Focal reducers camera project

[Jaron]

Hello,

I am doing a video camera project where I want to mount an SLR lens 50mm on a small 1/2.3 sensor for filming video.
On camera forums I was told that I was nuts, it wasn't possible, I would break the sensor, etc.
But, I see that people here do stuff like this with focal reducers, would it be possible to do this on a camera lens?

I try to make this happen solely with lens elements with a focal distance of 45mm.
(25mm diameter, 5mm thick) (I do this because they are cheap and readily available for me)
I tried doing some calculations myself, but I have some questions and I don't know how accurate my calculations are.

First I want to decrease the focal distance, so I put 3 of them in a row. (because I tried one, and it is not enough)

calculations: *S = SF/S-F*
(-40*45)/(-40-45)=21.18mm (45mm second image 45mm - 5mm)
(-16.18*45)/(-16.18-45)=11.9mm

Now I know the focal distance of the last lens is 11.9mm, but how do I now calculate the focal reduction multiplier from this?
I found on this (http://www.rc-astro.com/resources/reducer.html) website that
R = 1 - (D/Fr)
But from what point in the 3 lens combination do I take the distance?
Also, following this formula, I would be able to make an f0.18 reducer by placing one lens at 36.9mm distance.
This however doesn’t work, why is this?
Also, from where is the new focal distance measured? (taking the example of f0.18, 0.18*50 = 9mm)

Feedback is greatly appreciated :thanx: :)

[redbeard]

Hi,

I'm not so much into the specification side of things but I did put a 50mm lens onto a video camera for a particular purpose.

The reason I did this was to create a microscope. I found that the further away I put the lens from the video camera the greater the magnification. I use this for looking at integrated circuit markings. The distance I used between the video camera and the lens was about 45 - 55mm for my purpose. It was quite high magnification.

Cheers,

Damien.