Potentially useful LEDs for darkroom/alt applications

[Michael R]

In the process of exploring for really good plug-and-play LEDs, I came across Waveform Lighting. What’s good about the stuff this company sells is that they provide some of the specs you want for LEDs to help avoid potential pitfalls depending on what you are doing.

For example, rather than just indicating a CRI, which can be a murky measure, they give you Ra, R9, Re, what the continuous spectrum looks like, photometric reports, TLCI etc.

I was looking at their Absolute line for a specific purpose (currently they offer strips and modules, and I think individual components for those more skilled). They are supposed to be effectively flicker-free, and their dimmers are >25kHz (to accommodate high video frame rates).

Not exactly cheap of course, however they have other product levels a little less overkill and it occurred to me these might be of some use for making LED enlarger light sources, UV alt exposure devices, perhaps even safelighting.

Anyhow just mentioning for thought, discussion or whatever.

[Tin Can]

Why no link?

[Jason Greenberg Motamedi]

https://www.waveformlighting.com/film-photography

[Michael R]

Why no link?

Sorry about that...

https://www.waveformlighting.com/

[Tin Can]

Thank you both!

[bob carnie]

thanks for the link Michael - the UV flood light is interesting , I wonder if it is stronger than the current 1ks metal halide uv lights on Nuarks. Potentially with diffusion and attached to a Ian Leake measuring device which is linked to a timer shutoff device this could be exactly what I am looking for . I have the vacuum easels and am trying to source a very strong UV light to replace the Nuarc lights. I have need to do up to 30 x 40 and need lots of power as now its over 20 minutes for pt pd with the units I have.

[Michael R]

I don’t know enough about typical alt process wavelength ranges (UVA or UVB) and power requirements, or the efficiency/efficacy of the Nuarc lights. Someone else would have to answer.

My first though is wouldn’t you need a whole bunch of these?

Most UV lights are quite inefficient in actual UV output (mostly wasted power in violet/near UV). The Waveform UV LEDs seem to be significantly more efficient in this respect but the flood light is still just one 20 watt (power consumption) LED. You can generate more power with one of their 16’ strips I guess.


thanks for the link Michael - the UV flood light is interesting , I wonder if it is stronger than the current 1ks metal halide uv lights on Nuarks. Potentially with diffusion and attached to a Ian Leake measuring device which is linked to a timer shutoff device this could be exactly what I am looking for . I have the vacuum easels and am trying to source a very strong UV light to replace the Nuarc lights. I have need to do up to 30 x 40 and need lots of power as now its over 20 minutes for pt pd with the units I have.

[r.e.]

Andrew Lock, the Australian gaffer who presents the YouTube channel Gaffer & Gear (https://www.youtube.com/channel/UCOgN351K45vTrozaadFPXlA/videos), is probably as on top of what's happening with LED lights as anybody. He also gets into the technical details and often talks about the relative utility of scoring systems such as CRI.

[sanking]

I don’t know enough about typical alt process wavelength ranges (UVA or UVB) and power requirements, or the efficiency/efficacy of the Nuarc lights. Someone else would have to answer.

My first though is wouldn’t you need a whole bunch of these?

Most UV lights are quite inefficient in actual UV output (mostly wasted power in violet/near UV). The Waveform UV LEDs seem to be significantly more efficient in this respect but the flood light is still just one 20 watt (power consumption) LED. You can generate more power with one of their 16’ strips I guess.


The NuArc metal halide lights radiate in several UV bandwidths and for this reason are useful for a wide range of processes that have different bandwidth requirements for exposure. The downside is that they are quite inefficient and can create a lot of heat with the long exposures sometimes required in alternative printing.

LEDs radiate in a very narrow bandwidth around the stated wavelength and are very efficient, but may not work at all for processes well outside of the bandwidth. For example, LEDs of 385 nm, work fine for dichromate and iron based processes which are sensitive in this bandwidth, but are virtually useless for photopolymer which requires bandwidth of around 350 nm.

With regard to Bob Carnie's question, the most efficient and least expensive way to put together an LED unit of 30X40" that would print well with gum and iron processes would be to fabricate a bank of 6-8 100 watt LED flood lights. The best one to use in my opinion would be the 100 watt Everbeam flood that radiate at 365 nm. https://www.amazon.com/Everbeam-Black-Light-Flood-365nm/dp/B0863HD955/ref=sr_1_5?dchild=1&keywords=uv%2Bflood%2B365nm&qid=1629581258&sr=8-5&th=1

You could save few bucks with 385 nm floods, but for a range of processes the 365 nm flood is far better.

Sandy

[Tin Can]

Thanks for the reminder Sandy, just bought 5 @ 365mm 50 watt

1 as spare, I will be making smaller prints

100 watt out of stock

[Jim Noel]

Thanks for this link and to Sandy for his input.

[Drew Wiley]

CRI is meaningless with respect to ideal printing wavelengths in relation to UV and other alt processes, even with respect to conventional color printing. It's specific wavelength points that count. High CRI is relevant when displaying prints or making color evaluations. Those Waveform strips and panels are for sake of overhead lighting. The reason they're so expensive is that every one of the blue LED's needs to be fitted with a corrective violet filter to inch the CRI higher. But they what are marketing is actually assembled from components they obtain from others. So if I wanted to replace just one of my 4 ft overhead 5000K 95CRI fluorescent panels with something more modern LED-wise, it would cost me $450, dependent upon a special electronic controller which would probably interfere with certain of my darkroom controllers. But my actual matching lights are 98CRI already, so what's the point? (They cost quite a bit too).

[sanking]

Thanks for this link and to Sandy for his input.

Jim

You are very welcome.

One more general comment. Although there is an efficient heat shield on the back of the units I would still recommend ventilation of the backs of the units with air from a small fan. Radiation decreases with heat build up, and more heat also decreases life of the LEDs.

