Magnification of INON wet lenses

[JohnN]

I've added a INON UCL-165 lens to my Canon housing and enjoy the increased magnification, but am mystified by what actual magnification I'm getting, what would happen if I doubled up another UCL-165, what distances should I expect the camera to successfully auto-focus, ahd how much my field-of-view would shrink

I see other lens(s) advertised in diopters, but the "165" on the UCL only apparently specifies the focal length of the lens (16.5 cm), but that seems to contradict the auto-focus range the camera displays.

Can someone bring these mysteries into focus for me, please?

 

[JohnN]

Bump. Hoping for an answer

 

[bvanant]

The Inon UCL-165 is about a 6.5 diopter strength
Here is how to do the calculation
Magnification = focal Length of lens / focal length of Diopter
where the focal length of the diopter = 1000 / diopter strength.
(another way of putting it is Diopter strength is reciprocal of it focal length in metre)

or if you are lazy go to Keri Wilk's page and plug in the numbers
https://reefnet.ca/products/subsee/

Bill

 

[JohnN]

The Inon UCL-165 is about a 6.5 diopter strength
Here is how to do the calculation
Magnification = focal Length of lens / focal length of Diopter
where the focal length of the diopter = 1000 / diopter strength.
(another way of putting it is Diopter strength is reciprocal of it focal length in metre)

or if you are lazy go to Keri Wilk's page and plug in the numbers
https://reefnet.ca/products/subsee/

Bill

So how does the calculation work if I stack two UCL-165's?

 

[bvanant]

The diopter strength of two stacked diopters is simply the sum of the two. That is why diopters are handy. You can treat two +6.5 diopters as a single 13 (more or less).

Bill

 

[JackConnick]

Whoa, gonna have to wrap my head around those equations.:bonk:

Or what he said; Just add them up...

I will add that stacking diopters can usually add chromatic abberation and other wierdness, particularly on the outside edges.

 

[bvanant]

Actually the math is a bit more complex, but for diopters in general add the two numbers together to get the final diopter strength. A diopter lets you shorten the minimal focal length but does not magnify.
The equation is for focus distance is

The equation for magnification factor is

which is pretty much what I wrote in 2015.
Note that magnification is linear with D while the amount of reduction of focal distance is not,
Bill

 

[CWK]

Actually the math is a bit more complex, but for diopters in general add the two numbers together to get the final diopter strength.

Does this break down or no longer hold true after a point?

I stacked the UCL165 (+6) on a SMC-1 (+13) and the magnification measured by eye was about the same as stacking a UCL 67 (+15) on a SMC-1 (+13).

 

[bvanant]

Well it actually breaks down quickly, the math is based on the "thin lens" approximation. One concern is that with the 15+13, you probably can't get physically close enough to benefit from the magnification.
Bill