Case Study: How Lenses Work: September 2013

VisEffects Case Study: How Lenses Work

Outline

I. What are lenses and why do we use them?

A. They're glass that bend light in order to project it onto a surface, whether that's treated film, a sensor in a digital camera, or the retina of you own eye. Basically, it's used to control the way light bends.

a. light travels in straight lines, it gets absorbed and released and bounces (reflects) and bends (refracts), etc. Different lenses refract light differently.

c. concave/convex/aspheric, lens elements, optical aberrations (loss of contrast, chromatic aberration, vignetting, blurring, distortion)

II. Parts of a camera

A. Lens assemblies

The adjustment of distance (focusing) by moving the lens elements is called different things by different manufacturers. Nikon calls it CRC (close range correction), Canon calls it a floating lens system, Mamiya and Hasselbrand call it FLE (floating lens element)

B. Iris Diaphragm

Controls amount of light that passes through. The blades are called the "iris"; the opening or pupil is called the "aperture";

C. Shutter

Stops light (shuts it out, get it?) after a determined period of time.

III. Adjustable bits that make camera use so interesting

A. Aperture

Determines light intensity; wider aperture (smaller f-number) lets faster shutter speed and light exposure.

FOR EXAMPLE:

B. Focal Length

Determines magnification of image when projected onto image plane; shorter focal length gives wider angle (ANGLE OF VIEW), longer focal length gives narrower angle

FOR EXAMPLE:

Normal lens, wide angle lens, long-focus lens (telephoto lens)

C. Depth of Field