Sandy

[Michael R]

Obviously CRI is not for UV. My needs would be for white light to replace my non-LED source, and I was curious to see if I could find a good LED solution. Not the usual Ra CRI. A high Re CRI with high numbers for all 14 test colours, and a good continuous spectrum.

It’s not unique technology. As far as I know all really good white light LEDs use violet excitation with R, G and B phosphors (rather than the more common blue excitation with Y and R phosphors) to generate a much better spectrum. These Waveform products have the added benefit of being plug-and-play, so I thought it might be good to mention them here.




CRI is meaningless with respect to ideal printing wavelengths in relation to UV and other alt processes, even with respect to conventional color printing. It's specific wavelength points that count. High CRI is relevant when displaying prints or making color evaluations. Those Waveform strips and panels are for sake of overhead lighting. The reason they're so expensive is that every one of the blue LED's needs to be fitted with a corrective violet filter to inch the CRI higher. But they what are marketing is actually assembled from components they obtain from others. So if I wanted to replace just one of my 4 ft overhead 5000K 95CRI fluorescent panels with something more modern LED-wise, it would cost me $450, dependent upon a special electronic controller which would probably interfere with certain of my darkroom controllers. But my actual matching lights are 98CRI already, so what's the point? (They cost quite a bit too).

[Tin Can]

Sandy

Good point on heat danger

Safeties are needed, with very secure electrical on-off, perhaps a lockout or 3

We certainly do not want to 'forget' and leave the fire on



Jim

You are very welcome.

One more general comment. Although there is an efficient heat shield on the back of the units I would still recommend ventilation of the backs of the units with air from a small fan. Radiation decreases with heat build up, and more heat also decreases life of the LEDs.

Sandy

[j.e.simmons]

What’s the coverage on one of these floods a reasonable distance from the paper? For instance, would one cover 8x1? 2?

[sanking]

What’s the coverage on one of these floods a reasonable distance from the paper? For instance, would one cover 8x1? 2?

John

I tested one of the units last December and posted my findings on the groups.io site on 12/10/2020. I address your question in that post, which I am copying here along with other commends.

Sandy

"UV integrators are useful in printing, and also very nice to have if you need to compare UV output of specific light sources. I have some older Olix light integrators that I use in regular printing, and also own a PPM-1 meter that I use to compare different light sources.

I had the chance during the past several days to work with one of the 365 nm 100-watt UV floodlights, sold by Amazon with the Everbeam brand. I made a few quick comparison tests using the PPM-1 to compare output in various situations.

First, I measured useful radiation on center at 12", 18" and 24". Output decreases with distance more or less in accord with the what one would expect with point source light, i.e, every time you double the distance between the light source and the exposure plane, exposure times increase by 4. So here are the results.

12" Center of flood to exposing plane -- 1000 second gives UV Dose of 6400 -- Would print evenly about 8X10" in size.
18" Center of flood to exposing plane -- 1000 seconds gives UV Dose of 2744-- Would print evenly about 11X14" in size.
24" Center of flood to exposing plane -- 1000 second gives UV Dose of 1700 -- Would print evenly about 16X20" in size.

Other comparisons.

1) Measuring UV dose outside, on a sunny day in open shade, facing north at 12 noon on December 18, at north latitude 34º35 minutes, 1000 seconds gave UV does of 1820.

2) My regular Ryonet LED printing unit, with a mix of 365 nm and 385 nm leds, 1000 seconds gives UV dose of 6675. With this unit my typical exposures require UV Dose of about 5000, or about 750 units/seconds.

The 100 watt 365 nm flood is about 3 lbs. in weight, has an overall size of about 8X10", with the leds in an area in the center about 4.5" X 3" in size. There is good heat shield on the back but you would still need to cool the unit with a fan blowing over the heat shield to keep the unit cool as radiation decreases with heat build up. Combine it with a contact-printing frame and I think you have a pretty efficient UV source for making small and medium size prints. And one could also weigh the possibility of ganging up 4-6 of the floods for wider coverage. The most efficient flood for printing carbon with dichromate sensitized tissue would be the 365 nm leds, but 385 nm would be less expensive and probably almost as efficient. For DAS you would definitely want the 365 nm light.

BTW, have a look at the linked video, about salt printing, produced by the George Eastman Museum. https://www.youtube.com/watch?v=VDfdFjDL6bU&feature=youtu.be
In the video you will see that they are using what appears to be a couple of small UV flood lights ganged together for the exposure."

Sandy

[bob carnie]

I am hoping not to hi jack Michaels thread but I have a somewhat related question.

I make up to 30 x 40 pt pd and multiple gums, I currently have a 30 x 40 Nuarc system with a 1000k Metal Halide head, I am finding my exposures too long for my workflow ( I do multiple images each day and would like more power)
I have been talking with Ian Leake about modifying one of his density measuring devices to connect to a power supply that will shut off after a set exposure is met. He believes it is quite simple, I want to just use the base vacuum systems to hold my material I have two units ( one has already been modified so the vacuum turns on independently of the exposure) I would do the same to the other unit. I have a small exposing room where I walk out of the room as work is being exposed and I do need this automatic shutoff system.(important)
I would like to hang a light above each unit. If 1000k is what I have now I am thinking I would like 4000 k - 6000k to speed up my large printing time.

Is there a unit available Used and or New that can do this for me and of course replacement bulbs and parts for the future.
If I designed a bank of these types of lights or Led lights that would work with Pt, gum, cyanotype and salt... do you think the power could equal my needs posted above.. Somehow I think Sandy in the past has talked about (Carbon Arc hanging units) and I think this is something Calvin Grier in Spain may be using.
I have seen Jon Cones system which is quite good, but my space would really work well with a hanging light system above the vacuum table so I can take large film in and out of the unit with ease and not worry about lifting the whole head as I currently do with my
Nuarc 32 1KS unit.

any help

Bob

[bob carnie]

By the way Michael - If I go to a different route I have three heads 1 Ks available to give you , just a 5 hour ride .

Bob

[j.e.simmons]

Thanks, Sandy.

