This weekend was my first experiment with using an incident meter, and I’m really happy with the results. These photos were all taken at various Portland coffee shops, and would have been challenging had I relied on something like my KEKs shoe mount meter.

Here’s why. The two kinds of metering used in photography are reflective and incident.

Reflective metering is the kind you’ll find in shoe mount meters, the kind built into your camera, or if you’re using a metering app on your phone. Reflective metering is measuring everything in its field of view (often about 30° diagonal), and then averaging the entire scene, or whatever you point it at, to a middle gray value.

One problem with this is that different colors don’t reflect the same. If you point your reflective meter at something white and then something black, even if they are in the exact same lighting, you’ll get different values — maybe as much as two or three stops because of the reflectance difference of the colors. If you’re relying on a meter with a relatively wide view, and there’s any contrast in your scene, like a bright sky, or even just white walls, you can easily end up with photos that are both under and over exposed to various degrees.

There are ways around this, like pointing your meter at shadows and adjusting the exposure based on that. Ultimately, however, reflective metering is always going to be less accurate and struggle in certain situations.

Incident metering is different in that instead of measuring reflected light, you measure the amount of light falling on your subject directly by using a meter with something called a lumisphere and pointing it at the light source. If you can’t get exactly to the thing you’re photographing, you can also estimate if the light you’re measuring from is roughly the same as what you’re photographing. The result is that things tend to come out very close to what you saw when you took the photo. Because you’re measuring the actual light instead of reflectance, white things are white, black is black, and detail tends to get maintained where you wanted it to be.

In these two photos, you can see the light coming from through the window. If I’d simply pointed my reflective meter at these and taken a photo, it would have averaged the scene, and because the light coming through the window is so much brighter than my subjects, it would have underexposed and put them into silhouette.

Here, reflective metering might have worked okay, but there’s also a good chance that because the cabinets and ceiling are so much darker than everything else, it would have overexposed a bit.

In these last couple, I would have had the opposite problem. Because all of the walls were completely white, had I just averaged the scene with a reflective meter, it would have underexposed. I had to guess a bit from where I was sitting, but they still came out alright.

My instinct going forward is that I’m not going to use the shoe meter I have anymore. Because of its wide field of view, I’m never quite sure what it’s seeing, and I don’t trust it. The meter I got has a reflective mode, so I can always go to that if needed. If I’m using a camera with a built-in meter, like my Nikon FM2, I will probably use it when I can’t use incident metering, but even then, it’s going to be a backup.