Shooting under

Under what?  Under challenging light conditions, underneath your subject, under-exposed? All of the above?  I learned an important lesson in how to use my equipment that made a big difference in the outcome.  What I discovered about light metering and exposure values might not be news to seasoned photographers, but it might save some frustration for other beginners out there.

Let’s say you want to take a decent photo of a Ruby-throated Hummingbird, sitting up high on a plant in a brightly lit environment.

ruby-throated hummingbird

The bird is very pale, with its white belly and throat and pale green back. In fact, it’s the brightest thing in the well-lit environment. You have four choices on most SLRs for metering the light in this scene. Here’s what happens when you set the light metering mode to evaluative metering (the default mode that measures light across the whole frame).

ruby-throated hummingbird-overexposed; scene exposed with evaluative metering mode

All the details in the bright white subject are lost, and frankly the focus is not as sharp as it should be because the edges are washed out. The background looks nice though.  Evaluative metering would be a better choice for a landscape.

The most appropriate metering mode for this type of shot (small, bright object in the middle of a darker field) is spot metering, which measures the light intensity just in the circular area around the spot on which you focus (i.e., the head or other high contrast area on the bird).  The result looks more like the first photo — better contrast and better detail.

Pushing this focus on the light intensity of just the bird a little further, I decreased the exposure compensation by one stop (i.e., underexposed), and I like the result even better.  The details are much sharper in an underexposed photo, and the black background kind of makes the bird just pop out of the photo.

ruby-throated hummingbird-underexposed-using spot metering

For even more dramatic contrast, even more underexposure produces something like this.

ruby-throated hummingbird-underexposed

I am 20 feet below the bird, so the background is very dark.  Spot metering is necessary, and undexexposure helps highlight the subject.  The bird is sticking its tongue out at me.

The Digital Camera World website has some excellent discussions of subjects like this – here’s a link to one on Metering Modes that explains all four light metering modes very clearly.