L3,4,5 - Spatial Resolution of Vision Flashcards

1
Q

In perception, how do you measure how good something is quantifiably?

A
  • Assess how much signal is needed to successfully perceive the thing
    • SDT helps us quantify
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2
Q

What is spatial resolution (visual acuity?

A
  • Resolution is the ability to distinguish differences in the spatial distribution of light in an image
  • Visual acuity is the best known measure of resolution
  • Visual acuity is the spatial resolving capacity of the visual system. This may be thought of as the ability of the eye to see fine detail.
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3
Q

Is testing the smallest size of an object that no one can see a good measure?

A
  • Not good – may not always disappear
  • Blur makes it bigger on the retina, or neurons combining the neighbouring photoreceptors make it bigger in the brain
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4
Q
A
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5
Q

Is testing the smallest separation for which you can still distinguish two nearby objects a good method? What is actually testing?

A
  • E.g. Romans used to test sight by asking about whether they could see two stars that are close together or just the one
  • It can depend on the size of your receptive fields. If they are larger, unsure that they are two stimuli as opposed to when RF are smaller
  • The greater number of receptors contributing to the of a given ganglion cell, the larger that cells receptive field
  • Smaller receptive field has superior visual acuity because convergence is more limited for this cell
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6
Q

What are the different ways of measuring and testing for acuity (name only)?

A
  • Testing the smallest size of object that no one can see
  • Testing the smallest separation for which you can still distinguish two nearby objects
  • Testing maximum density visibility of a series of lines (grating) against a background of the same average luminance
  • Snellen eye chart
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7
Q

How can contrast alter the amount of signal?

A
  • Amount of light difference via contrast
    • Different depths result in the light varying when it comes back to the eye
    • Distribution of light will remain the same
    • Less contrast = Less signal
  • Contrast can be measure via the Pelli-Robson Contrast sensitivity chart that keeps letters at the same size, but downwards they decrease in contrast
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