A question popped into my head...

[MrFujicaman]

I was reading the posts about the LED enlarger head and a question popped into my head. I know safelight filters fade over time-I also know that they are now expensive. ($53 for a OC 5.25 dia for the Kodak "beehive" safelights!)

Which fades the filter more-the heat of the light bulb or the light it puts out ?

If it's the heat buildup from the light bulb-wouldn't using an LED light bulb extend the life of the filter ?

Any thoughts ?

[Amedeus]

If you use red LED's with the right wavelength, then you don't need a safelight at all ...

[giuliosteva]

In my little place i use a red led bulb (chinese) as safelight. Works for me.

[Tin Can]

Just to look cool and be old timey, I use the Kodak Beehives with red leds and throw out the useless damaged original filters.

Actually the Beehive is still useful because it is directional and you can easily move them with the quick release mount. I still want some more nice ones.

Gotta watch out and fix their wiring sometimes...


I was reading the posts about the LED enlarger head and a question popped into my head. I know safelight filters fade over time-I also know that they are now expensive. ($53 for a OC 5.25 dia for the Kodak "beehive" safelights!)

Which fades the filter more-the heat of the light bulb or the light it puts out ?

If it's the heat buildup from the light bulb-wouldn't using an LED light bulb extend the life of the filter ?

Any thoughts ?

[asuilin]

Yes, the red LEDs are much, much better for darkroom safelight than incandescent bulb. But you still need red filter. Red LED spectrum is broad enough to emit yellow and even green rays. So this light is not completely safe, it shoud be filtered.
If you would use usual white LED bulb, it's better than incandescent too (no heat). But red LED is much more effective.

[giuliosteva]

Yes, the red LEDs are much, much better for darkroom safelight than incandescent bulb. But you still need red filter. Red LED spectrum is broad enough to emit yellow and even green rays. So this light is not completely safe, it shoud be filtered.
If you would use usual white LED bulb, it's better than incandescent too (no heat). But red LED is much more effective.

I have it 50/60 cm away from the trays. Probably this distance is safe enough.

[asuilin]

Some time ago I constructed 15w red super-bright LED safelight (it is equivalent to ~300W incandescent bulb). Light was very bright and comfortable, but was not safe for paper. My safety test is: exposure paper as usual, cover half of print with opaque material, let it sit 5 min in front of safelight and develop it. If I can see the difference between two halfs of print, light is unsafe. Not many darkroom safelights can withstand this test, my LED safelight failed it too. It became safe when I put two layers of red Rosco lighting gel over the leds.

[Leigh]

But you still need red filter. Red LED spectrum is broad enough to emit yellow and even green rays.
That's only true if the LED has been doped to produce a broad-spectrum output.

"Natural/unmodified" LEDs are highly monochromatic, as shown in this graph from a datasheet:

108793 Click on the image for a larger view.

I added a box (red, unfortunately) at 589nm, which is the wavelength of the sodium vapor safelights.
That wavelength is known to be safe at high intensities with all papers.
The red LED output at that wavelength is essentially zero.

- Leigh

[asuilin]

I used Luxeon-III superbright leds. Don't know if they are doped, but I had seen intense green and yellow strips on a surface of CD disk, using disk as poor man spectroscope for LED light

[Leigh]

You have to go by the manufacturer's datasheet. LEDs vary all over the place.

This has become much more universal since they invented the blue LEDs, and now try to make broad-spectrum lights.

Before that, LEDs were just indicators because you couldn't get full-spectrum output.
Narrow bandwidth was desirable for that application, but not for general lighting.

- Leigh

[Tin Can]

A guy stopped in to do a Lith neg Red LED test and I haven't talked to him about results yet. I am curious. I'll report his results.

No matter what the safelight, I move paper and X-Ray quickly in and out of 'safelight' exposure.

Nothing is sitting in safelight long at all.

Enlarging I use scrap for focus.

I'm using these now, and keeping them at 4 feet or more.

http://www.superbrightleds.com/moreinfo/led-globe/2-watt-g11-globe-bulb-360-degree/440/

[gth]

Just to look cool and be old timey, I use the Kodak Beehives with red leds and throw out the useless damaged original filters.

Actually the Beehive is still useful because it is directional and you can easily move them with the quick release mount. I still want some more nice ones.

Gotta watch out and fix their wiring sometimes...


Ok, so what happens to the old Kodak safelight filters? Do they start letting through broad spectrum light?
Can you tell other than testing with (X-ray) film or paper.

