The term digital SLR stands for single lens reflex. It is so called because the SLR cameras use a mirror that is placed behind the lens.
Although SLR cameras for capturing still images have been in use for quite some time, those that could capture both the stills and the videos were introduced in 2008.
Earlier the SLRs were used only by the professionals. They were not very common and were costly as well. The good news is that the digital SLRs are becoming cheaper as the time passes and coming within the easy reach of even the amateur photographers. You can buy an SLR at the price of a high end digital compact camera.
How does the digital SLR work?
When the light enters through the lens, it falls upon the mirror. The mirror, in turn, reflects (throws) the light upon the focusing screen. The light passing through the focusing screen falls upon a block of glass called pentaprism, which reflects the image that can be seen on the viewfinder. When you take a photo, the mirror flips up opening the shutter which exposes the digital sensor to light.
What- you- see- is- what- you- get photos
The SLR uses the viewfinder to compose the photo and adjust the focus. You can, thus, get the photo of the original as you see it on the lens.
SLR camera allows for a wide range of lenses with different focal lengths. You can change the lens whenever you like. This is what makes the SLR ideal for serious photography. Moreover, the image sensors of the digital SLRs are large and produce high quality photos.
Lightness and compactness vs. versatility and image quality
An attractive feature of the digital compact cameras is that they are cheap, light, compact and easily portable. You can just pop in the compact camera in your purse or pocket.
The SLRs are weighty and voluminous. Some of them are tank-sized for professionals. But they provide the invaluable advantage of accommodating a large range of lenses and accessories that were originally designed for film SLR cameras.
Of late, new generation light weight ultra compact DSLRs have also been introduced in the market. They have small lens and weigh around 20 oz / 0.5 Kg.
While the crispness and sharpness of the photos taken with the digital compact camera and SLR camera in broad day is by and large same, the SLR scores over the compact camera when you have to shoot in dim light or capture the fast running scenes of actions. This is because the SLRs have high sensitivity larger sensors.
Anti shake/vibration designs
The photos shot with non-SLR cameras in dim light or with long telephoto lenses may be blurred. The reason is that the camera gets shaken during the exposure. The SLRs are equipped with Image Stabilization (IS) systems that protect them from the impact of motion during exposure. Therefore, the photos shot with SLRs even in dim light or at long focal lengths are sharp and excellent.
What makes the SLR much superior to the compact camera is its speed in taking pictures, which makes it ideal for action photography as there is a zero lag time. Even the entry level SLRs shoot faster than the best compact cameras. So you can easily shoot both a sleeping and a running tiger with this camera.
Dust Removal mechanism
If you have to shoot in arid, dusty or even in humid and damp conditions, no camera can beat an SLR. They have inbuilt dust removal systems that keep the sensor clean. They have weatherproof seals and solid magnesium alloy cases.
High Definition (HD) videos for HDTVs
This is another advantage of SLRs over the compact cameras. They can shoot High Definition videos. They come equipped with HDMI ports which allow the camera to be directly connected to the TVs. You can view your videos on the TV.
So which camera should you buy?
It all depends upon your needs. If you want speed, exquisite professional looking photos even in dim light and more control over the photos and are not bothered about weight and volume, go for an SLR. If you are just an occasional photographer wishing to carry the camera in your pant pocket, you can buy a compact camera.