Color enlarger using laser - Additive method

[arturo_rs]

It is possible to make a color enlarger using lasers. I think, in principle, that "should work".

Using 3 lasers:

• Blue: ~450 nm
• Green: ~530 nm
• Red: ~640–660 nm

The exposure and density will be controlled by the time the lasers emit light. It is an additive process.

The light before reaching the color negative should hit a diffuser for make the light even. Also, the lens of the laser should make a wider cone.

One problem that I found is the speckle. So, to avoid the granularity is using 3 o more lasers from every color to reduce that effect.

What do you think?

 

[arturo_rs]

This video explain less or more how should work this process:



Instead using filters, color lasers.

 

[Chan Tran]

I don't think you need to make it laser. There are printers on RA-4 paper that use laser but that is because they need to expose the tiny dots in a scanning like process. For projection enlargement LED would be OK as they can produce monochromatic light too.

 

[Carnie Bob]

It is possible to make a color enlarger using lasers. I think, in principle, that "should work".

Using 3 lasers:

• Blue: ~450 nm
• Green: ~530 nm
• Red: ~640–660 nm

The exposure and density will be controlled by the time the lasers emit light. It is an additive process.

The light before reaching the color negative should hit a diffuser for make the light even. Also, the lens of the laser should make a wider cone.

One problem that I found is the speckle. So, to avoid the granularity is using 3 o more lasers from every color to reduce that effect.

What do you think?

Lambda was developed in the mid 90's using RGB laser exposure, I owned one for years and did RA4 prints, Cibachrome prints and Fibre Base Silver prints on it, today there are still labs using this device.

 

[Carnie Bob]

Also ancient history , in 1974 I was using a Nord Enlarger which used Additive light RGB to make cprints.

 

[Chan Tran]

The Minolta/Beseler 45A color head which uses xenon strobe is also additive.

 

[ic-racer]

Fire the lasers into a light pipe. (for diffusion)

 

[Chan Tran]

With today's technolgy using additive method makes sense but there is no need to use laser.

 

[koraks]

The light before reaching the color negative should hit a diffuser for make the light even. Also, the lens of the laser should make a wider cone.

So you don't use lasers to begin with, as it just makes things unnecessarily complex, and exposures will be slow. Instead you use LEDs. Plenty of people have built LED light sources for enlargers by now. Mostly for variable contrast B&W, some for color. I've done the latter; I've built several versions and I've been using RGB LED exposure for both b&w and color printing for several years now.

 

[DREW WILEY]

There are several manufacturers of photosensitive laser printers. Those are very expensive industrial machines coupled to dedicated scanners, automated paper cutters, and direct RA4 roller processor output.

LED is the new kid on the block and shows a lot of promise.

I built a couple of narrow-band true additive RGB pulsed halogen enlargers, up to 8x10 inch film size capacity, designed for up to 30X40 inch prints. Makes that old Phillips design posted earlier seem like a tiny toy by comparison. Mine is over 14 feet tall. Then I have a second version for up to 5x7 film. The quality of color is analogous to what big pro RGB laser printer deliver; but the detail is even better, since no intermediate scanning takes place.

 

[arturo_rs]

So you don't use lasers to begin with, as it just makes things unnecessarily complex, and exposures will be slow. Instead you use LEDs. Plenty of people have built LED light sources for enlargers by now. Mostly for variable contrast B&W, some for color. I've done the latter; I've built several versions and I've been using RGB LED exposure for both b&w and color printing for several years now.

I am very stubborn

 

[koraks]

I am very stubborn

I know how it feels! I'm looking forward to seeing the results of your experiments. If you are bent on using lasers, you will indeed need to diverge the beam in order to cover the full image area. Diffusion would be an obvious route, and the easiest solution is likely to have two diffusors with some distance between them. You'll have to grapple with the problem of very low efficiency/light yield and difficulty focusing and very long exposure times esp. for B&W paper. It's a very sub-optimal setup that combines the drawbacks of diffusion with the drawbacks of lasers. A bit like taking a Tesla and hitching a donkey in front of it to pull it.

 

[Chan Tran]

I am very stubborn

But why laser? Because of their monochromatic light? You can achieve that with LED but you don't even need that for additive color printing. You do not need pin point light beam like drawing with light. I don't understand why you choose laser? Make no sense at all.

