Yes, that exactly what I mean. Unfortunately we have only about 2-3mm to move the focal reducer back- or forward, so we will need a focal reducer or something similar with much stronger light bending.
so if a focal reducer were found that put the entire ff image circle on the m4/3 sensor, and a 24mm f2.8 lens had a usable/crisp image at f5.6, then one would effectively have the equivalent of a 12mm 2.8 m4/3 lens?
@DanDOF Sad to here that you got stuck at the same point. But, as I know from my own experience, you learn so much more from trying than only thinking about it...;-)
@andres Yes, 0.5 means half the focal lenght, but only when used in a telescope (these reducers are designed for telescopes). So I would guess the 0.5 only works for parallel light rays. Beeing so close to the main lens and sensor means everything but parallel rays.
@pingpong If you get 20% more field of view, you also gain about 20% in brightness (in ISO or F-stop). Its a bit tricky to calculate as you have to take into account that you start with 20% width, a linear dimension, then convert it to area increase an then go from that to the ISO or F-Stop numbers. Sorry, I can't find the calculations I did when I tested this setup :-( But you really get the light of the bigger image circle on the m4/3 sensor - so if you get all the full frame image down to m4/3 size you would gain 4x the light per pixel = 2 F-Stops (minus the light the focal reducer eats up, but thats only a tiny fraction). With the 50mm F1.4 that would result in a crazy 50mm F0.7 lens!
The image gets more and more of that coma glow when you open up the aperture - a smooth transition.
This is an interesting topic, I think many have the same ideas, glad to see you are putting your hands on it. Funny I thought that a 0.5 reducer would divide the focal lengh by 2 instead it seems like 0.8. In the other thread there is a lot of work, I wonder what lenses have a built in reducer for making that effect.
This really pains me to see. Why? Because I spent 8 months between 2009-2010 developing a focal reducer by doing all the math, prototyping, and considering legal cracks between the definitions claimed in different patents. I did all of this - just to find out the same issue as you've come to - COMA (i.e. field curvature).
I was so looking forward to the day where I presented my product to you all. It sucks to try something and fail, but I learned a lot in the process.
Congrats on what you've done here (as shown in the first post). I'm impressed. I wish I could help get to the next step of solving the physical/optical limitations presented by designing a custom focal reducer + field flattener small enough to fit into the cavity of a m43 body. My dream murmurs in the back of my mind. Oh sigh!
I like the way you're thinking. I bought an early 90's Nikon/Fujix E3 digital camera to chop up for the excellent focal reducer, inside. This lens reduced FF to 2/3 chip size. Damn thing is now worth too much to do it. Next idea was to put an ole delph c-mount anamorphic adapter between the lens and sensor. ....This may just work....