Author Topic: Need for Speed Redux  (Read 1598 times)

Birna Rørslett

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Re: Need for Speed Redux
« Reply #30 on: March 06, 2023, 17:18:45 »
That would likely depend on the colour balance set?

MEPER

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Re: Need for Speed Redux
« Reply #31 on: March 06, 2023, 19:53:47 »
Ok....yes....the white-balance?   ....if it is set to auto or pre-set or set in post processing?
The light up there in the north may have more blue color now than during summer time?

Birna Rørslett

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Re: Need for Speed Redux
« Reply #32 on: March 06, 2023, 21:11:14 »
My Nikons are usually set to Auto w/b. That tends to bring colour rendition into the ballpark as it were.

The 'X-Ray' class of lenses are not designed for white light thus there is no guarantee their output is neutral. However, I haven't seen major colour casts from the optics itself. The Rodenstock and the Oude Ddelft lenses render colours slightly different as well.

MEPER

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Re: Need for Speed Redux
« Reply #33 on: March 06, 2023, 21:40:10 »
It is a quite interesting look. "Film" like color. A bit "pastel look"?
I tried the Kodak Ektar 100 yera ago. Think it reminds me a bit of Ektar 100 color look.

My Z50 is also set to Auto.
I wonder if the manuel pre-set D1, D2 etc is where you shoot a calibration target. I have not yet spent any time on the white balance options.

Chip Chipowski

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Re: Need for Speed Redux
« Reply #34 on: March 07, 2023, 04:46:54 »
A key to understanding these lenses, and how to use them for actual shooting, is to learn the actual image circle projected and its behaviour when focus varies. The image circle at infinity focus is approx. 23mm for the Rodenstock TV-Heligon 50/0.75, and at least 26mm for the Oude Delft Rayxar 50/0.75. The circle is smallest at infinity focus and will enlarge as the lens is focused closer. Concomitantly, field curvature, spherical aberration, and coma increases and eventually will be manifested also in the near centre of the frame.

In the typical X-ray application, two superfast lenses with apertures in the f/0.7-f/1.1 range were used either facing front to front or back to back. The usual close-focus loss of lens 'speed' was  avoided by the design, thus very weak X-ray images could be viewed on a TV monitor and/or recorded onto film. as shown below


From forum.mflenses.com



The TV-Heligon obviously was intended to transport the image onto TV. The initial record was through a corresponding XR-Heligon lens. The rôle of the Rayxar apparently is similar to that of the XR-Heligon, if I understood the [Italian] description at http://www.marcocavina.com/articoli_fotografici/Rodenstock_De_Oude_f_0,75/00_pag.htm . For our photographic applications, either system could be put to good use.

Another Norwegian, Espen Susort, describes his modification of the Rodenstock for Sony A7 cameras here: https://espensusort.no/2021/03/rodenstock-50mm-f-0-75-4/. I just became aware of his posts when my own adapters had reached the first prototype stage. Evidently, the additional 2mm of register distance of the Sony cameras created additional issues in the quest for infinity focus. His comments and the published test image for infinity focus clearly indicates he couldn't quite reach true infinity focus with his setup. He claimed best performance from 1.5 to 10m which is not consistent with my own observations. The lens indeed is at its sharpest for infinity focus, as it should be, and the performance graciously declines when the lens is focused closer. This behaviour is shared between the Rodenstock TV-Heligon and Oude Delft Rayxar lenses, and reflects the design criteria for their intended application as a component of a tandem relay system for X-ray machines.

Thus, the quality section of the projected image circle might be quite small, but with judicious framing of the subjects, we can make interesting images with most or all of what the lens projects. The aberrations increase very rapidly outside the core area, as evidenced below where I show the peripheral part of a Z9 frame done with the TV-Heligon. This was a blue-hour capture done well after the sun had set and thus the street lamps provided intense point-light sources.

Also note that even with the lens focused to a subject approx. 500m away, the depth of field still is inadequate to include much of the middle ground subjects. Consider the vintage of the lens and the effective speed of f/0.75, the lens really is amazingly sharp in the central parts of the frame. The designers needed 9 high-refractive elements in 6 groups to achieve such a performance, which obviously came at a considerable expense in its time.

The point light sources here are captivating!  Like a bird to an angel to a fish! 

Birna Rørslett

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Re: Need for Speed Redux
« Reply #35 on: March 07, 2023, 11:06:44 »
The most mundane objects take on a nice glow through the 'eye' of the superfast lens, in this case, De Oude Delft 50mm f/0.75 Rayxar on the Z9.



