a system used in some automatic cameras in which the shutter speed is selected by the user and the appropriate aperture is then set by the camera.
In a nut shell!
But what does it mean?
Essentially a camera is a light sealed box, even in the world of digital photography. Before digital, it was imperative that the film in the back off the camera was not exposed to any light, unless you were taking a picture. By simply exposing the film to the light, you’re essentially burning that image into the film. But you need the right amount of light.
The problem of allowing the right amount of light is solved by introducing a ‘shutter’ in between the lens and the film. Essentially it’s a set of mechanical curtains, the shutter - curtains will open at a predetermined speed (more about that later) and let a specified amount of light hit the film.
It’s exactly the same with digital photography. The shutter will open in exactly the same way, however, it will expose the cameras digital sensor to the light source.
So how long is the film or sensor exposed to the light for?
That depends. Each camera is different, but some are totally the same. I’m using a Canon DSLR, but this applies to all the other brands - You can choose the speed at which the shutter is open for.
My camera can open and close the shutter in 1/8000th of second. That’s fast. Considering a human blink is approx. half second! This is perfect for when you’re trying to capture fast moving objects and you want to freeze the action, like spots or wildlife photography. On the flip side, this camera of mine can open the shutter for as long as the battery will last if use the bulb mode. This is great for those night time exposures when taking pictures of the stars.
The ‘priority’ bit is describing the relationship with the other settings in the camera. In TV mode, you have full control of the shutter, but you you leave the camera to decide what the aperture setting should be. This is useful when you know you need a fast shutter speed for those fast moving shots. It also allows you to take the creative seat as this setting will give you the right exposure without having to worry too much about the other settings.
A photographer once said to me that they shoot only in manual mode and it’s an amateur who uses any other mode. I disagree. Whilst I can take pictures in full manual without thinking, it can sometimes be easier to let the camera decide. Every photograph is about the story in the frame, not the method that got you there.
Learning how to use the shutter to your advantage can really improve your creative edge.