Effect of diffusers on CRI and CCT?

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stephenk
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Effect of diffusers on CRI and CCT?

Hi, I’m interested to know if anyone has tested the impact of using plastic and silicone diffusers on CRI and CCT?

thefreeman
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not much difference :

Incan 3.5V :

CCT = 2708K (Duv 0.0001)
Color Rendering Index (Ra) = 99.8 [ R9 = 98.8 ]
R1 = 99.9 R2 = 99.9 R3 = 99.7 R4 = 99.8 R5 = 99.9 R6 = 99.8 R7 = 99.7
R8 = 99.4 R9 = 98.8 R10 = 99.8 R11 = 99.5 R12 = 99.8 R13 = 99.9 R14 = 99.8
IES TM-30-15 Rf = 99.59 Rg = 99.84

dc-fix :
CCT = 2696K (Duv 0.0001)
Color Rendering Index (Ra) = 99.8 [ R9 = 98.6 ]
R1 = 99.8 R2 = 99.9 R3 = 99.7 R4 = 99.8 R5 = 99.9 R6 = 99.9 R7 = 99.7
R8 = 99.3 R9 = 98.6 R10 = 99.9 R11 = 99.6 R12 = 99.8 R13 = 99.9 R14 = 99.8
IES TM-30-15 Rf = 99.58 Rg = 99.87

diffuser #2 (Boaz)

CCT = 2693K (Duv 0.0002)
Color Rendering Index (Ra) = 99.8 [ R9 = 98.8 ]
R1 = 99.9 R2 = 99.9 R3 = 99.7 R4 = 99.8 R5 = 99.9 R6 = 99.8 R7 = 99.7
R8 = 99.4 R9 = 98.8 R10 = 99.8 R11 = 99.5 R12 = 99.7 R13 = 99.9 R14 = 99.8
IES TM-30-15 Rf = 99.48 Rg = 99.79

diffuser #7

CCT = 2693K (Duv -0.0001)
Color Rendering Index (Ra) = 99.3 [ R9 = 96.4 ]
R1 = 99.3 R2 = 99.6 R3 = 99.8 R4 = 99.4 R5 = 99.3 R6 = 99.6 R7 = 99.4
R8 = 98.3 R9 = 96.4 R10 = 99.2 R11 = 99.5 R12 = 99.0 R13 = 99.3 R14 = 99.8
IES TM-30-15 Rf = 99.29 Rg = 100.04

That said plastics usually have a bit less transmission in the blue, I’ll test with a high CCT LED later.

jon_slider
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DC Fix lowered the CCT about 150K and lowered the DUV about 0.0012:

.

thefreeman
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There are two effects to differentiate :

  1. how much the color of the light is modified after passing through the diffuser
  1. blending from a non uniform source (such as an LED+ optic)

I measured only the first one by using an uniform light source (incandescent bulb ). jon_slider measured the two together, the second one will probably vary a lot depending on the source.

jon_slider
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> the impact of using plastic and silicone diffusers

the impact varies depending on the diffuser, this one is silicone

CCT 878K lower, DUV 0.0039 higher

stephenk
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Thanks for the information, much appreciated!

The reason I’m asking is I use four S2+ LH351Ds with diffusers for urbex photography (underground locations, etc). I’ve always been pretty happy with Convoy’s plastic diffusers in terms of light transmission and minimal visible effect on CCT and CRI.

When the 519As are out in different CCTs, I’m maybe considering getting D4V2s instead of S2+s. However, it seems that most diffusers that fit the D4V2 (e.g. Lumintop EDC18, Wurkkos TS21) are silicone or rubber, which may have more of an impact on light output and quality.

jon_slider
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I hope you find someone that can test a Convoy diffuser for you.

Lightbringer
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In short, it depends on the diffuser. If the film has a tint to it, obviously it’ll affect both ct and cri. But just the act of diffusing should do little to nothing on either.

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stephenk
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Lightbringer wrote:
In short, it depends on the diffuser. If the film has a tint to it, obviously it’ll affect both ct and cri. But just the act of diffusing should do little to nothing on either.