[Michael R]

No worries, hijack away. Just started the thread for discussion so whatever direction it goes in is fine with me, especially if you end up with a solution.



I am hoping not to hi jack Michaels thread but I have a somewhat related question.

I make up to 30 x 40 pt pd and multiple gums, I currently have a 30 x 40 Nuarc system with a 1000k Metal Halide head, I am finding my exposures too long for my workflow ( I do multiple images each day and would like more power)
I have been talking with Ian Leake about modifying one of his density measuring devices to connect to a power supply that will shut off after a set exposure is met. He believes it is quite simple, I want to just use the base vacuum systems to hold my material I have two units ( one has already been modified so the vacuum turns on independently of the exposure) I would do the same to the other unit. I have a small exposing room where I walk out of the room as work is being exposed and I do need this automatic shutoff system.(important)
I would like to hang a light above each unit. If 1000k is what I have now I am thinking I would like 4000 k - 6000k to speed up my large printing time.

Is there a unit available Used and or New that can do this for me and of course replacement bulbs and parts for the future.
If I designed a bank of these types of lights or Led lights that would work with Pt, gum, cyanotype and salt... do you think the power could equal my needs posted above.. Somehow I think Sandy in the past has talked about (Carbon Arc hanging units) and I think this is something Calvin Grier in Spain may be using.
I have seen Jon Cones system which is quite good, but my space would really work well with a hanging light system above the vacuum table so I can take large film in and out of the unit with ease and not worry about lifting the whole head as I currently do with my
Nuarc 32 1KS unit.

any help

Bob

[sanking]

Somehow I think Sandy in the past has talked about (Carbon Arc hanging units) and I think this is something Calvin Grier in Spain may be using.

Bob

Bob

I am getting older, but still not as ancient as you think!

The carbon arc light was invented in the first decade of the 1800s and was the first practical electric light. It was widely used starting in the late 19th century for street and large building lighting until it was replaced by the incandescent light in the early 20th century. The carbon arc was used in more specialized applications where a high intensity point light source was needed, such as movie projectors and printing until after World War II.

I knew an elderly gentleman (in his 80s in the 1980s) who used a carbon arc, but I never saw one used in practice.

Sandy

[Ron McElroy]

I am hoping not to hi jack Michaels thread but I have a somewhat related question.

I make up to 30 x 40 pt pd and multiple gums, I currently have a 30 x 40 Nuarc system with a 1000k Metal Halide head, I am finding my exposures too long for my workflow ( I do multiple images each day and would like more power)
I have been talking with Ian Leake about modifying one of his density measuring devices to connect to a power supply that will shut off after a set exposure is met. He believes it is quite simple, I want to just use the base vacuum systems to hold my material I have two units ( one has already been modified so the vacuum turns on independently of the exposure) I would do the same to the other unit. I have a small exposing room where I walk out of the room as work is being exposed and I do need this automatic shutoff system.(important)
I would like to hang a light above each unit. If 1000k is what I have now I am thinking I would like 4000 k - 6000k to speed up my large printing time.

Is there a unit available Used and or New that can do this for me and of course replacement bulbs and parts for the future.
If I designed a bank of these types of lights or Led lights that would work with Pt, gum, cyanotype and salt... do you think the power could equal my needs posted above.. Somehow I think Sandy in the past has talked about (Carbon Arc hanging units) and I think this is something Calvin Grier in Spain may be using.
I have seen Jon Cones system which is quite good, but my space would really work well with a hanging light system above the vacuum table so I can take large film in and out of the unit with ease and not worry about lifting the whole head as I currently do with my
Nuarc 32 1KS unit.

any help

Bob

Bob

Olec, Nuarc and I believe other companies made 5kw units for exposing plates and proofing during the film days of offset printing. I am not sure how easily they can be found at this time. I reached out to my former employer, I retired at the first of the year, to see if they still had the unit sitting unused in storage, but alas it along with the Douthitt vacuum frame were tossed during a warehouse purge. I would not recommend using carbon arc lamps. I used them in the late 70s / early 80s and NASTY. They need lots of good forced ventilation due to the ash produced when the carbon rods burn.

[koraks]

> Is there a unit available Used and or New that can do this for me and of course replacement bulbs and parts for the future.

Bob, I'm a bit far away from you geographically, but what you want isn't insanely difficult for someone with a little electronics engineering acumen. I'd go with a light head of an array of 50w or 100w UV COB leds mounted onto appropriate aluminium heat sinks with fans; fortunately these are standard off the shelf parts these days. Power supply can be an off the shelf unit; 48V would do. Driver and timer circuitry could be either off the shelf or custom engineered. Lately I've reengineered my enlarger light source (RGB color, ca 365W across all channels total) and made a tiny UV printing source (mostly for PCB's, but it does alt. process as well). The electronics aren't insanely complex. See if you can locate someone with a decently functioning "amps and volts" brain where you live. If I hadn't been a continent away I'd have been happy to do this for you.

[Tin Can]

My latest plan is getting bigger, but modular. I now have 10 of the 50 watt 365mm Everclear.

I also await a bench from a mfg I already know, Amazon was way cheaper. Seville Classics (UHD20247B) UltraHD Lighted Workbench (48L x 24W x 65.5H Inches) Stainless Steel (https://www.amazon.com/gp/product/B005NAVFEW/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1)

By using 10 lamps in different configs hanging over my pressure plate, I can switch them on and off, as needed

Yes, I will install curtains or metal light shields, making a simple rack to hang from, allowing adjustment of lamp pattern and height

Ventilation will be determined, if needed at all

Use timers, temperature and power meter to identify variation

I may put wheels on it

[sanking]

My latest plan is getting bigger, but modular. I now have 10 of the 50 watt 365mm Everclear.

