Digital Cameras

How digital cameras work

I assume that you know how cameras work, they takes still photographs or video , or both, by recording images on a light-sensitive sensor or on film.

I use almost only digital slr cameras so I will be covering those and especially Canon Cameras and Nikon Cameras because that is what I am most familiar with.

Click here for Point and Shoot Digital Cameras

DSLR:s Optical Viewfinder...

... vs. compact cameras LCD:s.

Depending on if the mirror is up or down, the light can only reach either the viewfinder or the sensor. On most digital SLR cameras you can therefore not view the picture you are about to take on the LCD display. You can always do that on a compact camera.

The advantage of an optical viewfinder is that it constantly shows the exact image that you are getting, you see the image throw the lens (WYSIWYG). There is no time lag as it is on compact cameras LCD:s or/and Electronic Viewfinders. This is important when the subject or camera is moving.

A disadvantage of the optical viewfinder system is that you can't view the picture on the LCD monitor before you take it. Electronic viewfinders may be better in low light situations because the display can be brightened.

Live Preview

Some of the latest digital SLR cameras have something called live preview or "Live View" which makes it possible to use the LCD monitor when you compose the picture.

When I write this in September 2008 some digital cameras from Canon, Nikon, Olympus, Sony, Pentax, Samsung and Leica have an option for live preview.

DSLR:s with Video Recording

As of 2008 both Nikon and Canon announced DSLRs that support recording of full motion video. The Nikon D90 is capable of 720p high-definition video while the Canon EOS 5D Mark II can record 1080p video.

Different Sensors

Most cameras use either a charge-coupled device or complementary metal oxide semiconductor, or CMOS chip, as an image sensor. The chips works the same way. It seems that the best cameras are using a CMOS sensor, at least when it comes to DSLRs.

With the exception of medium format DSLRs, the largest sensors are referred to as "full-frame", and are the same size as 35 mm film.
These sensors are used in quite expensive DSLRs such as the Canon EOS-1Ds Mark III, the Canon EOS 5D, the Canon 5D Mark II, the Nikon D700, the Nikon D3, Nikon D3x and the Sony Alpha 900.

Most modern DSLRs use a smaller sensor commonly referred to as APS-C sized, that is, approximately 22 mm x 15 mm, a little smaller than the size of an APS-C film frame, or about 40% of the area of a full-frame sensor.

Other sensor sizes found in DSLRs include the Four Thirds System sensor at 26% of full frame, APS-H sensors (used, for example, in the Canon EOS-1D Mark III) at around 61% of full frame, and the Foveon X3 sensor at 33% of full frame.

The sensors used in current DSLRs are much larger than the sensors found in compact style cameras, most of which use sensors known as 1/2.5", whose area is only 3% of a full frame sensor.

Even high-end compact cameras such as the Canon PowerShot G9 or the Nikon CoolPix P5000 use sensors that are approximately 5% and 4% of the area of a full frame sensor, respectively.

Sensor Sizes Compared

In general, a larger sensor in digital cameras provides lower noise, higher sensitivity, and increased dynamic range. There is also a connection between the digital cameras sensor size and depth of field, with the larger sensor resulting in shallower depth of field.