# Removing the IR filter from a C mount lens

**URL:** <https://boards.straightdope.com/t/removing-the-ir-filter-from-a-c-mount-lens/344882>\
**Category:** Factual Questions\
**Created:** [February 16, 2006, 10:54pm UTC](https://boards.straightdope.com/t/removing-the-ir-filter-from-a-c-mount-lens/344882 "2006-02-16T22:54:07Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Shalmanese](https://avatars.discourse-cdn.com/v4/letter/s/45deac/32.png) [@Shalmanese](https://boards.straightdope.com/u/Shalmanese)\
**Post date:** [February 16, 2006, 10:54pm UTC](https://boards.straightdope.com/t/removing-the-ir-filter-from-a-c-mount-lens/344882/1 "2006-02-16T22:54:07Z")

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I’m doing a couple of projects involving motion tracking that require me to detect IR LEDs. Right now, I have a choice between two cameras, an $80, 500xsomething B&W security camera with no IR filter on the lens and a $3000 1024x768 machine vision camera which has a c-mount lens with an IR filter over the top.

Obviously, if practical, I would far prefer to use the camera with the higher resolution but the LEDs just aren’t showing up bright enough for that to be practical out-of-the-box. A quick search on the internet reveals that there are either $400+ lenses which claim to be IR sensitive and $20 - $100 lenses which also claim to be IR sensitive and come with a ring of IR LEDs around the edge which turn on automatically in low light. I don’t claim to know why the second group is cheaper but my googling has not revealed a non-LED studded IR lens for less than $100.

Alternatively, I know that [people have removed IR filters from webcams](http://homepage.ntlworld.com/geoff.johnson2/IR/) but I was wondering if anybody had done it for c-mount lenses or knew how the IR filtering on a standard c-mount lens is achieved.

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**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\
**Post date:** [February 17, 2006, 12:54am UTC](https://boards.straightdope.com/t/removing-the-ir-filter-from-a-c-mount-lens/344882/2 "2006-02-17T00:54:38Z")

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If there’s not a flat filter on the lens, one of the actual lens elements is probably made with IR-absorbing glass, which would be impossible to change.

If there is a flat filter on the front, it’s probably held in with a skinny threaded ring. Look for two tiny slots on the ring. If you find 'em, try pushing with a small screwdriver in a counter-clockwise direction and it should unscrew.