Pupils And Stops And Related Effects 3 Flashcards
Depth of Focus
- refers to retina (whether its focused in front or in back of retina
- describes the interval surrounding the retina where an eye sees an object in focus
- blur is so small, retina can’t tell if it’s perfectly focused or not
Depth of Field
- outside space
- describes the interval surrounding the fixation plane where an object will still be in focus and there will be no perceivable blur on the retina (screen)
- in front of eye, focusing on a pen
Focal ratio, other names for it
F-number
F-stop
F/stop
What is the focal ratio?
(Focal length)/(diameter of aperture)
LArger F/stop
Fewer abbertion, larger depth of focus
Smaller F/stop
Brighter image, narrow focus
-more light gets in
Focal length and depth of focus
Power of diopter increases rapidly as you move closer to an object
Longer focal length
Larger depth of field
Increase in aperture size
Decreased depth of field and decreased depth of focus
Hyperfocal distance
The distance at which a camera (or system) is focused so that the distal limit of the depth of field is at optical infinity
-plot the far point at infinity so you can use the entire depth of field
Increase in F/stop (decrease in aperture size)
Larger DOF
Decrease in f/stop (increase in aperture size)
Smaller DOF
Pupil size and age
- naturally decrease with age
- smaller pupils increase the depth of focus and decrease blur, compensating for loss of accommodation with age
What are larger pupils correlated strongly with?
Worse night vision
Studies have found that you can read better if you have smaller
Pupils
