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

    TYPE OF POLYCARBONATE, NOT THE SAME AS IS USED IN CHEAP DSLRs. You
    sound like the goons pretending the material used in DSLRs was the
    same as used in the Raptor fighter's wings. "They are both plastic!"
    Remember that retarded conversation?
     
    RichA, Aug 11, 2008
    #41
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  2. Which polycarbonate is used in cheap DSLRs? How do you know it is not Lexan?
    -- Doug
     
    Douglas Johnson, Aug 11, 2008
    #42
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  3. RichA

    RichA Guest


    Are there any clear camera bodies?

    Lexan (LEXAN) is a registered trademark for SABIC Innovative
    Plastics' (formerly General Electric Plastics) brand of highly durable
    polycarbonate resin thermoplastic intended to replace glass where the
    need for strength justifies its higher cost.
     
    RichA, Aug 11, 2008
    #43
  4. No, but there is colored Lexan. From:

    http://www.geplastics.com/gep/Plast...PerformanceProperties/coreproducts_lexan.html

    "Lexan resin is available in a broad range of colors with a wide variety of
    additives."

    From:
    http://findarticles.com/p/articles/mi_m0EIN/is_2003_Jan_29/ai_97002072

    "Today, Dr. Fox's "goop" is available in a variety of finishes and over 35,000
    colors. In fact, with the help of GE Plastics ColorXpress(R) color-matching
    services, its colors are virtually limitless (it can even be made to glow in the
    dark!)."

    If you insist on black, from the same article:

    "1994- Using LEXAN resin and new thin-wall technology, Motorola
    once again revolutionizes the cell phone industry by
    developing the first Micro-TAC(R) Ultra-Lite mobile phone."

    From http://en.wikipedia.org/wiki/Lexan

    "The white plastic in iPods and iBooks is Lexan.

    Or how about a batting helmet in a nice blue?

    http://www.ivgstores.com/IVG2/Y/ProductID-30317-Batting-Helmet-MacGregor-B90-Pro.htm


    I'll ask again. How do you know the polycarbonate in cheap DSLRs is not Lexan?

    -- Doug
     
    Douglas Johnson, Aug 11, 2008
    #44
  5. RichA

    ransley Guest

    Metal transfers heat better than plastic, it isnt holding heat but
    loosing it where the sun isnt hitting it. Think why your car radiator
    is metal.
     
    ransley, Aug 11, 2008
    #45
  6. RichA

    RichA Guest

    Not all black things absorb the same, you must realize that?
    Why do you think IR reflects off some and not others, as I already
    showed?
    If IR is reflected, do you think it imparts as much heat as if it's
    absorbed?
     
    RichA, Aug 11, 2008
    #46
  7. RichA

    RichA Guest

    Depends on the metal and it's surface colour and reflectivity, the
    material covering it (if any). That's why they use metalized mylar
    blankets to keep things cooler, or to act as heat reflectors when used
    as emergency blankets.
     
    RichA, Aug 12, 2008
    #47
  8. RichA

    BlackShadow Guest

    Hey an idiot!

    I have been wanting to interview a genuine idiot for quite a while. Do you
    have any free time? I'll pay you in hell money.

    The car radiator is metal for cost and durability reasons.

    Loosing doe not mean what you think it means.

    Plastic, like wood, glass, other non-metallic materials is an insulator you
    idiot.

    BlackShadow
     
    BlackShadow, Aug 12, 2008
    #48
  9. RichA

    Ray Fischer Guest

    They're your words. I did not alter the meaning.
    "Heat" and "sulight" are not synoymous.
    A different article.
    "Probably" means that you don't know.
    I gave an anecdotal example. You don't like it.

    Tough shit.

    And now you change your mind yet again. First it's heat, then it's
    sunlight, and now it's heat again.
    Go figure.
    I doubt that you have a clue.
    Do your own homework.
     
    Ray Fischer, Aug 12, 2008
    #49
  10. RichA

    Ray Fischer Guest

    By definition, all things that are black absorb the same.
    Black is that color which absorbs all light.

    Not all things that look black are black.
    Here's a clue, idiot: "heat" is not the same as "IR".
     
    Ray Fischer, Aug 12, 2008
    #50
  11. RichA

    Ray Fischer Guest

    Acording to soem idiot who doesn't even know the difference between
    one version of polycarbonate vs. another much less what kind of
    plastic might be used in which camera.
    You sound like a stupid bigot who really doesn't even have a clue.
     
    Ray Fischer, Aug 12, 2008
    #51
  12. It depends on the design. It's possible to design lens systems where
    the thermal expansion and contraction of a lens doesn't push it off
    centre or disturb its optical performance much. It's possible that a
    small amount of thermal expansion would have a large deleterious
    effect on image quality, and it's also possible that a large thermal
    expansion would have very little. Without knowing about those aspects
    of the design, or carrying out specific heating experiments, it's not
    possible to know whether use of a specific material more liable than
    another to thermal expansion and contraction will cause any
    significant optical problems.

    Take the much simpler area of clock pendulum design and thermal
    expansion effects on timing. Some pendulum designs try to minimise
    the problem by using materials with the lowest possible thermal
    expansion. Others minimise the problem by using materials with much
    higher thermal expansion in such a way that the effects are cancelled.

    The same kind of engineering ideas are not unknown to optical
    engineers. They've long been used for example in large astronomical
    telescope design.
     