I also await a bench from a mfg I already know, Amazon was way cheaper. Seville Classics (UHD20247B) UltraHD Lighted Workbench (48L x 24W x 65.5H Inches) Stainless Steel (https://www.amazon.com/gp/product/B005NAVFEW/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1)

By using 10 lamps in different configs hanging over my pressure plate, I can switch them on and off, as needed

Yes, I will install curtains or metal light shields, making a simple rack to hang from, allowing adjustment of lamp pattern and height

Ventilation will be determined, if needed at all

Use timers, temperature and power meter to identify variation

I may put wheels on it

Wow,

You da man!

That unit should give you a great exposure unit for UV processes. With floods placed at 8-12" from the exposing plane you should have fast exposures and very even exposure over a large printing area. For consistent exposures, especially in warm conditions, you might consider installing a light integrator designed for 365 nm. Some of the old Olix sensors would be perfect for this.

I like the idea of wheels!!

Sandy

[Tin Can]

I have hesitated too long almost, you are a very good resource

I have PPM-1 LightMeasure UV Exposure Meters (https://www.alternativephotography.com/lightmeasure/)

and another UVA-B meter

Thank you





Wow,

You da man!

That unit should give you a great exposure unit for UV processes. With floods placed at 8-12" from the exposing plane you should have fast exposures and very even exposure over a large printing area. For consistent exposures, especially in warm conditions, you might consider installing a light integrator designed for 365 nm. Some of the old Olix sensors would be perfect for this.

I like the idea of wheels!!

Sandy

[Jeffz]

I found this as a recommendation on YouTube for Cyanotype UV light source. Anyone have experience with this light for other forms of Alt Processing?

https://www.amazon.ca/NEW-2020-MODEL-Performance-Ultraviolet/dp/B0863HD955

[Tin Can]

Adding a link from 2008

Alternative Process Darkroom (https://www.largeformatphotography.info/forum/showthread.php?40877-Alternative-Process-Darkroom&p=394006&viewfull=1#post394006)










There are many more to find

[Michael R]

Just a note of extra info for any fellow “white light” folks regarding Waveform Lighting plug-and-play stuff, based on a response I received from them. Their standard PWM dimmer operates at 25kHz.

[Ron McElroy]

For anyone still looking for LED exposure units, the 100 watt Everbeam 365nm floods are back in stock at Amazon. I just ordered 4 of them.
https://www.amazon.com/gp/product/B0863HD955/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

[Tin Can]

I got my last 2 of 12, 50 watt 365nm yesterday

I think many want them for Hell-O-Ween

Still configuring, but very close to using 6 in close formation


For anyone still looking for LED exposure units, the 100 watt Everbeam 365nm floods are back in stock at Amazon. I just ordered 4 of them.
https://www.amazon.com/gp/product/B0863HD955/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

[Michael R]

Thought I'd post a shot of my little light box made using an Absolute reel from Waveform.

220928

[Tin Can]

S11 LED Bulb - 7.5 Watt Equivalent LED Globe Bulb - 27 Lumens - Red (https://www.superbrightleds.com/moreinfo/globe-bulbs/s11-led-bulb-75-watt-equivalent-led-globe-bulb-27-lumens/440/1477/)

Just ordered 8 more for testing

They are cheap enough for anybody to self test

I am revamping my safelight environment to larger areas

[paulbarden]

A few years ago I bought an LED grow light to supplement the light in my orchid house during the winter - the Platinum Series P450 LED grow light, 450 watts. Its one of those lamps that gives a very intense pinkish light. Well, I retired my greenhouse 18 months ago (affordability issues - thanks pandemic) and so I have this $$$ grow light I have no use for. Until recently, that is. I started making Salt Prints of some 8x10 negatives and thought I would test this grow light to see if it could be useful in making Salt Prints. As it turns out, I can fully expose a Salt Print in 7-9 minutes under this light. Seems pretty good to me.

I wouldn't suggest anyone rush out and buy one of these for alt print making processes, but I wanted to share the fact that it does work very well.

[Michael R]

S11 LED Bulb - 7.5 Watt Equivalent LED Globe Bulb - 27 Lumens - Red (https://www.superbrightleds.com/moreinfo/globe-bulbs/s11-led-bulb-75-watt-equivalent-led-globe-bulb-27-lumens/440/1477/)

Just ordered 8 more for testing

They are cheap enough for anybody to self test

I am revamping my safelight environment to larger areas

When I bought the white LED reel from Waveform (see box above ~6,000 lumens, 5000k, continuous spectrum, super high Ra and Re, ie quality overkill), I added one of their red reels to my order out of curiosity. Their red has a relatively narrow band and might also lack the anomalous spikes that fog peoples' paper/films. I haven't done any safelight tests with it yet. I have 16 feet of it and a few inches are probably enough to light a darkroom LOL.

I might also get one of their amber reels and put a few inches behind my Kodak OC filter instead of the old incandescent bulb. Might help to increase the longevity of the filters.

[Tin Can]

Now that's an idea!

I now have a pile of KODAK Bullets, I love the Art Deco design, one will be my bed reading lamp, that will replace my DIY reflector below

Switching out the 15 watt incandescents will save the NOS KODAK filters

and I can use those bulbs in my fancy old contact printer




When I bought the white LED reel from Waveform (see box above ~6,000 lumens, 5000k, continuous spectrum, super high Ra and Re, ie quality overkill), I added one of their red reels to my order out of curiosity. Their red has a relatively narrow band and might also lack the anomalous spikes that fog peoples' paper/films. I haven't done any safelight tests with it yet. I have 16 feet of it and a few inches are probably enough to light a darkroom LOL.

I might also get one of their amber reels and put a few inches behind my Kodak OC filter instead of the old incandescent bulb. Might help to increase the longevity of the filters.

[John Kasaian]

A short string of red led Christmas lights serve as my safe light since GE discontinued their Guide Lamp night lights.
I got 'em on clearance at CVS.

[Carl J]

For anyone still looking for LED exposure units, the 100 watt Everbeam 365nm floods are back in stock at Amazon. I just ordered 4 of them.
https://www.amazon.com/gp/product/B0863HD955/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

I have one of the 100w Everbeam's for 8x10 and it works well for Salt (and presumably other alt processes). Earlier in the year I purchased 8 of the 24" Barrina 395nm 9w T5 LEDs but the single Everbeam gives much shorter exposures.

