Nobody's teasing anyone. Several people have explicitly stated that lasers are a dead-end street for this particular application.what's the point of teasing someone along with how something analogous might, or more likely, might not work?
It all does, even laser scalpels as an illustration. Why go to all the tech and trouble to make an intense linear point light source, and then go through all the trouble just to undo that, and revert back to a diffuse source? Why do you take issue with examples which more easily spell out the lack of logic,
which might be not so apparent to someone who has probably never designed an enlarger before?
Lasers do have imaging applications; but they work on a different premise than optical enlarging. And there is also a significant practical distinction between simultaneous and sequential additive printing; so I cited a few examples of that too.
NO - It is not subtractive. Subtractive means removing something from white to comprise something OPPOSITE across the color wheel. But Additive means just that - you add relatively pure primary red, green, and blue light as needed. We're talking basic color and optical theory here, with its own specific terminology. How those primary illuminants are constituted depends the specific light engineering approach. But once it is converted into actual RGB light, in their separate respective roles, these behave as separate primaries, not as CMY secondaries.
Color paper emulsions are sensitized to red, green, and blue light, NOT to yellow, magenta, and cyan light. What are visually PRODUCED or realized in the paper are yellow, magenta, and cyan dyes. Therefore, purer actual RGB illuminants will produce, at least in theory, cleaner better targeted color in a print than the ordinary subtractive approach.
With ordinary subtractive colorheads, by increasing the yellow portion of white light, you are truncating the blue; by increasing the magenta, you are truncating and removing green; increasing blue decreases the yellow. Whole different ballgame than additive printing, which does not truncate any opposites in white light to gain their effect, with a certain amount of unfiltered white light left over. How well the two different approaches correspond in the end result all depends. I gave a few examples on my preceding post.
This is correct.Whether RGB exposure or CMY exposure produces better results would have to do with the relationships between the light source spectral output, filter curves and spectral sensitivity of the paper. The physical principle, however, is the same in both cases.
I understand what you mean, but Drew is right w.r.t. the standard vocabulary. At some point, "additive" and "subtractive" made their way into this particular vocabulary and while they are technically speaking confusing in the sense that they confound characteristics of the light source with the process of exposing a light-sensitive material, it's the terminology we're kind of stuck with. The background to this somewhat odd 'additive' construct can relate to two concepts:If you choose to call RGB filters additive, I’m afraid CMY filters are just as additive.
Yes, I understand what you mean and that's technically more correct. It's also not just in theory either. You really don't need to filter with (the right) LEDs or lasers. It's true additive in the most strict sense of the word - although not necessarily in a temporal sense (see #2 above).Calling a system additive sort of makes more sense for RGB LEDs (or RGB lasers) where these are individually controlled since in theory you don’t need to filter.
The required power is ultimately a question of what kind of printing times you want on what kind of surface area of the paper, keeping the sensitivity of the paper in mind (this is more or less constant for available papers in the West). Diffusion need not be very complex as I've indicated earlier, but it'll come at the cost of light output since a considerable amount of light is lost in a diffusor.My completely uninformed question is how powerful would these lasers need to be and what sort of diffuser could handle this???
Not by definition and in practice it really depends on the wavelength distribution of the color channels, as @Milpool points out.Additive printing is more precise.
This is correct.
I understand what you mean, but Drew is right w.r.t. the standard vocabulary. At some point, "additive" and "subtractive" made their way into this particular vocabulary and while they are technically speaking confusing in the sense that they confound characteristics of the light source with the process of exposing a light-sensitive material, it's the terminology we're kind of stuck with. The background to this somewhat odd 'additive' construct can relate to two concepts:
1: Exposure systems with three discrete light sources whose color is mixed (added up) to make the exposing light. A practical example is the Philips PCS2000 enlarger, which in fact used 3 bulbs.
2: Exposure methods in which the exposure is built from three consecutive exposures, one after the other, each with a distinct wavelength distribution.
It's not entirely clear (and practically, it doesn't really matter either) which of these gave rise to the additive/subtractive printing nomenclature we use today. In common parlance, we have either way ended up with the notion that 'additive exposure' refers to the use of narrow-band red, green and blue light, while 'subtractive exposure' refers to the use of a single white light source that's filtered with M, Y and optionally C filters. Again, is it technically entirely correct or conceptually clear? No. In that sense you have a point.
Yes, I understand what you mean and that's technically more correct. It's also not just in theory either. You really don't need to filter with (the right) LEDs or lasers. It's true additive in the most strict sense of the word - although not necessarily in a temporal sense (see #2 above).
The required power is ultimately a question of what kind of printing times you want on what kind of surface area of the paper, keeping the sensitivity of the paper in mind (this is more or less constant for available papers in the West). Diffusion need not be very complex as I've indicated earlier, but it'll come at the cost of light output since a considerable amount of light is lost in a diffusor.
In practice, if you're talking about a solid state (semiconductor) laser, you'd be looking at power levels of well over 10W per color channel to get exposures similar to a system like a 35mm Durst M305. I do NOT recommend anyone to experiment with lasers at such power levels; it's a major hazard to one's vision as it takes just a fraction of a second of unfortunate stray exposure via a mirrored surface etc. to cause permanent eye damage. It's (almost literally) playing with fire!
Not by definition and in practice it really depends on the wavelength distribution of the color channels, as @Milpool points out.
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