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Old 19-01-2011, 09:31 PM
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Yoddha
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Wink DSLR sensor heating study

A friend of mine modified one 1000D for me The modification is cold-finger + peltier + temperature sensor on the finger near to the CMOS. It is an interesting project that possibly will evolve into modification service and/or DIY kits ... But this is other theme.

The temperature sensor gave me opportunity to measure in good approximation, how much the CMOS heats during the exposures.

The tests were made with external battery (astronomiser's DC Pro) and turned off display to minimize as much as possible the heating sources. All exposures are with ISO 800, duration 600s with 50s pause between them and with cooling turned off. The columns of the table show - T in the beginning of the exposure, T in the end of Exposure, T stored in the Exif of the image (APT was used to get this reading)

T-St. | T-End | Exif
21.9C | 25.0C | 20C
24.5C | 26.3C | 25C
25.9C | 27.3C | 25C
26.8C | 28.0C | 26C
27.4C | 28.4C | 26C
27.9C | 28.7C | 29C
28.1C | 28.9C | 29C
28.3C | 29.1C | 29C
28.5C | 29.2C | 29C
28.6C | 29.3C | 29C
28.7C | 29.3C | 29C
28.7C | 29.3C | 29C
28.7C | 29.4C | 29C
28.6C | 29.3C | 29C
28.8C | 29.4C | 29C

As we see with ambient temperature 22C, exposures heat the sensor with around 7 degrees. I think that with lower ambient temperature and with well tempered camera, is possible to have little bit lower value, but not under 5 degrees. It is visible that the EXIF temperature is quite accurate in this case... But some fast tests with turned on cooling showed that EXIF is unusable when there is cold finger because the internal sensor is in the DIGIC processor which in this mod is separated from the CMOS by the finger. I'll make serious tests with the turned on cooling and will post them if there is interest
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Old 20-01-2011, 07:39 AM
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wasyoungonce (Brendan)
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Its interesting to note, from what I know, unless the pause is equivalent to or greater time than the sub then any such short pause between subs...is not worth it. The sensor does not cool enough.

Active cooling is a great idea but I also get the feeling that one could end up with a "Frankenstein DSLR"!

That said I would love to see the results you get!

Keep it up Ivo
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Old 20-01-2011, 09:09 AM
pjphilli (Peter)
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Hi Ivor
This certainly interests me and I look forward to your further tests and results. A good cooling modification kit for Canon DSLRs would be welcome, particularly a fast acting compact one that cools the CMOS imager directly (instead of through the camera case).
Cheers Peter
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Old 21-01-2011, 07:21 PM
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Here is the second test, with turned on cooling The ambient temperature was again 22C. The sensor was cooled for 30min to temperature 4.3C. Same exposure parameters were used.

T-St. | T-End | Exif
4.3C | 6.8C | 18C
6.2C | 7.4C | 20C
6.8C | 7.7C | 22C
7.1C | 7.9C | 24C
7.3C | 8.0C | 24C
7.4C | 8.1C | 24C
7.4C | 8.1C | 24C
7.4C | 8.1C | 24C
7.4C | 8.1C | 24C
7.5C | 8.1C | 24C
7.5C | 8.1C | 24C
7.5C | 8.1C | 24C
7.5C | 8.1C | 24C
7.5C | 8.1C | 24C

And a link to is a noise comparison in the last images from both test : http://www.ideiki.com/astro/astroimages/noise.png
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