ISO: Cheap colored plastic filter film in red and green

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Jeff7

Jeff7

Lifer
Jan 4, 2001
41,596
19
81
I'm trying to track down something which I would have expected to be quite simple, but, well, it's not. Most of the links I find are either freepatentonline.com pages, or else Google Ad minefields that go nowhere.

What I'm really after is red and green transparent/translucent film, preferably to match up to some red and green LEDs. Ideally the film being sold would indicate the wavelength at which it is most transparent.
The best I've been able to find are lots of sources of clear plastic, and sources of opaque colored or metalized plastic.

Maybe my Google-fu is weak, but I'm having a hell of a time finding any of it. Couple with that the fact that English sucks for the information age.
Film = a thin sheet or covering of a material
Film = something you use in a camera
Film = a movie

Homographs + search engines = :twisted:



Clarification: This is something that would be used in outdoor signage. This animation shows what I'm trying to do.
The first frame, with white, red, and green shown is how the bare sign would appear if lit by white light, which won't ever happen. The frames afterward show how it would look with red and green light, respectively. Only one color would be active at any one time.
So I'd need cheap films that can effectively transmit red, while filtering out green, and vice versa.


Update: I got the filter swatch booklet. Two of the filters in particular seem quite nice.
The one green filter is cool to see - it blocks out almost all of the light from the red LEDs. You can juuuust about make out the lit die. High-brightness multi-die LEDs were similar - each die was only very faintly visible.

The red filters....not quite so impressive. I could easily tell that the green LEDs were lit up, as a fair amount of light (which appeared as a deep red) was passing through the filter. Something amiss with the green LEDs perhaps? Overdriven slightly?
Or else they just naturally put out a little bit of red?
I need the equipment they used to make these images and graphs. :(
 
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drinkmorejava

drinkmorejava

Diamond Member
Jun 24, 2004
3,567
7
81
like lxkllr said, "lighting gel"

possibly theater gel

It's what is used in theater and film production.
 
Jeff7

Jeff7

Lifer
Jan 4, 2001
41,596
19
81
"cellophane" - that's the word I was after.

Lighting gel - also good, thank you......
...hm, or not. Wikipedia says it has a limited life.
This stuff would have to last for several years at least, in an enclosure placed outdoors. (It would at least have UV-filtered polycarbonate in front of it.)


Edit: Wiki's page on cellophane mentions, "However, the fact that cellophane is 100% biodegradable has increased its popularity as a food wrapping."
How well would that stuff hold up over the years?



Also, searching for "optical cellophane" leads to this.:eek:
 
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shortylickens

shortylickens

No Lifer
Jul 15, 2003
80,287
17,080
136
Colored cellophane is good. But a while back I tried searching for colored transparancy sheets and couldnt find any. I wanted to make custom colors for my maglights. I would cut them out to fit. I wanted something like a rainbow pack. Never found a single color, much less a variety.

But I think colored cellophane should do the job too. Thanks OP for bringing this up.
 
Jeff7

Jeff7

Lifer
Jan 4, 2001
41,596
19
81
I'd kind of have expected 3M to have something like this. I know they make various sheets of thin film for not only reflecting lots of light, but also for diffusing point-source light, such as from LEDs.

I could always ask NASA - the Mars Exploration Rover uses some very precisely-calibrated color filters on its cameras. I'm sure they could get me something tuned to the wavelength I need. :D

I'll see if I can get ahold of some cellophane pieces and see who's got the most suitable colors. It's kind of a crapshoot with most places - they list things as "red" or "green," and not by wavelength. I'd be that the layman probably doesn't care about that sort of thing.:awe:
 
Rubycon

Rubycon

Madame President
Aug 10, 2005
17,768
485
126
What's the spectral bandwidth you need, i.e. the filter passband or Q? If it's less than ten nanometers it's going to be expensive. Non coherent sources even diodes are going to have considerably wider bandwidth than a laser. Both will appear monochromatic to human eyes even if refracted. Wider spectral widths start to show fringing on diffraction gratings, for example.

