The Mysterious El-Zoom Nikkor

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J_Rogers
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The Mysterious El-Zoom Nikkor

Post by J_Rogers »

I just acquired this monster of a lens. Not entirely sure how well of a tube/ macro lens it will be just yet, but ill begin testing in the coming days. Construction quality is that of some of the Nikon Rayfact lenses. Superb. Weight is roughly 15 pounds. Cant use any of my optical stages due to the massive offset cantilever load so I will likely have to source and dedicate a vertical milling stage just to mount it [must be mounted vertically to be able to focus/zoom?.] DC motors are Swiss made ESCAP's with a potentiometer wired to each one. Oddly the aperture motor, which is the motor closest to the mounting bracket is the only one wired as a true potentiometer. The lower one controlling zoom is wired as a rheostat. Due to the unknown conditions at time of purchase I was dreading having to pin it out on an oscilloscope but it appears to be originally controlled all via a central CPU unit with a simple power on power off scheme. Date on both of the potentiometers read February 1989. Cables are all branded Hitachi. Lens coating is also rather strange looking, in the realm of most common lenses, I can only compare it to that of some of the Ultra Micro Nikkor's. I dont think its the exact same but its definitely deep purple. --Ill try to upload some full size images somewhere and attach links.

Discussed by Enrico Savazzi here [ bottom of the page]: http://www.savazzi.net/photography/enlarger_lenses.htm
The only comparable looking lenses are seen on this Red Book page: https://redbook-jp.com/redbook-e/ultra4/d010.html
side view.jpg
top view.jpg
potentiometer.jpg
lens-2.jpg
lens-1.jpg
Edited to fix aperture photos I was in a rush taking all of these photos, but this is a diode pumped solid state laser (excellent beam dispersion properties) focused down to 1mm. 1st image is showing aperture blades. Not centered. Micro Nikkor 55mm 2.8 & f4 handheld about 1/4 inch from back of the lens focused on blades themselves. I didn't bother taking off the rear lens cap, which is actually an AR coated flat sheet of glass held on with a retaining ring. 2nd image is lens touching rear lens cap at the full extension of my Micro Nikkor (1:2 repro ratio) & laser distance is same as before just centered better. Focus point was give or take 7-8 inches away. Simply for some reference, ill do more precise measuring tomorrow.
aperture.jpg

J_Rogers
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Re: The Mysterious El-Zoom Nikkor

Post by J_Rogers »

Here is the 2nd aperture photo discussed above.
aperture-2.jpg

Scarodactyl
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Re: The Mysterious El-Zoom Nikkor

Post by Scarodactyl »

This looks like it could be an amazing lens. I'll look forward to hearing more!

J_Rogers
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Re: The Mysterious El-Zoom Nikkor

Post by J_Rogers »

Update: This lens appears, at least in my opinion, to be the big brother of the older 1x-4x Printing Nikkor 150 f2.8. I have been able to achieve minimum magnification at roughly .75x, and been able to achieve 6.5x towards the top end. On the topic of maximum magnification; this lens still has more to give, at least 20% more in terms of "zoom" rotation. I wont be able to test true maximum magnification until I can rigidly mount my camera to it. At 6.5x the extension is give or take 22 INCHES on top of the 10 inches of the lens and an additional 120mm of working distance. I dont want to comment just yet on true working distances because the optics are rather puzzling. I have been able to achieve identical magnifications at minimum 2 possibly 3 different extensions, zoom amounts, and working distances.

The one thing I have noticed, and maybe some of y'all can help confirm it, is the image circle appears to be gigantic. Bigger than the Printing 150mm & I would like to say larger than the Printing 105mm. At minimum magnification I can just about move the camera over a few millimeters and tilt the camera at a 45 degree angle in any orientation and still get a nice picture.

Aperture is something I have yet to make any conclusions about. Other than the fact it is as sharp as can be wide open, and only when stopped down half way does the image circle start to shrink. 3/4 of the way stopped down is when I start to see vignetting on my crop sensor.

