Creating a photo with a correct exposure is accomplished through the use of metering modes featured within most of today's digital cameras. Metering programs select the correct exposure based on the information coming into the camera through the lens. Based on this information, the camera selects the ISO, shutter speed and aperture and white balance. These settings may or may not be correct for what you the photographer are trying capture through your photo.The steps below will help you to learn measure photography exposure and metering.
Instructions
1. Understand that most of today's digital SLR cameras have multiple metering modes. Three of the common ones are spot, center-weighted and evaluative. Spot metering, as the name implies, reads the light from what is inside the small circle in the middle of your viewfinder and will be no more than 9.5 percent of the overall scene. The advantage of spot metering is you can pinpoint the area you want metered for reflectance light. Center-weighted metering is the most common metering system and one used in all SLR and point-and-shoot cameras. This mode reads light from a large section in the center of the scene, weights it heavily and then reads the light from the remainder of the scene.The light read from the center of the scene accounts for about 75 percent of the total exposure with the light from the remainder of the scene making up the other 25 percent. Multi-pattern Metering is also known as evaluative metering. With this mode, the viewfinder is broken down into several metering segments built around the auto-focus sensors. Once you choose the auto-focus sensor that will be used for the focusing, a center-weighted metering pattern is built around that selected auto-focus sensor. So, this system is basically the same as the center-weighted metering system except the center-weighted reading is taken from the selected auto-focus sensor instead of from the center of the viewfinder.
2. After selecting which metering mode to use and having your camera set on an automatic program selection, meter a scene by pressing the shutter button halfway down. Note the shutter speed, aperture and ISO the camera selected.
3. Depending on what you are trying to convey to the viewers of your photographs, the camera-selected setting may not be correct. For example if you are shooting a landscape scene, you want as much depth-of-field as you can get. If the camera selected f8, that is not the correct setting for landscapes. You will want to change that to a higher number such as f16. If you are going to shoot just one photo, you can change the aperture by rotating the wheel controlling the aperture. If you are taking multiple shots in that same light, turn your program dial to AV, and set it to f16.
4. The same line of thought applies to shutter speed. Shutter speed controls how motion is shown in your photos. Let's say the scene is flowing water. To show this as that soft, cottony effect, we need a slow shutter speed--somewhere around 1/8th second or slower. Either rotate the dial controlling the shutter speed to the slower speed if you are shooting just one photo, or turn the program dial to TV and set the shutter speed.
5. Know that the last part of exposure and metering is the ISO. ISO is a term brought over from the film days and referred to the speed of the film. The higher the number, the less light was needed to make an acceptable photo. The same logic applies to digital cameras. The higher the number, the less light needed at the sensor for a good shot. The difference with digital is you can change the ISO at will, and you are not locked into a specific ISO as you were in the film days. If you are shooting in low light and not able to use your flash or tripod, changing the ISO to a higher number will often give you the extra shutter speed needed to take a blurry-free photos.
Tags: shutter speed, higher number, light from, auto-focus sensor, digital cameras