Also if you're doing brightness matching it will be rather inefficient!
 
Jeff7

Jeff7

Lifer
Jan 4, 2001
41,596
19
81
Rubycon said:
What's the spectral bandwidth you need, i.e. the filter passband or Q? If it's less than ten nanometers it's going to be expensive. Non coherent sources even diodes are going to have considerably wider bandwidth than a laser. Both will appear monochromatic to human eyes even if refracted. Wider spectral widths start to show fringing on diffraction gratings, for example.

Also if you're doing brightness matching it will be rather inefficient!
Click to expand...
Tomorrow I'd have to find out the specs on the LEDs that might be used in this application.

And there'd be a fairly wide range of wavelengths, speaking in terms of nanometers. The LED supplier being used tries to bin the LEDs so that they match up in color, but they don't always do a good job; you can see one or two LEDs among the rest which are definitely not the right color.

The application in question: A sign where part of the message will light in red only (Part R), a part which will only light in green (Part G), and another part which will light up the color of whichever of those two is hitting it (Part B). So if you shine a bunch of red LEDs at the front, Parts B and R will light up, but Part G will absorb the red, and thus it won't be too visible.
And of course, if you shine a bunch of green LEDs at it, Parts G and B will light up, but not Part R.

So I figure it'd be best to use films with wavelength transmission windows reasonably close to those of the LEDs being used, while being largely opaque to all other visible wavelengths.

Brightness matching.....yeah, that'll be another fun aspect of it.
The original product specs mentioned something about "Kodachrome," which ventures into the photography realm, of which I know slightly less than almost absolutely nothing.D:
 
Rubycon

Rubycon

Madame President
Aug 10, 2005
17,768
485
126
You can always use Osram RGB emitters. This makes it fun because now you have three channels PER device to adjust. The good news is you can achieve perfect device matching.
 
IronWing

IronWing

No Lifer
Jul 20, 2001
72,112
32,418
136
Here's a link to some filters that come with spectral qualities. If you need something very specific I suggest calling them and asking for their industrial optics section.

Edmund Scientifics


Edit: Looks like they have a separate website for optics.
Edmund Optics
 
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Jeff7

Jeff7

Lifer
Jan 4, 2001
41,596
19
81
lxskllr said:
Wouldn't it be easier just lighting appropriately colored LEDs?
Click to expand...
With the way the customer wants the sign to look, that would cause bleed-over into the wrong areas.
I'd even hesitate to put some kind of divider in there to keep the colors segregated, as the necessary labor would likely make the sign too expensive.

With colored film, it's possible to simply stick the film over the appropriate spots on a sheet of plex, backlight the whole thing with red or green, and then the required messages will light up by virtue of the film's color.

Quick, cheap, and effective......except I just need to track down some appropriate film.:) It's one of those things where I figure it's got to be out there, somewhere.



Concerning the Kodachrome stuff mentioned earlier, "ortho film" has also been mentioned in my searches on what the heck Kodachome is. Unfortunately, there aren't a lot of sites that spell out, "This is what ortho film is, assuming you've never heard anything about it ever before:"
 
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Rubycon

Rubycon

Madame President
Aug 10, 2005
17,768
485
126
You may want to check out LISA plastic too.

Search the trade name Makrofol.
 
Jeff7

Jeff7

Lifer
Jan 4, 2001
41,596
19
81
Rubycon said:
You may want to check out LISA plastic too.

Search the trade name Makrofol.
Click to expand...
Roger that.


I checked out Lee Filter's site a bit more today. For their filters, they have a nice little graph of each one, showing the colors it lets through. Some look quite promising.
I ordered one of their swatch booklets. They've got an interesting pricing structure for them. $2ea if you order one or two, $100ea if you order 10 or more. I guess its their not-so-subtle way of saying, "This is for samples ONLY , dammit!"
 
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