What do the markings on a Tamron 5–50mm CCTV lens mean?
Asked 7/9/2013
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I’m new to lenses and have a Tamron CCTV zoom marked 5–50mm. It also says:
- Manual Iris: F1.4–Close
- Auto Iris: F1.4–360
I understand that 5–50mm is the focal length range. What do the iris/aperture markings mean, and what is the difference between manual iris and auto iris on this type of lens?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
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You have a CCTV lens made by Tamron, possibly the 5-50mm here: http://www.tamron.co.jp/en/data/cctv/13vg550as2.html
The aperture values are read in the same way as on photographic lenses. In this case, your lens has a maximum aperture of f/1.4 to f/360. f/360 or even smaller apertures are necessary for CCTV cameras which may have extremely sensitive CCDs.
Auto iris lenses automatically stop the lens down or open it up when needed for outdoor CCTV applications; manual iris lenses are adjusted manually and used for indoor CCTV.
Originally by user17201. Source · Licensed CC BY-SA 4.0
user17201
13y ago
0
Generated from our catalog & community — verify before relying on it.
5–50mm is the zoom range (focal length).
The other markings are the aperture/iris range:
- F1.4 = the lens can open very wide to let in a lot of light.
- Higher f-numbers mean the iris closes down, letting in less light and increasing depth of field.
- Manual Iris: F1.4–Close means on the manual-iris version you adjust the aperture yourself, from fully open at f/1.4 down to fully closed.
- Auto Iris: F1.4–360 means the auto-iris version can automatically stop down from f/1.4 to about f/360, which is extremely small and useful in bright outdoor CCTV use.
In general, manual iris lenses are set by hand and are commonly used where lighting stays fairly constant, while auto iris lenses adjust themselves as light changes.
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