There are two main ways to control amount of light entering camera
1) Aperture; 2) Shutter
In this episode of HSW.tv, we are going to talk about the camera’s shutter. The shutter is mechanism that determines how long light is let into camera. It is a physical curtain that is made of delicate lightproof fabric or metal blades that open or close to let light hit the sensor or film.
On DSLR cameras, this physical shutter can be found directly behind the mirror in the camera. This shutter is precisely regulated and standardized in its timing, which is called the shutter speed.
The shutter speed is expressed as fraction of a second (in most cases) or full secs for longer exposures. It’s shown on the camera’s LCD display as a whole number, such at 125, which is really 1/125th of a second.
Now, when you are looking at your shutter speeds, the larger numbers are actually shorter durations (faster shutter speeds) letting in less light.
Some modern cameras depict exposures longer than 1 second in a different color (often red) or followed by an “s” for sec.
Let’s take a quick look at the shutter speed numbers and what they mean. The traditional full shutter speeds usually starting at 1 sec and each increment in the shutter speed scale of one full stop cuts the amount of light in half
1 second, ½, ¼, 1/8th, 1/15th, 1/30th, 1/60th, 1/125th, 1/250th, 1/500th, 1/1000th
Do you notice the pattern? Each step of the shutter in a full stop is a doubling of the number, which cuts the amount of light in half.
Most modern DSLR default at 1/3 shutter speed per click on control wheel or dial, therefore 3 clicks are one full shutter speed. And most cameras can range from exposures of 30 secs to 1/4,000 sec
Also, most cameras have capability of allowing you to keep the shutter open until you manually close it. A ‘T’ designation for “time” (not too common) allows you to open the shutter with one click, then close the shutter with another click. The ‘B’ designation for “bulb”, seen on all cameras, will keep the shutter open as long as the shutter button is depressed.
In upcoming episodes, we’ll see a surprising correlation between ISO, f/stops and shutter speeds numbers.