The optical resolution notes the true ability to discriminate details while the

The optical resolution notes the true ability to

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The optical resolution notes the "true" ability to discriminate details, while the digital resolution describes the ability to "zoom" the optical
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1/29/2007 Calculations Page 6 output to larger scale with reasonable accuracy. If two different optical resolutions are given - for horizontal and vertical capability - the real optical resolution is normally the lower value.) 3.3 SOUND FILES - NUMBER OF UNITS The number of units in sound files is based upon time. Samples are normally specified as samples per second, so you must also know the total length of the recording. The number of samples can then be calculated from the relationship: (samples rate per second) × (total time in seconds) = total number of samples Any one of the three variables can be determined if the other two are known. Digital sampling of analog sound sources requires a minimum of two samples per Hz. Since the upper range of human hearing is considered to be somewhere near 20,000 Hz, the sampling rate for CD audio is standardized at 44,100 samples per second, and 16 bits per sample. CD audio is not compressed since the technology was developed before it was economic to embed compression technogy in consumer products. Compression techniques, such as MP3 format, compromise slightly on sound quality to obtain a much smaller file size. Digital cellphone and answering machine audio is highly compressed, and the resulting distortion quite audible. 3.4 VIDEO FILES - NUMBER OF UNITS The number of units in a video file is based upon time. Samples are normally specified as frames per second (fps), thus the total time of the video file must also be known. The number of frames can then be calculated from the relationship: (frame rate per second) × (total time in seconds) = total number of frames Any one of the three variables can be determined if the other two are known. Sampling of analog video sources signals requires a minimum of about 10 fps to provide low quality video, and at least 24 fps for high quality. 30 fps is quite common. A related issue for video is the refresh rate (how often a screen is updated) for the video monitor. Television uses a refresh rate of 60 Hz, which coincides with the frequency of AC power supplies. Some "flickering" of the picture may be seen, especially when viewed closely. On CRT computer monitors, refresh rates need to exceed 72 Hz or the eye may perceive flickering. Flickering is distracting, tiring on the eyes, and can cause headaches. Normally a higher refresh rate is better. 4.0 FINAL CALCULATIONS, AND THE EFFECT OF COMPRESSION ON FILE SIZE As stated initially, file size is the product of "unit" size and number of units that make up the file. In the case of alphanumeric and picture files, this calculation determines the uncompressed file size. For sound and video files, if the sample or frame rate is provided, the calculation determines the compressed file size.
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  • Pixel, Character Set, Color depth, Highcolor, memory requirement

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