Why 'Stops' for exposure?

Same reason your Window Manager doesn't allow you to send specific signals to each open process. And if you don't know what the hell I just said, there's your answer right there.

Most people don't care and what's more, most people wouldn't use it even if they did understand perfectly the why's and how's of the matter. Add in the problem of manufacturing tolerances and measuring errors and it simply makes no sense whatsoever, even for the most obsessive of pixel-peepers.

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