A Few Projects

 Posts: 528
 Joined: 09 Jan 2014, 01:19
 Location: Eastern Europe
Re: A Few Projects
Very nice

 Posts: 123
 Joined: 30 Oct 2017, 19:22
 Location: ireland
Re: A Few Projects
folks
just for information..
I received this 16m lens by post today.
https://www.ebay.co.uk/itm/Replacement ... SwY~laByPZ
and its definitely WAY BRIGHTER than the standard 16mm cctv lens.
I cant explain in words, but it's just amazing to see the difference.
No question about it.
Note its a Cmount and needs to be 1cm (+ 0.2cm) away from the camera ccd, I printed a m12 to C adapter, but you may need something else depending on your camera fitting.
this is what I mean by standard 16mm lens by the way...
https://www.ebay.co.uk/itm/28mm36mm ... PKXObioIrw
just for information..
I received this 16m lens by post today.
https://www.ebay.co.uk/itm/Replacement ... SwY~laByPZ
and its definitely WAY BRIGHTER than the standard 16mm cctv lens.
I cant explain in words, but it's just amazing to see the difference.
No question about it.
Note its a Cmount and needs to be 1cm (+ 0.2cm) away from the camera ccd, I printed a m12 to C adapter, but you may need something else depending on your camera fitting.
this is what I mean by standard 16mm lens by the way...
https://www.ebay.co.uk/itm/28mm36mm ... PKXObioIrw
Last edited by Trackerman on 16 Jan 2018, 19:04, edited 2 times in total.

 Posts: 77
 Joined: 08 Feb 2016, 23:58
 Location: Virginia
Re: A Few Projects
Thanks for the tip on the lens. What is the diameter of the objective lens? I'm curious to compare to my m12 lens I got here https://www.bhphotovideo.com/c/product/ ... Mount.html

 Posts: 123
 Joined: 30 Oct 2017, 19:22
 Location: ireland
Re: A Few Projects
Super slack, the objective lens measure 9.5mm and the exit lens measures 9mm
What does the bhphoto lens measure ?
What does the bhphoto lens measure ?

 Posts: 123
 Joined: 30 Oct 2017, 19:22
 Location: ireland
Re: A Few Projects
I suspect the bhphoto lens has wider glass.
Pity bhphoto charge crazy shipping to Ireland.
So I've ordered one of these
https://rover.ebay.com/rover/0/0/0?mpre ... 2456241776
It looks to have a wider objective lens.
Pity bhphoto charge crazy shipping to Ireland.
So I've ordered one of these
https://rover.ebay.com/rover/0/0/0?mpre ... 2456241776
It looks to have a wider objective lens.
Re: A Few Projects
if the focal length of the lens is 16mm and the diameter of the objective is 9.5mm then the aperture (f number) of the lens is 16/9.5 = 1.68
Lots of lenses claiming to be f 1.2 simply aren't
The quality of glass and construction have a lot to do with how bright the final image looks
Cheers
Bruce
Lots of lenses claiming to be f 1.2 simply aren't
The quality of glass and construction have a lot to do with how bright the final image looks
Cheers
Bruce
LAND ROVER  THE WORLD'S WORST 4X4 BY FAR

 Posts: 123
 Joined: 30 Oct 2017, 19:22
 Location: ireland
Re: A Few Projects
Cheers Bruce,
That's good to know..
It means my old lens was f 2.8 and my new one is f1.7
These don't seem much different on paper but in testing in dark conditions it's a huge difference.
I could never go back to o the f2.8 ! It's sooo dark.
I read that each f stop on a camera is a doubling of light.
F1.0, f1.4, f2.0, f2.8 , f4.0 etc each is half the light of the previous.
So going from f2.8 to f1.7 is three times more light (f1.7 is middle between f1.4 and f2.0)
That explains my experience above, three times more light is a massive improvement in anyone's book.
Wonder what the bhphoto lens measures ?
It's claimed to be f1.2 so the objective should be 13mm or so ...
That's good to know..
It means my old lens was f 2.8 and my new one is f1.7
These don't seem much different on paper but in testing in dark conditions it's a huge difference.
I could never go back to o the f2.8 ! It's sooo dark.
I read that each f stop on a camera is a doubling of light.
F1.0, f1.4, f2.0, f2.8 , f4.0 etc each is half the light of the previous.
So going from f2.8 to f1.7 is three times more light (f1.7 is middle between f1.4 and f2.0)
That explains my experience above, three times more light is a massive improvement in anyone's book.
Wonder what the bhphoto lens measures ?
It's claimed to be f1.2 so the objective should be 13mm or so ...
Re: A Few Projects
You're correct about the doubling (or halving) the amount of light passing through a lens with each full f stop
The amount of light passing through a lens depends on the surface area where the light enters the lens (the objective) and surface area is related the square of the diameter (pi r squared and all that)
In an f 1.0 lens, the diameter of the lens is equal to it's focal length, and if the amount of light entering the lens is reduced by half, the the area of the lens is reduced by half.
Reducing the area by half means reducing the diameter by the square root of 2 which just happens to be 1.4
Therefore a lens with an aperture of f 1.4 will pass half the amount of light that a lens with an aperture of f1.0 will pass
Similarly an f 2.0 lens will pass 1/4 the light of an f 1.0 lens (the square root of 4 is 2)
An f2.8 lens will pass 1/8 the light of an f 1.0 lens (the square root of 8 is 2.8)
etc, etc
Cheers
Bruce
The amount of light passing through a lens depends on the surface area where the light enters the lens (the objective) and surface area is related the square of the diameter (pi r squared and all that)
In an f 1.0 lens, the diameter of the lens is equal to it's focal length, and if the amount of light entering the lens is reduced by half, the the area of the lens is reduced by half.
Reducing the area by half means reducing the diameter by the square root of 2 which just happens to be 1.4
Therefore a lens with an aperture of f 1.4 will pass half the amount of light that a lens with an aperture of f1.0 will pass
Similarly an f 2.0 lens will pass 1/4 the light of an f 1.0 lens (the square root of 4 is 2)
An f2.8 lens will pass 1/8 the light of an f 1.0 lens (the square root of 8 is 2.8)
etc, etc
Cheers
Bruce
LAND ROVER  THE WORLD'S WORST 4X4 BY FAR

 Posts: 77
 Joined: 08 Feb 2016, 23:58
 Location: Virginia
Re: A Few Projects
The bhphoto lens is 16mm diameter. I measured it and it is also shown on the marshall electronics lens drawing.
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