Pink iron is of course a favourite in my new existence :)

In principle, I could have obtained the similar image with this lens on the Z30, because the latter camera in its present state allows focusing the Rayxar to approx. 2m distance before there is a conflict between the rear end of that lens with the film gate. More work with a scalpel or Stanley knife is required :) For the Rodenstock TV-Heligon, having a smaller rear end, there is no conflict and this lens will go all the way to infinity even on Z30.

Birna Rørslett

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Re: Need for Speed Redux
« Reply #36 on: March 09, 2023, 10:21:37 »
Another close-up with the Oude Delft lens. Again on the Nikon Z9 and I was able to utilise most of the FX frame for this capture..



The sharpness of this lens even for closer scenes is surprisingly good. However, compared to modern optics, the image contrast is fairly low and remediating steps might be required in the post-processing stage, at least for some subjects I'd presume.

Erik Lund

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Re: Need for Speed Redux
« Reply #37 on: March 09, 2023, 11:10:17 »
Very nice soft smear and Bokeh transition
Erik Lund

golunvolo

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Re: Need for Speed Redux
« Reply #38 on: March 09, 2023, 17:15:14 »
Love how it creates the background out of "nothing". Everithyng Get new meaning and body through the lens

Birna Rørslett

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Re: Need for Speed Redux
« Reply #39 on: March 13, 2023, 07:05:46 »
Very early morning blues at the first crack of dawn. A challenge for the Rodenstock TV-Heligon 50mm f/0.75, here on the tiny Z30.


Birna Rørslett

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Re: Need for Speed Redux
« Reply #40 on: March 16, 2023, 09:37:35 »
Action shooting with these 'X-ray' lenses is both funny and frustrating at the same time. One really has to do an approximate initial focusing to be able to catch any moving subjects, due to the fine-pitched threads of the focusing adapter. It is doable, though, here with the Rodenstock 50/0.75 grafted onto the tiny Nikon Z30. I cropped the frame to include the centre which shows less issues with smearing. Still a good number of pixels left.



As the shutter speed of the Z30 maxes out at 1/4000 sec and the lowest ISO is 100, I now add an ND 8X to the lens for daytime shooting with the Z30. This is not mandatory for the Z9 if I set the camera to ISO equivalent 32 as the top 1/32000 sec. speed usually suffices.

Birna Rørslett

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Re: Need for Speed Redux
« Reply #41 on: March 16, 2023, 10:13:25 »
The Rodenstock 50mm f/0.75 is excellent for shooting buildings !! This is one of the tallest buildings in Oslo and only the bridge in the foreground discloses the peculiar character of the image circle of this superfast lens. An ND8X filter was added to the Rodenstock as the tiny Z30 only has a top speed of 1/4000sec which is insufficient to deal with the light transmitting ability of the f/0.75 lens. As here, almost at infinity focus, the true nominal f/0.75 aperture is manifested and most if not all colour aberrations vanish as well.

The vantage point was too low to get the entire building rendered and I couldn't move back further lest I should fall into the Oslo Fjord :)


Birna Rørslett

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Re: Need for Speed Redux
« Reply #42 on: March 17, 2023, 11:29:13 »
Shooting the Rodenstock 50mm f/0.75 on the Nikon Z30 is advantageous firstly because most if not all of its DX format can be used for the final photograph, and secondly because pixel density is slightly higher than on the Z9. On the flip side, one cannot get the 'crystal ball' look with the DX camera since the projected image will be cut off.

With the Z30, an ND filter usually is required for daytime shooting lest massive overexposure should occur. The top 1/4000sec. shutter speed is *slow* when it comes to this kind of ultrafast lens :)

This early morning I required ND8X on the Rodenstock to bring exposures on the Z30 into range.



Although inherent image contrast is low and even lower during a thick snow fall, there is plenty of image detail to pull out in post-processing.

Birna Rørslett

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Re: Need for Speed Redux
« Reply #43 on: March 18, 2023, 13:27:53 »
For portraits, the  'X-ray' lens comes into the middle-to-near range in which spherical aberrations creep in and softens the image. Still, the 'X-ray' effect can be pushed further to enhance the final outcome.



A portrait of one of my transgender friends. She enjoyed the portrait :)

Achieved with Rodenstock TV-Heligon 50mm f/0.75 on my Nikon Z30.