red safelight: colour temperature?

[gandolfi]

......

for our new photohouse we will make one of the windows into a red safe light.

we found a compagny that can make the glass in any colour we want, so here's the question:

does any of you know the colour temperature in red safelights? in Kelvin.

it has to be red as we work a lot with emulsions, that are sensitive to other tones..

the question is - how red?

[ath]

The concept of colour temperature doesn't work well with these filters.
Colour temperature assumes a continuous spectrum, the temperature gives the relative intensity of the different colours.
For red filters the cut off wavelength is a better measure.
My darkroom is lit by LED bulbs with approx. 650nm. This is safe with all my papers...
A dark red filter like a 29 has a cut off wavelength of 630nm and looks alot like a red darkroom filter.

[Gary Holliday]

You could look for safelight gels to place over the window. I imagine this would be far cheaper than specialist glass.

[rob champagne]

Graphic arts store should sell rubylith which can be bought in rolls with one side being adhesive. That should work to a point. But I rekon that you would need several layers to make it dark enough to work well.

http://en.wikipedia.org/wiki/Color_temperature

[fschifano]

I've made serviceable safelight filters for a 5x7 safelight with a 15 watt bulb used at least 3 ft. from the paper with 2 layers of rubylith and an appropriately sized sheet of window glass. Lexan would work just as well. Very inexpensive, and very effective.

[Photo Engineer]

A reading in Kelvin implies a tilted but continuous visible light source from 400 - 700 nm. In the case of a red light, you are only getting the portion from 600 - 700 nm and therefore the degrees Kelvin would be hard to establish.

If one considers bluish daylight to be around 5000 K or higher, and tungsten around 3000 K or lower, then the red light would have to be below that if you could asign a value at all.

I hope I got all of that correct. I'm winging it from memory. Too tired to hit the books.

PE

[df cardwell]

Lee Filters ought to be able to help.

http://www.leefilters.com/lighting/products/colours/

[fschifano]

Originally Posted by gandolfi

......

for our new photohouse we will make one of the windows into a red safe light.

we found a compagny that can make the glass in any colour we want, so here's the question:

does any of you know the colour temperature in red safelights? in Kelvin.

it has to be red as we work a lot with emulsions, that are sensitive to other tones..

the question is - how red?

As I re-read your original question, the light bulb in my head switched on. Are you seriously considering using an outside window as a light source for a safelight? I'd be very careful about that. Daylight is a LOT of light and even the brightest safelights make only the tiniest fraction of that. I'd re-think that and make a way to block light completely from that window, then use a proper safe light.

[gandolfi]

Originally Posted by fschifano

As I re-read your original question, the light bulb in my head switched on. Are you seriously considering using an outside window as a light source for a safelight? I'd be very careful about that. Daylight is a LOT of light and even the brightest safelights make only the tiniest fraction of that. I'd re-think that and make a way to block light completely from that window, then use a proper safe light.

would like to do that also, but alas - here in Denmark, we have to do this!
somebody, somewhere up in the system is afraid that my students will get disorientated, if they can't see out....
(I am willing to bet, that those guys never have been in a darkroom)

I've been in a darkroom with lots of these "windows"! I was very surprised, that it actually worked out fine! and thsy had at least 4 or 5 red glass windows!

I "only" have to have one....

[Nicholas Lindan]

Originally Posted by gandolfi

does any of you know the colour temperature in red safelights? in Kelvin.

Color 'temperature' is the spectra of light emitted by a black-body of the given temperature.
http://en.wikipedia.org/wiki/Planck%27s_law

Safelight filters have _nothing_ to do with color temperature.

If you want to specify the transmission characteristics, they are available on the Kodak web site:
http://www.kodak.com/global/en/profe...5/ti0845.jhtml

(one more reason to support Kodak by buying their products ....????)