How are you going to mount yours? I'm thinking of picking up at least 1 (possibly more) for larger negatives.

[Carl J]

Thought I'd post a shot of my little light box made using an Absolute reel from Waveform.

220928

Nice. Those Waveform Absolute realUV strips look pretty cool (and available in 365nm), but looks to be more expensive than the Everbeam's. Visiting their web page, how many feet did you use for your light box?

[Tin Can]

My scheme to mount multi Everclear has evolved

I now have 2 SS folding shelf brackets, adding crosswise supports

They will fold away to wall

Black OR white TBD Coroplast folded will block stray rays as necessary

or perhaps just leave DR using timers

Winter work



I have one of the 100w Everbeam's for 8x10 and it works well for Salt (and presumably other alt processes). Earlier in the year I purchased 8 of the 24" Barrina 395nm 9w T5 LEDs but the single Everbeam gives much shorter exposures.

How are you going to mount yours? I'm thinking of picking up at least 1 (possibly more) for larger negatives.

[Michael R]

Nice. Those Waveform Absolute realUV strips look pretty cool (and available in 365nm), but looks to be more expensive than the Everbeam's. Visiting their web page, how many feet did you use for your light box?

Hi Carl, I wound the entire 16.4’ reel into the box. It fit nicely into 15cmx10cmx14cm. 1.5:1 was the aspect ratio I wanted for this box - it is for my sensitometer build which is why I went overkill with the Absolute strip. I really wanted the most continuous, high Re (not just Ra) spectrum.

Winding the strip around the perimeter of the box makes the whole thing function as a mixing chamber, and will require virtually no, or minimal diffusion (didn’t put the front/bottom on yet as you can see). Reduced diffusion requirements mean less light loss. This unit puts out approximately 6000 lumens.

I’m thinking I can likely scale this up a little to make an excellent 4x5 enlarger light source. Another option would be to use their tungsten strip or sheet. Those are not quite as good as the Absolute series but still excellent and plenty good enough for enlarging, likely much higher real CRI than any LED heads you buy off the shelf. The FilmGrade strips put out even more light than the Absolute strips, and a tungsten balance should work quite well with Ilford Multigrade filters.

A nice thing about their stuff being geared toward the video/film industry is there is almost no flicker in the system, and the PWM dimmer functions at 25kHz (they test up to 240fps video). This is all overkill for enlarging/printing of course, but is important for sensitometry, which was the original purpose of my project.

Sorry if this seems like marketing. I’m not affiliated at all with this company. Just a satisfied customer who needed something good but also plug-and-play/trivial to hook up (I’m not an electrician).

[koraks]

I’m thinking I can likely scale this up a little to make an excellent 4x5 enlarger light source. Another option would be to use their tungsten strip or sheet. Those are not quite as good as the Absolute series but still excellent and plenty good enough for enlarging, likely much higher real CRI than any LED heads you buy off the shelf. The FilmGrade strips put out even more light than the Absolute strips, and a tungsten balance should work quite well with Ilford Multigrade filters.
High CRI isn't really necessary for an enlarger light source. It even isn't for color, and for B&W it's entirely superfluous. It doesn't hurt either, of course, but it's just not a relevant consideration.

[Michael R]

High CRI isn't really necessary for an enlarger light source. It even isn't for color, and for B&W it's entirely superfluous. It doesn't hurt either, of course, but it's just not a relevant consideration.

I’d rather have a high CRI/smoother spectrum for sensitometry. Low flicker is necessary.

For enlarging/printing, the higher the “complete” CRI, the closer the approximation will be to whatever incandescent source, so even for black and white I would not go as far as calling it superfluous. Of course it isn’t necessary but for example if one is accustomed to using an incandescent source with VC filters things will be more wonky with typical garbage “white” LEDs.

Could also help to have a high CRI for digitizing film with digital cameras, as seems to be a trend.

Anyway I’m not trying to sell anyone anything. I was just happy to find some decent quality/violet emission LED plug-play systems with good photometric specs, low voltage drop and low flicker.

[koraks]

I’d rather have a high CRI/smoother spectrum for sensitometry. Low flicker is necessary.

For enlarging/printing, the higher the “complete” CRI, the closer the approximation will be to whatever incandescent source, so even for black and white I would not go as far as calling it superfluous. Of course it isn’t necessary but for example if one is accustomed to using an incandescent source with VC filters things will be more wonky with typical garbage “white” LEDs.

Could also help to have a high CRI for digitizing film with digital cameras, as seems to be a trend.

In all the applications you mention, you need to ask yourself to what extent the availability of a continuous spectrum is in fact beneficial. The comparison with incandescent bulbs is tricky and I'd say misleading - the question is not how well the new technology matches the old one. The question is to what extent the new technology matches the demands of the job.

Black and white paper? It's all sensitive to blue and/or green. There's no benefit whatsoever in having a continuous spectrum. In fact, for split grade printing, a continuous spectrum is more of a liability than an asset - albeit with minor impact. Appropriately chosen blue and green leds are by far the most efficient and effective approach conceivable with today's technology.

Color paper? All optimized for narrow band RGB semiconductor light sources these days.

Digital cameras? Again, RGB. Although I admit just throwing a high CRI light source at the job is a straightforward solution with little hassle.

Sensitometry? We can debate this one, because it's out in the open how you implement the actual sensor front end. But here as well, with today's technology, you'd always be working with a compound signal of fairly narrow-band wavelengths if you want any kind of decent channel separation.

In all cases above, CRI is far less interesting than a proper match between the light source and the application. In photography, interestingly, only in the recording stage CRI is important. THAT's where it's absolutely vital, as well as in judging prints. CRI matters, a lot. Just in different areas!

