Why black plastic cameras heat up like ovens in the sun

Discussion in 'Digital SLR' started by RichA, Aug 6, 2008.

  1. RichA

    RichA Guest

    They often hit temps 20 degs or more higher than metals.
    IR absorbtion. They don't reflect IR like metals do, they absorb it.
    Check out this IR image of lenses. Note the plastic lens caps and
    grips all stay black while the anodized barrels reflect IR back
    (purple colour). Another reason to detest plastic, if your goal is
    low noise because a hotter body = hotter sensor = higher noise.

    http://www.pbase.com/andersonrm/image/101272206
     
    RichA, Aug 6, 2008
    #1
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  2. RichA

    Scott W Guest

    So why would you want any lens that is black on the outside?
    My best lens is white, what color are your lenses?

    Scott
     
    Scott W, Aug 6, 2008
    #2
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  3. RichA

    Ray Fischer Guest

    Painted metal absorbs heat just as well. Maybe better. In fact,
    black painted metal gets a lot hotter to the touch than do plastics.
    You have to be pretty dim to not know the difference between near
    infra-red, which is used in this photograph, and far infra-red which
    is heat.
    You're still an idiot troll.
     
    Ray Fischer, Aug 6, 2008
    #3
  4. I love this guy. His comments aren't just unbelievable, they are
    ludicrous and it is really obvious that he doesn't give any practical
    thought to what he says.

    Ok genius, why is it that my black plastic enclosed security camera that
    is bolted above the front door, in full sunlight, gets hot, but never to
    hot to touch, while the metal alarm bell bolted to the wall next to it
    get so hot that it can raise blisters if handled before being allowed to
    cool?

    Why is my black plastic lens hood always cooler than my all metal lens
    when both have spent time in hot sun?

    Why is the black plastic shroud around my car radiator always cool
    enough to touch while the radiator it is bolted to will burn?

    You are a real dimwit aren't you? Black plastic doesn't reflect heat as
    well as a reflective coated metal, but neither does it retain it, while
    metal does retain it.
    Your biases are showing. You intellect is well hidden though.

    Cal
     
    Cal I Fornicate, Aug 6, 2008
    #4
  5. What if what he says is well thought out, his intention being to attract
    comment, the more negative the better. Then he can sit back and laugh at
    so many of us obediently talking about him, and he can feel superior,
    somehow.

    Well, it's a possibility.

    Rich, what's up, man?
     
    John McWilliams, Aug 6, 2008
    #5
  6. RichA

    HEMI-Powered Guest

    RichA added these comments in the current discussion du jour ...
    black anything absorbs more heat than silver or white anything, too
    but there's a tradeoff here between light weight/low cost and
    unproven image degradation.
     
    HEMI-Powered, Aug 6, 2008
    #6
  7. RichA

    jmeehan Guest

    I love that one, but somehow I don't think Rich will, if he gets
    it. :)
     
    jmeehan, Aug 7, 2008
    #7
  8. RichA

    jmeehan Guest

    Actually I believe the difference you are feeling is due to the way
    the heat is transferred, not the absolute temperature of the object.
    However that said, your comments make a lot more sense than his.
     
    jmeehan, Aug 7, 2008
    #8
  9. RichA

    RichA Guest

    Because you live in an alternate universe. Only certain types of
    PAINT applied to metals will allow them to absorb IR.
     
    RichA, Aug 7, 2008
    #9
  10. RichA

    RichA Guest

    Especially when you consider that the lens mounts in cheap lenses are
    almost certain non-compensating and will bind lenses if heated AND
    some of the crummier optics use (gulp!) plastic lenses (mostly molded
    aspheres) which will absolutely expand and deform when heated.
     
