The camera obscura (Latin; "camera"is a "vaulted chamber/room" +"obscura" means "dark"= "darkenedchamber/room") is an optical device thatprojects an image of its surroundings ona screen.
The first mention of the principles behind thepinhole camera, a precursor to the cameraobscura, belongs to Mo-Ti (470 BCE to 390 BCE),a Chinese philosopher and the founder of Mohism. Mo-Ti referred to this camera as a "collectingplate" or "locked treasure room". The Mohisttradition is unusual in Chinese thought because itis concerned with developing principles of logic.
A digital camera (or digicam) is a camera that takes video or stillphotographs, or both, digitally by recording images via an electronicimage sensor. Most 21st century cameras are digitalDigital camerascan do things film cameras cannot: displaying images on a screenimmediately after they are recorded, storing thousands of images on asingle small memory device, and deleting images to free storage space.The majority, including most compact cameras, can record movingvideo with sound as well as still photographs. Some can crop and stitchpictures and perform other elementary image editing. Some have aGPS receiver built in, and can produce Geotagged photographs
Point and shoot cameras mean just that, point the camera atsomething and trip the shutter. The camera does all the work for you.Unfortunately, the camera is rarely as smart as the photographer sothe results can be iffy. Point and shoot cameras are often abbreviatedas P&S. These cameras started out as a fixed lens that focused about 4feet in front of the camera with a fixed aperture and shutter speed. Itwas basically a box with a shutter. Then the lab that developed the filmdid what it could to fix the exposure. Todays P&S cameras are muchmore sophisticated.
SLR stands for Single Lens Reflex and DSLR stands for Digital Single LensReflex and refers to how the light enters the camera. These are the camerasyou see many professionals and serious amateurs lugging around. Thesecameras have a larger body than most P&S cameras and interchangeablelenses. While SLRs started out a fully manual, where the photographer had tocontrol all features including focus, most of these cameras are capable ofacting in a fully automatic mode just like a P&S. Many now allow thephotographer the freedom to also take control of all functions or anycombination of functions. These cameras allow for great control over thephotography process and allow the photographer to take images not alwayspossible with a P&S.
The demand for digital cameras has presented a strong outlook,including cameras fitted in devices such as mobile phones andshowed a positive response even in the economic downturn, during2008 & 2009. Technological advancement has helped the growth ofvarious consumer electronics products, digital cameras being oneof themSLR accounted for the highest growth rate in 2009, driven bygrowth in Asia, especially in China. The potential for growth ofdigital SLR cameras is very high because of technologicalinnovations, portability, falling prices and rising interest of teens.The growth rate has slowed down in Japan and the US, while it hasincreased in the emerging regions of China, India and EasternEurope Demand for Digital cameras and SLR has been mainlydriven by demand in emerging markets (China, Russia), risinginternet usage and favouring disposable income.