Paterson 12" Darkroom Certified Thermometer

I bought this mainly for the Celsius scale, and it's spot-on from 13° to 30°C—my developer temps are finally consistent. The 9-inch length is long enough to reach into deep tanks without splashing.

The temperature markings are super easy to read even in the dim safelight, and the 9-inch length lets me dip it right into the tank without any awkward reaching. It's consistently within half a degree of my lab's reference, so my negatives come out perfectly every time.

The dual range is handy for both C and F, and the 9-inch length reaches deep into my tank without splashing. It reads consistently enough, though I wish the markings were a bit darker for low-light work. Works fine for standard B&W temps, but don't expect lab-level precision from it.