Digital Camera Image Quality

Electronic image sensors have been evolving since the first analogue television targets to the appearance of the digital CCD ( charge-coupled device ), which is the origin of the digital image and of the present and future sensors. The first commercial photographic camera which used a magnetic support is from the beginning of the eighties. The camera recorded a static image on a diskette which was afterwards introduced in the computer to see them on the screen. The first digital images were very poor: the equivalent of a static television image. When these images were printed there was no comparison to a photo made with film. They had a plotted aspect with very low definition. They were useful mostly for archival purposes, but only for practical reasons, and it was almost exclusively seen only on the computer screen. A digital camera nowadays can compete with the quality of film photographs, but there are certain limits. In actuality there are many kinds of digital cameras which are differentiated by image quality and recording support.

Image Quality
The quality of a digital image depends mainly on the number of pixels that the camera's sensor provides. The number of pixels is to digital photography what format is to film. Small format cameras have there

equivalent in compact digital cameras, with a sensor around 3 million pixels (or megapixels) ; medium format can be compared to professional cameras of over 5 megapixels; and cameras that use medium and large format film can also hold digital backs which provide images between 8 and 150 million pixels. The only limit would be of digital cameras -in comparison with film- is in the maximum dimensions of the photographs. If we amplify a film image, the emulsion's grain is made visible, but that grain doesn't have a determined structure and may even pass unnoticed. On the other hand, in a digital image the pixels are placed on an orthogonal plot which calls your attention when made visible and produces a feeling of low sharpness. Therefore, a digital camera can produce a high quality image up to a maximum size. The limit of the dimensions depends on the number of pixels of it's sensor, because if we divide the number of pixels by the surface of the (printed) image there are maximum dimensions that give us an acceptable resolution. For example, a digital camera with a sensor of 2,560 x 1,920 pixels (approximately 5 megapixels) lets us print a maximum quality image (300 ppi) with dimensions equal to 21.7 x 16.3. If we consider that a lower resolution also gives us an acceptable image quality, we can increase the size to 26 x 19.5 cm at 250 ppi and even to 32.5 x 24 cm at 200 ppi. If our camera only has 3.1 megapixels (2,048 x 1,536), the maximum size for the qualities of the previous example are reduced to: 17 x 13 cm for 300 ppi, 20.8 x 15.6 cm for 250 ppi and 25 x 19.5 cm for 200 ppi.