I was watching Finding Bigfoot. I’ll let that sink in for awhile. Anyway on one night session one seeker had proper thermal imaging binoculars while the other had an app on a smart phone. This has got to be the coolest thing I have seen so far that I might want on my phone. But doing a search turns up mixed reviews for the ones I checked and the first one listed doesn’t seem to work well with Samsung phones. I have a Galaxy S7. Anyone have any experience with these apps?
I can’t see how it can be any good, or even how it would work to be honest. Does a smart phone have a heat sensor?
You need a thermal imaging camera.
“But wait!”, you say. “The app says it works through the normal camera!” Well, the app is lying to you, my friend.
I just looked on the play store. The honest ones have some version of “thermal imaging simulator” in the name. Both those and the less honest ones seem to have ratings in the vicinity of 2.5, which tends to indicate that the thing being rated is crap.
Also notice how low the resolution of the cameras in my linked review are, ranging from 0.03 MP to 0.1 MP.
From one of the links above "You need to purchase a thermal imager before using thermal imaging apps in an android or ios mobile. "
As I know it you have to buy a thermal imager, the phone is just the screen for it. It can connect via bluetooth, wifi or the cable input. I have something like it in concept, a small camera on a flexible ‘wire’ that I can place in things like ductwork and pipes. All the viewing and most of the controls is on the phone. Heck even GoPro works that way.
As a physicist who works with heat and temperature, and has two different thermal imagers at his disposal, I can swear to you that a phone app that does not have access to a separate thermal imager (like kanicbird references) is doing zero thermal imaging of living creatures.
Now, you can do thermal imaging with your unaided eyes, if you’re talking about things that are getting red hot. And by their nature, many ordinary digital cameras are able to see slightly longer wavelengths and therefore slightly less hot objects than your eyes (though this may be blocked with an internal filter to make color rendering more accurate). So, it might be that some cameras will see a bit of glow for objects you would perceive as not quite glowing. But an app isn’t going to change that.
I knew it was too good to be true. Thanks everyone for the input. I used to use a high end thermal camera at work that was fully calibrated and you could read the temperature off the screen by the color. The one on the TV show, although they did not mention much about it, looked more like a night vision type where the warm object was just white against a much darker background. I thought perhaps it was just filtering the infrared somehow. It appeared pretty much like the systems Cadillac uses on their vehicles which works quite well.
A smartphone camera can see the light from an IR remote control (try it!), which is 940 nm, while visible red light goes down to about 700 nm, so they do see at least a bit more into the infrared than human eyes. Apparently active night vision cameras, which produce their own illumination, use light around 1000 nm, so an ordinary phone camera could probably see the light emitted by an active camera. Passive thermal vision cameras see deeper into the infrared, down to about 1600 nm from what Google tells me, which I think is well beyond what an ordinary phone camera can see.
Passive thermal vision cameras see way longer wavelengths than that. As I recall, 10,000 nm and maybe longer.
Yes that is what I was thinking. My experience with infra red camera’s has been operating a FLIR turret on an aircraft. Its sensor was cooled to around 70 Kelvins, an ability that a phone obviously doesn’t have.
Ah the Flir. During a cold snap I have really lusted after getting one of these Flir smartphone attachements to see where the heat escapes from my home.
I have a Seek Thermal imager for my iPhone.
It’s pretty darn handy. I use it to find defective components on PCBs, find bee hives, and locate the dog in the bushes at night.
They usually have actively cooled sensors though, don’t they?
Since I wasn’t sure, I checked here:
This is a great article, which among other things cleared up that the wavelength range typically extends as long as 14,000 nm.
Aaaanyhoo, there are sections on cooled and non-cooled cameras. I think the smaller lighter handheld cameras, and certainly the cellphone add ons, are non-cooled (though the article doesn’t say).
As I understand it, phone cameras can detect near-IR. However, most phone cameras now have filters that block the IR since it makes it harder to image visible images.
I remember reading about hacks using old phones where the filters could be removed (obviously one only does that on old phones 
) and then there were apps that could display the resulting image.
I don’t know whether any of that is practical any more.
Almost all cameras … people were using that ‘feature’ to take pictures that allowed you to see through people’s clothes.
I seem to remember an old trick of testing whether a TV remote is working by looking at front through a smartphone camera, you can see the IR light flashing when you press a button. But I just tried it on my iphone 8 and I just about make it out. So that is maybe that is the IR filter in action.
The Raspberry Pi camera comes with an No Infra Red (NoIR) option with its IR filter removed. Good for those who like to do photography wildlife at night, where IR sensitivity is an advantage.
https://projects.raspberrypi.org/en/projects/infrared-bird-box/3
Those aren’t cameras, those are potatoes!