Why black plastic cameras heat up like ovens in the sun

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

  1. Interesting.

    Has any owner of a DSLR with optional live view LCD which runs off the
    main imaging sensor (e.g. not the Sony A350) noticed higher noise in
    images taken in sessions using live LCD as opposed to having it
    switched off? Even though live view at least sometimes uses a special
    low power mode on the sensor, I'd expect some warming.

    Has any owner of a DSLR capable of doing long burst mode runs on one
    shutter press noticed any higher noise in the last image of the burst
    compared to the first? I'd expect that to do some sensor warming too.
     
    Chris Malcolm, Aug 9, 2008
    #21
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  2. RichA

    Robert Coe Guest

    : >> 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.
    :
    : 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.

    No, he's right about that. Painting a metal object black does cause it to
    absorb more light and therefore heat up more. Of course it's the paint (the
    less reflective the better) that does the actual conversion to heat, but that
    heat is quickly transferred to the metal because of the latter's high
    conductivity. Now I suppose it may be the case that not all paint that's black
    to visible light is black to IR. But visible light carries energy too
    (sunlight carries quite a bit of it), and that energy will heat the object if
    it isn't reflected away. That's even true of UV, BTW. If you use a paint that
    doesn't reflect UV (don't put any sunscreen in it!), the UV will heat the
    object too.

    Bob
     
    Robert Coe, Aug 9, 2008
    #22
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  3. RichA

    Robert Coe Guest

    :
    : : > RichA added these comments in the current discussion du jour ...
    : >
    : >> 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
    : >>
    : > 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.
    :
    : There is little weight trade-off between cameras made of plastic or metal,
    : of the same size and same build quality. It's a myth, put out by the
    : plastic-lovers. If you talk about a plastic piece of crap like the new
    : D1000 (nearly all plastic with just a couple cheap, stamped steel plates
    : inside) then there may be a weigh savings. But the incentive here for the
    : camera mfg wasn't weight savings, it was COST savings.

    I don't entirely buy that. A metal camera body isn't all that hard to
    fabricate, and I don't believe that the cost difference would account for much
    of the price difference between, say, an XTi and a 40D, two cameras with
    almost identical sensors and similar electronics.

    But weight is a factor. Metals that aren't too brittle for the purpose tend to
    flex a lot, and correcting for that adds weight. A body made of modern
    polycarbonate plastic can be made much lighter than an equally stiff metal
    body. To cite my previous example, a 40D, which is only a little bigger than
    an XTi, weighs half again as much.

    Bob
     
    Robert Coe, Aug 9, 2008
    #23
  4. RichA

    RichA Guest

    I've seen this myself. Images taken with cameras out in winter have
    less noise at a given ISO. You can actually see this effect by taking
    shots, then putting the camera body in a freezer for 30 minutes and
    shooting with it. It's more pronounced in astronomical cameras
    because (gee, I wonder why) noise is high due to exposure times in the
    minutes, where the electronics heat up. Which is why many of those
    cameras have active or passive cooling devices on them. Which is also
    one reason why cameras have an auto-shutdown for their Live View
    function.
     
    RichA, Aug 9, 2008
    #24
  5. RichA

    RichA Guest

    Noise caused by increased dark current is going to happen. If you
    don't think so, take a shot at night for 1 minute without the dark
    framing function.
    That is, assuming the camera's is controllable, some automatically
    happen if the exposure is over 1 second and you can't deselect the
    function.
     
    RichA, Aug 9, 2008
    #25
  6. RichA

    RichA Guest

    It's not a little bigger, it is a lot bigger. And the internal
    construction has an effect on weight too. Plus, the polycarbonate
    which is stiff and brittle will crack way before a metal body will.
    They could rectify this using Lexan for bodies, but Lexan costs a lot
    more than polycarbonate and that would destroy the cost-savings the
    mfg use plastic for.
     
    RichA, Aug 9, 2008
    #26
  7. RichA

    RichA Guest

    Is it made of plastic, or stamped steel and plywood?
     
    RichA, Aug 9, 2008
    #27
  8. RichA

    RichA Guest

    But the camera has something to eliminate dark current noise on long
    exposures, dark framing where another shot is taken without imaging
    the scene, and subtracted from the first shot, thereby removing the
    images of irregular hot pixels. Could the extra 30 deg (maybe 50 more
    inside the body, thanks to the plastic shell) in the daytime possibly
    increase noise? I'd say so, since there would be no dark frame
    function happening in sub-1 second exposures.

