DSLR sensor heating study ;)

[Yoddha]

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

[Shibby]

Fascinating project! I love the idea of storing the temperature in the EXIF. Will be useful for matching up darks too.

It doesn't cool much between exposures, does it? But it does at least seem to stabilise a bit after 7th sub...

[Glider]

My experience over a range of ambient temperatures 0 to 20 centigrade is that the EXIF reads 5 centigrade above my thermometer next to the camera.

[Yoddha]

Lewis,

All DIGIC 3 and 4 cameras store the temperature in the EXIF information when RAW format is used

Don't want to advertise APT, but the full version can make this reading a part of the file name...

[Yoddha]

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

Attached is a noise comparison in the last images from both tests:

[Shibby]

:-O That's a massive difference!

Would be great if this did lead to a mod service; these ones are quite expensive!

[swag72]

Gosh, just looking at the 2 noise comparison test shots - That's a massive difference to my eyes.

[jgs001]

Nice work Ivo, and excellent results..

[TJSnapper]

Great post and very interesting results, it shows the effect of heat very well.

Out of interest, how do you cool a DSLR chip?

[Psychobilly]

The best way is with a "Coldfinger" and an external TEC Cooler... or the easier method is just put the whole body in a cooled container...

Billy...

[TJSnapper]

Thanks for the links, that is some pretty intense camera bashing I have so much to learn

[Yoddha]

Thanks to all!

My camera is modified with cold-finger and TEC (Peltier element) Here is a picture

It is not fully completed yet. There will be a box around the silver part that will hide the cables, and will keep the connector for power cable and power regulator...

[Abernus]

O.K so I don't know much at all about this but I do know alot about PC's and cooling in particular. Would it not cost less to buy a Peltier CPU cooler and mod this to a DSLR? I have followed posts about people doing the IR cut filert mod (if I got the correct) so opening a DSLR should be no problem for some.

I would then think poping a copper plate on the DSLR body that the Peltier could attach to for heat transferance? Just an idea and sorry if it's a stupid one.

LOL beaten to it by Yoddha

[Yoddha]

Abernus, in my camera there is a thin copper plate that is behind the CMOS sensor and the TEC is attached to it. There are a lot of sources to buy a Peltier element and the choice is more flexible than buying a PC cooler.

[pete_l]

That's a good piece of work. I've also noticed that with my modded 20D, the colour balance changes significantly, too.

Although I shoot RAW, when I take a sequence of 30s exposures and import them into Photoshop using the same raw profile for all of them the ones at the start of the shoot are noticeably bluer than later ones.

[Gina]

Very interesting I didn't know the EXIF T was measured in the Digic chip rather than the sensor. That makes me think! I was assuming the EXIF T was the sensor temperature in all my tests and thoughts on cooling. So I shall need to provide my own thermometer when using cold-finger cooling. That would be required for proper cooling control anyway.

[Yoddha]

You are absolutely right , this is the reason to use the external thermometer mounted on the flash shoe... The black cable is the probe that is mounted on the finger close to the sensor.

[Gina]

Thank you