Diffusion Test

RyanT

Veteran
Had a little hiccup with the last thread, but it's back! Just going to put a little more info in this one. I've just wanted to test different diffusion materials for quite some time and be able to compare them side by side. That's how this test came about.


What we did...
1 10k Full Flood, 25 feet away from the subject. We then put tape marks down for each distance of the 4x4 diffusion frame and proceeded to place every frame we had at each distance. The light was never moved, however a 4x4 floppy was brought in occasionally to help with a little negative fill.

Some choice examples:

OpalFrost.jpg


251.jpg


250.jpg


216.jpg


And my personal favorite....

1000H.jpg


Conclusions and interesting findings.

-First of all I’d like to retest a lot of this. Just need to make sure my findings are correct. It’d be great to do an inanimate object and see the lines that are created. Maybe have some sort of grid so you can see how much the light wraps around the object and quantify it. I think it is important to still see the light on the face though, so this test doesn’t become moot.

-252 and Opal are very similar. 252 however has a little bit better light transmission and the physical gel itself is much more durable. I can’t tell you how many opal 4x frames I’ve accidentally ripped through or how many scraps of opal I’ve thrown away because it never goes nicely into our gel crates. 252 would be a nice solution to these problems.

-Muslin is not as soft as I thought it would be and still has a pretty hard edge to it…Again, I’d like to retest this, but it makes me think a lot differently about using it as a diffusion.

-1000H as I thought is quite nice when you have the light. If you’re shooting a close up and you want it to be soft. 1000H is the way to go.

-Black silk? Still don’t quite understand the use for it. Would love a little enlightenment on this one. It doesn’t kill specular reflections, as you still see the light through the silk. It doesn’t have very good softening affects and it just really cuts the light output. I could maybe see if you really wanted to cut something down and also soften it up. Don’t run into that situation very often, but I guess it is a specialty soft good for a reason.

-As you walk a frame in, you lose light. I was constantly having to shift exposure as we walked the frame closer. Makes sense now that I think about it, but never thought that would be the case before…

-It’s interesting knowing how little a diffusion frame will help you from 20’ away. 14’ and you’re starting to get somewhere.

-Tough spun, while not very soft, has a bit of a breakup pattern that I never knew it had. Can definitely be used as a very soft cookie in a pinch.

Take a look on my website for the rest of the different kinds of diffusion.
http://rtcinematography.tumblr.com/

What do you guys think? It'd be interesting to hear what kind of conclusions other people draw from all this.

Also! Next up is comparing the specular reflections from all of these different kinds of diffusion materials. Fun!
 
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ryan-

very helpful.

thank you for the effort.

the numerical figure in the right column is the amount of light that has been cut by the diffusion?

(sorry to ask the obvious, i just want to make sure.)

the 1000h diffusion is "just" regular tracing paper?

or is there a film version that works with hot lights?

thanks in advance.

be well

rob
smalltalk productions
 
1000h is just normal tracing paper. There's no film version, but as long as you don't have it directly on the light it holds up well. I've put it directly on kinos as well with good success.

Also yeah, on the right is how much it cuts. I just got that info all from Lee's website, which I have to assume would be the most accurate.
 
Thanks for this test, Ryan. I was actually thinking about the thread you made a couple months ago asking if anyone would be interested. Some very interesting findings here. I hope you don't mind if I use it as a reference :)

I have come to love and hate 1/4 Tough Spun. It really is a decent diffuser and it's far more durable than 1/4 Diffusion when placed on or near a light. However, it can snag and it's harder to roll up and stow, but it does add a nice texture to the light (I've used it in a close-up with the Tough Spun really close to the talent's face, simulating light coming through a curtain) and it is a mild diffuser. It can just be bloody messy - cobwebs everywhere...
 
Yeah, I almost don't want to use it just because of how weird it is. Reminds me of dryer sheets or something.

Either way, I think I'd much rather just take some 252 or 251 with a few pieces of paper tape placed on it to break up the light. Seems like it would be the better way to go.
 
First, appreciate the effort, thanks.

Second, you mention that you had to adjust aperture to account for light loss... it does look like some shots are a little more exposed than others, any way to control this in the future? Maybe leaving it on auto-exposure would help, or am I missing something? I suppose it could just be the difference in distance makes against contrast, but again, it'd be nice to have the exposure controlled to take that factor out and know for sure. if i think a particular sheet is going to give me slightly more highlights, i may not use it, when in fact it was just a case of slightly different exposure.
 
Maybe auto exposure would have been a good way to go for me, but a waveform monitor or light meter would have been best...Unfortunately I had neither. I think it's just best to concentrate on the line shadow created by the nose and even with the slight changes in exposure it will give you a pretty accurate idea of what you would get with the given diffusion at the given distance. This is definitely something I would fix if I were to do it again, as I was getting varying exposures not only when I was changing diffusion materials, but also as I was walking the diffusion in closer.

Also, are you talking about exposure or are you also talking about how much fill there is? I definitely would have boxed the place in with 12x solids next time to control things a little more.
 
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