Why does looking through a traw improve the focus or resolution you see?

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SUMMARY

The discussion centers on the optical phenomenon where limiting the field of view enhances focus and resolution. By creating a pinhole effect, either with fingers or through a camera's iris, the rays of light entering the eye are restricted to those near the optical axis, minimizing distortion caused by aberrations. This principle is illustrated through the comparison with a Scanning Nearfield Optical Microscope (SNOM), emphasizing that both human vision and optical devices benefit from reduced light ray dispersion. The effect is further amplified in bright light, where the iris constricts, enhancing clarity.

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  • Familiarity with the concept of optical aberrations
  • Knowledge of how a Scanning Nearfield Optical Microscope (SNOM) operates
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  • Explore the effects of pupil size on visual acuity and light perception
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Optics enthusiasts, photography professionals, educators in physics, and anyone interested in enhancing visual clarity through optical principles.

philip041
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When I curl my hand up and look through it, even though I have terrible eye sight I can read the title of a book on my shelf even though I can't if I'm not wearing my glasses. Why is this? I just had a lecture on SNOM, (Scanning Nearfield Optical Microscope), where the lecturer made a comparison with this.
 
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Your imperfect eye doesn't focus all the rays of light to a single point
The rays at the edge of the field of view have to be bent most and so are affected most by any error in the bending. By putting a hole in front of your eye (it works with just your fingers making a loop) you limit the rays to only those near the axis which are ebtn least.

The same thing applies to all optics, it's why your camera takes sharper pictures with the iris stopped down.
 
You can also read better when in bright light, and not only for the obvious reason. When your eye is stimulated by bright light, your iris expands significantly, constricting your pupil to more of a pinhole.
 

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