[Michael R]

Of course you don't need a continuous spectrum to expose blue/green sensitive paper. But if you are using say Ilford MG filters and have light with violet-blue-green components more similar to a tungsten source, you're more likely to get closer to Ilford's specs for grade spacing and speed matching. Nothing mandatory here, but it's not simply a case of matching the old technology for its own sake.

I disagree that it is a liability vs blue and green LEDs, or RGB LEDs. White light is less efficient in principle, however in practice "appropriately chosen blue and green LEDs", or RGB LEDs doesn't happen. It could of course happen, but nobody does that properly. Then they complain. For anyone else interested, CRI is only one measure, and it can be misleading without detail/context.

I understand the physics. I'm sure you understand it. Perhaps I didn't explain myself well. I wanted specific characteristics for my sensitometer light source, and it occurred to me that high CRI LEDs might make for simpler LED implementations for things like enlarger heads and such. That's all.



In all the applications you mention, you need to ask yourself to what extent the availability of a continuous spectrum is in fact beneficial. The comparison with incandescent bulbs is tricky and I'd say misleading - the question is not how well the new technology matches the old one. The question is to what extent the new technology matches the demands of the job.

Black and white paper? It's all sensitive to blue and/or green. There's no benefit whatsoever in having a continuous spectrum. In fact, for split grade printing, a continuous spectrum is more of a liability than an asset - albeit with minor impact. Appropriately chosen blue and green leds are by far the most efficient and effective approach conceivable with today's technology.

Color paper? All optimized for narrow band RGB semiconductor light sources these days.

Digital cameras? Again, RGB. Although I admit just throwing a high CRI light source at the job is a straightforward solution with little hassle.

Sensitometry? We can debate this one, because it's out in the open how you implement the actual sensor front end. But here as well, with today's technology, you'd always be working with a compound signal of fairly narrow-band wavelengths if you want any kind of decent channel separation.

In all cases above, CRI is far less interesting than a proper match between the light source and the application. In photography, interestingly, only in the recording stage CRI is important. THAT's where it's absolutely vital, as well as in judging prints. CRI matters, a lot. Just in different areas!

[koraks]

Well, nothing wrong with using high CRI leds for the purposes you mention. It's one way of getting there. I must vehemently disagree on the notion that appropriately chosen blue/green or RGB leds doesn't happen. Especially for B&W, it's relatively easy to get there DIY-ing your way into it with some basic knowledge. For color it can be done as well. Heiland seems to do a pretty neat job at it, at least. I think I do, too, without any commercial interest or ambition.

I guess I just want to give a counterbalance to the sentiment that high CRI is the only or even the best way to go. There are several ways to skin this cat.

Btw, I have some fairly high CRI led strips on order for my new darkroom. Seems like low-cost Chinese sellers are starting to service this niche as well, which make sense. Today, we tend to call >95 high CRI (or even >90...); I bet that >95 will be default in 2-3 years and high will be >98. Today's special is tomorrow's fodder.

[Michael R]

I mostly agree, Koraks - except regarding appropriately chosen blue/green or RGB LEDs, although my disagreement is not vehement :). Since I know you understand light and emulsion sensitivity, I have no doubt it was relatively trivial for you to DIY it. Probably Heiland also - though a little expensive for what it is (just my opinion, even though it comes with the split grade bla bla).

However anecdotally when the average DIY person makes a blue/green or RGB head they seem to frequently have problems with things like contrast range and spacing, because they just buy whatever blue or green etc. LEDs. At least this has been my experience having read many threads over the years on forums. Therefore I still think for DIY LED conversions it would likely be simpler for many people to go with relatively high quality/CRI/Re white light even though bypassing filtration with “additive” mixing/successive exposures is certainly a more ideal end game as you rightly point out.

I think you’re probably right about the higher CRI and higher R9/Re LEDs (ie violet emission/excitation with RGB phosphors) rather than the traditional blue emission with yellow) making their way into cheaper stuff. Hopefully the same for flicker control and higher PWM dimming frequency, not that these matter for print exposure.

The “Absolute” strip I went with for my DIY is obviously overkill, and of course I won’t get exactly the output spectrum in the end anyway because of the mixing box, but I’m quite pleased with how it worked out.


Well, nothing wrong with using high CRI leds for the purposes you mention. It's one way of getting there. I must vehemently disagree on the notion that appropriately chosen blue/green or RGB leds doesn't happen. Especially for B&W, it's relatively easy to get there DIY-ing your way into it with some basic knowledge. For color it can be done as well. Heiland seems to do a pretty neat job at it, at least. I think I do, too, without any commercial interest or ambition.

I guess I just want to give a counterbalance to the sentiment that high CRI is the only or even the best way to go. There are several ways to skin this cat.

Btw, I have some fairly high CRI led strips on order for my new darkroom. Seems like low-cost Chinese sellers are starting to service this niche as well, which make sense. Today, we tend to call >95 high CRI (or even >90...); I bet that >95 will be default in 2-3 years and high will be >98. Today's special is tomorrow's fodder.

[bob carnie]

I have gone a bit further down the wormhole due to MR who are the experts in Nuarcs telling me they would not send in a technician to my lab because my 32 1Ks unit was built in 1994 and they are not servicing my unit or supplying parts. I have a electrical dude coming in and may have him look inside and decide what the issue is with my unit, I think it may be a ballast but what the hell do I know. I just print . So I have spoken with this Detroit Michigan company http://www.douthittcorp.com/ and they were extremely helpful and have refurbished units with light ballast and integrator shut off and on unit and send out a lot of power. They are not cheap but I do a lot of printing and with a hanging 1 ks system trying to do 30 x 40 inch gum over pd I am in 20 min per layer timelines which is 4 times what I am use to doing 16 x 20 so its a real solution, I just have to pick a few more brains here and on FB alt groups before I decide to go this route.

[Ron McElroy]

I have one of the 100w Everbeam's for 8x10 and it works well for Salt (and presumably other alt processes). Earlier in the year I purchased 8 of the 24" Barrina 395nm 9w T5 LEDs but the single Everbeam gives much shorter exposures.

