CMOS Temperature

[RenatoPhoto]

For 5D3
Confirm that room temperature and LV readout is within 2 C
No IR measurements.
For my camera normal operating temps 50 to 73 C

I tested my 5D3 from cold start:

LiveView from 15C to 66C in 30 minutes
Stabilized at 66C

I covered the camera with cloth in 6 minutes in climbed to 73C
Stabilized at 70C in 11 minutes

I started RAW REC 1920x1080 at 30 fps
Temperature increased to 72 C in 5 minutes
Stabilized at 72C

I started Playback in 8 minutes drop to 58C

I started LV again in 6 minutes stabilized at 67C

It would seem that normal operating temperatures 50 to 73C

[escho]

I  don´t know, how many sensors for measuring temperature are in an EOS-body. So I don´t know, whether the temp, shown in the exifs is from the same sensor than the temp, ML measures via efic_temp.

If i compare both, efic_temp and exif-temp, it is not the simple polynomial relationship between both, I thougt before (celsius = efic_temp - 128). This simple relation is true in a small temperaturerange from let´s say 25 to 35°C exif-temp. But with highter temp, efic_temp grows much more than the exif-temp. This difference can approximately be described with a linear funktion f(x).

I did some tests with my 600D and plotted the values with gnuplot to see, what happens. I will try to work out this function (must search first, how to do this).

What does that mean? That means, the high temperatures, shown with ML, are not correct. They are lower. Exemple: ML-temp: 83°C --> exif-temp 61°C!

So, all the hope of some photografs, they can prepare fried eggs on their camera-body, has gone. They have to buy a frying pan 

Edgar

[Frank209]

aaaw shoot. And i just wanted to bake lunch on that thing....

[escho]

The following function fits best to my 600D-values:

Code Select Expand

exif-temperature = 63/100 ML-temperature +8

This is the diagramm:


600D von seescho auf Flickr

I will do some more test to confirm this .

Edgar

[a1ex]

If you look at the exif raw value (exiftool -verbose), the temperature is indeed exif_raw - 128. But from this data set, it looks like either the exif temperature comes from a different sensor, or maybe the property is not updated fast enough.

Here's a previous attempt at measuring the sensor temperature: https://groups.google.com/d/topic/ml-devel/clrm9CTdKRc/discussion

[escho]

Hi Alex

Yes, I know that exiftool uses x-128 to convert to °C. For a better understanding, what´s up, here how I did this test:

1. Changed ML code to make sure, x-128 is really used in ML (displayed raw efic_temp instead of °F in debug-menue).
1.1 Yes, it is used to convert to °C, no hidden bug.
2. Started mov-recording monitoring the temps in debug menue
2.1 recording duration over all (2 movs): 41 min.
2.2 Taking CR2-pics from time to time and writing down displayed temperature
2.3 extended exif-temperature from these pics (exiftool -CameraTemperature *.CR2)

My observation:

1. I did not succed in overheating my 600D (no canon-warning)
1.1 I read in a forum, that it´s very hard to overheat 600D. 7D is much easier to overheat, they said (I don´t know anymore, which forum it was)
2. the relationship between exif-temp and ML-shown-temp seems to be constant for my 600D
2.1 I guess, propery is updated fast enough
    Temps after 33min: ML-temp: 81°C - exif-temp: 59°C
    Temps after 41min: ML-temp: 83°C - exif-temp: 61°C
    8 minutes should bo long enough for updating some property.
   
What do I think:

1. Even if there are 2 sensors, one for exif and one for efic_temp, the relationship between these two temps seems to be constant (on my 600D, using the formula, I introduced above). I think, this reastionship can be used, to show more realistic temps in ML.
2. Measuring temps in the camera body with an infrared thermometer (thanks for the link) makes not more sense,than using exif-temperature, because you don´t know, where the temp-sensor is located.

What is not clear to me:

I did not succeed in overheating my camera. So I cannot say, at what point ML should warn. The warning-temps (50°C and 60°C) now used by ML are good, if they use exif-temp, generated with a formula and not efic_temp-128.

What´s to do:

Measurements from other cameras would be fine, to find out the point of canon temperature warning and to see, if my formula only is valid for 600D or for other cams too,

Edgar

[g3gg0]

took into consideration that the CMOS temperature and the EFIC (Flash IC) might be different because they are measured on different devices?
(my theory)

[escho]

Yes, it looks like there are more temperature-sensors.

efic_temp used in ML is not the same than the temp shown with exiftool. So it is not correct, I guess, to use "efic_temp -128", which comes from exiftool-code and was introduced by me some months before. I did not test this in a wider temperature-range, so it was my fault, to suggest this x-128.

Now there are three possibilities, I think:

1. Finding out the property, which contains the temp-value which goes into the exifs. That would be the cleanest way, I guess.
2. Measuring temp with an infreared termometer, but you have to know, where this temp-sensor is located and not so much people have such a thermometer
3.Taking the relationship between efic_temp and exif-temp, which would be easy by an math-funktion but would need tests on the other cameras, to find out the function for each camera.

I would prefer way 3 for the moment (with the function for 600D, if no tests for other cameras are introduced) until way 1 is possible.

Edgar