The AH-M1 Light Meter from Chinese company AstrHori is a real-time light meter developed for older cameras, particularly film cameras, that lack a built-in light meter. The AH-M1 is made of aluminum alloy and weighs about 48 grams. The light meter is 14 millimeters (0.55 inches) thick, 38 millimeters (1 inch) broad, and 1 inch in height. On the top, there is a dial for adjusting and changing settings. The light meter works in the ISO range of 5 to 6,400, the f/1.0 to f/32 aperture range, and the 30 second to 1/8,000 second shutter speed range. At ISO, AstrHori says the metering range is ~1 to 22 EV.

The AstrHori AH-M1 has two metering modes: A and T, and it can continually track changing light values in real time. When the photographer has a known ISO sensitivity and shutter speed, they use the A, or aperture, mode. When operating in this mode, the light meter will recommend the appropriate aperture setting based on the ISO, shutter speed, and ambient light. Photographers can input known ISO and aperture values when using the “T” mode, and the AH-M1 will automatically calculate the appropriate shutter speed for the available light.

A detachable cold shoe attachment allows the AH-M1 to be fastened to cameras. Photographers may adjust the AH-M1’s cold shoe location to fit a wider variety of vintage cameras using the hex wrench that comes with the camera. To accommodate certain vintage cameras with dials close to the cold shoe, the cold shoe can be shifted to the left or right or even turned around.