from the way it lights that it isn't really a dish - the whole thing doesn't flood with light, instead it lights in a series of concentric rings. I was skeptical before I first tried my Mantti (had to buy it having never tried it thanks to Mola's terrible UK representation) but it does produce a beautiful look. The shadows it creates are still defined but softer and more delicate than any other dish I've used. It's also surprisingly efficient and just as efficient with the diffusion sock.

On the other hand, I bought one of those 27" silver eBay dishes with grids (mine was lencarta branded) wanting to like it, hoping that it would be just as good as the more expensive options. In use, i found that it has a noticeable hotspot at the point of focus and the surrounding beam was much dimmer. Tried it out in a fitness catalogue shoot and the unevenness was so bad I initially thought I had lens flare coming from somewhere. I gave it a second chance on another shoot and the light I got from it was equally ugly. Near the end of the second shoot, the thing toppled over (a dish this size really should have an independent mount) and the dish and grid basically folded in. This was quite a while ago and I haven't even bothered to try and bend it back to shape as I know I'll never use it. I may try to salvage the grid to use for something else and bend the dish into a strip light.

On the deflector issue, I've found it's usually best to leave the dish with whatever shape it comes with. The Mola PAD lets through way too much light but blocking it off with foil tape was all I did to modify it.

Hermes wrote in post #10103436
Yes is the honest answer, although I don't have all the explanations as to why.

If you've ever used a Mola for example, you'll see from the way it lights that it isn't really a dish - the whole thing doesn't flood with light, instead it lights in a series of concentric rings. I was skeptical before I first tried my Mantti (had to buy it having never tried it thanks to Mola's terrible UK representation) but it does produce a beautiful look. The shadows it creates are still defined but softer and more delicate than any other dish I've used. It's also surprisingly efficient and just as efficient with the diffusion sock...

Thanks for the detailed post, Hermes (one of these days you'll tell us your real name ) I don't doubt the Mantti is something special but then it is more than two times the diameter of the BDs most of us own. Your experience with the 27" Lencarta is also not surprising. However, just to keep the discussion more apples-to-apples, I would ask if (in your opinion) the Mola Demi might be expected to produce results in any way distinguishable from a Speedotron or Kacey BD as they all share very similar profiles. Let's also add that for our little thought experiment, they all have solid deflectors.

I think it would be interesting to see sample photos taken under controlled conditions using the better known 22" BDs. My experience with BDs is limited but, I must admit, I see very little difference in results among the dishes I have used.

Dave F.