LEDs for the darkroom
1...@canoemail.com
reflection, I took them down the the room I will be using as a dark
room and plugged them in. They give much more light than the Kodak OC
filter with a 15 watt bulb.
I will have to do some exposure tests to see if they fog paper.
BTW, the cost for 35 lights is about $9.00 CDN.
BTW2: They produce no noticeable heat...
Jorge Omar
Jorge
1...@canoemail.com wrote in news:nd3stvscifgt1joji8rr5c690sobh2p666@
4ax.com:
1...@canoemail.com
will have to "put them up" every Christmas..
And by VC, you mean variable contrast papers like poly contrast
papers?
Jorge Omar
fixed grade.
Jorge
1...@canoemail.com wrote in news:5nastvobtl25493prdh67ctiu6ejnivqh2@
4ax.com:
Jan T
<1...@canoemail.com> schreef in bericht
news:5nastvobtl25493pr...@4ax.com...
just look how the light of your 'amber' LEDs reflects on the surface of a
CD; in the spectrum you'll find an inportant amount of green light, which
affects VC papers.
Test before using, there's a thorough method on Kodak's website (pub. no.
K-4)
Jan
1...@canoemail.com
<ja...@TAKETHISAWAYBEFOREYOUMAILtiscali.be> wrote:
>
>>
>just look how the light of your 'amber' LEDs reflects on the surface of a
>CD; in the spectrum you'll find an inportant amount of green light, which
>affects VC papers.
>Test before using, there's a thorough method on Kodak's website (pub. no.
>K-4)
I just tried your method. , hold a single led bulb cluster right and
there is a very obvious amber to green spectrum generated. I suspect
some Amberlith film might take this out. I have some ordered.
I live six hours drive from the nearest photoshop or art supply shop
that stocks these things.
I will also be attempting to rejuvinate a Thomas Safelight filter with
amberlith.
And I do intend to test before using. There is nothing more
frustrating than muddy prints due to light leaks.
Dan Quinn
> I will have to do some exposure tests to see if they fog paper.
If they don't work for VC they may work for Graded. Dan
Paul Repacholi
> Yes, variable contrast papers. They are more sensitive to amber than
> fixed grade.
Amber are best for colour paper with the Na D line gap in
its sencitization. Anyone have a figure for the wavelength
cut off of VC papers?
--
Paul Repacholi 1 Crescent Rd.,
+61 (08) 9257-1001 Kalamunda.
West Australia 6076
comp.os.vms,- The Older, Grumpier Slashdot
Raw, Cooked or Well-done, it's all half baked.
EPIC, The Architecture of the future, always has been, always will be.
Jorge Omar
Jorge
Paul Repacholi <pr...@prep.synonet.com> wrote in
news:87y8tco...@prep.synonet.com:
Claudio Bonavolta
news:87y8tco...@prep.synonet.com...
> Amber are best for colour paper with the Na D line gap in
> its sencitization. Anyone have a figure for the wavelength
> cut off of VC papers?
>
> --
> Paul Repacholi 1 Crescent Rd.,
> +61 (08) 9257-1001 Kalamunda.
> West Australia 6076
> comp.os.vms,- The Older, Grumpier Slashdot
> Raw, Cooked or Well-done, it's all half baked.
> EPIC, The Architecture of the future, always has been, always will be.
LED do not emit a single frequency like a lazer, they emit a spectrum, ok a
pretty narrow one. Amber LEDs may fog classic VC paper like Ilford's and
surely others like Bergger which require a red safelight.
Safe LEDs for any VC paper are deep red models.
I doubt an amber LED is safe for any color material.
Check the LEDs specs and you'll see the published curves are usually linear
and not logarithmic like paper sensitivity curves, so what may look like a
quickly falling curve is not so.
Cheers,
--
Claudio Bonavolta
http://www.bonavolta.ch
Peter Irwin
> pretty narrow one. Amber LEDs may fog classic VC paper like Ilford's and
> surely others like Bergger which require a red safelight.
