Appendix C Understanding Automatic Exposure And Nightshot; About The Lens Iris Or Aperture And The F-Number - Honeywell ACUIX User Manual

Understanding Automatic Exposure and
NightShot

About the Lens Iris or Aperture and the F-Number

Document 800-05662V1 Rev A
04/11
This appendix contains the following sections:
• About the Lens Iris or Aperture and the
• About Video Gain, Shutter Speed, and Spectral
• About ACUIX PTZ Dome Manual Exposure
• Operating NightShot (TDN) on ACUIX PTZ Camera
This appendix provides additional information about automatic exposure (AE) to
assist you in configuring the ACUIX High Speed PTZ dome to meet your specific
requirements.
The lens iris, or aperture, determines how much light is transmitted through the
lens to the sensor. This is measured as an f-number, which is the focal length of
the lens divided by the equivalent diameter of the front lens element. Therefore,
a large f-number transmits less light to the sensor. The standard f-numbers are
integer powers of the square root of 2 (for example, 1, 1.4, 2, 2.8, 4, 5.6, 8, 11,
16, 22, 32, 45, 64, 90, 128, and so on). Each successive f-number transmits one
half the amount of light as the previous f-number.
The f-number is the first factor changed in an auto exposure system. That is to
say, the other factors are not changed until the lens aperture reaches its open or
closed limit. The lens aperture also controls the depth of field of the lens. The
depth of field is a measure of the distance that an image is in focus to an
acceptable degree. The larger the f-number (a smaller aperture) the greater the
depth of field.
F-Number, page 97
Response, page
Control, page 100
Blocks, page
C
98
101
97