I only use “clear” diffusers, however most semi-translucent materials will still have some (from minimal to significant) effect on CCT, DUV, and CRI. Silicone diffusers (some of which are GITD) may have more of an effect than plastic diffusers?
Lightbringer
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Depends. Look at “clear” window-glass edge-on, and it’ll be that nice pretty blue-green color. It’s just a matter of degree…

Forgot to add, a lot of those almost solid-white diffusers, I likely wouldn’t use. Best ones would be those that are normally clear but “frosted” somehow (physically scuffed, textured, etc.).

Dunno which material would be “more neutral”, though.

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KeepingItLight
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Lightbringer wrote:
In short, it depends on the diffuser. If the film has a tint to it, obviously it’ll affect both ct and cri. But just the act of diffusing should do little to nothing on either.

Photographers and videographers often use diffusers over their strobes and lights. They use them for the same reason flashaholics do: to smooth out or “soften” a light source. The ones they use cost big bucks, and are almost perfectly neutral. They shift neither CT nor CRI.

Might be worth checking at a high-end photo supply store. Usually you see large “light boxes” that would not be useful for most flashlight work, but there may also be some filter-like materials available.

stephenk
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KeepingItLight wrote:
Lightbringer wrote:
In short, it depends on the diffuser. If the film has a tint to it, obviously it’ll affect both ct and cri. But just the act of diffusing should do little to nothing on either.

Photographers and videographers often use diffusers over their strobes and lights. They use them for the same reason flashaholics do: to smooth out or “soften” a light source. The ones they use cost big bucks, and are almost perfectly neutral. They shift neither CT nor CRI.

Might be worth checking at a high-end photo supply store. Usually you see large “light boxes” that would not be useful for most flashlight work, but there may also be some filter-like materials available.


This isn’t for anything professional like portraits. Just lighting up underground places, but trying to keep the light “quality” nice. With lots of graffiti and earthy tones, CRI, tint, and CCT are important.

For portrait photography I use Weeylite RB9 panel lights.

Lightbringer
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KeepingItLight wrote:
Might be worth checking at a high-end photo supply store.

Naw. Someone would have to pay me to care about the 2% slip in cri or whatever.

I’m just not interested in losing 40% of light output by shrouding a light with a nearly opaque white piece of plastic.

At home, if I absolutely have to do so, I’ll use ceiling-bounce for a nice diffuse source of overhead light, vs a harsh still-nearly-a-point-source light that’s almost always in my eyeline.

Of course, there are exceptions, like my Zanflare for when I had a blackout a coupla years ago, etc. But while high-cri is nice, it’s not a dealbreaker to me as it might be to other people. I just set my Zanflare to 100% WW and maybe half-brightness, and it lasted overnight quite nicely.

Similarly, my Wuben E0whatever with an alkaleak and diffuser, magsnapped to an overhead light fixture, right over the catbox. I don’t think they particularly cared about the ct or cri of the light.

Now, if I were doing photography and notchy light output would screw up my colors, yeah, I’d spring for a fancy diffuser, but not for run of the mill flashlights.

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Sari33
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I cutted discs from a roll of baking oven paper then applied on my convoy S12 2700k SST20. On the sight doesn’t seem to raise DUV and creating a pleasant diffused light
Like it

Boaz
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Good diffusion adds a better mix of what its already there . The #6 diffusion film I used to sell (but have run out of) had a brown/tan cast to it but when you shot light thru it you never saw it as adding any tint . That was a very extreme case and so I'm guessing that diffusion film won't cast any added hue ..unless it's a really bad one . 

 * my guess is that oven baking paper is doing to be pretty horrible 

My Nichia 219B lights are improved by good diffuser film . Yes a smoother beam but also a better tint . It's subtle but after hundreds of visual side by side comparisons it always ends up being  219B diffused .

                 υμεις εστε το φως του κοσμου ου δυναται πολις κρυβηναι επανω ορους κειμενη

                            Dc-fix diffuser film  >…  http://budgetlightforum.com/node/42208

Lightbringer
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Yeah, parchment paper can have a beige tint, but not too objectionable, but waxpaper should be more neutral.

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Sari33
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Baking papers have variations on type of texture and hue.
Tried diffents like happen on bath paper Big Smile
My sample give a nice tint