Unsharp Masking/Contrast Control with Photochromic Glass ("Transitions" lenses)

Discussion in 'Enlarging' started by holmburgers, Jul 1, 2010.

  1. holmburgers

    holmburgers Member

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    Hey all,

    So I'm sure everyone's familiar with transitions lenses, the glasses that automatically turn dark when exposed to light. Well I had a thought about using these for masking in photography, and as is usually the case, I wasn't the first to have this idea!

    Initially I wondered about using it for in-camera (LF) masking to control bright lights, like in a nighttime cityscape for instance, but it's use in printing would certainly be easier and probably more practical to employ.

    I know it has also been used for astrophotography.

    Are there any optometrists around here that might have access to a big sheet of this stuff? I think a single plate of 8x10 photochromic glass could go a long way in a darkroom, and would undeniably be a "game changer".

    Just imagine the possibilities.... and then join me in my search! :wink:

    I haven't looked exhaustively, but there doesn't seem to be an easy source for this material.

    Here are some references...
    http://en.wikipedia.org/wiki/Photochromic_lens
    Google "US Patent #4948705"
    http://www.opticsinfobase.org/abstract.cfm?uri=ao-48-19-3570
     
    Last edited by a moderator: Jul 1, 2010
  2. ic-racer

    ic-racer Member

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    There was a commercial product back in the 70s for masking 35mm slides to do better Cibachromes that was similar. I don't recall the name and searched the internet but could not find reference to it. I may still have an old issue of Modern Photography with an ad for it.

    There was some 'trick' to make the image semi-permanent. Like putting it in water or uv exposure to erase the image and start over.
     
  3. holmburgers

    holmburgers Member

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    Hmm, interesting. I had thought that it was relatively newer technology, but perhaps not. Maybe I'm just thinking that because of the Transition's lenses.

    One of the patents mentions heat will erase it quicker.

    I saw a optometrists "blank" (for lack of a better term) on eBay once, for cutting to fit frames. So it's around, and it's not prohibitively expensive.

    I'd be very curious to see that Modern Photography ad.
     
  4. ic-racer

    ic-racer Member

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    Looks like patent #4948705 is similar to the product I remember. The patent is from 1980s, so I may be off a decade. Though, there is probably a delay in getting a patent. I did Ciba around 1975 to 1976 and that is when I saw the ad for the product.

    They DID have the photosensitive glasses back in the 70s. My brother had them.
     
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  5. holmburgers

    holmburgers Member

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    I think Corning makes the glass, maybe I'll shoot them an email for giggles.
     
  6. holmburgers

    holmburgers Member

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    Check out this Corning ad from the 60's. eBay item #230486163800.... This is exactly what one would need.
     
  7. Ian Grant

    Ian Grant Subscriber

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    I remember the product as well, that was when I was doing Cibachromes. It wasn't that easy to control back then, so the idea was quite attractive.

    From what I remember the glass was proposed & tested and written about in magazines, it may have been sold but I can't remember evers seing an advert for it.

    Ian
     
  8. ic-racer

    ic-racer Member

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    Yes, a magazine test rather than an advertizement seems right. Or maybe a "new product" blurb.
     
  9. Ian Grant

    Ian Grant Subscriber

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    Also the smallest size was I think 5x4, but maybe they made 4x5 for the US market :D It may have been smaller but it definitely wasn't 35mm.

    I do remember that I wouldn't be able to use it. I didn't move up to 5x4 until late 76 or early 77.

    Ian
     
  10. holmburgers

    holmburgers Member

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    I've found some leads. There is a by-all-accounts crappy product for car-shades, however, it probably doesn't work well because a) it has to stick to a window vertically and b) most window glass with block UV anyways, thus rendering its effect useless. It might be fine for our purposes. However, I can't seem to find a "reputable" dealer.... http://www.mybabytravelgear.com/Stay-Put-Photochromic-Car-Shades-2-Pack.html

    And then there's this website http://www.photochromicwindows.com/ which is also pretty ghetto, but I've emailed to see what the deal is.

    So why would the smallest size of 5x4 be a problem? I was thinking you did the masking at the print, not the negative. But perhaps masking at the negative would work too?
     
  11. Ian Grant

    Ian Grant Subscriber

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    It was used just below the negative needing a special holder in most cases, so may well have been a big issue with some enlarger designs. Apart from some initial press reports I never saw or heard of it again. I was a subscriber to the BJP by that time and can't remember it ever being written about seriously, and the BJP never misses anything new.

    Ian
     
  12. Greg Davis

    Greg Davis Member

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    Keep in mind that photochromic glass or polycarbonate is activated by UV light. If you don't have any, it won't change. At least the stuff made for opthalmic lenses is UV activated. It also takes a few minutes to fully react and then more to clear and it stabilizes after changing a few hundred times then stops reacting altogether.
     
  13. nick mulder

    nick mulder Subscriber

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    oooh,

    this is a really nice idea!

    you smart farts

    I wonder with a collimated enough light source that it could be sandwiched between a neg and a alt paper like DOP Pt/Pd - for whatever reason POP Pd prints dont have the same tonality and blacks I can get with DOP, but I do love the blocking effect of POP - could be the best of both worlds huh...

    Might be out in the sun again soon
     
  14. holmburgers

    holmburgers Member

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    Yes, the UV light would be a challenge, but I think it's still worth experimenting with. The guy over at photochromic glass said he would send me a sample once he has one. Who knows how long that will be....

    and as nick mulder mentions, alt-processes might benefit the most from this, since they're always out sunbathing!
     
  15. Nicholas Lindan

    Nicholas Lindan Advertiser Advertiser

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    Photochromic glass/plastic blocks UV even when it is clear to visible wavelengths. This would make it rather useless for alt-process and wet-plate.
     
  16. holmburgers

    holmburgers Member

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    good call