Loren Pechtel

I was interested in whether a location has enough light to grow a plant. Lacking the right tool for the job I grabbed my camera and snapped a shot.

ISO 100, the camera did f/3.5, half a second. Unless I'm messing up that translates to a light value of 4.5.

According to this page typical indoor light is LV 7 and this is a location near a window. I was expecting maybe an 8 or 9.

CPRich

Unless you were using a calibrated 18% gray card, filling the frame, the target will greatly change your readings. I just pulled my 7D out and pointed at my black camera bag, a white sheet of paper, the darkish green carpet and my WhiBal gray card, lined up together under the same light. I got EV readings of -4.3, 6.4, 3 and 5.2 respectively.

If you were pointing at your plant, and if it is close to the green of my carpet, I'd guess you were 2-3 values low.

nar0

If you have something light gray then set your light metering mode to spot metering and place the gray thing with the outdoor light shining directly on it and point the center of your camera on it (or the center of your focus point, depends on the camera. Best to just put focus in center to be safe) you can get a decent approximation.

That's why the actual light meters have the spherical bulbs on them. So they don't need to rely on the reflectance of the objects in the scene to try and get a light reading.

Loren Pechtel

Of course a black target would have messed it up--I grew up with a black cat and had quite a time photographing her (especially after the day she got too inquisitive about the camera--and sniffed the button on the strobe that would fire it. It was set on manual, full power flash and it was a pretty powerful strobe. It was sitting in a chair pointed at the back of the chair maybe a foot away. From that day forward she would not be in the same room with the charging strobe (it emitted a faint whine, she could hear it) and I was forced to use an el-cheapo camera with flash cubes.) While the plant is green there was a bunch of white paper behind it and most other things in the shot were reasonably neutral, I wouldn't have expected to be off by more than 1 EV.

I guess I need to put some big gray target there.