This is a potentially a pointless endeavour, but I'm looking into trying to assemble a mirrorless camera using a CCD sensor mounted to the back of an M42 lens using a series of converters.
Primarily, I'm doing this as a learning exercise in developing image capture software and to understand optics a bit more, however as an affectation, I would like to install the components in an old SLR body.
Due to the size of the sensor unit attached to the lens, it will extend back into the body where the mirror currently sits, so if I were to use the existing viewfinder, it would have to be converted to digital.
As it stands, my plan is to place a small LCD display where the focussing screen currently sits, and route the output from the CCD sensor to that LCD, effectively turning the viewfinder into a digital unit with a prism in it.
There will be no autofocus on the CCD, so all focussing will have to be done via the lens itself.
When the shutter release button is pressed, the LCD display will be turned off, and the CCD signal will be saved to a file, after which time, the LCD will be switched back on, essentially making a digital viewfinder.
Retaining the prism would allow me to use a larger (and cheaper) lcd than in commercial digital viewfinders, but at the expense of weight and size of the viewfinder assembly.
What I would like to find out is whether the split ring on the focussing screen will still work to aid focussing with an LCD attached to it directly. My gut feeling it that it wont, as the split ring will effectively be focussing on the LCD surface, rather than a real world view - is this assumption correct?
If this is indeed a dead end, if I were to remove the focussing screen completely and replace it with an LCD, assuming that I orient the image on the LCD correctly, would it be possible to view it through the viewfinder, or does the angle of the mirror when the shutter is closed play a part in the way the image is presented in the eyepiece?
Any help in this would be appreciated. I'm very new to photography, but have a background in software and electronics so the technical side should be feasible if it transpires that the optics will do the trick.