subject: Basic Photography - Exposure - Aperture, Shutter and ISO [print this page] Basic Photography - Exposure - Aperture, Shutter and ISO
In most cases, we never give much thought to what's happening inside the camera to produce the actual image. In reality, most people probably don't care. But just in case you are curious or would like to use your camera in the manual mode rather automatic, read on.
The way an image comes out is determined by the exposure. Exposure determines if the image is just right, too dark, or too light. (depending on the viewer)
Three factors determine the exposure. They are shutter speed, aperture setting, and ISO setting. These are pretty technical things, but I will explain it in the simplest terms that I can.
Shutter Speed: This determines how long the camera sensor is exposed to light. That is determined by the length of time the shutter stays open. The time the shutter stays open is expressed in fractions of a second. For instance, a shutter speed of 1/125 means the shutter will stay open for 125th of a second and then close. A speed of 1/30 means the shutter will open for 1 30th of a second.
The Aperture: This is an opening which decides the quantity of light reaching the sensor. The size of the aperture opening will vary depending on the setting. Aperture settings are expressed as f stops. A very small aperture opening would be set maybe for f16 or f11. A large opening which would allow a lot more light to reach the sensor would be set at perhaps f2.8 or f4. (there are other settings in between)
ISO setting: Again, this is how sensitive the sensor will be to the light. For instance, on a sunny day, the camera can be set to a low ISO to get good exposures. ISO 100 is pretty normal for that situation. However, an hour before dusk, the strength of the light has weakened and the sensor setting will have to be changed to may ISO 400 to get a good exposure. Remember the sensor can pick up more light at higher ISO settings like ISO 400 or ISO 800.
Ok, let's wrap it up. These three thing work together to make an exposure. You can change any one of them to alter the image. If you have all three set to give you a great exposure, changing any one will require changing another to get the same exposure. For instance if you make the aperture opening smaller, you will need to keep the shutter open for a longer amount of time to adjust. (that is to get the same exposure). Luckily, most cameras will make these adjustments automatically. But many cameras will give you the option to juggle with the settings as you please.
I don't want to get too technical. At least now you know a little about whats happening before you press the shutter.
This was just a brief overview. A lot more technical stuff could be involved but I hope this helped.
