Most cameras - both DSLRs and compacts - offer different metering modes. Simply said, your camera reads the light that is reflected from your subject onto its sensor. The metered data is used to calculate how long the shutter remains open and how large the lens opening (aperture) must be. The different metering modes allow you to help your camera, by telling it what's important in your scene. The three most common modes are Matrix metering, Center-weighted metering and Spot metering. Matrix metering is sometimes called multi-segment metering.
The factory default is most likely to be Matrix metering on any camera. This means that the software that's built into your camera calculates the required settings to ensure a properly exposed scene, taking everything in the scene into account. Both the foreground and the background. While this is what you'll want for most types of photography, trying other metering modes can really improve your wristwatch photos.
Center-weighted metering - as its name implies - will give you a calculated exposure based on what is in the center of the frame, taking some of the background into account, but with less importance. Typically the meter will give 75 percent emphasis to what's at the center of the frame and 25 percent to the remaining area. Spot metering more or less ignores everything that's not in the center of the frame.
Considering that the watch is the most important thing in a watch photo, it doesn't really make sense to make your camera try to properly expose both the background and the watch. The calculated exposure will always be a compromise between what would be correct for the background and what would be the best exposure for the watch. Especially with a high contrast scene, e.g. a shiny polished steel watch on a dark background.
Metering mode selector button on a D700
Most cameras have a selector button on the back of the camera that allows you to change the default metering mode. On other cameras you may have to dig into the menus to change this setting. I have found that I got best results with Center-weighted metering with both a D300 and with my D700.
Just selecting Center-weighted metering will probably improve your results already. But there's one problem with using any metering mode other than Matrix metering... Your subject is most likely not exactly in the center of the frame. And although digital cameras are pretty smart, mine doesn't figure that out on its own...
Shutter speed and aperture shown on the camera display
You can however let the camera help you to figure out a good exposure starting point and then you can take things into your own hands from there. Put the camera in Program (P) mode, focus on the watch, press the shutter button half way down and read the exposure settings on the display (see picture above). The F-number shows the calculated aperture and the S-number is the shutter speed. Put your camera in Manual mode (M) and then select the Aperture and Shutter speed that your camera calculated for you. You can now change the composition (e.g. the wristwatch not exactly in the center of the frame) and your camera will not recalculate the exposure based on what's in the center. Take a few test shots and adjust the settings as required. You may for instance need to select a longer shutter speed if the result is a bit too dark.
If you already know what aperture you want to work with, you can of course put the camera in Aperture priority mode (A) instead, to let the camera just calculate the required shutter speed for you.
If you want to read more about aperture settings and depth-of-field: follow this link.
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