 

[Milpool]

In principle it should work. The challenge will be divergence/diffusion / long exposure times. Check the spectral sensitivity of the paper.

One plus is calling it additive will make more sense than usual.

It is possible to make a color enlarger using lasers. I think, in principle, that "should work".

Using 3 lasers:

• Blue: ~450 nm
• Green: ~530 nm
• Red: ~640–660 nm

The exposure and density will be controlled by the time the lasers emit light. It is an additive process.

The light before reaching the color negative should hit a diffuser for make the light even. Also, the lens of the laser should make a wider cone.

One problem that I found is the speckle. So, to avoid the granularity is using 3 o more lasers from every color to reduce that effect.

What do you think?

 

[koraks]

Check the spectral sensitivity of the paper.

Yup. This will also show that the listed 530nm for green is not optimal (but...). I have demonstrated this empirically as well and have freely published the results on my blog. In practice, however, you can make very decent prints even with the 'wrong' green wavelength as the penalty in terms of hue purity is limited and will only manifest strongly in extreme conditions. This is about printing color on RA4 paper; for B&W the story is different and much less critical to begin with.

 

[Chan Tran]

I just don't think one should use laser. I quote Wikipedia below and hope it's correct

"A laser differs from other sources of light in that it emits light that is coherent. Spatial coherence allows a laser to be focused to a tight spot, enabling uses such as optical communication,[6] laser cutting, and lithography. It also allows a laser beam to stay narrow over great distances (collimation), used in laser pointers, lidar, and free-space optical communication. Lasers can also have high temporal coherence, which permits them to emit light with a very narrow frequency spectrum. Temporal coherence can also be used to produce ultrashort pulses of light with a broad spectrum but durations measured in attoseconds.[7]"

None of the characteristic of laser is an advantage except the ability to emit light with very narrow frequency spectrum (I am not sure if this is an advantage) but this can be done with LED. Other characteristics like focused to tight spot, allow the beam to stay narrow over great distance are rather disadvantages.

 

[Carnie Bob]

In principle it should work. The challenge will be divergence/diffusion / long exposure times. Check the spectral sensitivity of the paper.

One plus is calling it additive will make more sense than usual.

on the lambda we printed at 400 ppi and the three beams of light channeled through a prism system to direct the light at the paper, the machine ran two speeds 200 ppi and 400 ppi , I prefered the slower 400 speed as the resolution of final silver print looked crisper. to expose a 30 x 40 inch print at 400 ppi it would take about 5 min if I remember, we would cut the paper and then hand process like an enlarger print.

 

[Milpool]

The difference is printers like Lambda, Lightjet exposed the material by scanning with the beam, whereas OP is just contemplating using lasers as light sources in place of LEDs or incandescent bulbs in an otherwise conventional enlarger (ie it’s still a projection system).

on the lambda we printed at 400 ppi and the three beams of light channeled through a prism system to direct the light at the paper, the machine ran two speeds 200 ppi and 400 ppi , I prefered the slower 400 speed as the resolution of final silver print looked crisper. to expose a 30 x 40 inch print at 400 ppi it would take about 5 min if I remember, we would cut the paper and then hand process like an enlarger print.

 

[DREW WILEY]

There are two basic categories of photo paper laser printers. Three of the primary brands like Lambda use full laser output running linear across the image via multiple passes. The other category uses laser dots; Chromira would be the notable example. All of these are based on programmable scans, and none operate by diffusion - that would be quite unrealistic. The whole point of lasers is their tight non-dispersing coherent character.

Fiber-optic bundles have been used to redirect and distribute enlarger light (the Salthill model); but doing this with laser for that kind of application would seem an especially complicated way to do the job. In the past, serious additive enlargers used either xenon flash tubes or pulsed halogen. A few DIY examples used rheostatic tungsten halogen (rather inefficient), plus there was the little Phillips version of that, suitable only up to 6x7 cm usage as most.

The problem with green in lasers is that, to my knowledge, there is still no suitable green diode. It is residually filtered out of red diodes, as a leftover, so comparatively weak. Just the opposite as foliage, where green chlorophyll is dominant until it faded in the Fall, when the residual yellow and red finally express themselves.

 

[MattKing]

I am very stubborn

Moderator hat on:
If you need help making this last post into your Photrio signature line, don't hesitate to ask!

