As the term suggests, the meter pattern is a multi segment meter. This is the main metering pattern that can be used quite successfully on maybe 90% of typical photos. This pattern will work best where there is a fairly balanced lighting for the foreground and background. Most modern cameras will have anywhere from a minimum of 16 to over 77 segments across the frame. This type of metering takes all the separate readings and calculates the best exposure settings to record the whole scene without blown highlights or shadows. But, if the lighting is too extreme, (especially strong back-lit subjects), than maybe one of the other two patterns will be a better choice.
How to use the built in Center-Weighted Meter
This type of pattern used to be the modern approach to metering. Back in the mid 60’s, Nikon introduced it with the Nikon F FTn metering prism. How it worked was simple enough. The center 20mm of the frame was where the light is metered at 100% of its intensity, then in small 2-4 mm rings extending out to the edges, The meter would read lower percentages of the light, to the edges of the frame where very little influence was added to the final reading. This was an important improvement over an “overall reading of the whole scene”, where the whole frame was “ONE” metered area. This kind of meter could be fooled by a strong back-lit scene. And the photographer would have to make a final tweak before they tripped the shutter. And, experience would tell them how much “Exposure Compensation” (EC) to employ. This advance allowed more properly exposed images without using “EC“. And allowing the photographer to take more images, thus saving time in the field. The same as using the “EC” +/- function on modern DSLRs.
This is best used where back lighting is a problem (like a portrait on a beach, where the beach/sky is “much brighter” than the subjects face). Get close to the subject, so the central area covers the person and take the exposure reading. Now, lock the reading and move back to recompose the image. Focus and shoot. (You will need to read your camera manual on how to use the exposure lock function.) Also using the built in flash or an external flash in the hot shoe can be used instead to get a proper exposure for your subject. I discuss this in Flash 101 in more detail.
How to use the built in Spot Meter.
Spot metering is for scenes where the back light is so strong and you don’t care if the background is blown out. Birds in Flight would be a photo where you would use “Spot” metering on the bird only. By looking at the above image, the spot meter is the center of the frame. Typically, the area is only 3%-9% of the image. There is no metering outside that circle. Now, spot metering has another hidden advantage. You can take multiple readings of the areas you must have good exposure and average them for your final reading. Olympus had a film camera that had a build-in multi-spot with averaging function in the top end OM-4. you could take up to 9 readings, and the camera would automatically average them for the final exposure setting. For example, take a highlight reading where you want that detail to show, and take a mid-tone reading where you want a nice gradation of colors and tones. And average the two readings. For example: the Highlight reading is f/11, and the mid-tone reading is f/5.6, the average will f/8, the f/stop you will use in manual mode. (halfway between f/5.6 and f/11, because you only have two readings). This will cause the shadows to get fairly dark and might cause loss of some deep shadow detail. But, it is the mid-tones and highlights that usually more important anyway.
Another scene you could use the spot meter is on an outside portrait at the beach. The best way to do this is to set your EC to +1 and take a reading off the brighter part of the face, if there is one. You may need to adjust the EC a little. But remember, the background will be over exposed. So choose it carefully. A darker background works better for this type metering of a person. It will darken even more and help bring out the person, the main subject.
If you want to take a photo of the Moon, (with a long Tele-Photo lens (300mm and above on a crop camera)., Take a reading of the Moon only. This will turn the sky jet black and give plenty of detail of the Moon patterns.