Nikon 35mm adapter which works! NO focussing screen.
Hi all,
Where do I start? I bought a static Twoneil adapter a few years back and a bunch of Nikon lenses. Was sadly disappointed with the results, particularly the vignetting (dark intrusion into corners of the frame) and the visible grain. Zooms lenses were right out. I must say that this is in no way Twoneils fault, it is what it is.
A few nights ago, at a time which I confess I may not have been entirely sober, I performed a few experiments using bits of the other adapter plus one of the nice opteka 10x macro lens. I was trying to find a way to refocus the output of a nikon lens onto the small sensor in my hv20. After a few hours messing about, I was getting quite astonishing results. Ordered some more extension tubes online, which thankfully arrived saturday. Tinkered further over the weekend, made a few refinements giving me a fully working prototype.
What I have now:
1) Gives bright results. Ive been filming after 8pm in the evening (UK in April) and getting shots that look decently lit. Im using the CINE setting
2) No vignetting (when set up properly). Seriously, no sign of those dark corners.
3) No added grain, the light is focussed straight in and through to the sensor without any optical barrier.
4) No chromatic aberations. Picture looks as good to me as via the HV20s own optics.
5) I believe it is using as much of the lens as there is, no crop factor.
6) If pointing at a flat surface, the centre and the outsides of the picture are on the same focal plane.
7) Depth of field control by choice of lens, not by the iris (explanation below)
8) Manual focussing in a proper way.
9) Sadly, the image is still inverted - oh well, can't have it all I guess.
Depth Of Field
Because there is no focussing screen, it behaves differently to a normal 35mm adapter. What we seem to get is that a wide lens gives quite deep depth of field, whereas a telephoto lens gives quite shallow DOF . The iris on the nikon lens is kept fully open else you see the iris in the frame. A bit ike looking throught the gun barrel at the start of the Bond films.
Ive tried these
Nikkor 35mm 1:2.5 (AIS) -> plenty in focus.
Nikkor 50mm 1:1.8 (AIS) -> slightly shallower DOF
Nikkor 100mm 1:2.8 (AIS) -> shallow DOF (maybe less than 15cm (6 inches) in focus at 1.5m (5 feet))
Once the HV20 has been setup for these (Manual focus) I can swap between these lenses with no problems nor any further calibration required. If you knock the zoom or focus wheel on the camera it needs to be recalibrated again.
I have a 28mm 1:2.8, but I have to add or remove some macro rings and re-zoom/focus to remove black corners. I'd rather stick with the setup that works for the others as I think its pretty much optimal.
Calibration Procedure
1) Set HV20 out of Auto mode and into 'P' mode. Set to manual focus
2) Set focal length on Nikon lens to known distance (e.g 1m)
3) Put something in from of it at that distance
4) zoom out on HV20 till black outer ring shows.
5) zoom in till black ring disappears from view, then a bit further to make sure.
6) tweak focus on HV20 till object is in focus.
I'm going to post some vids and screen captures over the next couple of days, so keep popping back. When some more bits arrive from china, I will attempt to reduce the number of taped joints.
Manufacturing Instructions
To make your own, you will need
2 x nikon macro extension tubes (each containing a #1, #2 and #3 macro ring)
2 x Opteka High definition 10x macro lens (the main body has 55mm threads, but usually ships with screw on adapters front and back)
1 x reel of Electrical insulation tape (preferably black),
1 x dustblower to remove dust from surface of lenses. After its been apart as much as mine has, the threads have ground many small particles loose.
2 x 55mm to 57mm step up rings (probably listed online as for 55mm lens to accept 57mm filter)
1 x 43mm to 55mm step up ring (listed online as for 43mm lens to accept a 55mm filter
Total cost of buying the bits in the UK can be under 70 pounds. The main expense are the opteka lenses which are far cheaper in the States. No special skills required for assembly.
Assembly: (+ indicates a screwed together join)
43mm to 55mm step up ring
+
Opteka High definition 10x macro lens (facing away from the 43mm (HV20) end)
+
55mm to 57mm step up ring
+
#1 macro ring
+
#2 macro ring
Tape join - we reverse direction so the #2 and #3 arent screwed together
#3 macro ring
+
55mm to 57mm step up ring
+
Opteka High definition 10x macro lens (facing towards the 43mm (HV20) end)
Tape join
Nikon lens flange - with siver screw-in parts removed, leaving a well in the centre where the exposed thread of the opteka sits.
tape join covering where direction reverses (exposed thread behind flange buts against exposed thread of #3 ring)
#3 macro ring
+
Nikon lens Flange (ready to accept lens)
Screw to your HV20, fit lens, calibrate and happy filming.
The leftover bits:
A #2 and #1 macro ring.
The discarded siver ring from the nikon lens flange
Both F mount parts from the macro extension tubes
Troubleshooting
The most critical measurement is distance from where the Nikon lens attaches to the back of the opteka. I believe just a few millimeters difference may prevent the outsides and the middle of the frame being in focus at the same time
Conclusion
I was seriously considering buying the Panasonic AF101 when it came out because I wanted to use my 35mm lenses and have DOF control. I'd even bid on one a few days before making this discovery, as the second hand price is getting quite acceptable. With a nanoflash recorder and prime lenses (all of which I already have), the resolution and picture from my HV20 is pretty comparable to that of the panasonic. How cool is that. Spend 60 quid, save a couple of grand!
Reply With Quote
Originally Posted by red5
