The main principle for all cameras is always to collect light of the surrounding scene and have either a photographic film (for older cameras) react to this light or an electronic sensor (for all digital cameras) convert light into an electronic signal. No matter how many variations camera manufacturers have ever brought up, they all rely on this basic composition. If you compare this main principle to the human eye, unsurprisingly you will find similarities. Nonetheless, digital cameras have adapted to their fields of application and this is the reason for the huge variety of camera models. Here is an overview of the four categories of digital cameras:
Compact Digital Cameras
Compact Digital Cameras are also known as Point and Shoot cameras. These digital cameras are characterized by their smaller size and ease of use. Today’s compact cameras come with a fully automatic mode which is great for beginners or those who just want to “point and shoot” when taking pictures. In return, manual camera controls like the shutter speed or lens aperture setting can not be done on a basic digital compact camera. All of the current compact cameras have a minimum three time zoom lens and an image resolution of at least 10 megapixels.
Bridge Compact Digital Cameras
Bridge cameras are also known as advanced compact cameras. These feature some more functions than basic compact cameras. They are called Bridge cameras because their available settings fill the gap between basic digital compact cameras and digital single lens reflex cameras.
The main difference between Bridge cameras and basic compact cameras is that they allow the photographer to have more control over the cameras settings. Bridge cameras will have semi automatic aperture priority (AV), shutter priority (TV), and program modes. Most Bridge cameras will also have a manual mode that will allow the photographer to have full control over the camera exposure settings. The lens on a Bridge camera is fixed and cannot be replaced with a different one. However, many Bridge cameras provide lenses with a much longer zoom range than many other cameras and these are also called Super Zoom cameras. The image sensors used for Bridge cameras are still smaller than those used in digital single lens reflex cameras. Also their lenses are much smaller which makes these cameras quite compact but still clearly larger than compact cameras.
System Cameras / Mirrorless Interchangeable Lens Cameras
These types of digital cameras are very similar to digital single lens reflex cameras. System cameras allow the photographer to use the camera in full manual or automatic modes the same way digital single lens reflex cameras can be operated. System cameras are also commonly referred to as mirrorless cameras or compact system cameras. A great benefit of system cameras is that the lens can be changed just like on a DSLR camera. The most significant difference between the two types of cameras is that mirrorless cameras are much smaller than DSLR cameras, because they do not have optical viewfinders like the DSLR type. Optical viewfinders that are found on DSLR cameras use a system of mirrors and a pentaprism to show the scene that will be photographed. Mirrorless interchangeable lens cameras do not have a mirror system as their name already implies. They are equipped with an LCD screen and in some cases also an electronic viewfinder for previewing the scene that is about to be photographed.
Digital Single Lens Reflex (DSLR) Cameras
Digital single lens reflex (DSLR) cameras are the most advanced type of cameras available on the consumer market. DSLR cameras allow to change their lens in the same way as system cameras allow to use different lenses. This is a major advantage over Compact or Bridge cameras. The ability to choose a lens allows the photographer to adapt to different scenes. For example, landscape photography requires a lens that provides a wide angle while animal photography usually requires a telephoto lens with a small opening angle. Also, some lenses may be excellent for shooting at bright daylight but render a poor performance in dark situations. The exchangeablility of lenses is great way to always use appropriate lenses required for individual situations. In general, the lenses for DSLR cameras are typically of a better quality than those found on compact cameras which will result in better image quality. Furthermore, one of the most unique features of DSLR cameras is that they take advantage from a system of mirrors and a pentaprisma to deflect incoming light onto a variety of different sensors and detectors that can assist the photographer in getting a better result. Another big difference between DSLR cameras and compact cameras is the image sensor size which is normally larger in DSLR cameras due to their increased body size. Larger image sensors typically result in a better image quality and better low-light performance. In terms of build quality, some DSLR cameras feature bodies made of aluminum or magnesium alloy what makes them both lightweight but also extremely durable.
The functional range of DSLR cameras normally leaves nothing to be desired. These cameras allow to take full control over the parameters such as aperture values or exposure values. Therefore, DSLR cameras allow to use a full manual mode, semi-automatic modes or program modes. Some DSLR cameras include functions such as a repeat timer for time-lapse photography, high dynamic range settings or even an electronic level for accurate alignments.
If you are interested in some details of the technology used, check out the DSLR Principles article.