Open

by damned truths

submit your photo


Hall of Fame
View past winners from this year

Please participate in Meta
and help us grow.

Take the 2-minute tour ×
Photography Stack Exchange is a question and answer site for professional, enthusiast and amateur photographers. It's 100% free, no registration required.

Sensor cooling is a common technology to get less noise. Why isn't it available on high-end D-SLRs ?

(see http://www.andor.com/scientific_cameras/ikon-m_cooled_ccd/ for an extreme example)

I'm not saying D-SLRs should be cooled with liquid nitrogen. Just some cooling system !

share|improve this question
1  
It has been done, but I think this will demonstrate some of the downsides: youtube.com/watch?v=W4QYPIlMnVQ astro-fotografie.blogspot.com/2009/04/… astro-fotografie.blogspot.com/2010/05/… –  ESultanik Jun 20 '12 at 18:09
    
The astrophotographers do it now. It does not need to be as large as they do it. I want to try it sometime. Most people who answered have missed your point. Very small Peltier on rear of sensor wold do. Ideally you'd have it in a dry air chamber to avoid fogging. –  Russell McMahon Jun 21 '12 at 0:17
    
@RussellMcMahon - Saying you can't do it for energy reasons is still valid, even if you scale the technology as small as possible. It's basically impossible to perfectly insulate something. As such, you will have to continuously expend several watts of power to keep a CCD/CMOS of any decent size cool. There is a reason astrophotographers cart around giant car-battery sized batteries to run their cooled cameras. You need the capacity. –  Fake Name Jun 21 '12 at 8:20
    
@FakeName - Energy reasons were well down my list of erroneous responses. The 1st link had a 'noise fee' half hour exposure. That's not a minor improvement and many shots would benefit in selected cases. Then ... –  Russell McMahon Jun 21 '12 at 8:32
    
@RussellMcMahon - The noise reduction from cooling a sensor is largely proportional to the length of exposure, as cooling a sensor mostly serves to reduce the dark current. As such, it's really kind of pointless unless you're doing long exposures. Furthermore, there are many products on the market that do use the tiniest cooler they can get away with, and even so, they still use lots of power. See my answer for more. –  Fake Name Jun 21 '12 at 8:49

3 Answers 3

Most likely because it would be bulky, and have a very high energy consumption.

Most cooling for electronics is for bringing it down closer to room temperature, but that wouldn't do much for a camera sensor, as it is mostly used for fractions of a second, so it won't heat up much. You would need a cooling element to get the temperature down, so it would essentially be a mini fridge or a mini AC.

This would need an element on the outside of the camera to dispose of the heat, which of course would be very inconvenient. The batteries needed to run all this would further add to the size.

So, what you get is a huge, heavy camera, with a hot surface, and a long startup time. Too impractical to make up for the reduced noise.

share|improve this answer
    
Hasselblad cameras are huge. And in low light conditions, you have all the time you need. (stars, animals in the forest with moon light) –  Skippy Fastol Jun 21 '12 at 8:38
    
@SkippyFastol: Yes, you would only put up with the camera when used for things like night fotography, and the people who would buy an extra camera just for that is too few to get it down to a price where anyone would buy it. –  Guffa Jun 21 '12 at 8:53
1  
@Guffa - There are many manufacturers that make cooled cameras. They're just non intended for consumers. They're generally targeted at scientific imaging and astrophotography. They're also many thousands of dollars to many tens of thousands of dollars. Google "cooled ccd" to have a look. I count 6 different manufacturers on the first result page. –  Fake Name Jun 21 '12 at 8:57
1  
@FakeName: Yes, but the question was why they aren't use in D-SLRs. –  Guffa Jun 21 '12 at 9:03
    
@Guffa - Good point. I guess I generalized the question to "Why aren't there hand-help cooled-sensor cameras out there. You are correct. –  Fake Name Jun 21 '12 at 9:21

Cost. Every price raise results in fewer sales.

