The additive print and LED... Idea!

[photoexpedition]

I have an idea to use the lighter on the basis of RGB light-emitting diodes for the additive press of colour prints.
Frequencies of radiation of light-emitting diodes practically coincide with a maximum sensitivity of layers of modern colour photographic papers. Necessary brightness is reached by increase in number of light-emitting diodes.
What do you think about it?

[mhulsman]

And if you can also use the RGB leds for black and white printing, VC and graded papers it would be great.
One lighthead for all processes.
I do not know if that is possible ?

[Mike1234]

Heh... I must have stolen your idea. I just posted something smilar but using a tightly packed bank of LED's. Maybe I should just delete mine.

[photoexpedition]

Mike, if you used the similar device for the colour press, tell please about results.

[mhulsman]

photoexpedition.
I haven't used a led device before.
Only investigation on how it could be done.
I only know at the moment of a blue/green led head for VC papers.
See: http://www.apug.org/forums/forum43/5...roic-leds.html

[keithwms]

I have an old 36-bulb contact printer that is a very low res version of what you say The bulbs are controllable in concentric rings so you can correct for falloff, dodge and burn, etc. Actually it's a feat of clever engineering, a very nice thing. I wouldn't want to think about scaling it to millions of LEDs though! As I mentioned in the other thread, a computer monitor is pretty close to what you want.... and about as close as you will ever get for reasonable money.

[SuzanneR]

Heh... I must have stolen your idea. I just posted something smilar but using a tightly packed bank of LED's. Maybe I should just delete mine.

Here's a link to yours...

http://www.apug.org/forums/forum41/6...-tweaking.html

I started to merge these threads, but I don't want to do that if the technical details are sufficiently different, so I think it's helpful to have relative links. Ok... I'll confess, I don't fully understand the technical jargon here!!

[Mike1234]

Mike, if you used the similar device for the colour press, tell please about results.

A device such as the one I suggested doesn't exist. At least I've never heard of one. You're idea is far more practical and certainly someone here could build one. My idea is impractical due to techical difficulty and expense, I'm sorry to admit.

Thanks for the link, Suzanne, and sorry for the similar post.

[keithwms]

Ok... I'll confess, I don't fully understand the technical jargon here!!

For the sake of clear discussion, I will offer a little dictionary

ADC= analogue to digital converter, takes an analogue signal and 'bins' it. In the simplest case a b&w image is 'bitmapped' into a 1-bit file... ones and zeros. ADCs take a *huge* amount of information and compress it into a much smaller series of bins, with which you can quickly do logical operations.

Bit depth= how many bits the ADC translates the analogue file into. 1-bit means the image gets rendered in terms of only 2^1=2= two tones, i.e. pure white and pure black dots.... 'line art.' 8-bit means that you have 2^8=256 different tones.

LVT= light valve technology, a method for 'printing' on traditional negative material with very high resolution. LVTs predate digital cameras by many decades. You can still have LVTs made. The cost is about the same as a drum scan.

Drum scanner= scanner that uses no image lensing to collect the information from the negative or positive. A PMT detector, with ~zero noise, records the information as it is rastered to the very limits of optical resolution. At this stage the signal is still fully analogue; however, when you store it, it gets binned and hence meets an ADC. At that stage the file is digital. Drum scanners can deliver far more resolution than can be stored in any practical way... short of piping the signal directly to an LVT and essentially recreating the negative kind of like teleportation

I do not have the security clearance to verify the following assertion, but I would say that there must be (or must have been at some stage) a Drum/LVT coupled pair that was used in aerial recon, linked by purely analogue transmission. In other words: there was a full-res LF neg created by a satellite that was then drummed onboard and recreated on the ground by LVT for enlargement. My guess is that such a setup has been superceded by a multi-sampling digital process with the added advantage of high IR sensitivity at the imaging stage.

[Mike1234]

Keith... what would one need to take advantage of a hi-res LVT scan? Some sort of ultra hi-res analog projector in lieu of an enlarger? A tri-color laser device perhaps?