[Tin Can]

Most of the ones, all used, I have got, have 'light passing holes' in them from chem spill drops or something. Previous owners taped them up, but mostly they look ruined, edges pealed, cracks, etc and new one ares $50! Led's are $4.

I bought out a few darkrooms and I think some people were angry failures and didn't take good care of their 'junk'.

I have 6 Beehives and only one had a good clean filter, I did save that. I throw very little away.


Ok, so what happens to the old Kodak safelight filters? Do they start letting through broad spectrum light?
Can you tell other than testing with (X-ray) film or paper.

[rcmartins]

LEDs should emit pretty narrow wavelength bandwidth photons due to their physical design - the frequency of the emitted photons depends on the energy bandgap of the p-n junction which is determined by the doping material. Broader spectrum bandwidths typically require phosphors, i.e. materials that emits photons with frequencies (energy) different from the photons they receive. This is one way of producing white light with LEDs. Broader wavelengths can also be attained by mixing several different p and n doping materials in the junction which, if properly chosen, can also increase the current density thus allowing for brighter LEDs. The trend for extremely bright LEDs has killed the pure wavelength of the LED bulbs. Nowadays is very hard, and I am speaking from experience, to buy a really narrow spectrum bandwidth red light. Most of what I have bought in the last three years emits a lot of yellow/orange and even some green as others here have noticed. This is why I find it important for people to share their experience regarding red led safelights and this would be beneficial to be done continent wise since most of the times USA and european bulbs are incompatible.
raul

[rcmartins]

Also, another thing I have noticed is that less and less commercial bulb manufacturers reveal their bulbs true spectrum behaviour. When they do they simply state the wavelength as, for example, 635 nm. The trouble with this is that this wavelength is probably the highest energy wavelength but tells us nothing as to the width of the spectrum emission. The bulb might have its center frequency at 635 nm but emit as high as 500 nm (higher frequency) or more. Main stream chains also have more and more white light LED bulbs and less single color bulbs, which I understand perfectly are less interesting from a comercial point of view. This leaves us niche consumers a bit frustrated.
raul

[jose angel]

Another solution is to simply use led based replacement bulbs on the filtered safelights. They are cold, white or warm white light, they does`t warm up and can be fitted in the same E27 or E14 type base. They work like a charm.
I wonder why people don`t talk about it, maybe they are not available in the US? (!!)

[MrFujicaman]

Another solution is to simply use led based replacement bulbs on the filtered safelights. They are cold, white or warm white light, they does`t warm up and can be fitted in the same E27 or E14 type base. They work like a charm.
I wonder why people don`t talk about it, maybe they are not available in the US? (!!)

Uhhhh...that what I was talking about ! I was trying to find out what faded the safelight filters more...the heat from the old style bulbs or did the light slowly fade them out ?

[rcmartins]

Yes, that is true, however that solution has not the same convenience since it requires the expense of buying a filtered box which would be avoided if bare bulbs could be used. In my case I was able to buy a 1 W red bulb that works like a charm in a bathroom (its one of the two ceiling bulbs) 3 years ago. A year ago I bought a standing enlarger that I put in my tiny office (another division) an require more safe light yet I'm not able to find anymore a suitable bare bulb red LED. I am almost quitting searching for one and buying a filtered box replacing the incandescent light with a white LED version. But I would rather prefer not to.
raul

Another solution is to simply use led based replacement bulbs on the filtered safelights. They are cold, white or warm white light, they does`t warm up and can be fitted in the same E27 or E14 type base. They work like a charm.
I wonder why people don`t talk about it, maybe they are not available in the US? (!!)

[jose angel]

AP safelights work and are quite cheap. Also are the old Paterson ones, these are conical coloured thick plastic filters that are screwed into a base.
The problem with these is that tungsten bulbs are so hot, up to the point that the plastic cone is damaged. Along the years it will fade, I actually don`t know if the reason is the extreme heat, or the light, or just plastic material degradation.
As far as I can say, my older Patersons still work, I believe they have faded away but still safe at a longer distance. I also have some AP and two 5x7" old metal Kodaks. BTW, AP safelights require a little modification to use LED bulbs (easy, no materials needed).
My darkrooms (2) are not small, I have five lamps in the biggest one, right now and after testing them with 3 watts, one LED lamps, E14 fit. Light power is higher in comparison with older 15 watts tungsten bulbs, so a safelight test is obviously needed.
I really don`t mind about filter lasting. My Patersons are decades old and work, the AP ones are new and work.
Right now I`m using one of the Kodaks with an amber Ilford filter, but I prefer a wider light spread. Filters are insanely expensive, so I have my second one with a 2900ºK light for print evaluation. I`m planning to add another AP.