I'm curious about the temperature data in DSLR subs. When I download subs from my Canon 1000D, there is a FITS keyword CCD-temp, filled in with a temperature. WHen I download CR2-files, the raw files, I cannot find any information about temperature in the EXIF-tags of the images.
So where does the FITS-keyword information on temperature come from? My belief was that the fits-files were converted form the cr2-files - and if the cr2-files do not contain information about temperature, where then does it come from? Or do the CR2-files contain this information, but I just cannot find it?
the (sensor) temperature is embedded in the raw DSLR format. Try e.g.
>exiftool IMG_8327.CR2 | grep Tem
Camera Temperature : 28 C
Color Temperature : 5200
Color Temp As Shot : 5200
Color Temp Auto : 5200
Color Temp Measured : 5200
Color Temp Daylight : 5200
Color Temp Shade : 7000
Color Temp Cloudy : 6000
Color Temp Tungsten : 3200
Color Temp Fluorescent : 3720
Color Temp Kelvin : 5200
Color Temp Flash : 6277
The gphoto2 driver uses LibRaw to unpack the raw DSLR and uses exactly these EXIF information to read out the temperatures:
if (lib_raw.imgdata.other.SensorTemperature > -273.15f)
gphoto->last_sensor_temp = lib_raw.imgdata.other.SensorTemperature;
else if (lib_raw.imgdata.other.CameraTemperature > -273.15f)
gphoto->last_sensor_temp = lib_raw.imgdata.other.CameraTemperature;