LensesAre classified by their Focal Length

Focal LengthThe distance from the optical center of a lens to the front surface of the imaging device.

Short Focal Length

Wide Angle ViewWide Angle Lens

Short Focal LengthEXAMPLEEntire Football Team

Long Focal Length

Narrow Angle ViewTelephoto Lens

Long Focal Length

EXAMPLEOne Football Player

Zoom LensVariable Focal Length

Zoom RangeHow close to how far a lens can see

Lens SpeedHow much light can pass through a lens

Fast LensLets a great amount of light to pass through

Fast LensUse in the evening, when there isnt much light.For low light settings

Slow LensLets a small amount of light to pass through

Slow LensUse this on bright, sunny daysFor bright light settings

IrisAdjustable lens opening mechanism

ApertureHole in center of irisMeasured by f-stops

ApertureSimilar to the pupil of your eye

ApertureCan adjust larger or smaller depending on the amount of light

ApertureWhat type of aperture opening would you use for a sunny day?

ApertureWhat type of aperture opening would you use for a dark room with only a candle for light?

Auto IrisMany cameras have auto irisAdjusts automatically depending on setting

FocusWhen subject in viewfinder is sharp and clear.

*********************