How a camera works for all cameras is the light image travels through the lens. The lens focus on the object being photographed and the lens also projects the image onto the back plate of the camera through a small hole called the apature. There is a shutter mechanism that opens and closes quickly to allow the image to be projected on to the back plate. The camera takes the picture when the shutter release button is pressed. The back plate is where the image is captured, either by sensors that are light sensitive in digital cameras, or a photosensitive emulsion for film cameras.
The amount of light that enters the camera is governed by two functions, the apature, the size of the hole and the shutter speed, how fast the image is projected on to the camera to the back plate.
Digital Single Lens Reflex (DSLR) work in the way described above. There are however some refinements. The DSLR has a view finder that ‘looks down’ through the lens that will take the photograph. The image comes in through the front of the camera and is focused be one or more lenses. The path the image takes is yellow on the diagram above. There is a mirror that lies in the path between the lens and the back plate (Blue), this is so that the image through the lens is projected up reflects through a prism so the photographer can see what the camera can see, can frame and focus the camera accurately via the viewfinder. The viewfinder will also display additional information such as the apature, shutter speed, areas that the camera has taken light meter readings. If the camera lens is set to autofocus, the areas the camera has identified as points to focus upon such as peoples faces.
DSLR have interchangeable lenses. The lens can be swapped by the photographer for the most appropriate lens for the subject they are wanting to photograph. The lenses range from wide angle with a short focal length. These are great for taking pictures that you want to see a wide shot, get a lot of background and have good detail, ideal for big landscape shots, or when standing close to an object and you want a lot of the surrounding background included. Long focal length ideal for taking shots of things that you want to focus in upon. Long focal length compresses the focal distance so that less items will be in focus, these are ideal for portrait work or taking photographs of objects that you want to study, and put the background out of focus.
Another method of influencing the depth of filed is the size of the apature. The smaller the apature (bigger the f-stop number eg. f16) the greater the depth of field. The larger the apature (smaller the f-stop number eg.f5.6), the shallower the depth of field.
The lens contains one or more precision ground optical lenses to allow focusing or zooming (telephoto) on to the photographic subject, and cause minimum of distortion or loss of light. Telephoto/zoom lens has the flexibility to magnify or zoom-in in on subjects.
The lens contains the aperture (Grey), the aperture is the hole along the barrel of the lens which the light travels through to get to the digital sensors. The aperture is a method controlling the amount of light that strikes the back plate and also affects the depth of field. The size of the apature isvari able and can be opened up wide or made tiny like a pin whole. The smaller the apature (bigger the f-stop number eg. f16) the greater the depth of field, but less light is passed through the apature. The larger the apature (smaller the f-stop number eg.f5.6), the shallower the depth of field, but a greater amount of light passes through the apature.
To compensate for the small amount of light that passes through a smaller apature, the shutter speed will be slower. For larger apatures the large amount of light is restricted by a faster shutter speed.
The back plate of a DSLR consists of digital sensors. The sensors detect red, blue and green light, the sensors are tightly packed and the number of sensors is indicated by the number of mega pixels a camera has. The sensors convert the light/image that is projected in to digital pixel information that can be used to produce quality photographic images in a variety of digital image formats such as JPEG, RAW TIFF.
The sensors in the camera also are sophisticated and can be used to help the photographer take the optimal picture with such features as autofocus, auto-aperture selection for spot light meter reading, or overall image light metering, image stabilisation to reduce effects such as camera shake.
The DSLR will store the photographs to SD card or cables can be attached from the camera to a computer to store pictures immediately.
The DSLR also has a LCD (Liquid Crystal Dispaly) on the back of the camera where information is displayed about the camera settings. Menu button to access and change settings via the LCD such as volume, grids overlayed upon viewfinder or LCD, set the quality of the image to be stored, duration of self timer, the exposure compensation.
Self Timer release button, Mode selector for auto-everything through to manual everything (focus, apature, shutter speed), Exposure compensation button to override the automatic settings of the camera. A view button to review photographs, delete button to remove rubbish pictures.Flash On/Off/Automatic button
Compact Digital Cameras,
Typically these cameras are pocket cameras with many features.
On/Off switch, built in flash, Lens (could be fixed, most are now zoom) that retracts into the body and a protective shutter closes to protect the lens when the power is switched off. Shutter release button. LCD (Liquid Crystal Dispaly) on the back of the camera where the image is displayed, Mode selector (autofocus plus a series of preset funtions). Zoom switch to zoom in or out of the scence/subject. Menu button to access and change settings via the LCD such as volume, grids overlayed upon LCD, quality of image to be stored, duration of self timer. Flash On/Off/Automatic button, Self Timer release button, macro mode button for close-up photographs, Exposure compensation button to override the automatic settings of the camera, View button to review photographs, delete button to remove rubbish pictures.
Digital cameras store the image as JPEG (.jpg) file format or raw TIFF format depending what the camera supports. The file formats can then be transferred to a printer or PC for immediate printing or if transferred to a PC the photographs can be edited or manipulated before printing. The simplest image editing such as removing ‘red eye’ from a picture of a face taken with a flash, through to correcting of distortion, changing colour saturation, hues or contrast, or the application of effects and filters available in many photo editing software packages.
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