1) What do DSLR cameras consist of ?
The photographer can see the subject before taking an image by the
mirror. When taking an image the mirror will swing up and light will go
to the sensor instead.
- Camera lens
- Reflex mirror
- Focal-plane shutter
- Image sensor
- Matte focusing screen
- Condenser lens
- Pentaprism / pentamirror
- Viewfinder eyepiece
A digital single-lens reflex camera (also called a digital SLR or DSLR) is a digital camera combining the optics and the mechanisms of a single-lens reflex camera with a digital imaging sensor, as opposed to photographic film.
The reflex design scheme is the primary difference between a DSLR and
other digital cameras. In the reflex design, light travels through the
lens, then to a mirror that alternates to send the image to either the viewfinder
or the image sensor. The alternative would be to have a viewfinder with
its own lens, hence the term "single lens" for this design. By using
only one lens, the viewfinder presents an image that will not perceptibly differ from what is captured by the camera's sensor.
DSLRs largely replaced film-based SLRs during the 2000s, and despite the rising popularity of mirrorless system cameras in the early 2010s, DSLRs remained the most common type of interchangeable lens camera in use as of 2014.
DSLRs largely replaced film-based SLRs during the 2000s, and despite the rising popularity of mirrorless system cameras in the early 2010s, DSLRs remained the most common type of interchangeable lens camera in use as of 2014.
2) Design & Working Of DSLR cameras
Like SLRs DSLRs typically use interchangeable lenses with a proprietary lens mount. A movable mechanical mirror system is switched down (exact 45-degree angle) to direct light from the lens over a matte focusing screen via a condenser lens and a pentaprism/pentamirror to an optical viewfinder eyepiece. Most of the entry level DSLRs use a pentamirror instead of the traditional pentaprism.
Focusing can be manual or automatic,
activated by pressing half-way on the shutter release or a dedicated AF
button. To take an image, the mirror swings upwards in the direction of
the arrow, the focal-plane shutter opens, and the image is projected and captured on the image sensor,
after which actions, the shutter closes, the mirror returns to the
45-degree angle, and the built in drive mechanism re-tensions the
shutter for the next exposure.
Compared to the newer concept of mirrorless interchangeable-lens cameras this mirror/prism system is the characteristic difference providing direct, accurate optical preview with separate autofocus and exposure metering sensors. Essential parts of all digital cameras are some electronics like amplifier, analog to digital converter, image processor and other (micro-)processors for processing the digital image, performing data storage and/or driving an electronic display.
Phase-detection autofocus
Main article: Phase detection autofocus DSLRs typically use autofocus based on phase detection. This method
allows the optimal lens position to be calculated, rather than "found",
as would be the case with autofocus based on contrast maximisation.
Phase-detection autofocus is typically faster than other passive
techniques. As the phase sensor requires the same light going to the
image sensor, it is only possible with an SLR design and not with a
camera having a separate viewfinder.
