Digital cameras take photographs using an image sensor that
converts light to electronic signals. The distinguishing feature of single-lens
reflex (SLR) cameras is that the optical viewfinder displays the view through
the camera lens. The “single lens” in the name “single-lens reflex” is a
reference to this feature: a single lens serves both for taking photographs and
for the viewfinder. The “reflex” portion refers to the reflection of light.
Some newer digital SLR cameras can display the view through the
lens in the monitor: this is known as “live view.” The mirror is raised during
live view; blocking the light that would otherwise reach the focusing screen
and preventing photographs from being framed in the viewfinder.
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Before the shutter-release button is pressed all
the way down, the mirror inside the camera is positioned between the lens and
the shutter curtain, reflecting the light from the lens upwards. A pentaprism
or pentamirror guides the light into the optical viewfinder.
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When the
shutter-release button is pressed all the way down, the mirror is raised and
the shutter curtain opens, allowing the light passing through the lens to
proceed directly to the image sensor and a photograph is taken. The
shutter then closes and the mirror drops back into its original position.
Source: Nikon Website
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Source: Nikon Website
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