My Cheap DIY Beauty Dish

[DigMe]

I bought my Krylon plastic spray paint at Home Depot FWIW.

brad

[Saltwater Servitude]

Thought I'd post some very odd test results I got from my 18" dish.

I have a center reflective dish that's just a plastic plate that happens to be pretty dang reflective. It's about 8.25" in diameter and I have it set 3" from the bottom of the bowl I used for the dish.

I'm triggering an SB-800 with my Radio Poppers and measuring with a Sekonic L-358 set for aperture mode at about 3 feet away, ISO 200, 1/125th.

I was getting a solid average of f16.4. The light meter measures in one tenth increments.

In the spirit of DIY, I tried to outsmart myself today and bought some reflective tape. I covered the bottom of the reflector plate and set up my experiment again. I averaged f11.6 using the same settings. Just a hair short of a full stop lost. Pulled the tape off, put the plate back into the dish, and I was right back at f16.4.

Ah! I'll put a 4" mirror in there and give that a try. Results? f16.0 on the nose, right about a third stop lost. Pulled the mirror off, back to f16.4.

Then I tried putting the reflector plate at 2.5", even though the directions I followed said 3" was the sweet spot. f16.1. Back to 3", f16.4.

I was going to try mylar, but I don't think it'll make a difference. The plain white reflective surface of the plate is the best result.

For the meticulous experimental design folks, I did the tests with the lumisphere in both positions. There wasn't any difference at all due to ambient light possibly contaminating the results. I fired the SB-800 five times for each trial, including each time I went back to the control of the plain white plate by itself.

I'm going to shoot the dish with a high gloss coat in the next few days and see if that brings any changes.

[adamsheehy]

Originally Posted by Saltwater Servitude

Thought I'd post some very odd test results I got from my 18" dish.

I have a center reflective dish that's just a plastic plate that happens to be pretty dang reflective. It's about 8.25" in diameter and I have it set 3" from the bottom of the bowl I used for the dish.

I'm triggering an SB-800 with my Radio Poppers and measuring with a Sekonic L-358 set for aperture mode at about 3 feet away, ISO 200, 1/125th.

I was getting a solid average of f16.4. The light meter measures in one tenth increments.

In the spirit of DIY, I tried to outsmart myself today and bought some reflective tape. I covered the bottom of the reflector plate and set up my experiment again. I averaged f11.6 using the same settings. Just a hair short of a full stop lost. Pulled the tape off, put the plate back into the dish, and I was right back at f16.4.

Ah! I'll put a 4" mirror in there and give that a try. Results? f16.0 on the nose, right about a third stop lost. Pulled the mirror off, back to f16.4.

Then I tried putting the reflector plate at 2.5", even though the directions I followed said 3" was the sweet spot. f16.1. Back to 3", f16.4.

I was going to try mylar, but I don't think it'll make a difference. The plain white reflective surface of the plate is the best result.

For the meticulous experimental design folks, I did the tests with the lumisphere in both positions. There wasn't any difference at all due to ambient light possibly contaminating the results. I fired the SB-800 five times for each trial, including each time I went back to the control of the plain white plate by itself.

I'm going to shoot the dish with a high gloss coat in the next few days and see if that brings any changes.

Did you have everything in fixed positions on tripods or whatnot? What was the variability like in the sets of five shots?

Also, 8.25" seems pretty big (at least to me) and could be resulting in some problems there.

[DigMe]

What was your flash zoomed to? That makes a big difference IMO.

brad

[70400]

Looks good,like this! I will try one.Thanks.

[Saltwater Servitude]

Originally Posted by adamsheehy

Did you have everything in fixed positions on tripods or whatnot? What was the variability like in the sets of five shots?

Also, 8.25" seems pretty big (at least to me) and could be resulting in some problems there.

Everything was in the exact same position for each replication of the experiment. These weren't actual photos, just firing the flashes to measure the output via the light meter.

Zoom never changed from 24mm. I read through the comments section on the design I built, and it also mentioned someone who got no difference using a mirror either.

8.25" is only a quarter inch larger than the design I built mine from, using the same circumference bowl for the dish.

[Saltwater Servitude]

Ach, I figured it out. I was metering too close to the dish and skewing the results.

Once I backed off to 6 feet the light smoothed out and the re-taped reflective tape gave me about a full stop boost over the plain white plate while the 4" mirror gave me a half stop.

Where I was metering before, even turning the light meter a minute amount with the lumisphere up was giving me a little fluctuation. I thought I had it figured out, but once I put the light meter in a 100% fixed position where I couldn't inadvertently change the angle even a few degrees, then the readings started making sense.

It was just blind dumb luck that I kept getting back to 16.4 with the plain white plate.

Science are phun.