Re-packaged my opteka lenses by unscrewing the retaining rings, and carefully layed thing strips of insulation tape around the inside of the holder. This was to keep the lenses central and prevent them moving about when tightening the retaining ring.
Have been beavering away at trying to balance this thing out and got something I was happy with. Went and filmed some bits and pieces at my parents on Sunday taking it in turn with each camera. Got back and found that in some of the stuff I shot through the adapter there was a softening of the image down the right hand side, while the center and left both look fine. Very disappointed. Got back and found that the one remaining taped joint (still awaiting the last metal filter adapter ring from china) was slightly lop-sided. Decided to glue the joint with epoxy and made a perfectly straight tube. Alas, now I am unable to get a crisp focus on the left hand 20 percent of the screen. If you rotate the whole adapter 180 degrees, keeping the camera where it was, I still get a slightly blurry left hand side. Sigh. Tried many times and with both HV20s, but after hearing mention of the HV20's sensor being off center on several places online I realised that the remaining misalignment may not be something I cant compensate for.
Messed around on monday and found some position where I could get left, right and centre to achieve better focus by splitting the adapter in two and leaving one piece at a slight angle to the other. But this may be exagerating the uneven bokeh issue I had seen. Not sure if the optics would still work the same when upside down. I have now decided it is just not worth carrying on for something which:
1) Adds some chromatic abherration.
2) Has uneven bokeh near the extreme left/right for objects just slightly out of focus (though I have seen the HV20 also do this sometimes)
3) Which is impractical to use, particularly if trying to compensate for an off center sensor.
4) Although seems to offer some shallower DOF with telephoto lenses, given the above issues I don't think its worth the effort
So at this point I am throwing in the towel. I shall publish my final design in a few days and some pictures showing equivalent HV20 vs Nikon lenses shots. This is in the hope that if someone ever wants to try it for themselves and take the design further they may at least save some time. Sorry guys, but I really had high hopes for this at the start and Ive put in a lot of time and effort to get it to this stage. I may be a little harsh in my assessment above, as some of the things mentioned may not be noticable except in certain circumstances. Have a look at the pictures when I put them on (probably the weekend) and you decide.
I will use my canon as nature intended for now but may buy a cheap secondhand AF101 or maybe the Blackmagic cinema camera when it goes on sale in a few months