Moderator hat off.
I understand well the issue of stubborn!
My wife and I have friends who during their working days owned and ran a business that may have been the most successful producers of commercial holograms in the world - the type of holograms that everyday consumers might end up with.
They still have at home a really interesting collection of historically significant lasers, along with some fascinating and very tiny new ones.
Those help augment their amazing camera collection, and their even more amazing collection of equipment, materials, software and historic and modern three dimensional photography and cinematography.
I bet they could whip up a laser based RGB light source, and make it work.
But it probably makes much more sense to use LEDs.
I do wonder though, whether lasers would make sense in a scanner application.

 

[DREW WILEY]

A surgeon uncle of mine was experimenting with lasers as potential surgical instruments as early as 1960. All his colleagues called him nuts. Now laser scalpels and other sorts of other laser medical instruments are everywhere. Today high-powered industrial lasers not only cut thick steel every day of the week, but have been adapted to etch bas-relief photographic images into very hard surfaces like ceramic tile and polished granite. It's a big industrial field with tons of resource information out there, along with University degrees. But it would be a rather circuitous difficult route to solve an otherwise already long solved enlarger application problem.

Have fun. If it were me, I'd peruse something like an Edmund Industrial site or catalog, order some laser application textbooks from them, learn the basics first. I interacted quite a bit with the development of survey lasers. I think you're barking up the wrong tree if you want to go additive; but it's your time and money.

I spent $15,000 on my 8X10 additive enlarger; if I had subcontracted it out, instead of building it myself, it would probably have been more like $75,000. Even if you get appropriate light dispersal, you'd still need to figure out all the electronics per controls, power supply, and feedback monitoring.

If you enjoy these kinds of shop challenges, that can be rewarding in its own right - or frustrating when one step after another proves to be more difficult than you first thought. Hopefully you have some basic machine shop skills and equipment.

 

[Bill Burk]

Would you plan on scanning?

 

[koraks]

There are two basic categories of photo paper laser printers.

This is incorrect.
But the distinction and how it really works is irrelevant to a thread about enlargers. Like the talk about laser surgery, which bears no relevance to this thread either.

 

[DREW WILEY]

Extant examples that sometimes turn up used :

1) Those little Phillips ones; the later version is better. Good only for small prints and small film sizes.
2) The Beseler-Minolta flashtube system. A bit weak itself, but suitable for up to 16X20 RA4 prints. It can be difficult to find replacement tubes, and don't expect any help from Beseler themselves in terms of repair or parts.

3) The Beseler Universal additive colorhead. Complicated electronics very sensitive to EMI (electromagnetic interference). Most of the used ones that come up for sale had problems to begin with. They can be made to work wonderfully if one has, or has access to, electronics testing skills. There is one outfit that will work on the power supplies and control panels, with a minimum $500 charge. Don't expect an iota of help from Beseler themselves. These are wonderful colorheads to work with, but are also capable of throwing schizophrenic tantrums if they get overheated or an EMI or sudden voltage shift issue. They're a lot more complicated than conventional CMY colorheads. These use a trio ordinary EVW halogen bulbs, which are easy to find.

4) Once in awhile a huge of commercial SEQUENTIAL ADDITIVE (versus simultaneous additive) enlarger will turn up, left over from the prepress industry. These used powerful expensive xenon flash tubes for enlarging halftone directly onto printing plates. Film size capacity was up to 12X16 inches.
Not realistic for ordinary darkroom printing.

5) What you'll never find : Durst's own additive RGB 8x10 colorheads. A limited quantity of these were built and sold to a specific government agency, but never offered to commercial photo labs. I've seen the insides of these. They ran very hot and were very expensive to maintain.

 

[DREW WILEY]

Koraks - if it's irrelevant how it works, what's the point of teasing someone along with how something analogous might, or more likely, might not work? One learns to dissect frogs in a biology class before applying to medical school and studying human anatomy. Laser printers are very sophisticated industrial machines with a great deal of engineering and patents behind them, and still, some operators have a hard time getting good prints out of them. I know a lab owner who never did cure banding issues with his Lambda; if that isn't a linear artifact, I don't know what is. Chromira results could look almost Pointillistic close-up; it used a big platen-like device instead.

The point being - both categories work in principle only because the laser output is not diffused or diluted, and remains coherent, whereas what is being proposed in this thread is apparently otherwise.