is there much difference in 16" vs. 22" beauty dish ?

is there much difference in 16" vs. 22" beauty dish ?

Would larger beauty dish produce more even light ?

The difference is 6 inches.
A 22" light source is 37.5% larger than a 16" light source.

The size of the light determines the softness of the shadows. Bigger isn't always better, but in the world of lighting, if you don't have the size you need, nothing else matters much.

Standard opinion says that a beauty dish produces it's specific quality no further away than double it's diameter. So a 16" must be no further than 32" and a 22" no further than 44". That's a huge difference if you are trying to get the light out of the frame. As usual, the bigger the light source, the softer.

Curtis N wrote in post #12654742
A 22" light source is 37.5% larger than a 16" light source.

37.5% larger?

area of a circle = pi * radius squared

8^2 * 3.14 = 201 sq"
11^2 * 3.14 = 380 sq"

16" dish x 189% = 22" dish

clarence wrote in post #12655512
37.5% larger?

area of a circle = pi * radius squared

16^2 * 3.14 = 803 sq"
22^2 * 3.14 = 1519 sq"

16" dish x 189% = 22" dish

You're using the diameter instead of the radius so you figures aren't entirely correct.

yep, you're right. I changed to the radius at r=8 vs r=11 and still get 189%

sheesh. you guys are too nerdy.

Shadow quality is related more closely to a light source's linear size than its total area. That's why I compared diameter instead of area.

If we were discussing exposure as it relates to aperture, well, that's another story.

Curtis N wrote in post #12657145
Shadow quality is related more closely to a light source's linear size than its total area. That's why I compared diameter instead of area.

So a 72"x12" strip light and a 72" PLM umbrella have comparable "shadow quality" since they have identical linear size?

clarence wrote in post #12657271
So a 72"x12" strip light and a 72" PLM umbrella have comparable "shadow quality" since they have identical linear size?

Depends on what you're lighting, and how the light is positioned.

I'm not gonna get into a pissing contest about this. That won't help anyone learn.

I was just interested in learning how/why shadow quality is limited to one-dimension.

Not sure why you'd see that as a pissing contest.

I didn't say one dimension.

We were discussing the diameter of two circular lights. Increasing the diameter increases the linear size in two dimensions. And we're talking about how a quantitative property of a light source affects a qualitative property of an image. There's no formula for that.

But when we discuss the size of a light source, it's the apparent size that matters (linear dimensions of the light, relative to distance). A 22" beauty dish from 44 inches has the same apparent size as a 16" beauty dish from 32 inches. Calculating the area of the dish won't help anyone learn how to use it.

For a more definitive guide on this subject, I recommend the book Light - Science & Magic by Hunter and Fuqua.