Long exposures burning the sensor.

Discussion in 'Beyond the Basics' started by Ptyler22, Jul 21, 2009.

  1. Ptyler22

    Ptyler22 TPF Noob!

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    OK, great so somewhere around a 10 minute exposure should be no sweat. Thanks!


     
  2. Garbz

    Garbz No longer a newbie, moving up!

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    I have seen this happen but unfortunately there is no simple answer. Each sensor in each camera model is setup differently and generates a different amount of heat. I would go so far as to say high end full frame cameras would possibly be able to go indefinitely but I wouldn't try it based on my word.

    The camera in question was a 350D which took a 40 minute startrail I think it was, and then never recovered. I took a hour long startrail one day and aside from the picture being garbage due to the purple thermal effect of a CCD that's heating up the camera survived. But my D200 was burning hot to the touch so I won't ever try one that long again.

    Sensors generate heat when they are on, and DSLR sensors are not heatsinked. Sensors for telescopes and other dedicated long exposure equipment have large heatsinks or peltier units to keep them cool.

    Not an issue because the camera would have time to cool between shots. Worst case your sensor was off and on for 100 minutes out of 240, I'd expect any camera to do this without even getting warm.

    I would also say 15 min is not an issue. I'd be worried getting longer than half an hour though, but then again modern cameras *may* last longer still. The 350D is a bit old.

    The 450D is plastic! The sensor is in the very middle of the camera away from the body! If your camera is warm I would say it IS something to be worried about. If it was an all metal camera with good heat transfer I say non issue, but some thick hardened plastics can almost have the heat transfer characteristics of styrofoam.

    Do you have access to a laser temp meter? I'd be interested if you do this again if you quickly flip the camera into cleaning mode and take a reading on the sensor.




    For those interested in doing startrails the best way to do it on a DSLR is by stacking images. I have taken a exposure made up of 120 30second exposures with a 5 second gap between each one totalling 70minutes. The camera wasn't anywhere near as warm as my one hour continuous shot, and the image had zero noise as this was averaged out due to the stacking process, not to mention no purple thermal effects.
     
  3. IgsEMT

    IgsEMT No longer a newbie, moving up!

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    You could just call Canon tech support and ask them this question.
    It'll probably be safer that way. But if you're a maverick and willing to push your toy, please report
    :thumbsup:
     
  4. Garbz

    Garbz No longer a newbie, moving up!

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    You're assuming that you'll call tech support you'll end up with an engineer and not some dork behind a helpdesk in New Delhi.

    Search this very forum and you'll find cases of people who have been told some very stupid things from a helpdesk.

    It's hard enough to speak to an engineer of an engineering company when you're a multi-million dollar client of theirs, good luck :)
     
  5. Moglex

    Moglex TPF Noob!

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    Does anyone know why (or, indeed, if) the camera manufacturers don't do the obvious and include a temperature sensor that will shut down the exposure if the sensor temperature nears critical?

    A lot of times you have problems early in the life of a technology and the danger enters folk-law even though the engineers have found and implemented a way to prevent the danger years back.

    Take as a prime example the amount of contradictory nonsense talked about batteries of various types.
     
  6. Garbz

    Garbz No longer a newbie, moving up!

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    One reason is they probably get too few failures to even care. Many camera models wouldn't last more than half an hour to an hour battery wise let alone doing the exposure. And then that's not something the camera is capable of. To get more than 30 seconds on any camera I believe you need to buy a remote.

    I don't think it makes economic sense to include the extra part and programming in every camera when far less than 0.1% of them would fail due to this "issue" if it is still in fact an issue. I mean it's not exactly a big problem, I haven't seen anyone on this board who has first hand experience, I have second hand experience with a 350D which isn't a new camera either, and the rest is just talk.
     
  7. IgsEMT

    IgsEMT No longer a newbie, moving up!

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    Not assuming, but hoping... I had to contact Nikon and Canon tech support in the past and surprisingly we actually had a fluent conversation rather then hearing "one moment sir, let me look it up"
     
  8. Moglex

    Moglex TPF Noob!

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    I wonder if they route P&S enquiries to a different department to enquiries about top of the range DSLR's.
     
  9. Sw1tchFX

    Sw1tchFX TPF Noob!

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    I've done 5 minute to 1 hour long exposures off my D700 and they've been great, and the camera still works awesome too! The hour one one was noisy as hell and ran my battery down, but it still worked. I don't know if i'd do another hour long shot though. 30-45 minutes might be tops. 15 minutes though...cake.

    [​IMG]

    My D70 has trouble, I can't do a 5 minute exposure without Long Exposure NR, and that's about as long as i'd want to go too on that body.
     
  10. Garbz

    Garbz No longer a newbie, moving up!

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    Funny enough I saw a post on some hacking forms where someone built a peltier cooling unit for his camera. He does cool 3 hour exposures of the sky using image stacking. 30x5min exposures with a few second gaps between each. The peltier unit cools the camera down to negative temperatures and dramatically increases his signal to noise ratio too.

    A novel idea that may work even better on metal bodies. If I had a telescope I'd be all over that hack :)
     
  11. musicaleCA

    musicaleCA TPF Noob!

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    Link please? I might be able to scrounge a telescope from somewhere...*ponders* In any case I want it in my bookmarks for later.
     
  12. Jaszek

    Jaszek No longer a newbie, moving up!

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    Yestarday I was doing star trails with 5 minute exposures for 1 hour and 10 minutes with 5 sec. break in between. that was my second star trail and so far nor problems with my XSI.
     

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