artist inventer

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Its no use for a red glass or film to filter a uv ray.

thety hve different wave lengh. red glass or film can only filter red color or ray

from color theory, its subtract principle.

I agree with comment #2. There are many different applications of glass for filtering of UV light. The part about trying to get a tan inside vs. outside has a confounding that wasn't mentioned. As far as I understand, most glazing (windows) now have technology pioneered by FORD called low-e that drops heat transfer coefficients considerably. some have almost imperceptible micro layers of metal or special gasses like argon inside to help keep the environment inside separated from the environment outside.

But your question about red glass or films doesn't have an easy answer. There are a lot of different characteristics of dyes and colors. Most of the time when we talk about colors, we talk about pigment-colors. Colors that work by subtraction. They absorb (by in large) the full spectrum of light except for the small range of frequencies responsible for our perception of that color. Depending on what the dye/pigment is made out of it will have a very characteristic light absorbancy. Some will have very, very narrow frequency ranges of reflected light, others will have broader more tapered ranges. All will have additional little peaks here and there giving the pigment it's own particular color. At night, take two sheets of red film by separate manufacturers…into a room with an incandescent lamp, then into a room with a fluorescent lamp, and finally outside under a "peach" sodium street lamp. You'll typically see differences in how the two appear—Why? Because each of those lamps generate different ranges of visible light. Incandescent lights are typically considered full-spectrum (practically, only sunlight is truly full spectrum), fluorescent lamps are "cooler" because they have lower emittance of infra-red—but also have more emittance in the ultra violet spectrum. Sodium, mercury, and other metal based lamps have a single frequency band or a small collection of several very specific frequency bands emitted. What that means is that if you were able to develop a pigment that absorbed only light wavelengths right around 590 nanometers it would look black under a sodium lamp, but nearly white in the sun. (a quick search for frequency of sodium light returned this link – it might provide a better explanation. http://science.howstuffworks.com/light4.htm)

What all this means for your red glass or film is that some will work much better than others at filtering UV light depending on breadth of spectrum absorbed. Other factors that could affect this is the opacity of the media and saturation of the pigment in the media. (is it really dark red? Is it a lighter red? Is it a milky-red?

My suggestion is to contact the manufacturers to see if they have any information on the light absorbance of their pigments. A simple red film might be all you need.

Sorry if it makes things more complicated...but I hope this helps.

Thanks for the answer. It fills in blanks on complex subject that must be developing in importance for the growing population of older people. The Government gives me dire warnings each day about the mid-day highs that weaken the skin and can cause my cancers. I fear for the birds, bees, and my orchids that arn,t looking so good this time of year.

(The posts after post number 2 have it right.)

Here's an oversimplification for how to think about it as an artist.

The red filter passes red wavelengths, blocks non red wavelengths.

UV is not red ...

inference is ...

milo

I disagree, you are referring to just the visible spectrum, the question includes Ultra-violet.

As the ultraviolet filtering characteristics can't be seen the filters may be percieved as being red only filters, but they can easily pass other wavelengths such as UVA,B & C X-rays infra-red etc.

It is only the material that will effect these unobservable wavelengths.

I bet you half a crown that the red filters both pass radio waves through them!!!

Frank, I don't bet and Wouldn't know a half a crown from a shilling if I had one.

I do have a couple of remnimbi left over from a trip a few years ago...

However, Just as you said in your first post, the glass itself, regardless of color, is pretty effective at stopping the UV.

My experience with photographic filters indicates to me that I have no need of the UV filter when I am using a red filter for B&W...

And I would be hard pressed to explain how the infrared filter I use would allow UV through but not let blue and violet visible wavelengths through.

You are absolutely right about the radio waves. I agree with your first post 100%, I was just trying to give a simplified way of reframing the problem...

Cheers.

milo

Ah that's alright then

and its not Frank its Francesco