What are SLR digital cameras?

Question

What are SLR digital cameras?

Answer 1

OK in the old days there were a few major types of camera, the only ones we will talk about here are rangefinder and Single Lens Reflex Cameras. Rangefinders have a completely separate viewfinder. Little piece of glass on the back looks through a little piece of glass on the front. This viewfinder is technically a lens too. So the lens that takes the shot and the view finder are both lenses making this type of camera a "twin lens" cameras. There were also triple lens cameras as well with one shooting lens one viewfinder for landscape orientation and one for portrait orientation (camera on its side).

The problem with a rangefinder or twin lens camera is that the Lens does not necessarily see what the viewfinder does. For instance in close up you needed to remember that the viewfinder was slightly off to one side of the shooting lens. Also if the shot was out of focus, there was no way to tell.

So along came a type of camera where the light came in the shooting lens but never hit the shutter, because instead it hit a mirror first which reflected light up into the viewfinder of the camera. So for one you get to see what the shooting lens is really seeing and for two this camera now only has a single lens on the front.

Once you had composed and focused your shot, you press the shutter. This flips (or "reflexes") the mirror up out of the way whilst the shot was taken. Light now falls on the shutter and the shutter lets it through to the film.

So the combination means that it is a single lens camera with a mirror that reflexes out of the way, or a single lens reflex camera.

In fact this has nothing to do with being able to remove the shooting lens from the camera.

Modern "point and shoot" cameras are slightly different. Most have a system where light enters the shooting lens and travels to the digital sensor. You then look on your live preview screen at the back to view the image about to be shot. There is often no shutter, instead an electronic circuit simply takes a timed reading of the sensor and processes this into an image.

So this is a great system right? Well not quite. There are two major problems, one with focus and one with low light.

Modern camera sensors have at least 6 million dots (pixels) that make up an image. On the review screen you are typically seeing an representation made up of around 230 000 dots. This means for every dot of review screen there are over 26 dots on the sensor. This means that if the shot is to be blurred by 26 pixels (A big blur) it still looks perfect on the review screen no matter how perfect your eyes are! This makes focusing via a review screen very much a hit and miss idea. It also makes you totally reliant on the camera's auto focus system. This is OK for average users, but not so cool when you want to do really creative things like focus on one point in an image, or focus under really bright light or really dark light.

Speaking of light when you take photos at night, the review screen cannot see dark images as well as your eyes can. This can be frustrating when you are required to manually focus and yet you can't see anything on screen when you can clearly see the scene with your eyes!

For this reason when taking a step forward in photography it is far better to have a real "optical" viewfinder for full creative control, you can sometimes make better decisions than the camera about focus etc, when you can see properly.

SLR cameras are a step forward! Enjoy!

Regards, teef_au

Answer 2

A digital single-lens reflex camera (digital SLR or DSLR) is a digital camera that uses an automatic mirror system and pentaprism or pentamirror to direct light from the lens through the viewfinder eyepiece.

The basic operation of a DSLR is as follows: for viewing purposes, the mirror reflects the light coming through the attached lens upwards at an approximately 90 degree angle. It is then reflected by the pentaprism to the photographer's eye. During exposure (when the photograph is taken), the mirror swings upward, and a shutter opens, allowing the lens to project light onto the image sensor.

Answer 3

These top-of-the-line cameras deliver high resolution, best-of-class optics, and extensive manual controls. Like less-sophisticated cameras, they are capable of functioning fully automatically, but also offer an extensive range of manual controls. Like traditional film cameras, digital SLRs offer the added advantage of using detachable lenses. Though certainly not cheap, these cameras deliver professional-quality performance and the ultimate in creative control.