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Digital Image Basics for non-Photographers • Blaise Tobia
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Analyzing a typical specification for image submission (a recap)

Submit ten images as JPEG files (quality 10) RGB-8
72 DPI resolution with maximum pixel dimensions of 1280x1280
and a file size no larger than 5 Mb.

This specification is better than some, in that it isn't self-contradictory, but it has several unnecessary components.

If the image file submitted is a JPEG, its mode will almost certainly be RGB-8.

Specifying print resolution ("dpi") is unnecessary for screen-viewed images.

A 1280x1280-pixel RGB-8 image has an open file size of 4.69 Mb. So, it cannot possibly be larger than 5 Mb.

Note on stored file size: this image, as a JPEG Q10 file would be about 500 Kb. As a JPEG Q6 file it would be about 250 Kb.

 

The specification could instead simply be:

Submit ten images as JPEG files (Q 10) with maximum pixel dimensions of 1280x1280.
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other examples of real-world image submission specifications (with analysis)

 

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