depth of sharpness

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when i was lying in the grass in spain one day, i started thinking about depth of sharpness/field.
you know – low f-number >> very unsharp background, high f-number >> sharper background.

since a low f-number stands for a wide aperture (and so on), this basic optical correlation must also apply to the human eye – with the iris as a “biological aperture”.
if so, our range of vision would look like this, depending on how much light is available:



but it doesn’t really matter, because of the retina’s structure, and the mind’s way of interpreting the optical information into our vision: the only spot in the retina with a high enough resolution to allow seeing a clear image is the yellow spot (or macula lutea) [wikipedia: en, de].
the actual image produced by our eyes is pretty much like a totally blurred overview with a tiny, perfectly focussed circle.
the impression of the completely-in-focus-world we see everyday is just what our conscience fabricates from the blurry picture, and the high-quality information it gets by moving the eye around to get everything interesting into the macula‘s region.

if there wasn’t such a big difference in the retina’s quality, we wouldn’t have to follow the lines with our eyes to read a newspaper. then, this optical effect would also apply to our vision.
but it’s the other way round – if you see something interesting, you “look there” (e.g. you adjust your eye to get that part’s light into your yellow spot) and get the additional information…

yes, i had too much time to think during my holiday :neutral:

[categories: nature, photo]

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