Canon EOS R5 - Firmware Update (La fine dell'Odissea Overheating?)

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In the beginning of his video today Gordon relays information provided to him by Canon regarding the thermal management on the R5. Here are the key points summarized:

Two internal temperature sensors, "near the AF and imaging sensor" and one for measuring external ambient temperature, near the ports.
R5 uses readings from all three sensors along with a timer to figure out when to report overheating and how much recording to allow while the camera cools down
Canon hasn't changed the temperature which overheating is reported but will now check the sensors more frequently, giving more accurate feedback and potentially allowing you to record again sooner, or for longer
The external ambient temperature now plays a bigger role so cooler surroundings may allow the camera to recover more quickly, so a fan or other active cooling could actually now become beneficial

#1 - Three internal temperature sensors

One sensor is described as being "near the AF". On previous Canon bodies the temperature report in the EXIF is from what's called the "EFIC temp" (source), which on previous Canon bodies was a secondary chip responsible for the lens interface and speedlites. Canon actual documented this chip in their 1DM3 technical whitepaper (page 33), where Canon refers to it as follows "EFIC as the interface for the lens and external Speedlite" and explicitly states it's located on the camera control board, separate from the image sensor and DIGIC. The verbiage Canon conveyed to Gordon sounds similar, so it may be safe to conclude the EXIF-reported temp is the EFIC temp, as it has been on previous Canon bodies.

The second sensor is described as being near the imaging sensor. If that's true then our efforts to induce the relative image sensor temperature from blackframe noise measurements (on the previous thread) may gain new importance as a proxy for this newly-disclosed temperature sensor.

The third sensor is described as measuring external ambient temperatures and is located near the ports.

#2 - How the three temperature sensors are used

Canon discloses all three sensors are used in combination a "timer". The fact they use a timer "in combination" with the sensors implies that 1) They're attempting to project the temperature ramp (both up and down), perhaps as part of a hysteresis algorithm that's attempting to account for temperature lags and/or 2) Enforcing a total heat exposure metric (temperature x time, ie how long the chips are exposed to heat rather than peak temperature), perhaps as an effort to ensure longevity of the internal ICs.

#3 - Sampling the sensors more frequently for more accurate feedback [presumably into their thermal algorithm]

This one strikes me as very peculiar. If you look at all the data we've collected, which includes calculations for the rate of temperature change per minute (4K30 HQ ramp-example and 8K ramp-down example) the rate of temperature change rarely exceeds 1c to 2c/min - the fastest I've seen it climb is approx 3c/min for a single 8K test. Which begs the question - how fast were they sampling the temperature before and how could it not be fast enough to track this rate of ramp? Why would they not sample the temperature at least every 15 or 30 seconds? And regardless of how often they sample, the rate is pretty linear on both the way up and down, so why would more samples yield "more accurate feedback" since the trend line would be the same?

#4 - External ambient sensor now plays a bigger role, esp for cooling calculations

This one is interesting. It implies they're partly relying on the ambient temperature to project the rate of cooling rather than relying exclusively on the two internal sensors to directly measure that trend/rate, and even more so with the new firmware. I assume they're comparing the rate of decline of the internal sensors relative to the ambient, either by some dynamic heuristic or a lookup table they built during the R5's design/testing, either of which attempts to use that relationship to project the temperature at points in the future.

Initial Thoughts

On balance the new thermal details provided by Canon and the description of how that logic changed in today's firmware sounds a bit contrived to me. Thermals must have been one of the biggest challenges during the development and testing phases of the project. How could it be that they overlooked some elemental relationships between the three sensors and also not have sampled them frequently enough? It doesn't make much sense to me. IMO it sounds like misdirection to simply obscure the fact they may have simply loosened the reins a bit on the temperatures allowed, either peak or more likely total heat (temp x time). The fact the cooldown periods were most affected by the new firmware (shortened) suggest they're simply allowing the camera to operate warmer for longer. The fact the temps usually plateau near the end of the recording time allowed also supports the notion it's a total heat consideration rather than a peak or "overheating" consideration.
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“ Chi si aspettava l'8K "light" rimarrà deluso e dovrà attendere ancora. „