Need for Speed Redux

[Birna Rørslett]

That is a very creative setup for online meetings 

Yes, apparently it is. People keep asking me about the "special" filter I'm using ....

[Birna Rørslett]

I finally got around to trimming a focusing adapter for the Oude Delft Rayxar 50mm f/0.75 lens, to allow it to be used for infinity. The problem with this lens is of course the extremely short back focus, around 0.8 (!) mm, which means that during experiments, the likelihood of scratching the sensor is very high. In fact, it is near unavoidable.

In the previous attempt, I damaged the shutter cover curtains on my Z9. This won't prevent the camera from being used, as the curtains only functions as a dust shield in front of the sensor (there is no mechanical shutter at all). However, seeing how easily one can unintentionally scratch the sensor surface led me away from using the Z9 for more experiments of this kind. The tiny Z30 is rather inexpensive, provides a lot of pixels to allow full use of the 50mm "X-ray" optics, and happily accepts my Rodenstock TV-Heligon 50mm f/0.75 even for infinity (ab)use; however the internal opening is insufficiently wide for the rear portion of the Rayxar even when the metal shroud around the rear optical block is removed. Besides, the lack of a viewfinder hampers the field use and critical focusing unless the camera is tripod mounted. Which means I should be better off with a finder-equipped body like Zf, Z6, or Z7. Due to the finder overhang, adapting these monster lenses for Zf although possible is not straight forward, so I decided to experiment with a spare Z6 floating around, and aim for final use on a spare Z7.

My experiments are not completed, but I found it necessary to add internal shims to my bespoke mount to ensure the rear part of the Rayxar did not come into contact with the sensor surface. One can readily imagine why this measure was required .

Anyhow, I have now verified the Rayxar 50/0.75 indeed can focus to infinity on the chosen Z Nikons, and due to the shims the scratching danger is mitigated (to some extent).

A proof of concept is shown below, by Z6. Focus here is set to around 100m, to allow the buildings to reside inside a zone of passable sharpness. I had initially focused on the hilltop in the background, but then the frames mostly contained subjects badly out of focus. Thus deemed a little closer would be better. About 20 frames stitched in PTGui. I did these captures with a hand-held camera and didn't fine-tune the stitching, thus there might be the odd mismatch in the final image. However nothing major, presumably.

[pluton]

I finally got around to trimming a focusing adapter for the Oude Delft Rayxar 50mm f/0.75 lens, to allow it to be used for infinity.

The shallow depth of field somewhat mimics the 'wide open lens on an 8x10 camera' look, which I personally like.

[paul hofseth]

If one can accept a smaller image circle in exchange for scratch risk , I would recommend the Schneider 50/0,9 which is reasonably sharp and contrasty. Presumably an "industrial" lens (needing a bit of surgery to remove an internal fixed rear aperture that limits the image circle). I used it on an M4/3 camera with good results without needing anything sticking in beyond the mount.

p.

[Dr Klaus Schmitt]

Impressive Birna!! How clever that adaption is!!
Unfortunately I gave all those ultra-fast lenses away, so cannot replicate what you have done....

[Birna Rørslett]

The first working version for my little Z30 provided infinity focus only with the Rodenstock TV-Heligon 50mm f/0.75. It also showed the danger in using metal-metal focusing helicoids with insufficient lubricstion and remining gunk in the threads ... . Thus the focus suddenly froze and I now cannot remove the lens from its focusing mount. Fortunately, the lens got stuck at a position giving focus at approx. 1.2m, thus now I'm using it for my web camera sessions on Zoom and Teams. I continued with other copies of the Rodenstock TV-Heligons for next series of experimentation.

While it were working, I managed to shot "action" with the massive 50/0.75. Due to the excesively long focus travel, pre-focusing become a necessity. However, results were surprisingly good, as seen here. I had to add an ND 8X filter to keep shutter speeds within the max. 1/4000 of the Z30. Shooting at a manifested f/0.75 in sunshine is not easy unless you can set ISO very low and shutter speeds can go to 1/32000 sec.Z9 csan do this, while Z30 cannot hence the ND filter requirement.  Do note that our common usage before, making close-up shots, never realised the f/0.75 brightness due to the very asymmetric entrance:exit pupil size. Getting to f/0.75 demands focus approaching "infinity" or at least 50m away with the 50mm lens.