Size. Cooling has to fit somewhere, those handgrips are already full of batteries...

Weight. There's a reason P&S are popular and not lugging around a brick is one of them =)

Battery Life. Cooling costs energy, lost energy means fewer shots in each battery pack.

Minor Improvement: only shots pushing the envelope would even benefit.

Condensation: artificially lower temp + humid air = water. Water + electronics = brick.

Heat Sink: all that heat has to go somewhere, in this case probably your hand.

Complexity: one more thing to go wrong in the field.

share|improve this answer

It boils down to power, and lack of market demand.

There are specialty cooled-sensor cameras out there. They're generally just used for astrophotography.

The cooler that is used in almost all cooled cameras is what is called a thermoelectric cooler, commonly colloquially called a "Peltier" or "Seebeck cooler".

Generally, you will need a fairly chunky peltier to keep a image sensor cooled. For example, the Orion StarShoot G3 draws 12V at 1A to keep a 1/3" image sensor cooled to -10°C. That's 12 watts!

To calculate battery size needed, you multiply the current draw times the running time. As such, you would need a 1 Ah, 12V battery to run a cooled sensor for just one hour. As a comparison, the common Canon LP-E6 battery (as used in a Canon 5D2) is just 7.2V at 1.8Ah. Even ignoring the voltage difference, that's less then two hours of runtime with the camera on, for a much smaller sensor.


Furthermore, cooling a sensor is unlikely to do much to reduce ISO noise! Cooling a CCD/CMOS sensor largely reduces the dark current. However, the effects of dark current are purely a function of exposure time, so it only really helps with long exposures. High-ISO exposure noise is as much or more of a function of the CCD/CMOS sensor read noise then the dark-current noise of the sensor.
Readout-Noise is not affected by cooling the sensor, so high-ISO levels will be noisy, even with a cooled sensor.


Basically, there is really no reason to bother cooling a image sensor other then long-exposure. It offers very few benefits, and requires considerable additional system complexity, and massively increased power draw. A cooled system has to run continuously for the duration in which one expects to take photographs, as the cooling system will likely take many minutes (10-30) to cool the sensor down, and for the temperature to stabilize.

Furthermore, thermoelectric coolers are highly inefficent, and dissipate all the transfered thermal energy as heat. As such, a 5W peltier will dissipate 5W + any energy removed from the image sensor. This will almost certainly require active cooling, as the cooling efficiency is directly related to how cool the "hot" side of the peltier is.

It's actually common for high-end cooled image sensors to use liquid cooling, and they can dissipate many tens or hundreds of watts of heat.

share|improve this answer
    
FN - My continued, and still, disagreement with what you say relates to power levels, not to other photographic related aspects. Just because people do things really badly at present it doesn't mean it must be so. Peltier coolers are marvellous tools, but horrendously inefficient, as you note. You are unlikely to see anyone producing Stirling cycle coolers for 35mm domestic market sensors, but they would vastly exceed Peltier efficincies and are actually "quite easy" and could be quite low cost if eg Sony decided to use them. Cool down times ... –  Russell McMahon Jun 21 '12 at 19:44
    
FN ... When eg a Stirling cold-finger is attached to a sensor cool down time to Liquid Nitrogen order of temperatures can be a few seconds. Some guided artillery shells have Joule Thomson expansion nozzle cyrocoolers used to cool the IR sensors which guide the shells to their targets(!). The cooling cycle is triggered by the firing impact, the sensor is cooled to LN temperatures as the shell rises and by the time it tops its ballistic arc the IR seeker is ready for work. That they go to this effort for real time motion related use suggests substantial gains for short exposure IR use. –  Russell McMahon Jun 21 '12 at 19:49
    
@RussellMcMahon that's unique to (far) IR. Warm objects emit IR, that includes the IR sensor itself. So, you'd like the sensor to be as cold as possible. –  derobert Jun 26 '12 at 20:52

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.