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Passive heat sink for DSLR?

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#1 MCovington

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Posted 14 June 2017 - 10:49 PM

Has anyone experimented with sticking a heat sink to the back of a DSLR with the screen swung out?

It could be held by adhesive or supported from the tripod socket.

I know one of our members makes thermoelectric coolers that press against the back of a DSLR.

 



#2 Herra Kuulapaa

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Posted 15 June 2017 - 01:38 AM

There is one problem, way too much material between the sensor and plastic outer body to passive cooling make any real difference. I don’t say there can’t be any, but it’s most likely very small to make it worthwhile.

 

A passive heat bridge from sensor to outside of camera however does make a difference (considering temp difference to be meaningful between those two points).

 

EDIT: Found this in my archives:Temperature measured from sensor frame at 22 C room temp.

Passive.jpg


Edited by Herra Kuulapaa, 15 June 2017 - 02:02 AM.

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#3 mmalik

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Posted 15 June 2017 - 05:35 AM

Has anyone experimented with sticking a heat sink to the back of a DSLR with the screen swung out?

That's not going to do anything; sensor is far removed. A passive 'Cold finger Inside'... is one option. Regards



#4 calypsob

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Posted 16 June 2017 - 07:21 PM

Has anyone experimented with sticking a heat sink to the back of a DSLR with the screen swung out?

It could be held by adhesive or supported from the tripod socket.

I know one of our members makes thermoelectric coolers that press against the back of a DSLR.

I know the nasty athens summer heat all too well. Your best option is to use LENR when it is that hot outside and dither heavily.  You can do it for 25% of your subs then take some more darks at the end.  The iso can be dropped to 400 and an external battery cuts a bit of thermal heat buildup too.  



#5 MCovington

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Posted 16 June 2017 - 08:54 PM

LENR is simply dark frame subtraction, isn't it?



#6 mmalik

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Posted 18 June 2017 - 06:18 AM

LENR is simply dark frame subtraction, isn't it?

Yes; it is in-camera automatic dark subtraction per image (dark applied to one image only, can't be used again); means it doubles the acquisition time. Regards


Edited by mmalik, 18 June 2017 - 06:21 AM.

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#7 Jon Rista

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Posted 18 June 2017 - 03:22 PM

Has anyone experimented with sticking a heat sink to the back of a DSLR with the screen swung out?

It could be held by adhesive or supported from the tripod socket.

I know one of our members makes thermoelectric coolers that press against the back of a DSLR.

Both Mike Malik and I have built bolt-on camera TEC-based coolers. Mike had more success, but he was using a metal-body A7s, which was able to be cooled better by the external cooler. My testing with various DSLRs demonstrated that while over time a very high powered (two 65W TECs in my case, cooled with a water cooler) bolt-on cooler could bring the sensor temp down to ambient, there was simply too much thermal resistance to overcome in order to really get any effective cooling out of it.

 

You would need some kind of direct thermal channel between the sensor and the camera body, better to the outside of the body, in order to get effective cooling of the sensor. A "cold finger".



#8 Jon Rista

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Posted 18 June 2017 - 03:28 PM

LENR is simply dark frame subtraction, isn't it?

It is, but the key with LENR is they tend to be ideally matched in temperature to the preceeding light frame. That allows for more ideal calibration, without leaving remnant FPN behind. I recently did a LENR vs. master dark calibration comparison. The master dark, generated with frames ranging from 35C to 47C EXIF temp, usually left remnant FPN in the data. An example 35C master-calibrated dark:

 

E4Kc0oy.jpg

 

The LENR calibrated frames, even at higher temps, were perfectly flat:

 

uD622vc.jpg

 

Now, technically speaking, if you could match the lights to the darks ideally, then it doesn't really matter when you take them. If you have the ability to get darks every 2C for a wide range of temperatures that your camera may operate in, and create separate masters for each temp, then you could calibrate batches of lights each with a matching dark, and potentially get better results. That tends to be extremely tedious, extremely time consuming, and even with light to dark matching and library management tools, there is still one critical flaw: the EXIF temp of Canon cameras (most other DSLRs don't even have a recorded temperature, or if they do it's even farther removed from the sensor) is from the DSP, not the sensor! There can actually be fairly large discrepancies between true sensor temp and the EXIF temp, enough to have as much as a doubling/halving of measured dark current for the same recorded EXIF temp. So...matching by recorded temperature will often have an undefined outcome. 

 

LENR, on the other hand, will usually match within a fraction of a degree. It may cost you more imaging time...however, it's worth testing to figure out if the remnant FPN you'll have to deal with if you get more integration time will actually give you a better image or not. Sometimes, half the time with LENR will actually deliver more pleasing results. 


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#9 MCovington

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Posted 18 June 2017 - 06:32 PM

Got it!  Thanks!  I shall no longer be hesitant to use LENR, particularly when the temperature is high.


Edited by MCovington, 18 June 2017 - 06:37 PM.



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