I have a voltage regulator, 17.2V input, 3.3V output, 80mA of current passing through it. That's about 1.18W of power dissipation.

The voltage regulator is a SOT-223 and the theta-JA is supposed to be 50°C/W (from datasheet). The T_J_MAX is rated 125°C

My room thermostat has been set to 75°F, rougly 24°C.

Theoretically this means T_J = 24 50 * 1.18 = 83°C

My thermal photo shows 57°C at the surface of the chip (and a wall behind it shows 25°C)

So my question is, is there a way to calculate my actual T_J from the thermal photo? I'm like 99% sure I'm supposed to use theta_J_Case instead of theta_J_Ambient for that but the datasheet doesn't specify that.

I did find this, https://www.richtek.com/Design Support/Technical Document/AN044?sc_lang=en , it says theta_J_Case is 15°C/W, so is this a good ballpark 57 15 * 1.18 = 74.7°C ?

It's lower than the theoretical calculation made with just theta_JA though. If I plug in the new theta_JA 135°C/W from the above appnote then I get a 24 135 * 1.18 = 183°C which is wayyyy too high.