R5 recording limits temp/sensor correlations

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Horshack Veteran Member • Posts: 8,522
R5 recording limits temp/sensor correlations
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I've been participating on the FM thread (link) where the experiment was done which proves the R5's video thermal shutdown is not an indiscriminate cripple timer that has been described on some sites.

Right now the only temperature indicator we have from the R5 is what's reported in the EXIF data of images. However, if the R5 follows previous Canon bodies that temperature is sampled on a separate part of the PCB that is removed from the image sensor and DIGIC (see my post here - I'm "snapsy" on FM). This explains why a recent test shows the EXIF topping out well before the R5 reaches thermal shutdown.

There is however an alternate, indirect method to induce the relative temperature of the sensor. When CMOS image sensors heat up they produce more detectable image noise. I have a collection of R5 blackframes I've been using for the R5 raw noise-reduction investigation. A few have higher EXIF-reported temps than others. If I compare the noise between the lowest and warmest EXIF-reported temps I see a 4% difference in the standard deviation of noise:

EXIF temp 33C:
R: mean=511.84, stdev=1.44
G1: mean=511.90, stdev=1.30
G2: mean=511.91, stdev=1.31
B: mean=511.81, stdev=1.39

EXIF temp 46C:
R: mean=511.88, stdev=1.50
G1: mean=511.95, stdev=1.38
G2: mean=511.96, stdev=1.37
B: mean=511.89, stdev=1.45

The above is data for two blackframes, one where the EXIF-reported temp is 33C and the other 46C. In each of the 4 color channels there is approximately a 4% difference in the standard deviation of noise.

Even though the EXIF-reported temp seems to top out at around 46C I'm guessing the image sensor and DIGIC continue to get hotter as video recording occurs, and it's those rising temps which trigger the eventual thermal shutdown. I'd like to prove/disprove this theory by performing an experiment where raw images are taken before, during, and after thermal shutdown, plus additional raw frames during the recovery period, then comparing the image noise of the raw frames to see if there's a relative correlation between the noise (and thus sensor temperature) and the shutdown/recovery period. I don't own an R5 so I'm looking for volunteers who can perform the experiment then send me the resulting raw files

Experiment

  1. Starting from a completely cooled-down body, power on the camera and take the initial raw blackframe.
  2. Start recording 8K 30fps raw video. At 3 minute intervals, stop the raw recording and take another blackframe. Keep track of what the reported "available video time left" indicator reports on the EVF/LCD for each blackframe taken. Also take a blackframe the instant the camera starts showing a thermal warning. Continue this process until the camera reaches thermal shutdown.
  3. Power the camera back on after the thermal shutdown and take a blackframe. Power the camera back off
  4. Over the next 2 hours, power the camera on every 15 minutes to take a blackframe. Keep track of what the reported "available video time left" indicator shows for each blackframe.

Blackframe instructions

  • Exposure set to ISO 100 1/4000 f/8 with lens cap on. Shutter type set to EFCS (Electronic First Curtain Shutter)

Thanks!

Canon EOS R5
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