Digital Versus Film Photography - Image Quality - Spatial Resolution

Spatial Resolution

The quality of digital photographs can be measured in several ways. Pixel count is presumed to correlate with spatial resolution. The quantity of picture elements (pixels) in the image sensor is usually counted in millions and called "megapixels" and often used as a figure of merit. Digital cameras have a variable relationship between final output image resolution and sensor megapixel count. Other factors are important in digital camera resolution, such as the number of pixels used to resolve the image, the effect of the Bayer pattern or other sensor filters on the digital sensor and the image processing algorithm used to interpolate sensor pixels to image pixels. Digital sensors are generally arranged in a rectangular grid pattern, making images susceptible to moire pattern artifacts, whereas film is not affected by this because of the random orientation of its grains.

The resolution of film images depends upon the area of film used to record the image (35 mm, Medium format or Large format) and the speed. Estimates of a photograph's resolution taken with a 35 mm film camera vary. More information may be recorded if a fine-grain film, combined with a specially formulated developer, are used. Conversely, use of poor quality optics or coarse-grained film yield lower image resolution. A 36 mm x 24 mm frame of ISO 100-speed film was initially estimated to contain the equivalent of 20 million pixels, although this estimate was later revised to between 4 and 16 million pixels depending on the type of film used.

Many professional-quality film cameras use medium format or large format films. Because of the size of the imaging area, these can record higher resolution images than current top-of-the-range digital cameras. A medium format film image can record an equivalent of approximately 50 megapixels, while large format films can record around 200 megapixels (4 × 5 inch) which equates to around 800 megapixels on the largest common film format, 8 × 10 inches, without accounting for lens sharpness. Medium format digital provides from 39 to 80 megapixels.

Thus film and digital work each provide a wide range of performance in this regard, overlapping but with film tending to higher resolution. Resolution of both film and digital are subject to the quality of lens fitted to the camera. The medium which will be used for display, and the viewing distance, should be taken into account. For instance, if a photograph will only be viewed on an old analog television that can resolve approximately 0.3 megapixel or modern HDTV set of 1080p with 2 megapixels, the resolution provided by high-end camera phones may suffice, and inexpensive compact cameras usually will. Similar or more expensive hardware may also fill the screens of computer displays, though those few that show tens of megapixels will be out of reach of low-end film photography and all but specialized scientific or industrial digital cameras.

Read more about this topic:  Digital Versus Film Photography, Image Quality

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