The additive print and LED... Idea!

Discussion in 'Darkroom Equipment' started by photoexpedition, Dec 1, 2009.

  1. photoexpedition

    photoexpedition Member

    Messages:
    9
    Joined:
    Nov 17, 2009
    Location:
    Belarus
    Shooter:
    Medium Format
    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?
     
  2. mhulsman

    mhulsman Member

    Messages:
    288
    Joined:
    Jan 18, 2007
    Location:
    Waddinxveen,
    Shooter:
    8x10 Format
    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 ?
     
  3. Mike1234

    Mike1234 Inactive

    Messages:
    1,884
    Joined:
    Jul 6, 2009
    Location:
    South Texas,
    Shooter:
    4x5 Format
    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.
     
  4. photoexpedition

    photoexpedition Member

    Messages:
    9
    Joined:
    Nov 17, 2009
    Location:
    Belarus
    Shooter:
    Medium Format
    Mike, if you used the similar device for the colour press, tell please about results.
     
  5. mhulsman

    mhulsman Member

    Messages:
    288
    Joined:
    Jan 18, 2007
    Location:
    Waddinxveen,
    Shooter:
    8x10 Format
  6. keithwms

    keithwms Member

    Messages:
    6,073
    Joined:
    Oct 14, 2006
    Location:
    Charlottesvi
    Shooter:
    Multi Format
    I have an old 36-bulb contact printer that is a very low res version of what you say :wink: 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.
     
  7. SuzanneR

    SuzanneR Moderator Staff Member Moderator

    Messages:
    5,888
    Joined:
    Sep 14, 2004
    Location:
    Massachusetts
    Shooter:
    Multi Format
    Here's a link to yours...

    http://www.apug.org/forums/forum41/68997-full-analog-prints-digital-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!! :wink: :D
     
  8. Mike1234

    Mike1234 Inactive

    Messages:
    1,884
    Joined:
    Jul 6, 2009
    Location:
    South Texas,
    Shooter:
    4x5 Format
    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. :sad:

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

    keithwms Member

    Messages:
    6,073
    Joined:
    Oct 14, 2006
    Location:
    Charlottesvi
    Shooter:
    Multi Format
    For the sake of clear discussion, I will offer a little dictionary :wink:

    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 :wink: kind of like teleportation :D

    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.
     
  10. Mike1234

    Mike1234 Inactive

    Messages:
    1,884
    Joined:
    Jul 6, 2009
    Location:
    South Texas,
    Shooter:
    4x5 Format
    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?
     
  11. keithwms

    keithwms Member

    Messages:
    6,073
    Joined:
    Oct 14, 2006
    Location:
    Charlottesvi
    Shooter:
    Multi Format
    I contact print my LVTs. You can also enlarge therm. In other words, you treat them just as you would a normal neg.

    But I think you meant to ask: what would I need to take full advantage of a high res drum scan. Well, I drum for LVT(for a dupe neg) or for lightjet (for a print). Even though you could argue that those two output methods ultimately have some finite dpi resolution and bit depth... there's no important limit to how much information one can get out with the drum at least at the actual scanning stage.... we can scan right up to the optical limits of diffraction (and I would argue even beyond). I mean, with a drum you can extract absurd amounts of information. It just beats DSLRs all to crap, even the older drums, not to mention the newest Azteks. The virtually limitless scan resolution coupled with ~16-bit per channel bit depth means that virtually the only thing you aren't recording is the smell of the negative. And for the record, I do not deny that smell is important :wink:

    There is the issue of how grain works in the image though, that is another *big* topic. Some rightfully assert that they like grain and how it is renderd by optical printing, and I think much of the enmity surrounding this topic is the lousy way grain is rendered by non-drum scanners. I mean, people do crappy cheap scans and the moan. You get what you pay for.
     
    Last edited by a moderator: Dec 1, 2009
  12. bdial

    bdial Subscriber

    Messages:
    5,413
    Joined:
    Jan 2, 2005
    Location:
    NE U.S.
    Shooter:
    Multi Format
    I think a possiblity might exist in adapting a LCD projector, and use it as a light source, it has seemed like an interesting idea, but I've never been inclined to go find the bits and do it.
     
