The Perfect VC Light Source

Discussion in 'Darkroom Equipment' started by MurrayMinchin, Dec 9, 2006.

  1. MurrayMinchin

    MurrayMinchin Membership Council Council

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    If you could design the perfect variable contrast light source, what features would it have?

    I'd want;

    - No warm up time.
    - Dials for control (not buttons to push for LED displays).
    - Consistant light output from the first second, to several minutes.
    - On/Off switches for Soft and Hard lights.
    - Soft & Hard lights would be predictably and independantly dimmable throughout entire range.
    - Both lights together would be dimmable, for drydown.
    - Would calculate exposure changes for different print sizes, and...
    - Would also indicate % change in time, to apply to dodges and burns.
    - Optional integrated timer with metronome.
    - Have a probe to measure light intensity at paper plane, and...
    - Focus (white light) would be consistant for probe, and for making masks.
    - Focus would be dimmable, for making masks.
    - Foot switches for focus and exposure.
    - Wouldn't suffer from fall off.
    - Would compensate for power line fluctuations.
    - Would be completely even from edge to edge and corner to corner.
    - Programmable max-black times at several points throughout contrast range for ones own combination of film(s), developer(s), paper(s), developer(s), and or toners...for making work prints.

    Anyways...those are the basics I'd be looking for from the top of my head...what's your idea of the perfect VC light source?

    Murray
     
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  2. Marc Leest

    Marc Leest Member

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    And the good news izzz...

    A VC lightsource of your specificaion exists... A LED coldlight with analyser and splitgrade;
    Presented new at the photokina by Heiland Electronics, it has ALL the features you want.
    It's so new, I can only give a link in German. RHDesigns distributes Heilland products in the UK.

    http://www.schwarzweiss-magazin.de/swmag_frame_aktuell.htm

    Marc
     
  3. Fotohuis

    Fotohuis Member

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    It's a perfect solution but rather expensive.

    First units are tested and their results are indeed very good. We will sell them in Holland by the end of this month.

    best regards,

    Robert
     
  4. RalphLambrecht

    RalphLambrecht Subscriber

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    You forgot to mention that Heiland's new invention only works with his split-grade controller and not with the one from RHDesigns. You'll prpbably spent several thousand $ by the time the system works.
     
  5. RalphLambrecht

    RalphLambrecht Subscriber

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    A desirable but not very basic list. If you can live without one or two features, you can get it all with a normal color head and an f/stop timer from RHDesigns.
     
  6. jeroldharter

    jeroldharter Member

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    Sounds like a Saunders 45 VC light source with an RH Designs timer with Zone Master
     
  7. srs5694

    srs5694 Member

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    Something with many (but not quite all) of those features is the Philips PCS150, which is the color light source and controller for the Philips PCS130 enlarger. (The PCS2000 enlarger has a similar unit.) I've heard of people adapting this unit to work with other enlargers. It was a very innovative unit in the 1980s, but it never caught on in the marketplace. It uses three 35W halogen bulbs, each with its own filter (red, green, and blue) to implement an additive color scheme. Each channel is independently dimmable. I've toyed with the idea of building a replacement control unit that would include a few more of the features you mention, but I lack the motivation and skill to carry it off. Certainly modern electronics would make it relatively easy to integrate features like the ability to compute exposure changes for changes in head height.

    As a side note, Pat Gainer wrote a piece for Photo Techniques magazine a while back entitled (IIRC) "Hazards of the Grain Focuser," in which he investigated various methods of using a grain focuser. Among other things, his conclusion was that you'll get the best focusing accuracy using either green light or white light. For this reason, I routinely focus using green light only. (Because the PCS150 is an additive light source with independent red, green, and blue lights, its "white" light isn't really pure white, so I trust using green alone more than using all three together.)
     
  8. MurrayMinchin

    MurrayMinchin Membership Council Council

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    Thanks guy's :smile:

    Any other combinations of light sources and timers out there that would be close to my wish list? I'll be buying in the new year, so my quest is getting into high gear!

    I was in touch with them about a month ago, and was given a price estimate of 1,693.00 Euro's ($2,572.00 Canadian) for the complete system, or 984.00 Euro's ($1,495.00 Canadian) for just the light source and an adaptor for my Beseler 45MXT. This makes it more than compatible with Zone VI's LED VC light source at $1,399.00US ($1,608.00 Canadian) which doesn't come with an adaptor.

    I trusted Zone VI in the Picker days, but have lost faith since Calumet took over, so I'd lean towards the Heiland source...if I go LED........

