| In the old days, if your camera (35mm of course) had | | | | Spot metering as the name indicates only reads a |
| a battery die on you in the middle of an important | | | | small spot or portion of the overall image (usually 1% to |
| shoot, you still had options. I mean after all; the only | | | | 3%). This type of metering is useful in any situation |
| thing you needed the battery for was the light meter, | | | | where the lighting is extreme. Backlit subjects, macro |
| it's not like your whole camera will shut down if you | | | | shots, or even pictures of the moon can benefit from |
| have no battery. Oh, I'm sorry . . . if you are using all | | | | this type of metering. This type of metering is usually |
| digital that might have stung just a little bit. | | | | found on the more costly upper end cameras. |
| The point was if your battery died, you still had a way | | | | Center-Weighted metering averages the overall scene |
| to get a good picture. If you were using 100 speed film | | | | with an emphasis on the center area of the frame. |
| you could set your shutter speed to whatever the | | | | Usually this type of meter bases its reading with 75% |
| flash sync speed was (usually 1/60th or 1/125th of a | | | | of the light hitting center frame and 25% for everything |
| second), set your f-stop to f-16, and bracket every | | | | else. It assumes that the subject is dead center, most |
| shot. Besides the obvious dependency on batteries, | | | | of the time. It is worth noting that most center |
| there are other differences between film and digital | | | | weighted systems have a greater sensitivity in the |
| cameras. | | | | bottom half of the frame; to avoid an overly |
| If you have ever shopped for a digital camera you | | | | contrasting sky from throwing off the readings. This |
| have no doubt heard the phrase: "35mm equivalent". | | | | type of systemis the most common used in both digital |
| This means that the optics are not exactly the same in | | | | and traditional cameras today. |
| a digital camera. Since the 35mm SLR camera has | | | | Matrix Metering splits your image up into anywhere |
| been the standard for so long, that's what newer | | | | from 3 to 16 metering zones and evaluates the |
| cameras are compared to. The difference between | | | | different zones to come up with one over all reading. In |
| the two is a ratio of 1:1.4. Simply put, a 35-200 zoom on | | | | this process of evaluation it takes into account factors |
| a digital camera would be like having a 49-280 zoom | | | | like: subject size, position, distance, point of focus, over |
| lens on a traditional 35mm camera. | | | | all lighting, color and more. This system uses a |
| The main reason the optics are different is because | | | | microchip which has been exposed to thousands of |
| the sensor (the device that actually reads the light) is | | | | different picture-taking situations. Currently this is the |
| also a different size. Film cameras use film (sensitive to | | | | most complex and the most accurate metering |
| light) that is placed directly behind the lens. When the | | | | system to date. This system is usually found on the |
| correct exposure is calculated, that image is literately | | | | higher end Digital SLR's. |
| burned into the film. Digital cameras use a sensor; that | | | | I used the word "digital" several times, but these are |
| also sits behind the lens. This sensor is made up of | | | | the same types of metering systems used in traditional |
| millions of individual points that each represents 1 pixel. | | | | film cameras as well. The only other way of reading |
| Once the sensor has gathered the information for | | | | light has to do with "reflected light" verses "surface |
| each pixel it transfers that data to a digital media card | | | | light". Most meters in the camera are reading reflected |
| (which can be used repeatedly.) | | | | light (light reflected off the main subject that goes back |
| The sensor is the physical device that gathers | | | | toward the camera.) Every so often you might see |
| information about the quality of light coming into the | | | | someone with a hand held light meter that will go right |
| camera. The process of "how" the sensor goes about | | | | up to the subject and read the light that falls on the |
| gathering information is referred to as "metering". The | | | | surface of that subject. Some photographers still |
| human eye can distinguish a range of about 16 | | | | debate which way is more accurate. In my opinion; |
| different f-stops; camera meters only have a range of | | | | "Spot Metering" does basically the same thing. |
| about 5 f-stops. This is why camera meters are | | | | All photographers have their favorites; Canon, Nikon, |
| calibrated for a "mid range" exposure of 18% gray, | | | | Kodak. Some choose digital, some choose film. The |
| because 90% of the time that is as close as they can | | | | thing to remember is what we actually need to get a |
| get to the human eye. It's not the camera's fault that it | | | | great photo. Things like composition, leading lines, |
| can not see as well as you do, it's simply a fact of life. | | | | framing, and the rule of thirds are much more |
| There are basically only three types of metering | | | | important to our success as great photographers than |
| systems. | | | | the physical tools we use. On the other hand, knowing |
| A) Spot Metering | | | | what your camera can or can not do, let's you know if |
| B) Center-Weighted Metering | | | | you have the right tool for the job. |
| C) Matrix Metering | | | | |