  13. Mike1234

    Mike1234 Inactive

    Messages:
    1,884
    Joined:
    Jul 6, 2009
    Location:
    South Texas,
    Shooter:
    4x5 Format
    Hmm... okay. So can any manipulation be done to the LVT image before it's written to film? This would allow straight printing, more or less, of the new neg. How large can an LVT be made? BTW, sorry for the brain-picking. I hope it isn't too painful. :smile:
     
  14. keithwms

    keithwms Member

    Messages:
    6,073
    Joined:
    Oct 14, 2006
    Location:
    Charlottesvi
    Shooter:
    Multi Format
    I think you can get LVTs up to 20x24 from Chicago Albumen. IIRC top res could only be had to 4x5 or so, though, and that was in excess of 3000-4000 ppi, permitting 10x enlargement. At the larger sizes I think you are getting a ~508 ppi neg, IIRC.

    And yes, you can do any evil manipulation you want to the file that gets fed to the LVT! E.g. scratch and dust removal....
     
  15. Mike1234

    Mike1234 Inactive

    Messages:
    1,884
    Joined:
    Jul 6, 2009
    Location:
    South Texas,
    Shooter:
    4x5 Format
    Hmm... I must look more intensely into LVT's.
     
  16. photoexpedition

    photoexpedition Member

    Messages:
    9
    Joined:
    Nov 17, 2009
    Location:
    Belarus
    Shooter:
    Medium Format
    Mike Hulsman, thanks for the link. Very interesting information. I have gone to consider technical subtleties...:smile:
    But for print B&W on a multicontrast paper a bit different installation is required, I think. The additive way of the print means serial exposuring of photographic paper by three (R, G and B) LEDs. For a multicontrast paper, as I understand, it is required to mix three colours in a different proportion and to exposure once. I see a problem in mixing of colours. Small LEDs in dense packing and good "mixer" are required, I think.
     
  17. Mike1234

    Mike1234 Inactive

    Messages:
    1,884
    Joined:
    Jul 6, 2009
    Location:
    South Texas,
    Shooter:
    4x5 Format
    I like it!! :smile:
     
  18. mhulsman

    mhulsman Member

    Messages:
    288
    Joined:
    Jan 18, 2007
    Location:
    Waddinxveen,
    Shooter:
    8x10 Format
    Photoexpedition,

    See also: http://www.apug.org/forums/forum41/11082-led-enlarger-head.html
    And also http://www.huws.org.uk/ for a working 4x5 head and electronics.

    For VC paper you need a combination of blue or green light or a combination of both.
    Grade 5 needs the royal blue led in combination with an UV led, as I read here on apug.
    For graded paper you need blue light.
    For color you need YMC.

    I think when you use an RGB led you can have every color you need, but maybe you also need an UV led.
    On huws site he is using only 30 1 Watt leds for a 4x5 head.
    Today you can buy 3 Watt RGB leds for 10 euro's a piece.

    I do not have any knowledge on electronics, I just want a 10x10 led head as cheap as possible :smile:

    Just gathering a lot of information on the net, prior to building mysel one.
    With some help of people who knows their electronics.

    Mike
     
    Last edited by a moderator: Dec 1, 2009
  19. photoexpedition

    photoexpedition Member

    Messages:
    9
    Joined:
    Nov 17, 2009
    Location:
    Belarus
    Shooter:
    Medium Format
    It appears for VC and graded papers all is more difficult , than I thought...
    But I print B&W images on classical barit paper, without use of filters. And I wish to have an opportunity the print of colour images in my old enlarger. This problem is slightly easier.

    For colour I require YMC if I "isolate" necessary colours from white (substractive method). I require RGB if I "collect" white (additive method). In Fuji Frontier and similar systems use RGB. For this reason modern photographic papers are adapted under frequencies of LED. It also has pushed me on idea to use LED for the print in colour.