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Thread: Shooting UV with a MFDB

  1. #1
    Super Duper
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    Shooting UV with a MFDB

    Hi,

    Does anyone know anything about shooting UV with a MFDB?

    In the film days you loaded UV film, slapped a filter on the lens that only allowed UV light in and shot (longer exposures as regular or flash light is only partially UV). Or you used black lights and very very long exposures.

    UV light shows up faded text far better than regular lighting so it could be a valuable tool for use in the project I'm putting together to photograph ancient documents and books.

    How does it work these days?
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    Senior Member thrice's Avatar
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    Re: Shooting UV with a MFDB

    It wouldn't work. I'm not aware of any commercially available full spectrum MFDB's, you might be able to have one converted?

    Standard cover glass (UV/IR filtration) is VERY good at filtering UV, you would be looking at ridiculously long/noisy exposures and probably still no usable results.

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    Re: Shooting UV with a MFDB

    I had suggested to Yair Shahar that the new IR version of their backs might help as the cover glass is now a user replaceable filter but he didn't think it would help.

    If the problem is just one of the cover glass, I wonder what they would charge for a custom back, specifically one like the IR back where you can use it for standard or regular photography but make it UV instead of IR. Probably more than the difference between the standard and the IR back which we could just about manage.

    Yair, we wait for your wisdom on this subject...
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    Senior Member yaya's Avatar
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    Re: Shooting UV with a MFDB

    The IR cutoff filter is just that...and IR filter so it does not affect the transmission of UV or near UV light.

    The Aptus-II 7 is currently available in the US as an IR back with a "plain" glass replacing the IR filter.

    There is also the Achromatic P45+ that uses a B&W 39MP Kodak sensor. I have not tried it with UV lights so I can't comment on its performance

    Note that most commercial CCDs start "seeing" at around 400nm which is just about where UV stops.

    However we do have several museum-type customers who use standard IR filtered backs with UV lights, UV filters on normal lights and UV on-lens filters with satisfying results. Naturally there is less light getting trough so as Daniel suggested the exposure times need to go up or the iso has to be pushed up a bit

    Yair
    Yair Shahar | Product Manager | Phase One | Mamiya Leaf
    e: [email protected] | m: +44(0)77 8992 8199 | yaya's blog

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    Re: Shooting UV with a MFDB

    These folks got all the aspects (lenses, lights and the sensors) covered:

    http://www.mega-vision.com/

    Also contact Dr. Brian Caldwell (PM or email).

    Currently, there is only one lens in the market (Brian's via Megavision) that is suitable for MF UV shooting.

    The achromatic back and such, though the manufacturers would go to great lengths to do a technical sensor/back, have not had the time/willingness or the ability to test it for UV.

    Capturing an image is (when all the hardware is in place) easy. What the image tells us and how to interpret it is a totally different game.

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    Senior Member yaya's Avatar
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    Re: Shooting UV with a MFDB

    Quote Originally Posted by Vivek View Post
    The achromatic back and such, though the manufacturers would go to great lengths to do a technical sensor/back, have not had the time/willingness or the ability to test it for UV.
    Just to clarify what I said was that I have not tested the Achromatic back with UV lights. It should not be read as if the manufacturer has not done so!

    Yair
    Yair Shahar | Product Manager | Phase One | Mamiya Leaf
    e: [email protected] | m: +44(0)77 8992 8199 | yaya's blog

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    Re: Shooting UV with a MFDB

    Yair, My post was NOT a response to your post. It is a continuation of PM to Ben's query.

    AFAIK, the manufacturers of achromatic back and such have not tested it for its (their) suitability for UV. If they had done that, the information is not available which makes is, AFA UV shooting is concerned, useless.

    Despite the esoteric nature/ very specialised area of UV imaging, it is interesting to note that highly specialised and pricey MFDBs such as achromatic backs lack information in that area.

    Clearly, it (UV and such) is not in the realm of commercial photography outfits.

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    Re: Shooting UV with a MFDB

    Vivek, I had a look at the website, I see that they have specific sensors, lenses, setups etc. I have to make a solution work using a Leaf back on a DF camera with a variety of lenses because the vast majority of the work will standard photography using tools already chosen for various reasons including portability, use by non experts, etc. I had been asked by the sponsers if there was a way to capture UV images using this equipment. It seems to be possible using filtration, or at least that is the impression Yair seems to be giving. I would help if he has any more specifics such as which filters work best with a MFDB, whether the Aptus II 8 we are intending to buy is less useful for this purpose than the Aptus II 7 which I could sell to the sponsers if it had better UV capability and also if I'm using flash lighting, how many stops I'm going to be losing to filtration so I can judge if the current planned equipment will be sufficient.
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    Re: Shooting UV with a MFDB

    Ben, If any commercial lens transmits UV, it is less suitable for most photography. Besides, UV transmitting glass is expensive to be used for regular use. I doubt any of the lenses for MDFB (barring the one from Megavision that i mentioned) would transmit UV.

    In addition to plain vanilla transmission, there is focus shift. None of the lenses for MDFB (or for that matter any format) are corrected for UV unless they are specifically made for it.

    Just as lenses, most commercial (barring the ones advertised for with proper specifications) digital sensors have little UV sensitivity. I would welcome any test results/specs from the manufacturers and or sellers disclosing what their gear is capable of. Such information would help them sell better, I would reckon.

    Flash: Not all flashes would emit UV. Again, most manufacturers make sure UV is cut off (GN number gives no indication of the UV in the light!). You would need to look for flashes that do.

    Filters: What worked for monochrome film (most had very little IR sensitivity unlike a current digital sensor) doe not work for digital UV. The only and the best filter for this purpose (320nm to 390nm with the best IR suppression) is made/sold by Baader Planetarium.

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    Re: Shooting UV with a MFDB

    Yair seems to be suggesting that there are museums doing just that Vivek, I'd love some practical information such as what equipment they are getting their results with.
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    Re: Shooting UV with a MFDB

    Ben, With all due respect, that is not reflected UV photography. But, if someone is willing to dole out cash for that, all the more power to the folks involved!

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    Re: Shooting UV with a MFDB

    maybe worth considering a camera rig already converted for UV like this one

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    Re: Shooting UV with a MFDB

    Ben, this is an old thread, but the general idea is to use a monochrome ccd, and stack several images together, each image is illuminated using a different flash color, one with a filter that covers a small band of the color spectrum; not only R,G, and B but violet, indigo, and saffron or tootie frootie (I can't remember) ... 5-7 images are taken, each monochrome image is assigned the value of it's illuminator, and wa-la, full spectrum image is yours to disertate upon anon.

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