Everybody knows to check how many mega pixels their new camera has. Although more mega pixels does not necessarily mean better photos most people understand why mega pixels are important. One characteristic of digital cameras that many ignore is the sensor size. Digital cameras capture digital photos. A digital photo is a collection of pixels. Each pixel has its color and intensity. When all these pixels are put together the result is an illusion of a photo. Pixels are captured by the camera using an electronic sensor known as a CCD. The CCD sensor is a silicon chip that is built of many tiny light sensors. When taking a photo each such tiny sensor measures the amount of light also known as intensity and some other attributes such as the color. Each such sensor results in one pixel and all the tiny sensors put together represent one digital photon. This is very interesting to know but why should you care? The reason is that there is a relationship between the size of that CCD sensor and the number of mega pixels that it supports. This relationship is important and has practical consequences. It is intuitive that for the same CCD sensor size, the more mega pixels the smaller each CCD tiny sensor is. The same is true if the number of mega pixels is fixed: the bigger the CCD sensor the bigger each tiny sensor is. For each CCD sensor size and number of mega pixel we can calculate the pixel sensor size. The pixel sensor size is important and influences the characteristic of the digital camera especially in marginal light scenarios. Your digital camera sensitivity to light is directly influenced by the pixel sensor size. The bigger the sensor size the more light it can accumulate in a certain period of time. The result is that bigger pixel sensor sizes allow for faster shutter speeds at lower light conditions. In addition bigger pixel sensor sizes result in less noise captured by each such sensor. In practical terms if you take two digital cameras with the same number of mega pixels but different CCD sensor sizes - the camera with the larger CCD sensor size will be provide digital photos that are sharper and have less noise. It will also be able to take digital photos in scenes that are too dark for the other camera. In normal light scenes the higher light sensitivity allows more range for changing the aperture and shutter speed and more freedom with getting different focus depths. Bigger CCD sensors are more expensive. There are many reasons for that one of them is the lower manufacturing yield. For that reason cheaper pocket cameras use smaller sensors than high end digital SLR cameras. CCD sensor size also influences other optical attributes of the camera for example the aperture needed in a specific scene changes as the CCD size changes. The depth of field is directly influenced by such aperture changes. To normalize optical figures many cameras manufacturers choose to normalize their optical attributes to the good old 35mm film (film can be seen as a sensor too, 35mm in size).
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