Basic Photography Course

incorporated in a single circular piece of glass (fig.

CHARACTERISTICS OF LENSES

There are several factors that must be included when

you are considering the characteristics of lenses. To
perform well as a Navy photographer, you must
recognize the effect of these lens characteristics. Realize

also that it is the recognition and use of these various
lens features and/or qualities that can make the
difference between good and poor photography. You
must learn to recognize the photographic effect of these
characteristics and be able to apply them to produce top
quality photography. Finally, you must learn how some
of the lens characteristics may limit photographic
quality or operational capability.

Lens Focal Length

In photography, lens focal length is the distance

between the optical center of a lens and the focal plane

(film plane) of the camera when the lens is focused at
infinity (fig. 1-17). To understand this definition, you
must fully understand the terms focal plane, optical
center, and infinity.

Figure 1-17.Focal plane and optical center.

Figure 1-18.Effects of lens-to-subject distance on light rays.

Focal plane-The surface (plane) on which an

image transmitted by a lens is brought to sharp focus;
the surface or area at the back of the camera occupied
by the film.

Optical center-The optical center of a lens is a

point, usually (although not always) within a lens, at
which the rays of light from two different sources
entering the lens are assumed to cross.

Infinity-This term is not easily described. When

light is reflected from the point of an object, the closer
the point is to the lens, the greater is the angle of the
spread of light rays from the object (fig. 1-18). As the

1-13

contents

Basic Photography Course

<- previous page

next page ->


DOFMaster for Windows On-line Depth of Field Calculator DOFMaster for Mobile Devices On-line Depth of Field Table Hyperfocal Distance Chart Articles FAQ Recommended Books Support Contact Links Home As an Amazon Associate I earn from qualifying purchases.	contents <- previous page next page -> incorporated in a single circular piece of glass (fig. 1-16). CHARACTERISTICS OF LENSES There are several factors that must be included when you are considering the characteristics of lenses. To perform well as a Navy photographer, you must recognize the effect of these lens characteristics. Realize also that it is the recognition and use of these various lens features and/or qualities that can make the difference between good and poor photography. You must learn to recognize the photographic effect of these characteristics and be able to apply them to produce top quality photography. Finally, you must learn how some of the lens characteristics may limit photographic quality or operational capability. Lens Focal Length In photography, lens focal length is the distance between the optical center of a lens and the focal plane (film plane) of the camera when the lens is focused at infinity (fig. 1-17). To understand this definition, you must fully understand the terms focal plane, optical center, and infinity. Figure 1-17.Focal plane and optical center. Figure 1-18.Effects of lens-to-subject distance on light rays. Focal plane-The surface (plane) on which an image transmitted by a lens is brought to sharp focus; the surface or area at the back of the camera occupied by the film. Optical center-The optical center of a lens is a point, usually (although not always) within a lens, at which the rays of light from two different sources entering the lens are assumed to cross. Infinity-This term is not easily described. When light is reflected from the point of an object, the closer the point is to the lens, the greater is the angle of the spread of light rays from the object (fig. 1-18). As the 1-13 contents Basic Photography Course <- previous page next page ->	As an Amazon Associate I earn from qualifying purchases.
	WWW.DOFMASTER.COM © 2006 Don Fleming. All rights reserved.