There’s a new voice in town… that’s the voice of the DAG (Dave, Anna and George) podcast team! Here’s our first effort; a discussion of a topic which has already appeared on this blog before, but this time, in a chatty conversational style… yeah, OK, I lose the plot a couple of times, but Anna saved me. Have a listen, and to read more about it, check out George’s take and Anna’s post here!
- This is the trail of the meteorite we discuss. Cool! Image source: Science
David Robertson 
haha “put that thing away dave”
And you could have your own piece of a “falling star”! :-)
Hate to talk good about digital (a melting camera would be so cool!), but I don’t think it is possible for a CCD sensor (or a CMOS sensor that quite a lot of the modern cameras use nowadays instead) to melt. In fact, I don’t think it overheats at all. Where heat comes into the game is noise. The hotter the electrons in a body are, the more they move around randomly and so the more noisy your picture will end up being. So, if you could cool down a CCD sensor to absolute zero for example, you would get a considerably clearer picture! Maybe such noise is smaller in film cameras.
You’re right they don’t melt. But there are problems with the CMOS (durrr got that wrong too, camera nerd fail) shooting video under certain conditions in DSLRs. Apparently it is not as bad as manufacturer warnings say (clip lengths in some DSLR video cameras were limited to 12-14 mins to ‘prevent overheating’ but apparently it actually takes hours in most conditions before the camera ceases to function).
The biggest functional difference for this application is that there simply isn’t anything remotely affordable capable of delivering a digital multi-hour exposure with controlled noise on the market.
Current DSLRs, to compensate for long-exposure noise, will take a second exposure with the shutter closed to mimic the background noise then subtract that from the original image. That means the image takes twice as long – so a 2 hour exposure actually takes 4 hours, and most camera batteries can’t last that long, let alone 12 or 16 hours of continuous processing.
In a film camera there is no ‘noise’, the grain comes from the film itself. So in the inset of the image above the film grain is visible but that’s not noise in the DSLR sense.
I like the idea of an absolute zero camera, but I imagine batteries wouldn’t last long?
Thinking about it in terms of video, overheating could be a problem. But that would most probably be because of the camera processor needing to work on full load continuously rather than the sensor. In a very simplistic way the sensor just “piles up” electrons caused by photons. And yes, there is all sorts of way to reduce this kind of noise, the most common one being taking lots of shots, but, as you say, it’s not economical at all!
They do use very very cold sensors for particle detection and stuff. But in a camera it would give you some really cold hands!
Don’t know about the batteries, ask a chemist!
Oh, and my “analogue” intuition tells me that there definitely will be some similar kind of noise in a film camera. It’s probably just smaller. Go analogue!
Oh and that’s me above, pressed post accidentally.
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Interesting. Perhaps I should actually look into the mechanisms behind photoreactive chemicals used to emulsify films and make a sunday science about it… considering I worked with those chemicals in the lab!
And yes it’s probably a processor issue. This is the problem with science communication, offhand comments =/= good science. That said I’d expect the pathways linking the sensor to the processor could get overloaded with time; it may depend on the actual amount of light hitting it too, if you just pointed the camera at the sun and left the shutter open it could well melt!
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