Images are by no means an extensive test since im still hand holding a camera above this lens. Any aberrations are almost guaranteed to be caused by me tilting the camera or the fact I havent even taken the rear lens cap off which is just a piece of flat glass ( im trying to avoid getting dust inside from my make-shift cardboard & felt bellows.) Also please note for anyone reading in the far future these pictures are probably not in "perfect" focus. I'm still trying to come up with a way to properly test this / focus stack.
lowest magnification uncropped
lowest-mag-full-frame.jpg
these are 1/16 inch gradations on a measuring tape- 100% crop
ruler 100 percent crop.jpg
college ruled paper has a spacing of about 7.1mm. full size image
half-zoom-full-size.jpg
here is a 300% far corner crop of a pack of crafting stickers (nearest neighbor resampling to get it to size)
300% corner crop.jpg

J_Rogers
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Re: The Mysterious El-Zoom Nikkor

Post by J_Rogers »

To better document this completley unknown lens here are some more measurements.

This is the lens cap I've mentioned flipped upside down.
-Outermost major diameter: 85.4mm
-Top inside diameter (in the photo its on the bottom): 57.59mm
-Inside threads major diameter: 78.95mm point of binding is exactly 79.00mm so its likely a high tolerance class 79mm
-Thread pitch 1mm
lens-cap-ring.jpg
This is the numbered ring that sits on the outside of the mounting plate. It can travel all the way down and come off the threads from the bottom side. This leads me to believe it acted as some type of slip nut style fastener for added security when mounted. I'm not sure what the numbers are for other than the fact that the only position to thread it on is when 0 is lined up to the white arrow on the mounting plate.
-11.00mm thick
-Overall diameter 170.70mm (148.70+2x(11.00))
-14.20mm tall
-Inside threads major diameter 148.70mm
-Thread pitch 1mm
numbered-ring-2.jpg
This is where the lens cap screws on. I havent bothered to take off this mounting plate to accurately measure the inside diameter and the threads its currently on. It appears to be made of some high quality high carbon steel or some compound metal. The actual singular lens thread I was able to measure was 59.90mm. Which should place it outside of the 60mm metric threads but its right there at it. I cant confirm which it is nor the thread pitch.
locking-hub-nut.jpg
A view of the inside mechanisms, or at least all that I could easily photograph.
inside-of-lens.jpg
Would also like to note that it is definitely a quality lens coating. I have performed my usual procedure of 70% distilled water 30% 3M Novec 71IPA with a drop of Palmolive pure+clear using mil-spec lens tissue followed by a 50/50 solution of diethyl ether and ethanol using a pec-pad with absolutely zero problems.

rjlittlefield
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Re: The Mysterious El-Zoom Nikkor

Post by rjlittlefield »

J_Rogers wrote:
Sat Aug 21, 2021 9:11 am
Aperture is something I have yet to make any conclusions about. Other than the fact it is as sharp as can be wide open, and only when stopped down half way does the image circle start to shrink. 3/4 of the way stopped down is when I start to see vignetting on my crop sensor.
This is an interesting observation.

As background info, note that vignetting happens when two limiting apertures fight with each other, so that fewer light rays can reach the corners of the sensor than can reach the center. Stopping down one aperture will not cause vignetting, unless there is another limit lurking on the sidelines waiting to cause problems.

So now I'm curious. The location of one aperture is obvious: that's the iris that you're stopping down. But then when you stop down the iris, what blocks the light that would otherwise pass through the iris to reach the corners of the sensor?

--Rik

chris_ma
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Re: The Mysterious El-Zoom Nikkor

Post by chris_ma »

Great find, very curious how it performs.

Could it be a lens from a Noritsu machine?
Found a picture of a similar looking lens here:
https://www.worthpoint.com/worthopedia/ ... 1790752167
chris

Scarodactyl
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Re: The Mysterious El-Zoom Nikkor

Post by Scarodactyl »

Don't zoom lenses sort of inherently stop the image down at lower magnifications? Or at least they can be designed to. Maybe that's involved with the vignetting.

rjlittlefield
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Re: The Mysterious El-Zoom Nikkor

Post by rjlittlefield »

Scarodactyl wrote:
Sat Aug 21, 2021 2:58 pm
Don't zoom lenses sort of inherently stop the image down at lower magnifications? Or at least they can be designed to. Maybe that's involved with the vignetting.
Zoom lenses at fixed f-number always make the entrance pupil get smaller as the focal length gets shorter. That's an inevitable feature of the math, since f-number is defined as focal length divided by entrance pupil diameter.

