Sony a9 self heating

This is the ninth in a series of posts on the Sony a9. The series starts here.

There have been reports of Sony a9s shutting down because of internal temperature buildup. There are many camera modes that can affect power consumption, and I hope to eventually be able to do the fixturing to measure that directly as I have done with the a7RII so that we’ll know what modes to avoid on hot days.

But today I did something simpler. In a 25-degree C room,  made a series of 6475 1/10 second electronic shutter exposures 1 second apart of the back of the body cap with the ISO set to 1000, the camera in single shot mode, the file type to raw compressed. That took a bit under 2 hours. The LCD screen was flat to the body. Here’s a look at the camera and battery temperatures at the beginning of the test.

And at the end:

The battery temperature rose 10 degrees C, and the camera temperature 13 degrees. I expect that nearly two hours is long enough to get the camera temperature pretty close to equilibrium.

Here are the stats for the full frame at the beginning:

And at the end:

The column to look at is the last one, which is the sigma, or standard deviation, and is also the rms value of the dark-field noise. There is virtually no change.

Here are full frame histograms:

There are no significant differences. The distribution looks Gaussian in both cases.

At the end of the test, the camera was warm, but not hot, to the touch.

I would expect that in a environment 15 degree hotter, that the start and end temperatures would have gone up by 15 degrees. That would have put the camera temperature at 57 degrees C or 134 degrees Fahrenheit. I don’t know if that would have caused the camera to shut down.

[Added 6/1: I just received the following message from a reader who goes by MikeSul on DPR:

I have sets of photos from two days where the warning came on. On both days I continued shooting and the camera never shut down. The first day the warning came on and off over about half an hour after it began about 45 minutes into the shoot. I am in Phoenix and the temp was at or slightly above 100f all the time.

I asked Mike for the EXIF values for the camera and battery temperatures when the warning came on. This is what he said:

…when the warning came on the camera was 48c and the battery was 47.8. The hottest it got (about 20 minutes later) was camera 53c and battery 49.4. I was in direct sun for about an hour and a half. Airplane mode. I made no effort to shield the camera or 24-70gm lens.

We still don’t know the temperature that causes the camera to shut down. Let’s assume the camera temp is the one that the a9 uses to decide whether to warn the user about overtemp, and that 48 degrees C is the threshold. Ignoring the sun load for the time being, lets convert 100 degrees F to 38 degrees C.

In my tests above, I saw a rise in the camera temperature of 16 degrees C over ambient. Had the ambient been 38 degrees C, that would have gotten the camera to 54 degrees C, and triggered the warning. I am surprised the warning temperature is so low in a camera whose maximum ambient operating temperature is 40 degrees C. That only allows for an 8 degree C rise before the warning comes on.

Here are graphs of the camera and battery temperatures versus time:

Looks like an exponential, as you’d expect. The time constant is about half an hour.

If you go to Suitcase > page 2/7, you’ll see Auto Pwr OFF Temp. There are two settings, standard (the default) and High. If you set it to High, it sounds like it’s setting the actual turn off temp higher. It may also be setting the warning higher. It probably isn’t just setting the warning higher.

One side note: about 6500 exposures drew the battery down from 95% to 57%. That’s pretty darned good.