Hello,
I am doing a video camera project where I want to mount an SLR lens 50mm on a small 1/2.3 sensor.
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?
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 are focal distances of a multi part lens measured?
Feedback is greatly appreciated
TL;DR: Where can I learn in depth about lenses and such?
DIY Focal reducer?
