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If you have a DSLR or plan on buying one, it’s nice to understand how it works. I mention DSLR but this information pertains to any camera.
As mentioned before, if you don’t have light, you can’t take a picture. Any light at all will work.
Since light is a must, I’ll try to provide a little info on how a camera handles light in order to get proper exposures. Mind you, I am not an expert and will not claim to be one but, when learning photography, I wanted to learn and understand everything about photography so I did extensive reading and research concerning the workings of a camera.
There are two things that control exposure on all cameras: Shutter speed and aperture. On some P&S (Point & Shoot) cameras and cell phones, the apertures and shutter speeds are factory set and can’t be changed. This is where DSLRs come into they’re own. The lenses have the apertures and the camera has the shutter speeds. Hand-in-hand, they control exposure by automatically adjusting each other to each individual lighting situation. The same can be accomplished in “Manual” mode.
I don’t want to get real technical, so I’ll try explaining this info as simple as possible.
A camera’s metering system works on the exposure of “18% gray” and it will adjust settings to accomplish this with every subject.
Aperture is the opening in the lens that is noted in F-stops. Full F-stops are: F-1.4, F-2.8, F-4, F-5.6, F-8, etc. Modern cameras can also set fractional apertures. Each full F-stop will let in twice the light of the next F-stop or, put another way, it will let in half of the light of the previous F-stop. The strange thing is that the lower numbers provide a larger “hole” than the higher numbers. Strange, but true. It all has to do with physics.
Aperture examples (Not to scale):
Shutter speed is the amount of time the shutter stays open to allow light to hit the film/digital sensor. Shutter speed may be from 30 seconds to whatever the manufacturer makes it (1/1000th second, 1/2000th second, etc.). Full shutter speeds are usually noted as; ½ second, ¼ second, 1/8 second, 1/30 second, 1/60 second, 125/second, etc. Note: Each shutter setting is twice as fast as the one before it or, stated another way, it’s half as fast as the next number.
Let’s say your camera sets proper exposure at F-8 and shutter speed at 1/60th second. If you set F-5.6 for the aperture to let in twice the light, your photo will be overexposed without compensating with the shutter to stay open for a shorter time (half the time to be exact…1/125th second). By the same token, if you set the shutter speed to 1/30th second to let in twice the light, the aperture must be set to F-11 to reduce the additional light falling on the film or sensor.
If left in “Program” mode or “Automatic” mode, your camera will compensate for changes in light in the manner of a different aperture or shutter speed that will give the same exposure, depending on how the manufacturer set the camera to compensate.
Setting the camera to “Aperture Priority” you’ll choose the aperture you want to use and the camera will automatically set the proper shutter speed. Setting the camera to “Shutter Priority” you’ll choose the shutter speed and the camera will automatically set the proper aperture.
So, why would you want to shoot at a certain aperture or a certain shutter speed?
Check the next blog entries.
Shoot, shoot, shoot!
