Packet 2: magnification Flashcards
what does magnification do in low vision (and what does it NOT do)?
- does produces a large enough retinal image for identification
- does NOT provide clarification
what are the 4 different types of magnification
- relative size magnification
- relative distance magnification
- projection magnification
- apparent angular magnification
relative size magnification=
final object height / original object height
relative distance magnification=
original object distance / final object distance
projection magnification=
final height of object / original height of object
large print is an example of what type of magnification?
relative size magnification
this is most common type of magnification used in near low vision devices
relative distance magnification
an overhead projector is an example of what type of magnification?
projection magnification
what type of magnification is achieved with optical instruments like telescopes, hand magnifiers, and tele microscopes?
apparent angular magnification
how does apparent angular magnification work?
the size of the image is enlarged without modifying the object or changing the viewing distance
in apparent angular magnification, the enlarged image is an optical illusion created by:
changing the convergence angle at the eye of the light coming from the object
total magnification is determined by the ____ of the individual magnification sources
product
for near devices, work in terms of:
equivalent power (D), diopters
for distance devices, work in terms of:
magnification, (x)
what is equivalent power?
the total dioptric strength needed by the patient to achieve their near visual goal