> Safe LEDs for any VC paper are deep red models.
>
a few thicknesses of amberlith/rubylith? That ought to ensure
the light is "safe" and you could still have something bright,
but small and possibly battery powered.
Peter.
--
pir...@ktb.net
1...@canoemail.com
wrote:
The LED light clusters I refered to are amber Christmas lights.
They come in strings of 35 and 70 light clusters. They run off 110
volts and they run cool.
They also show a bit of green when you use a cd as a prism to break
out the diferent wavelengths.
I hope you are right on the Amberlith. I intend to try it later when I
can get some.
Malcolm Stewart
news:nd3stvscifgt1joji...@4ax.com...
A short time ago, I picked up one of the expensive Italian made Barbieri LED
color safelights at the local market for a song, and there's definitely an
additional filter material between the orange/yellow (?) LEDs and the outside.
There's also a brightness adjustment. Don't know when or if I'll ever use it,
and it graces my darkroom walls, but printing is now done on my 1270.
--
M Stewart
Milton Keynes, UK
www.megalith.freeserve.co.uk/oddimage.htm
http://myweb.tiscali.co.uk/ms1938/
John Stockdale
.....
> LED do not emit a single frequency like a lazer, they emit a spectrum, ok a
> pretty narrow one. Amber LEDs may fog classic VC paper like Ilford's and
> surely others like Bergger which require a red safelight.
> Safe LEDs for any VC paper are deep red models.
>
> I doubt an amber LED is safe for any color material.
> Check the LEDs specs and you'll see the published curves are usually linear
> and not logarithmic like paper sensitivity curves, so what may look like a
> quickly falling curve is not so.
This is exactly right. I have found that only the 660nm leds are
suitable for Ilford and Agfa multigrade. Forte VC papers (at least
some of them) are even more sensitive to yellowish light.
Agfa and Ilford both publish the wavelength response of their papers,
and so do LED manufacturers. They are not comparable without altering
the intensity scale from arithmetic to log units.
A sheet of Rubylith cured my problems with 635nm LEDs.
Try viewing the light from the LEDs by reflection from the surface of
a CD at the angle that gives the "rainbow" effect. You might be
surprised by how much yellow-green, green and even aqua is emitted.
Paul Repacholi
> "Paul Repacholi" <pr...@prep.synonet.com> wrote in message
> news:87y8tco...@prep.synonet.com...
> I doubt an amber LED is safe for any color material. Check the LEDs
> specs and you'll see the published curves are usually linear and not
> logarithmic like paper sensitivity curves, so what may look like a
> quickly falling curve is not so.
From the tests I did with colour paper, and this was around 25 years
ago :( I found that it was critical to keep current, and thus
temperature as low as possible. Sumise at the time was that the
emission was broadened by higher junction temp enough to get into the
cyan layer. I *think* this was the current at the time Agfa paper.
Chris Ellinger
>I bought a string of 35 amber LED CHristmas lights. After a minutes
>reflection, I took them down the the room I will be using as a dark
>room and plugged them in. They give much more light than the Kodak OC
>filter with a 15 watt bulb.
>I will have to do some exposure tests to see if they fog paper.
To do a proper safelight test, the paper must first be exposed to
enough white light to produce a very light gray tone when developed.
Kodak has detailed instructions:
http://www.kodak.com/global/en/consumer/products/techInfo/k4/k4TestSafelite.shtml
Chris Ellinger
Ann Arbor, MI
Chris Ellinger
>> Amber are best for colour paper with the Na D line gap in
>> its sencitization. Anyone have a figure for the wavelength
>> cut off of VC papers?
>>
>http://www.ilford.com/html/us_english/pdf/mgivrc.pdf
>
>Jorge
The Ilford VC papers seem to be less sensitive to amber than some
other VC papers. Berger and Forte VC papers require red safelights.