    Murray
     
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  9. Lee L

    Lee L Member

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    I have one of these, along with the conversion kit they sold to mount it on my Omega D5. I found the acrylic light piping they used for efficiency a bit uneven on color mixing and ended up making my own box to hold the light source above the condenser housing. It was slow for Cibachromes from Kodachrome, but good for printing on Ektacolor papers. I haven't tried it since the R4A papers came out, but am thinking about trying some room temp tray processing with it. I did try printing a negative in three sections, one section each under R, G, and B light (you can switch each channel on the PCS150 off/on separately), and got clean C, M, and Y images. It would probably work well for split filter VC printing using only the B and G lights.

    If I run across a good complete MF Philips enlarger with this light source, I'll probably buy it.

    Lee
     
  10. MurrayMinchin

    MurrayMinchin Membership Council Council

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    I see from the German magazine link above, that the price for the 4x5 Heiland light and timer combination now stands at 1,998.00 Euro's ($2,998.00 Canadian)...yikes!

    Murray
     
  11. srs5694

    srs5694 Member

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    Philips PCS150

    I can't speak to its use in an Omega D5, but in the Philips PCS130 enlarger, it's plenty bright enough for use with modern RA4 papers. For making 8x10 prints, I often have to dial down all three lights (100+ "filtration" on each channel) to get printing times in the 10-20s range with apertures of f/8 on a 50mm lens from 35mm negatives. "Filtration" has to be quite extreme to print smaller sizes.

    I turn off the red light when doing my B&W printing -- those bulbs are fairly expensive ($15-$35 apiece), so I don't want to burn the red bulb unnecessarily! I've never tried actual split-filter printing with it, but I'm sure it would work well with that technique.

    They turn up on eBay with some regularity; you could set up a search with e-mail notification if you're more than idly interested. Just be sure you get one with all the accessories you want; the model's been out of production for ~20 years, so finding condensers, negative carriers, etc., can be hard.
     
  12. Lee L

    Lee L Member

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    I'm not that hard up for one for a couple of reasons, I already have one light source for the D5, and the MF Philips goes either 6x6 or 6x7 max, and I shoot a fair bit of 6x9 in folders, a Fuji 690, and roll film backs. So it would mostly be for 35mm, and then the two advantages would only be a dedicated color enlarger and the perspective correction movements built into the Philips chassis. It takes about 5 minutes and one thumbscrew to change the D5 from condenser/diffuser B&W to the PCS-150 color head. Most of that is getting the controller out of the box and onto the enlarger table.

    BTW, I've been thinking about trying the MR-11 LED lamps from http://superbrightleds.com/bi-pin.html in the PCS-150 head. I just need to make sure the electronics are compatible (proper dimming and range) and the passband on the dichroic filters match well. You might also set up these lamps in your own mixing box and run them off the Philips controller.

    Lee
     
  13. srs5694

    srs5694 Member

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    I've considered that, too, but my understanding is that the dimming function would probably not work very well. The response of LEDs to dimming is very different from that of halogen bulbs, so at the very best it'd still work but the calibrations on the dials would become worthless, and at worst the dimming would be so erratic the whole setup would be useless. My investigations also turned up big question marks about bulb life, brightness, and color frequency matching of bulbs to paper (for blue, IIRC).

    That said, using LEDs as light sources for enlargers makes some sense, at least if bulbs with the right color output can be found. If I had appropriate electronics knowledge and time, I might look into using these bulbs in the PCS150 light source and replacing the control unit with one custom-designed "from the ground up" to use the LEDs. Sadly, I lack the necessary skills and time.
     
  14. MVNelson

    MVNelson Subscriber

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    You didn't mention enough light intensity to print all the current medias in a resonable time at reasonable enlarger lens f/stops. The Zone VI VC head was a good concept but lacked signifigantly in light intensity. Also as mentioned Zone VI has dead ended with Calumet...! My unit never worked consistently and is on its way back for yet another stab at fix. Another head that had great potential and is no longer was the Beseler/Minolta 45A which is quite non convential using strobe light source but was precise enough and repeatable enough to do dye transfer work including color seperations and Matrix film exposure. Since my Zone VI is gone I am enjoying using it again. It certain has no problems squeezing every bit of rint tones out VC papers. the Heiland sounds great but I am a bit dubious about new technologies that have not stood some test of time, espacially when they come with high price tags! I certainly would be looking into whether the company will be around to stand by its product and its willingness to do so.

    Miles
     
  15. Curt

    Curt Subscriber

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    If all you have is Lemons then make....

    I am going to take one of my two Beseler dead heads and convert it to LEDs.

