orange-ish safelighting will flood your darkroom.
Easy to see about and evaluate your prints
as they develop. Graded papers are blue
sensitive only. Dan
Yeh, but I want it ALL. My first choice is graded: in fact I have some original French made Zone VI Brilliant still in the freezer; ditto for the old Oriental Seagull. But I sometimes use VC paper and would like to get rid of those red safelights. I bought an amber LED bulb but it fogs the VC. Plus, of course, frugal me would like to do it all as cheaply as I can.
John, Mount Vernon, Virginia USA
Brown is a mixture of red and green light and VC paper is sensitive to green light. Looking at Ilford's safelight filter responses we see that the light-brown filter (902) is a high-pass filter that allows everything above approximately 560nm through: from a deep green through red and into the IR. Likewise, the dark-brown (904) filter allows everything above 575nm.
So, in practice, a "brown" filter allows as much red light through as a purely red filter does... In addition, 560nm is just within the published sensitivity range of MGIV. This implies that in fact lower light levels may be required than with a pure red (>620nm(ish)) light.
I suspect the advantage of the "brown" filter is that being less monochromatic it allows greater clarity at lower light levels. The human eye is relatively insensitive to red and most sensitive to green, so people will tend to have brighter red lights than with lights emitting at lower wavelengths in order to see with a given level of clarity.
I use amber (590nm) or orange (615nm) LEDs in a bright darkroom for VC paper. These have the minor irritation of being highly monochromatic and I keep meaning to mix 3 different colours in one safelight (red + orange + amber) to make a (theoretically) more comfortable light...
Re' the observation that an amber LED lamp fogged: commercial LED lamps intended for home use seem to often emit all over the place - presumably due to cheap LEDs and hopeless driver circuits. With amber being so close to the sensitivity of VC paper, you need quality LEDs driven with low-ripple d.c at their rated current to avoid out of band emissions. Also, a similar "amber" lamp I bought turned out in fact to be green which may be another possible cause of the problem...
Nevertheless you may simply have it too bright. Shade it, or otherwise reduce the light, and do the usual pre-fogged paper safelight test. If you are not familiar with the test, download the Safelights fact sheet from the Fact Sheets menu at http://www.ilfordphoto.com/products/...+%26+Equipment for how to test effectively (Kodak has a similar one on its site too but I don't have a link to it). If it still proves unusable, try again with an orange LED lamp which, emitting further away from the sensitivity of the paper, may work.
My bottom-line is: choose brown or orange if like me you dislike red, but whatever you choose, do test it.
Have fun, Bob.
If you're relying on LEDs being monochromatic, you might be surprised to view their light reflected from the base of a CD at the angle that gives the "rainbow" effect. I think it's hard to estimate how much green is in the light this way, but it often reveals the presence of it.
With an incandescent lamp wired with a dimmer, an advantage of dimming is that it shifts the colour of the light towards red. With LEDs, I have read that lowering the current they are passing does not alter the basic colour, but it narrows the spectrum, and this might be helpful too. I can't verify this, I read it somewhere.
Brownies over my counter, each with on-sale-after
Christmas Chines 5 watt tree bulbs. Beat that for
Consider wattage and paper handling technique.
My paper can see as little light as is practical.
A flick of the wrist turns the over-the-tray
safelight off. Same at the enlarger. Dan