DFGH : April 16, 2008
Image Data
File Name: 20D_20188
Model: Canon EOS 20D
Lens: Canon 100mm F/2.8 USM Macro
Date: 04.15.08 11:30pm
Focal Length: 100mm (160mm)
Shutter: 20 s
F-Stop: F22
ISO: 800
Ex Bias: -2/3 EV
Program: Aperture priority
Metering Mode: Evaluative
Flash: Off
Focus Mode: Manual focus
File Name: 20D_20188
Model: Canon EOS 20D
Lens: Canon 100mm F/2.8 USM Macro
Date: 04.15.08 11:30pm
Focal Length: 100mm (160mm)
Shutter: 20 s
F-Stop: F22
ISO: 800
Ex Bias: -2/3 EV
Program: Aperture priority
Metering Mode: Evaluative
Flash: Off
Focus Mode: Manual focus
Corrective lenses modify the focal length of the eye to alleviate the effects of nearsightedness (myopia), farsightedness (hyperopia) or astigmatism. As people age, the eye's crystalline lens loses elasticity, resulting in presbyopia, which limits their ability to change focus.
The power of a lens is generally measured in diopters. Over-the-counter reading glasses are typically rated at +1.00 to +4.00 diopters. Glasses correcting for myopia will have negative diopter strengths. Myopia requires a divergent lens, whereas hyperopia requires a convergent lens.
The power of a lens is generally measured in diopters. Over-the-counter reading glasses are typically rated at +1.00 to +4.00 diopters. Glasses correcting for myopia will have negative diopter strengths. Myopia requires a divergent lens, whereas hyperopia requires a convergent lens.
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