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View Diary: Origins of English: Para- (55 comments)

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  •  Parallax is also used in photography (8+ / 0-)

    to describe the discrepancy between the view seen by a camera lens when compared to what is seen through the viewfinder.  This is why the SLR (single lens reflex) camera was so revolutionary:  suddenly a photographer would see precisely what his lens saw because the system of a pentaprism and a 45 degree angle mirror allowed him to look directly through the lens.  Although parallax was not much of a problem when dealing with anything beyond about 3 feet or so, for close-ups, it was a nightmare.  The closer you get to the subject, the more the image on the film differs from what is seen through the viewfinder. I suspect this is why no camera phone manufacturers have ever bothered to add a viewfinder, though the support one gives a camera when it's held close to the eye helps to avoid camera shake-induced blurring of the image.

    -7.13 / -6.97 "The people never give up their liberties but under some delusion." -- Edmund Burke

    by GulfExpat on Sat Nov 24, 2012 at 09:41:42 AM PST

    [ Parent ]

    •  and in Astronomy (6+ / 0-)

      Say you observe a single star over the course of a a year.  If it is near enough to earth (compared to nearby stars) it will appear to move between observations.  I think the idea originated with the Greeks, but it took 19th century telescopes to make it detectable (Bessel 1838).

      The motion is very small.   Proxima Centauri, the nearest star, has a parallax of approx. 0.8 arc-seconds.  That's 0.8/3600 degrees - a very small angle

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