DIY safelight

[salihonba]

I agree with laphro, that red LED bulb is exactly what I am using now, works very well, I live in Taiwan, and 3 watts red LED bulb is available in E27 standard thread in market now, they said 5 watts are coming soon.

[RalphLambrecht]

The light was too intense. If you take a sheet of paper and hold it up against your safelight, it will fog immediately. Intensity is proportional to the square of the distance, and lasers don't lose their intensity the same way as diffuse light does.

Exactly, but why is light at a wavelength outside the spectral sensitivity of the paper creating an exposure?

[Ian Grant]

There's a phenomena where light that in theory is completely safe has an effect on an emulsion, if the intensity is high enough it can have an effect on an emulsion, it has a name which escapes me at present.

So below a certain intensity the emulsion isn't fogged, the then there's point where the fogging is enough to seriously affect the contrast in VC papers, yet still show no visible fogging.

Ian

[RalphLambrecht]

I agree with laphro, that red LED bulb is exactly what I am using now, works very well, I live in Taiwan, and 3 watts red LED bulb is available in E27 standard thread in market now, they said 5 watts are coming soon.

I wish I could find them on the web. I found product specifications but no retailer.

[Ian Grant]

The problem with certain red safelights

The Herschel Effect

If a photographic emulsion is exposed to blue light and subsequently to red light before development, some of the effect of the original exposure are destroyed; this was discovered by Sir John Herschel in 1840.

While this can in theory affect all modern B&W paper emulsions it really only causes problems with VC papers when the wrong safelight is used (too close or at too high an intensity) while the red light may be insufficient to cause physical fogging, but enough to seriously affect the contrast grades achievable.

The early emulsions Herxchel worked with where of course all blue sensitive.

Ian

[RalphLambrecht]

The problem with certain red safelights

The Herschel Effect

If a photographic emulsion is exposed to blue light and subsequently to red light before development, some of the effect of the original exposure are destroyed; this was discovered by Sir John Herschel in 1840.

While this can in theory affect all modern B&W paper emulsions it really only causes problems with VC papers when the wrong safelight is used (too close or at too high an intensity) while the red light may be insufficient to cause physical fogging, but enough to seriously affect the contrast grades achievable.

The early emulsions Herxchel worked with where of course all blue sensitive.

Ian

Ian

Wouldn't this be the opposite of fogging?

[Ian Grant]

Maybe, it's called latent image bleach, but it's a detrimental effect of the safelight and often gets overlooked when people wonder why they can't achieve a full range of Contrasts with some VC papers. Some safelight filters are worse than others.

It's fogging in the sense that it's unsafe exposure to too much red light of a harmful intensity.

Ian

[joe7]

thanks all for replying,very appreciate it.

[Mark Fisher]

Well, I'll have to pipe in.....consider simple screw in LED lights. I use the OptiLed red and amber 2.5W Festival series lamps. I've found that they are extremely bright and very safe. I use them for lith printing and keep them on the entire development cycle (10 minute range). My darkroom is about 10' x 6' and one lamp is adequate (2 better). I can't imagine using anything else.

[DeBone 75]

I use a DIY safe light made out of a 3 lb. coffee can with a red lid. I use a 15 watt bulb. Works for everything, paper and X-ray film. I have it about 4' from the enlarger and 9' from the dev trays.