How are you going to mount yours? I'm thinking of picking up at least 1 (possibly more) for larger negatives.

I haven't had an opportunity to work up anything yet.

[Ulophot]

"At least this has been my experience having read many threads over the years on forums. Therefore I still think for DIY LED conversions it would likely be simpler for many people to go with relatively high quality/CRI/Re white light..."

I continue to hope for someone to offer a plan/model for hopelessly inept constructors like me to make (or make for us) a simple, white-light LED source for our D2s, etc. at less than "Mercedes" prices. I have allied component costs and they really are fairly reasonable, even at Meanwhile, a question:

Does anyone reading this have an idea of whether the Waveform or other strip lights, used for 4x5 (not 8x10) mounted in, say, a 6.5x6.5inch box (the approx diameter of the D2 diffusion or condenser housing) would equal the illumination of an Aristo or Zone-I coldlight head? That's what I use now, and while a bit more light would be nice, less would not be so great with slow paper/developer combos. Waveform, for instance, lists 450 lumens per linear foot of the 1/2-inch wide strips. I have no idea how that translates and compares.

[Michael R]

Why do you want to replace the existing coldlight?

There are different ways of arranging the LEDs in an enlarger head, which affects the amount of light you have at the negative stage. Also depending on how much you pack in, you might want some type of passive or active cooling. I can think of a few ways of making something relatively simply, but you might also prefer the approach Koraks argued for above - ie some appropriately chosen blue and green LEDs.

[koraks]

I continue to hope for someone to offer a plan/model for hopelessly inept constructors like me to make (or make for us) a simple, white-light LED source for our D2s, etc. at less than "Mercedes" prices.
There's a good chance that this will happen - sooner or later someone with the same enlarger will crack that nut and talk about it. The only problem, as you may have noticed, is the enormous choice of options and specific products. Someone might have a solution, and when you try to replicate it, it turns out the product offering has changed and you have to improvise again. That's just a fact of DIY life...


Does anyone reading this have an idea of whether the Waveform or other strip lights, used for 4x5 (not 8x10) mounted in, say, a 6.5x6.5inch box (the approx diameter of the D2 diffusion or condenser housing) would equal the illumination of an Aristo or Zone-I coldlight head? That's what I use now, and while a bit more light would be nice, less would not be so great with slow paper/developer combos. Waveform, for instance, lists 450 lumens per linear foot of the 1/2-inch wide strips. I have no idea how that translates and compares.
In general, efficiency of leds is way higher than that of traditional light sources, even 'cold light'. So a quick and dirty answer might be: if your current cold light source is for instance rated at 30W, just throw in 30W worth of LEDs and you'll likely have way more light than with the old source. It's kind of a crappy answer, but you need to get into specifics to give a really good answer.
For B&W, as Michael R said, I would recommend not going for white leds but a mixture of green and blue ones. The green ones are not critical in terms of color; they're all pretty similar. For the blue ones, you want royal blue with their emission peak around 450-460nm although lower, between 430 and 450 will likely work just as well. This is pretty much the only caveat when selecting leds for B&W printing. Don't get the regular blue ones as you will be bereft of grade 5, but get ones explicitly sold as 'royal blue' with the appropriate wavelength indicated as well. Most blue led strips (or RGB strips) will NOT give the proper blue light. It'll work fine, but only up to grade 4 or so.
Also, when taking the blue/green route, I would suggest using 2x or even 4x the power for green as you have for blue. There are a few reasons for this, but empirically this kind of ratio seems to give the most flexibility in e.g. equalizing printing times over the entire contrast range. So if you go with strips (and manage to find royal blue ones!), you might put in for instance 1 meter of blue strips and 2 to 4 meters of green strips.

[Michael R]

Ideally blue LEDs for this would be a little lower than 450-460 since most of them emit a little beyond what you want for “maximum” contrast - although honestly how often does one really need grade 5? On the other hand for some reason I’ve seen this complaint relatively often.

Waveform blue peaks at 460nm if I remember correctly. I’m sure there are other options, probably cheaper also.

If one were really concerned with getting maximum contrast Waveform has a violet strip peaking at 415nm. Of course paper sensitivity is a variable when it comes to grade spacing and speed. I’m not actually suggesting adding violet LEDs. In the rare case you can’t get enough contrast from the blue LEDs you could resort to a sharp cutting filter in the light path to attenuate longer wavelengths emitted by the blue LEDs. Or just intensify or dupe the negative.

Anyhow, my diversion aside, this can certainly be done without going too far down ratholes or spending a fortune.

[koraks]

Re: the blue led wavelength: the usual wavelength is/was indeed something like 470nm or so, but these days, you can get pretty much any hue ranging from 365nm (UV) all the way down to IR in narrow spacings. So for blue leds, take your pick; you can get 460, 450, 440, 430, 420...etc.
I settled for royal blue because it also works well with color RA4 paper as part of an RGB array. RA4 is of course far more critical in terms of light source selection. For B&W it doesn't matter all that much, just don't pick a blue led that has too long a wavelength (too close to green) as that impacts the highest achievable grade.
Also note that there's no benefit in choosing a lower wavelength with the idea that it may somehow unlock even higher grades in the paper that are otherwise unachievable. This is not the case; the highest contrast grade is always paper-limited and there will be no meaningful difference between say 430nm and 450nm leds in terms of paper grade.
There is, however, quite likely a significant downside to selecting leds that are too close to UV (so e.g. 430nm and lower) as this will most likely activate also the low contrast layer(s), effectively reducing contrast. So the royal blue 'peak' is a pretty sensible compromise.

[Michael R]

Quite right. You're not going to get a magical grade 5+ using shorter wavelength LEDs. The issue with the longer blue wavelengths isn't a matter of peak but simply that the emission band extends too far toward green.

In any case, someone ought to start a lower cost (relatively) LED head business :)

[Ulophot]

Glad for the responses, though there's not much I can do with them directly. Again, for the record, I am not one who could construct such a thing.

