 BetterPhoto Member |
File Size When they say 640x480 or 1280x1024, what does that all mean?? Also when you buy a digital camera and it says it is 1.5 Mega Pixels or 2.3 Mega pixels, what does that mean??
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Gregour A. Beatty |
Those numbers describe the resolution of an image - each unit refers to a pixel (picture element) and they can be compared to the dots used in printing. If you look closely at photos in newspapers, the less expensive processing uses large dots in small numbers to fool the eye into seeing the image, and you can see the dots pretty easily there. Ever seen a chunk of billboard print up close? Dots the size of Detroit. A strong magnifier (8 or 10 X) will show the same dots are used even in fine reproductions that were printed (unless done by lithography, serigraph & other special methods). Those numbers, then, tell you what kind of image quality the camera will produce. For fine prints you want to PRINT out at least at 150 lines or dots per inch. You can do some math and figure out how little your snapshots would print out, to have that kind of resolution, once printed. To simulate really photorealistic results (which is still seldom seen except in film technology), you'd want to be able to print at 300 dots per inch. That's about what most people are used to seeing in decent printed books. Resolution can be confusing, but it's really pretty straightforward. It's like you have different window screens in front of your face at all times, and once in a while you need to change screens or figure out how to get at an image where the details seem the same res as the screens and wipes out the details. Maybe stand back and zoom in, or stand close and zoom out, whatever means necessary ... The next problem becomes data storage ... to describe full colour, an image's file needs to store a lot of data, and "bit planes" refers to the sets of data needed to describe red, green, and blue light intensities and any brightness or other control info, FOR EVERY pixel ... when a given image is made twice as big in dimensions, the file size goes up FOUR times (actually, instead, probably you get a big checkerboard or interpolated approximation, if you really do that enlargement). That's why less expensive cameras will offer lower resolutions, and why most all will store the images in the JPEG format. Just for comparison, a high quality 35mm film has light sensitive grains of chemicals, where the film's grain is measured in microns ... while such images are usually archived more affordably at one or two thousand pixels per inch, we'd really need about 4000 by 4000 ppi res to truly capture all the info in it.
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