    The list of options would be more than enough for my uses. A diffusion light that doesn't use tube bulbs and has a long stable life with consistent color output. VC would of course be the best. I just have to get way up to date on my electronics.

    Curt
     
  16. RalphLambrecht

    RalphLambrecht Subscriber

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    Photography is not for the faint of wallet.
    (source unknown)
     
  17. Loose Gravel

    Loose Gravel Member

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    Ralph, Maybe that should be, Technology is not for the fain of wallet. I don't know how much this is photography or a case of 'greener pastures'. It seems like a good idea because LEDs are nice and wouldn't a new light source be fun. It would solve all our problems.

    If that we the case, then why hasn't the Calumet LED source taken the world by storm? Why aren't my neighbors buying them? They are expensive and it is difficult to get very high contrasts from them (not blue enough). The blue can be fixed with expensive LEDs. Expense is a bugger. Darkroom light sources is not a thriving market. I'm surprised anybody has gone this far with them. I wouldn't want to be the first to buy one and what should happen if it breaks. Who will fix this light source in 10 years?
     
  18. MVNelson

    MVNelson Subscriber

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    One thing I have learned over the past few years is that after all is said and done, the technology and expense , become less and less important as your personal artistry and craftmanship becomes better and better. The wallet and the technology mostly aide expediency.... (Sorry , I was feeling a little "Weston-ish") :smile:

    Miles
     
  19. jeroldharter

    jeroldharter Member

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    I have a dead Beseler 45S also and would be interested if you could share your plans. I am pretty inept at this sort of thing but it seems potentially convenient because it will certainly fit.
     
  20. Steve Smith

    Steve Smith Member

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    If you need electronics advice, please ask. I'm sure there are others here who can help out too.

    Steve.
     
  21. MurrayMinchin

    MurrayMinchin Membership Council Council

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    As far as LED's go, it appears there's a few ways to go about it. Huw Finney; http://www.textklick.demon.co.uk/ledhead.html used 32 Lumiled's for his, Zone VI (IIRC) uses 24 for theirs and Heiland, judging from the photo in the magazine article, uses 840.

    All a person has to factor in is their time...how much extra time do you have available to learn how to build one, compared to how much it costs to buy one already made, and then you have to make a choice from only two companies.

    Murray
     
  22. Loose Gravel

    Loose Gravel Member

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    Steve, true enough. I'd be happy to help with circuits. That is the easy part. If I were to design an LED head (which you can tell is not high on my list), I'd be concerned about the thermal issues and the optical issues. Maybe Heiland used 840 LEDs to increase diffusion and decrease hot spots; though it sure adds to assembly costs.

    Is anybody out there tried the 395 nm LEDs? Also, those of you printing with an LED head, what kind of printing speeds are you getting?

    Carry on. -LG-
     
  23. resummerfield

    resummerfield Subscriber

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    I’m no EE, but the biggest problems I’ve seen with these LED heads is accurate and consistent dimming of either blue or green for a uniform, even light that gives one specific grade. I would be interested in a simple LED head that operated all blue or all green, by toggling a switch, for split-printing only.
     
  24. Steve Smith

    Steve Smith Member

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    That's probably the simplest way to do it. If I was planning a variable blue/green light I would drive the LEDs with pulse width modulation. That means that they are driven with a high frequency (say 1kHz) square wave with a variable duty cycle.
    The terms 'pulse width' and 'duty cycle' refer to the amount of time the LED is on. or the ratio of on time to off time.

    e.g. 50% on, 50% off is obviously half power. 67% on and 33% off is two thirds power. 99% on 1% off is just about full power.

    I would arrange that the blue is opposite to the green so if blue was 25%, green would be 75%, blue 50%/green 50%, blue 75%/green 25% and so on. That would give an accurate, linear variable control from full green to full blue with all intermediate settings.

    Another advantage with this method is because the LEDs are switched either on or off, there is no unknown in between state which may cause non-uniformity.


    Steve
     
  25. Loose Gravel

    Loose Gravel Member

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    Steve,

    doing this, one would probably want to drive at twice the nominal recommended steady state current to maintain brightness. One also needs to compensate for brightness vs temperature, slightly different for blue and green. Looking at the Avago website, it is apparent that there is a brightness decay over lifetime, too, but maybe this is too small to worry about for this application. I found it interesting that Avago bins its parts into many grades for brightness and that these bins can vary in brightness by over 10X and within a grade by over 30%. Color can shift by about 10 nm over temperature and a couple of nanometers per bin. I don't know how much color shift can be tolerated for a lightsource, but I would think this would matter.

    I'd still want to know if 425 nm is blue enough for higher, harder, grades of paper.