Sony SSC-M370CE Handmatig - Pagina 18
Blader online of download pdf Handmatig voor {categorie_naam} Sony SSC-M370CE. Sony SSC-M370CE 40 pagina's. Cctv products
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- 1. Table of Contents
- 2. Introduction
- 3. When and Where Should It be Used
- 4. Light
- 5. Choosing a Camera
- 6. Selecting the Correct Lens
- 7. Which Monitor
- 8. Transmission of Video Signals
- 9. Video Switching and Multiplexing
- 10. CCTV Systems Control
- 11. Recording
- 12. Sony CCTV Products
- 13. Basic CCTV Terminology
- 14. Basic CCTV Terminology
Selecting the Correct Lens
Aperture range
The aperture is the clear opening in the centre of the lens that allows light to pass
to the pick-up device.
The aperture size is described in relation to the focal length (F). Thus the
aperture is specified by an F number. If the lens has a focal length of 50mm and if
the diameter of the clear opening of the lens is 25mm, then the lens is said to have
an aperture of F:2 (50mm divided by 25mm = 2). A 50mm lens with an aperture of
F:2 has the same light gathering ability as a 150mm F:2 lens but the glass
components will be more complex in order to achieve the telephoto effect.
Most CCTV lenses have a built-in mechanism called an iris. This allows the
aperture to be changed to accommodate varying light levels. The largest aperture
setting is often used to define the maximum light gathering capability of the lens,
the lens speed. A lens with a maximum aperture of F:1.6 is referred to as an F:1.6
lens and is said to be 'faster' than, say, an F:4.2 or F:8 lens.
The iris setting of the lens is numbered from the largest F stop down to the
smallest F stop. CCTV systems are rarely installed in situations where light levels
are constant, so lenses with automatic iris adjustment are important components of
most systems.
16
Focus set to 20m.
Lens f = 1.4
Depth of Field
The Sony Guide to CCTV . Issue 3
Depth of Field
Lens f = 5.6
Depth of Field