    Ever left a car in the sun? I've measured plastic dashboard temps at
    160 deg. F.
     
    RichA, Aug 9, 2008
    #28
  9. RichA

    Ray Fischer Guest

    Shrug. They were high-ISO 30-second exposures. That's as
    noise-sensitive as you can get.

    As another data point: Digital cameras for astrophotography routinely
    have coolers to keep the chips cold. With 30-minute exposures noise
    is a real issue.
     
    Ray Fischer, Aug 9, 2008
    #29
  10. I guess that all those Glock pistols favored by many LE and Military
    agencies will fall apart. I guess that someone should tell them to go
    back to all metal full-frame handguns.

    You really are a cocksnot. I like that word.

    Cal
     
    Cal I Fornicate, Aug 10, 2008
    #30
  11. Yes but those high interior temperatures are a manufacturer's design
    feature. They are used for post natal abortions. Don't you read the news
    in summertime. Very common in TexASS.

    Cal
     
    Cal I Fornicate, Aug 10, 2008
    #31
  12. RichA

    Ray Fischer Guest

    Because it was nighttime.
    It was Death Valley. In July. At midnight it was 90 degrees.
    The other times I take 30-second exposures it is invariably a lot
    cooler.
     
    Ray Fischer, Aug 10, 2008
    #32
  13. Lexan is a brand name for polycarbonate.
    -- Doug
     
    Douglas Johnson, Aug 10, 2008
    #33
  14. RichA

    RichA Guest

    Do you think Glocks are constructed the same way as plastic camera
    bodies?
     
    RichA, Aug 10, 2008
    #34
  15. RichA

    RichA Guest

    Lexan itself, if you go examine it is different from regular
    polycarbonate. One, it's more flexible, two it is far less brittle.
    You can see this stuff for yourself at any Home Depot. They sell it
    in thin sheets for security windows. You can almsot bend it almost
    over on itself and it won't break. They also use it as part of the
    sandwich in bulletproof glass. My guess is that it is too flexible
    for camera bodies or it doesn't hold its shape well enough after
    extruding or casting to make it accurate enough for the drilling/
    fitting of a camera body.
     
    RichA, Aug 10, 2008
    #35
  16. RichA

    Ray Fischer Guest

    This episode of Non Sequitur Theatre brought to you by: Alan Browne
    Clever of you to figure that out. If only you'd done so before your
    non sequitur about "sun loads".
    Do your own test.
     
    Ray Fischer, Aug 10, 2008
    #36
  17. RichA

    Ray Fischer Guest

    Congratulations. You're still an idiot.

    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. It is a polycarbonate
    polymer produced by reacting Bisphenol A with carbonyl chloride, also
    known as phosgene. Lexan is the brand name for polycarbonate sheet in
    thicknesses from 0.75 mm (0.03 in) to 12 mm (0.48 in).
    http://en.wikipedia.org/wiki/Lexan
     
    Ray Fischer, Aug 10, 2008
    #37
  18. RichA

    Ray Fischer Guest

    You're the one who's forgotten your own words.

    "Indeed have you ever seen an image from a pro or amateur demonstrated
    to be affected by body (or lens) distortions due to heat?"
     
    Ray Fischer, Aug 10, 2008
    #38

  19. Sure.

    In fact on some where the quality control wasn't too good, when you
    release the mag, a built-in flash pops up. That's the giveaway.

    Idiot, I wasn't suggesting that they are the same, just that modern
    plastic technology is far more durable than you seem to allow. A Glock
    costs less to produce than any decent camera, so I see no reason why
    they can't use a plastic as durable as that in a Glock.

    I watched a demonstration last year of a tradesman's mobile phone made
    with plastic similar to that used in some new camera bodies where the
    phone was ricocheted off the walls by two guys with squash racquet's. It
    was then picked and a photo taken with it then and a call made. I
    witnessed the demonstration, not a video of the demonstration. The phone
    was undamaged.

    Cocksnot!

    Cal
     
    Cal I Fornicate, Aug 11, 2008
    #39
  20. You are engineering a camera body based on picking up a sheet of plastic in Home
    Depot? Really?

    -- Doug
     
    Douglas Johnson, Aug 11, 2008
    #40
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