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  1. #11
    keithwms's Avatar
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    Quote Originally Posted by Loris Medici View Post
    (As you probably already know) Best UV reflector is Aluminum. You'll gain some speed if you line inside the box with aluminum panels...
    Well, the reason why I cautioned against bare metal is that the reflections can be irregular. If you take the time to make a really good half cylinder or something, then yes, maybe it's a good idea, but otherwise I think the reflected light will be uneven.

    Of course, if the reflective surface is a long way away, then ... inverse square law... it won't matter.
    "Only dead fish follow the stream"

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  2. #12

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    I think one would get better coverage and more even light with aluminum panels on top and sides (including the front cover)... That would prove very useful especially with large (close to the max. printable area) prints. Reflected light will not be stronger than what you get at the very center, right below the bulbs, so the possibility of exposure getting more uneven is out of concern. You'll get just more light (that won't exceed the max. that you get in the center) on the edges and corners, and that's compared to usual setup -> you don't have the risk to overexpose the edges/corners. (Even if it was that way, then there's the fact that more exposure at the corners is much better than less exposure. We tend to burn the corners in S/G printing right?)

    Regards,
    Loris.

  3. #13
    Ian Leake's Avatar
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    I expect that the type of light source has a bigger impact than the interior coating. If you have a bank of UV tubes then you've got yourself a very soft light source - so soft that interior reflections, fall-off, etc are not worth worrying about. If you've got one or more UV bulbs then you've got one or more hard light sources - reflections, fall-off, etc may then be worth worrying about. Choice of hard light or soft light will also have an effect on your contact print, but that's for another thread :-)

  4. #14
    Ian Leake's Avatar
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    And another thing... How much time is one internal coating over another actually going to save? My standard starting point for one paper is 3 minutes, and 6 minutes for another. If coating the interior with a super-special coating reduced my printing time by a stop (which is highly unlikely - perhaps 1/3 of a stop is more realistic), then that would save between 90 and 180 seconds. Compare that with the end to end processing time of a print, which for me is about 45 minutes before it goes in the wash: that's a saving of about 5%. My maths isn't up to working out what a 1/3 of a stop saving would save, but obviously it would be quite a bit less.

    So, if painting the interior white or lining it with aluminium makes you feel better then go ahead and do it. But don't think that it's going to save you any significant amount of time or increase print quality. If you want faster exposure then buy more lights. And if you want more even coverage then buy UV tubes which are longer than your biggest printing size and pack them close together.

  5. #15
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    It depends on what you are exposing and what you are exposing it with.

    If it is relatively insensitive to / or the source produces little light at wavelengths shorter than 440nm then white house paint is an excellent choice, better if you add about 50% barium sulfate.

    If shorter than 440nm then aluminum may be a better choice.

    If you are using aluminum it has to be aluminum that has been polished and coated for UV reflector purposes. You want a textured or dimpled surface, not a mirror finish. Google will turn up several manufactures.

    Aluminum foil is probably the most dismal choice there is.
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  6. #16
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    Quote Originally Posted by keithwms View Post
    Well, the reason why I cautioned against bare metal is that the reflections can be irregular. If you take the time to make a really good half cylinder or something, then yes, maybe it's a good idea, but otherwise I think the reflected light will be uneven.

    Of course, if the reflective surface is a long way away, then ... inverse square law... it won't matter.
    Keith,

    This is just pure drivel ....

    Don Bryant
    Don Bryant

  7. #17
    keithwms's Avatar
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    lol
    "Only dead fish follow the stream"

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