[Birna Rørslett]

I finally had my supplier RAFCamera make a bespoke "X-ray" adapter for the Z mount. I sent them a sketch and they returned very nicely finished adapters. Price was more than affordable as well. The adapter, entitled 'M80x1 female thread to Z', can be found at  https://rafcamera.com/adapter-m80x1f-to-nikon-z .

After having played around with the first version with a handful of my "X-ray" items,  I think there are some minor, possible improvements to be implemented in a Mk.2 model. However, as it is now, you do get a rapid solution to put those "speed monters" to some serious use. Provided the rear part of the lens clears the inner opening on the Z models, getting infinity focus is a breeze. For the Rayxars, one might need to remove the outer shroud of the rear group. This will allow infinity focus with Z5/6/7/8/9. The finder overhang on the Zf & Z fc prevents mounting the adapter unless you do a bit of Dremel adaptation.  The DX-sized Z30 can do infinity with the Rodenstock TV-Heligon 50mm f/0.75, but the Rayxars or the Kowa 55mm f/0.8 are too "fat" to allow distant focus. Also, the inherent nominal aperature (f/0.75 for most of my items) is fully manifested meaning an ND filter usually is required in order not to max out the camera's shutter speed.

A quick panorama of the neighbourhood, taken with the Oude Delft Rayxar 50mm f/0.75 on Z7, hand-held exposures f/0.75 @1/2000 sec ISO 50 at dusk (!). 39 frames stitched in PtGui. I did a quick-and-dirty shooting session so partial image matching could have been better, however the outcome serves to demonstrate the potential.

[Birna Rørslett]

The new M80x1>Z  adapter is very neat. I think the collar material could be 0.5mm thicker in order to make the adapter a bit more robust, since the target lenses are very heavy. However, if you add a tiny amount of helicoid grease (#500 for example), the focus travel of the lens gets smoother and that in turn leads to less wear on the Z bayonet mount.

First photo is a Nikon Z7 with Oude Delft Rayxars 50mm f/0.75, taken with Z30 and the APO-Lanthar 65mm f/2 at f/4, the next is the same gear with a Kowa 55mm f/0.8 in the new adapter, mounted on the Z30.

All these "X-ray" lenses focus to infinity on the Z5/6/7/8/9, but the inner frame of the Z30 blocks the rear end of the Rayxars and the Kowa -- the Rodenstock TV-Heligon 50mm f/0.75 works to infinity though. Since the projected image circle is smaller than the DX frame when the lens is at infinity, it is beneficial to deploy these lenses on a high pixel density host camera. The Z30 is excellent for that purpose.

Do note the Z50/Zf /Zf Nikons have a finder overhang that prevents the use of the M80 adapter. I'm working on a bespoke adapter version for these cameras.

[ARTUROARTISTA]

The first working version for my little Z30 provided infinity focus only with the Rodenstock TV-Heligon 50mm f/0.75. It also showed the danger in using metal-metal focusing helicoids with insufficient lubricstion and remining gunk in the threads ... . Thus the focus suddenly froze and I now cannot remove the lens from its focusing mount. Fortunately, the lens got stuck at a position giving focus at approx. 1.2m, thus now I'm using it for my web camera sessions on Zoom and Teams. I continued with other copies of the Rodenstock TV-Heligons for next series of experimentation.

While it were working, I managed to shot "action" with the massive 50/0.75. Due to the excesively long focus travel, pre-focusing become a necessity. However, results were surprisingly good, as seen here. I had to add an ND 8X filter to keep shutter speeds within the max. 1/4000 of the Z30. Shooting at a manifested f/0.75 in sunshine is not easy unless you can set ISO very low and shutter speeds can go to 1/32000 sec.Z9 csan do this, while Z30 cannot hence the ND filter requirement.  Do note that our common usage before, making close-up shots, never realised the f/0.75 brightness due to the very asymmetric entrance:exit pupil size. Getting to f/0.75 demands focus approaching "infinity" or at least 50m away with the 50mm lens.

Birna, it seems incredible that cameras capable of achieving shutter speeds of 1/32000 s exist. Only Clint Eastwood could pull a trigger at that speed.