But vignetting is a different problem. We often see vignetting when a zoom lens is used as a tube lens, because the apertures in the front and rear lenses conflict with each other away from image center. In that case the zoom/tube lens would not vignette by itself, looking toward a distant wide angle scene, but when you stick the other lens in front its aperture blocks some of the rays away from center. Similarly you might see vignetting because of a lens hood, where the hood blocks light rays that the lens would otherwise accept from the corners. Sometimes you get vignetting because of an extension tube that is too narrow, so corner rays are blocked behind the lens. In every case, it's not the lens aperture by itself that causes the vignetting; it's always in combination with something else that also blocks light rays. I'm curious about what the something else is, for this lens.

--Rik

J_Rogers
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Re: The Mysterious El-Zoom Nikkor

Post by J_Rogers »

I suspected it was likely an error on my part, as opposed to some hidden element of the lens creating an unknown field stop (I think that is the right term). So I rebuilt the cage that I had initially used to mount it. Used a Bishop-Wisecarver Hepco track as a temporary mounting position for the camera. It was about the only thing I had to mount to a 2x4 in which I could then mount the camera high enough above the lens. Bellows is 4 inches of Thorlabs SM2 tubes, coupled to 4 inches of SM3 tubes, with the remaining working distance comprised of a solid piece of rolled up black felt touching the lens flange & shoved inside the Thorlabs tubes. Haven't bothered on a temporary focusing contraption, as im just waiting to order something that will work & accommodate everything.

With all that said, this test should be more reliable and accurate. Calculated magnification: 3.7x. Working distance: roughly 145-150mm. Extension: exactly 32 INCHES from lens flange to Nikon D3300 flange. Image is still not in crisp focus. Images go from left to right then next row, so on, and so forth. Single speed light at 1/4 power located about a foot away. Light source in the images is coming from the top pointing down. I tried to get as even spacing from the different aperture adjustments as I could, but I have yet to make a program for the motors themselves to be controlled so its as good as I can get at the moment. There is a piece of lint from the felt in 2 frames, and there is an odd banding partially visible on the bottom 2% of the images. Once again likely attributed to my own personal error in terms of either bellows shifting or camera motion. I repeated the test at a different lighting position and lower intensity, and picked a few aperture positions & the banding was gone. So it was one of the above (see noted image.)

Composite of the Full Images
composite-light-comparison.jpg
First Three Shots. Increasing Order.
first-three.jpg
Last Three Shots. Decreasing Order. Sorry.
last-three.jpg
Here is the different image mentioned above. This is at maximum aperture on the lens I cut the power by 2 & moved the speed light a few inches trying to replicate the bottom banding noticeable towards the last few shots. The raw image was awfully dark, on purpose, so the camera raw settings to get to the following image was -> exposure +1, contrast +100, shadows -100, blacks -100, dehaze +100. I really wanted any image / light imperfections to stand out. While not perfectly uniform lighting, it does give an idea of image circle and quality.
example-case-from-max-aperture.jpg
My overall conclusion is that my previous comments on image circle was due to a compounding of high magnification, extreme extensions & distances, light fall off, and a huge image circle in and of itself. The vignetting was almost certainly there to some extent, albeit just not in the true "center" of the frame. Imagine taking a Christmas wrapping paper tube and holding it to a window, eventually with enough angle you'll see a wall it was mounted on. I think that's what was happening there.

When I get a few extra minutes ill try this test again at lowest magnification and see what changes.

J_Rogers
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Re: The Mysterious El-Zoom Nikkor

Post by J_Rogers »

chris_ma wrote:
Sat Aug 21, 2021 1:52 pm
Great find, very curious how it performs.