    RichA, Aug 7, 2008
    #10
  11. RichA

    Robert Coe Guest

    : As Ray astutely points out the IR shown here (if that's what it is) is
    : not that due to a significant rise in system temperature, merely IR
    : light that is invisible to the eye.
    :
    : Further, plastics are usually less conductive than metal (as Ray also
    : states) so they will not heat up much and not transport heat inward.
    :
    : There are two factors at play:
    :
    : - IR absorption
    : - IR emissivity
    :
    : As most children know darker colors usually absorb more IR.

    But as they get older and study physics, they understand that IR absorption
    isn't the only problem; visible light absorption is a significant contributor
    as well. By definition, the blacker an object is, the more it absorbs, rather
    than reflects, visible light. The energy carried by visible light striking a
    black object has to go somewhere, and it goes into heating the object up. The
    object's subsequent radiation at IR frequencies is a mitigating effect of that
    heating. Black-body radiation isn't very efficient at low temperatures, so a
    dark-colored object in the sun can get pretty hot before it reaches an
    equilibrium temperature.

    : But they also emit more IR than lighter colors (why aviation electronics
    : are (mostly) painted black).
    :
    : The best heat management is always to avoid generating or absorbing heat
    : in the first place. Regardless of the material type, outdoor systems in
    : high sunlight areas are best made white or unpainted stainless/aluminum
    : and in some cases (say the Mojave) an external shell with a free
    : circulating open air gap to provide an insulating layer of air and
    : shielding from the sun.
    :
    : Minolta came out with some all white bodies and flashes at one point
    : (800i ?) but weren't very popular. I doubt this was for heat issues,
    : however; more likely a marketing ploy that fell on its face.
    :
    : White lenses should have less expansion than black lenses in the
    : sunlight and this may reduce optical effects.
    :
    : As to bodies, it probably does not matter very much. Indeed have you
    : ever seen an image from a pro or amateur demonstrated to be affected by
    : body (or lens) distortions due to heat? Please post references,
    : examples, data, etc.

    Ah, yes: ostrich logic. If we haven't happened to see a carefully documented
    manifestation of the phenomenon, then the phenomenon must not be real.

    Bob
     
    Robert Coe, Aug 7, 2008
    #11
  12. Were you awake when you posted this or is posting nonsensical gibberish
    a new hobby of yours?

    Cal
     
    Cal I Fornicate, Aug 7, 2008
    #12
  13. If you actually have evidence that the thermal expansion coefficients
    of optical plastics are significantly higher than those of the optical
    glasses used in these lenses that would be interesting to learn. But
    without any reference to the physics involved, plus your other weird
    claims in this thread about metal and plastic heating up, it looks as
    though you haven't much clue and are simply trying to alarm other
    people who don't have much clue either.
     
    Chris Malcolm, Aug 7, 2008
    #13
  14. I seem to have lost track of which universe we're supposed to be
    discussing. Which universe is it in which metals don't absord IR
    unless painted with certain kinds of paint? I suspect I've never
    visited that one.
     
    Chris Malcolm, Aug 7, 2008
    #14
  15. RichA

    D-Mac Guest


    I guess Chris, you haven't realised yet that Rich is a cut and paste
    scientist?
     
    D-Mac, Aug 7, 2008
    #15
  16. RichA

    Alan Hoyle Guest

    It it most definitely not a "new" hobby.

    -a
     
    Alan Hoyle, Aug 7, 2008
    #16
  17. Chris Malcolm, Aug 8, 2008
    #17
  18. RichA

    Ray Fischer Guest

    As a purely anecdotal example, I took my camera on a trip to Death
    Valley and nighttime shots seemed to be perceptably noisier because of
    the higher temperatures.
     
    Ray Fischer, Aug 9, 2008
    #18
  19. RichA

    Ray Fischer Guest

    But you haven't done any of that.
    Blah, blah, blah.
     
    Ray Fischer, Aug 9, 2008
    #19
  20. RichA

    Ray Fischer Guest

    A metal-lover who thinks that everything plastic must be crap.

    Must be a bitch living in the 21st century.
     
    Ray Fischer, Aug 9, 2008
    #20
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