Metering Off Colors
We've talked about metering off of a blue sky and a cloudy sky. But we can meter off of nearly everything. You just have to be aware of how your camera sees color. Cameras can record color, but when it comes to its in-camera meter, it only sees in shades of gray. Ideally, your camera wants to meter off of a middle-ground element. The ideal shade to meter off of would be 18% gray. If you have a gray card or something gray, you can of course meter off of that. But you may not have such tools handy. In that case, you can meter off of dependable colors. Here's some rough rules of thumb for you based on my own experiences):
- Blue – look for shades that would match a blue sky. You can meter off of a sky blue shade of blue without making much adjustment. If you're metering off of something darker like royal blue, meter as if you were under-exposing by about a full stop.
- Green – green is a great resource for metering. If you meter off of green grass or the leaves of a tree (usually darker than an 18% value), you'll want to meter as if you were under-exposing by 2/3rds of a stop.
- Red – fire engine red is a tiny bit darker than 18% gray to your camera. If you can meter off of such a shade, you'll want to meter as if you were under-exposing by 1/3rd of a stop. A bright red will expose well without adjustment.
Lucky Yellow #8 Filter – in my kit, I always carry a Yellow #8 filter. I have an old one that only fits my 50mm prime lens. Truth is, I rarely use it on that lens, but I still carry it. The colors above are great guidelines, but they aren't always available. There are at least a dozen colors in any setting that will act like 18% gray for metering. Rather than remember them all, I carry my yellow filter. Looking through the yellow #8 filter with the bare eye, the scene before me will render as a tinted monochrome scene. The colors that I can meter off of will not appear to change in value (value, not color) with or without the filter.