Could it be a lens from a Noritsu machine?
Found a picture of a similar looking lens here:
https://www.worthpoint.com/worthopedia/ ... 1790752167
Yes that is it. There was also another listed on eBay not too long ago. Not sure if it's still there or not. I do have to laugh at the description of "wonderful glass" because I can see some specs on the outermost element. If that's wonderful, mine would have to be "new-open box" because I can shine a light through it and there isn't even the first trace of dust.
My biggest question with the lens is what on earth did it actually go in. I am by no means a photographic history expert, but I do not know of any minilab's that could even remotely accommodate the insane distances that's required for it. No serial numbers documented in the extensive Nikon list, no mention in theBig List of Enlarger Lenses. Last places that I need to check are the Nikon anniversary books by Uli Koch, though I need to buy them first.

Playing around with the curves adjustment & one of the images on the WorthPoint listing shows a serial number of 184123. That eBay listing I mentioned had a serial number of 184598. And mine has a serial number of 185006.

chris_ma
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Re: The Mysterious El-Zoom Nikkor

Post by chris_ma »

J_Rogers wrote:
Sun Aug 22, 2021 2:27 pm
My biggest question with the lens is what on earth did it actually go in. I am by no means a photographic history expert, but I do not know of any minilab's that could even remotely accommodate the insane distances that's required for it. […]

Playing around with the curves adjustment & one of the images on the WorthPoint listing shows a serial number of 184123. That eBay listing I mentioned had a serial number of 184598. And mine has a serial number of 185006.
Interesting, that seems to indicate that it‘s well possible 1000 lenses have been made.

The noritsu scanners were usually for 135 and 120 film, I have no idea of the sensor size in various models, but it seem unlikely they were larger then FF, so I‘d expect magnification more in the 0.25x to 1x range. Why on earth would they need 3x or even 6x?

Maybe the lens was actually used the other way around?
That still wouldn‘t solve the question of the long optical path though. Very strange.
chris

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Re: The Mysterious El-Zoom Nikkor

Post by rjlittlefield »

Assuming this is the same type lens, then Enrico Savazzi's page offers the following description:
The EL-Zoom-Nikkor for Noritsu 99-230 mm f/8 (above) is, with good margin, the largest enlarger lens in my collection. In fact, it is quite a bit larger than a 500 mm or 600 mm f/8 catadioptric lens. It is shown here with the EL-Nikkor 50 mm f/4 for size comparison. The EL-Zoom-Nikkor is a true parfocal zoom like the Betavaron, but is not meant to be used with a manual enlarger.
The way I read this description, especially the magic word "parfocal", the lens is designed to be used in a configuration where the lens is fixed in position with respect to both the sensor and the focused subject, and in that configuration the zoom control will change the magnification without changing the focus. Enrico notes that he does not know the "focus distance, which must be used if the zoom is to remain parfocal."

It seems to me that if you want to learn how the lens was intended to be used, then a good approach is to find the parfocal configuration first, then measure the min/max magnifications in that configuration.

There's probably some clever way to compute the parfocal configuration, given measurements of focal distances and magnifications in other configurations. But I expect that it's simpler and more reliable to just search for the parfocal configuration directly by repeated trials.

--Rik

Scarodactyl
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Re: The Mysterious El-Zoom Nikkor

Post by Scarodactyl »

I'd use the same procedure as setting up a stereo microscope. Zoom to maximum mag at a given camera distance and change subject to lens distance to get it in focus, then zoom to minimum mag and adjust the camera distance to get in focus. Repeat a few times and you'll quickly converge on parfocality if it's possible (ie, there aren't other optics needed). I will note I have a mitutoyo enlarger zoom lens that I was not able to get parfocal with this method, but then again that one definitely had other optics in its original configuration (and not ones meant for our kind of usage).

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Re: The Mysterious El-Zoom Nikkor

Post by rjlittlefield »

Depending on the configuration, for example reducing versus magnifying, I can imagine that Scarodactyl's process might diverge instead of converge.

If that happens, then try reversing the association: zoom to max and change camera distance, zoom to min and change subject to lens distance.

--Rik

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