    Chris Malcolm, Aug 12, 2008
    #52
  13. RichA

    Ray Fischer Guest

    You're not smart enough to be condescending.
    Yes, I am.
    And STILL sunlight is not the same as heat.
    Sit on it and spin, asshole.
    And yet here you are, still whining about it.
    No, idiot, it's been the effect of heat on cameras. It doesn't matter
    where the heat comes from.
    I don't waste time on argumentative assholes.
     
    Ray Fischer, Aug 13, 2008
    #53
  14. RichA

    Ray Fischer Guest

    Yes, I realize that, but some people do not. Some people don't even
    realize that some things which appear black can be quite reflective
    in IR. Some people don't even know that "IR" includes frequencies that
    are not heat at all.
     
    Ray Fischer, Aug 13, 2008
    #54
  15. RichA

    Ray Fischer Guest

    Oooo! "I know you are but what am I?"

    The riposte of a 5th grader!
     
    Ray Fischer, Aug 13, 2008
    #55
  16. RichA

    Mike Guest

    So what's this threadlet about then?
     
    Mike, Aug 13, 2008
    #56
  17. Not a problem here in the UK.
    We haven't seen the sun since Christmas.
     
    Whersmee Daps, Aug 13, 2008
    #57
  18. RichA

    Robert Coe Guest

    : RichA wrote:
    : >> RichA wrote:
    : >>>> RichA wrote:
    : >>>>> They often hit temps 20 degs or more higher than metals.
    : >>>>> IR absorbtion.
    : >>
    : >>>> 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?
    : >>
    : >>> Because you live in an alternate universe. Only certain types of
    : >>> PAINT applied to metals will allow them to absorb IR.
    : >>
    : >> Anything that's black absorbs a range of electromagnetic energy
    : >> (including IR) and is heated by it. It doesn't take a "certain type
    : >> of paint." Walk barefoot on a beach where there's black sand as well
    : >> as white sand in the sunlight and you'll find yourself hopping to
    : >> get off the black sand very quickly.
    : >>
    : >> Neil
    : >
    : > Not all black things absorb the same, you must realize that?
    :
    : Sure. Some materials hold or transfer heat better than others. Black plastic
    : for example typically won't feel as hot as black metal when left in the sun,
    : because plastic doesn't transfer heat as well as metal. But generally
    : speaking, anything that's black becomes hotter from EM radiation than
    : similar substances that are light colored. It doesn't take a special paint.

    That depends on your definition of the word "special". It doesn't follow that
    a paint that is black in visible light absorbs as efficiently in IR and UV.
    The more the paint absorbs EM radiation, regardless of its frequency, the more
    the object will heat up.

    : Also, black *radiates* heat a lot better than a lighter color, especially if
    : it has a matte finish. That's why air-cooled engines are usually black
    : and/or matte finished. If the same engine is polished bright it won't be
    : able to get rid of heat as well and will run hotter.

    An air-cooled engine is not the same as a camera. At the temperatures to which
    a camera is normally subjected, the material's ability to absorb radiation is
    more important than its ability to radiate, because black-body radiation is
    inefficient at low temperatures. That's why a camera (especially a metal
    camera - sorry, Rich) gets pretty damn hot before it reaches equilibrium (the
    temperature at which the energy it absorbs equals that which it radiates). The
    engine is quite different. Its main source of heat is the combustion of its
    fuel, and it operates above the equilibrium temperature. Anything that
    promotes radiation (like painting it black) helps, and you can essentially
    ignore the effect of incident radiation. (Full disclosure: I once owned an
    air-cooled Volkswagen, and its engine was not painted black. Presumably the
    heat transfer advantage due to the increased radiation wasn't worth the cost
    of painting it.)

    : > Why do you think IR reflects off some and not others, as I already
    : > showed? If IR is reflected, do you think it imparts as much heat as if
    : > it's absorbed?
    :
    : I think you mean "absorbs as much heat." No, though the difference may be
    : small and the substance may be more important than what it's finished with.

    Whatever is reflected does not, by defintion, impart any heat. (There are, of
    course, various kinds of reflection. The reflected light may have lower energy
    than the incident light, and the energy differential does heat the object.)

    Bob
     
    Robert Coe, Aug 14, 2008
    #58
  19. RichA

    Robert Coe 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
    :
    : Metal transfers heat better than plastic, it isnt holding heat but
    : loosing it where the sun isnt hitting it. Think why your car radiator
    : is metal.

    Be careful; you're starting to confuse apples and oranges. Up until now we've
    been talking about actual absorption and emission of electromagnetic
    radiation. But a car "radiator" isn't really a radiator; it's a convector. Its
    primary method of heat transfer is by direct contact with passing air
    molecules. The amount of heat it loses by radiation is negligible by
    comparison.

    Bob
     
    Robert Coe, Aug 15, 2008
    #59
  20. OK, here's some information regarding lenses and heat.

    There are two major effects of heat. Thermal expansion and change in
    refractive index, both being much higher in plastic than in glass. By
    far the most deleterious effects are caused by thermal gradients in
    the lenses. Changes in refective index across a lens very quickly
    damages the image quality.

    Hence any non steady state situation (which is always when using a
    camera) where there is a heat source is a problem.

    By the way, the photos shown in the original post are not thermal
    photographs. They are ordinary snapshots as can be seen by the
    color. There is no color (except false color which is not the case
    here) in thermal photogarphs.
     
    Helpful person, Aug 15, 2008
    #60
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