RE: Why replace the coldlight: My original Zone VI died. I found another about three years ago at a thrift store. It works okay, but life for lamps and the rest of the stuff in the head (sorry for the advanced technical terminology) is undoubtedly increasingly borrowed. The lamp flashes dimly after exposure, not enough to be a problem in printing, but surely an indication that something is dying. A new lamp from from Aristo is $180 plus shipping, and I can't even get the head cover off, let alone know how to replaced the very delicate lamp without breaking it. Nor do I solder. I have what was to be a back up unit, but it buzzes loudly and the lamp broke in shipping. I'm out of my league trying to repair such things. LED is the future.

I'm happy to continue using my Ilford filters under the lens. I would thing economy and simplicity of design would indicate white LEDs, which, all being the same, would not require extra (whatever that would be) diffusion to blend blue and green.
RE: koraks's 3 meters of LED strips ("you might put in for instance 1 meter of blue strips and 2 to 4 meters of green strips. ")-- I don't know how that is being imagined in a 6.6x6.5" box.

[Michael R]

Diffusion is just for uniformity of any light (and depending on how you construct the box you might not even need supplemental diffusion). You don’t need to mix the blue and green as long as they each light the negative stage uniformly. You can then expose them together or in succession.

Remember the paper doesn’t see mixed colour. Only our eyes/brains do that. The paper just sees whatever wavelengths of radiation the individual LEDs emit.

Think of it this way. Suppose you had an enlarger head filled with two types of LEDs. One type emits a single 450nm wavelength which we see as blue. The other type emits a single 550nm wavelength which we see as green. Assume there are enough of each type, and some diffusing material above the negative so that either the green or blue LEDs can evenly illuminate the negative. Now suppose you turn them both on. You would see some cyan type of colour, an additive mixture of blue and green. But the paper does not see cyan. It sees just the blue and the green. The two wavelengths do not actually mix to produce an intermediate wavelength. The mixed colour is a purely psychophysical phenomenon.

This is why it dos not matter to the paper whether we make one exposure using a mixture of green and blue, or a green exposure followed by a blue exposure.

The same thing applies when VC filters are used under white light, except that the process is subtractive. The light we see as white includes many wavelengths. The paper sees the various blue and green wavelengths in white light. When you put the VC filters in the light path all you are doing from the paper’s perspective is varying the relative proportions of blue and green wavelengths that get through.

[andreios]

Guys, this whole thread makes me feel very inadequate. I think I would be able to make such a thing - got some practice with soldering kitchen LED strips as well as some basic RC model stuff for the kids, but I would echo Philips' (Ulophot's) hope for someone putting together a somewhat foolproof how-to or a chart what is needed and how to put it together...
I use a Durst 138, all the bulbs that I have are not big enough to illuminate 13x18cm negatives so I have to help them with diffusion and would really like to change the light source for something more energy efficient than the 300w or 500w bulb...

[Tin Can]

It is hard as LED are constantly evolving

Usage still requires big $$$ for Heiland or personal experimentation

Many are experimenting, I hid in our DIY section for years, experimenting, condemnation is not fun

Most here are amateurs of varying expertise, we don't make money, we spend it for our love of the hobby

Some dominate by absolute declarations of perfection we never see

Never helpful

Today I am searching eBay for what I need, they now sell darn near anything

Then I compare and contrast with Amazon

Industry doesn't help, they want volume sales

Blue and Green light separately

[koraks]

Yeah, there's many challenges Tin Can, I know. Before you know it you'll be going through a crash course of electrical engineering instead of making images. 'Luckily' for me electronics has always been a hobby for me so it's trying to find synergies between one hobby and another.

To make matters worse than the list of issues you mentioned there's also the topic of optics. It's not addressed much save for an odd thread here and there on Photrio. With LED you've basically got two choices, as with any other light source: diffuse or (quasi-)point source. They're both challenging if you try to implement them with LED. If you make a diffuse light source and you want any kind of significant light output also for bigger enlargements, there's the issue of heat dissipation. You'll be handling a fairly big box or plate with many high-power LEDs and you'll have to somehow get rid of the 100+ Watts (or in case of my latest contraption 360W) of heat in a way that doesn't interfere too much with...well, anything. Not to mention getting really even light output across your color channels. Going for a point source/condensor setup is even trickier since a single LED is just about a perfect point source...but you never have just a single LED. Try to take the light from an array of dozens or hundreds of point sources and somehow coax them into behaving like a single apparent point source. Sure, it could be done, but you may add optics design and with any bit of luck lens manufacturing to your list of newly acquired hobbies.

I hope to pick up actual printing again in a few months when we have moved and I'm done renovating our new place. Between posing as an electrician, plumber, carpenter, ensuring that there's food on the table and also attempting to keeping my violin practice up a bit, there's just no time to spend on photography at the moment. Not to mention I really want/need to engineer my new darkroom work/safe/evaluation light system...

[Tin Can]

LED evolution, they are getting better fast

I have printed up 30X40 from 8X10 film with simple LED panel with LED diffusion plastic

I had to reduce power to 10% as my panel was way too bright

Not perfect, an experiment, 8 years ago and posted here in DIY

I have been experimenting with electricity since a young child

KD0IJD

Perfection is the enemy of progress

[koraks]

Lucky you. My first LED color head had around 100W net power. This was insufficient to conveniently print on warm tone paper from 35mm negatives onto sizes of 11x14". I like to keep exposures between 6 and 20 seconds, roughly. No problem with color, from any size negative from 35mm up to 4x5", and neutral tone B&W paper was also perfectly fine. But warm tone and especially lith prints were too slow to my taste. The new 360W head is about 2 stops faster, although I haven't printed much with it yet. 5x7 RA4 prints from 35mm color negatives are now 2-5 seconds at f/22 or thereabouts. I have a feeling this head is fast enough to handle all my printing needs.
It doesn't help of course if you design a head for color printing that you 'waste' most of the power on the red channel - which is a waste only when printing B&W of course.