Portal:Optics

From ProPHOTO WIKI

Contents 1 Introduction 2 Lens Characteristics 3 Optical Characteristics 4 Lens Designs 5 Lenses 5.1 Nikon 5.2 Canon 6 See Also

Introduction

A critical component of any photographic equipment are the optics used to generate the image. The following articles detail both the underlying principles and the various optical devices used by photographers.

Lens Characteristics

• Focal Length - The optical characteristic that controls the field of view and magnification of the image being captured.
• Aperture - An optical characteristic that controls both the ammount of light entering the camera and the depth of field.
• Depth of Field - A measurement indicating the range of focus distances that are considered 'in focus'.
• Field of View - The range of angles that will be captured by a specific focal length on a given sensor size.
• Defocus Control - An optical mechanism that allows photographers to control the way that out of focus regions of the image are projected.
• Diffractive Optics - Optical components that make use of diffraction rather than refraction to help focus light.
• Shift - An optical technique used to adjust the perspective of the image being captured.
• Tilt - A method used to adjust the plane of focus by tilting the position of the lens relative to the camera.

Optical Characteristics

• Resolving Power - A measurement of an optical system's ability to resolve detail.
• Chromatic Aberration - An optical defect caused by different wavelengths of light being focused at slightly different focal planes.
• Diffraction Limits - A characteristic that limits the resolving power of a lens due to diffraction effects caused by the edges of the aperture.
• Barel/Pincusion Distortion - Optical distortions that bend the edges of the images.

Lens Designs

• Telecentric
• Retrofocus

Lenses

Nikon

• Lens Designations
  • DX - Lenses designed specifically to use the smaller 25x15mm sensors used in Nikon's DSLRs. These designs may not work correctly when attached to full-frame cameras.
  • AF-S - Lenses making use of a silentwave autofocusing motor. These lenses provide both higher performance and quieter operation.
  • VR - Signifies that the lens contains Nikon's Vibration Reduction technology.
  • PC - Perspective control lenses provide Shift and/or Tilt capabilities. This provides the photographer with the ability to alter the perspective and/or plane of focus captured by the lens.
  • DC - Lenses equipped with Nikon's Defocus Control technology. Allows the photographer to adjust the characteristics of the out of focus regions of the image.
  • G - Signifies lenses that replace the mechanical aperture ring with a pure electronic interface.
  • D - Lenses that report distance information to the camera to assist flash exposure calculations.
  • ED - Extra-low dispersion elements have been used in this lens design.
  • IF - Uses an internal focus mechanism where the front element of the lens is in a fixed position.
  • RF - The lens focuses by moving the rearmost elements of the lens.
• Modern Lenses
• Older Lenses

Canon

• Lens Designations
  • EF-S - Lenses designed to be used with Canon's 1.6x DSLRs. Will not mount on cameras with larger sensors as the rear element may interfere with the reflex mirror.
  • L - Designation provided to differentiate Canon's best-of-breed lenses.
  • IS - Lenses containing Canon's Image Stabilization technology.
  • DO - Designation identifying lenses that make use of Canon's diffractive optics technology.
  • USM - Lenses that contain an Ultrasonic autofocusing motor.
  • TSE - Signifies a lens that has Tilt and Shift controls.
• Modern Lenses
• Older Lenses

See Also

• Cameras - Information on various cameras and camera related technologies.
• Accessories - Articles covering various accessories to be used with digital cameras.