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"X-ray" lenses for 1x-5x
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Lou Jost



Joined: 04 Sep 2015
Posts: 1798
Location: Ecuador

PostPosted: Mon Oct 30, 2017 9:38 pm    Post subject: "X-ray" lenses for 1x-5x Reply with quote


My new weird X-Ray and microlithography lenses

I brought back a big load of exciting lenses from the US last week. I'll slowly write about all of them. I will start off with the short fat lenses in the front row, the "X-Ray" lenses that are often ridiculed on photography forums.

These are some of the fastest lenses available today, including the so-called “X-Ray” lenses, such as the Rodenstock 100mm f/1.3 X-Ray Heligon and the Canon 75mm f/1.0 X-Ray lens. They are perennial eBay favorites for do-it-yourselfers looking for fast glass, and they are the subject of a lot of misinformation. First off, contrary to some reports, they don’t image x-rays and they are not radioactive. They get their name because they are salvaged from x-ray machines, where they are coupled face-to-face with equally-fast "TV lenses; the coupled pair sends an image of the phosphors of an x-ray detector to a video camera sensor, sometimes with a beamsplitter between the two coupled lenses to send some of the light to expose an image on (monochrome) x-ray film:
http://forum.mflenses.com/where-in-x-ray-machines-are-these-fast-lens-located-t68865.html
https://www.photo.net/discuss/threads/alright-what-the-heck-is-this-also-recommendations.482530/

The fact that these are meant to be used as coupled lenses explains several of their odd characteristics. Marco Cavina (http://www.marcocavina.com/articoli_fotografici/Rodenstock_De_Oude_f_0,75/00_pag.htm) noted that these lenses are optimized for infinity even though they are designed to be used as close-up lenses, which might seem puzzling, but this is exactly how coupled lenses should be designed. This also explains why they have no focusing helicoid; coupled lenses always have to stay focused at infinity. Most of these lenses also have no aperture (some Canon examples are rare and coveted exceptions; I have one with a beautiful 18-bladed aperture), so they may have resolutions that are diffraction-limited in their designed applications.

These lenses are often used in their “normal” orientation (large front element facing forward) by people trying to make close-ups with very shallow depth of field, but even the “sharp” parts of the resulting photos are rarely sharp (https://www.diyphotography.net/converted-rodenstock-50mm-f1-1-x-ray-lens-fit-micro-four-thirds-camera/). This has given the lenses a bad reputation:

“Small children with more money than brains play with these lenses, but they're useless for nearly all photographic purposes.” https://www.photo.net/discuss/threads/alright-what-the-heck-is-this-also-recommendations.482530/

“Two words I have to describe them- Utter Crap.” https://www.getdpi.com/forum/4-3rds-cameras/7407-what-rodenstock-tv-heligon.html

But in reality these are highly corrected lenses with 7-9 elements, designed to be sharp when used as intended. The softness is due in part to the fact that people are mounting them incorrectly. Since they are optimized for infinity, they should be used as intended, as infinity-corrected lenses reversed in front of a tube lens. When used in this way they still have extremely shallow depth of field but are extremely sharp. They could probably be made sharper by placing a one-stop paper aperture between the two lenses; if the aperture is placed at the reversed lens’ front focal plane, the lens pair has the added bonus of telecentricity. I have yet to try this.

Here is my first test, using green light. This is the Rodenstock 100mm X-Ray Heligon at f/1.5, reversed with no aperture on a 300mm Nikkor ED-IF lens. I misjudged the stacking interval so I got severe focus banding, but I'm too tired to do it over tonight. These are from a DMap in Zerene; the PMax showed some astigmatism. No sharpening was used but I did make a slight brightness/contrast adjustment.

Whole image:



100% crop; apologies for the severe focus banding from too large a step size:


This image isn't perfect but it is amazingly good considering it has been made with an f/1.5 lens wide open.

Telecentric stops

For these lenses, the distances from the big front element to the front focal plane, where a telecentric aperture should be placed, seem to fall into two groups: 60-120mm for the nominate x-ray lenses, and 20-30mm for the fast Kowa lenses that look like x-ray lenses but may have some other designed use.

Prices and magnification range

Because almost no one knows how to use them, these are the cheapest fast lenses on eBay today. It is possible to find decent specimens for less than $100. For very little money I accumulated six of them from 50mm to 100mm and from f/0.75 to f/1.5. When used reversed in front of a typical 200mm tube lens, this set covers magnifications between 2x and 4x, with the effective aperture probably determined by the slower tube lens. Used in front of a fast 135mm tube lens like a Sigma or Zeiss, my set of x-ray lenses covers 1.4x to 2.7x, with effective apertures of EA=1.8-2.2 wide open. These are difficult magnifications to achieve at such wide effective apertures using other techniques. Of course these lenses should probably be stopped down at least one stop in practice, but even stopped down a bit, they are still faster and cheaper than most alternatives.

Optimizing image quality

These lenses were probably designed for a particular range of phosphor colors, but I have been unable to discover how precisely they have been optimized. Because of this probable optimization, they almost certainly behave like Ultra-Micro-Nikkors, best used to make black-and-white images with monochromatic green or blue light. But there seem to be several types of phosphors in use. Some phosphor screens used in x-ray imagers emit most of their light near the g-line of mercury (436 nm), so the same light sources used for g-line Ultra-Micro-Nikkors should also work well for lenses that were designed for those phosphors. But other kinds of phosphors may also have been used, so there is probably some variation on optimal wavelengths between lens types.

Nevertheless even when these lenses are used on natural scenes in daylight, no obvious color artifacts are visible in the aerial image (when viewed with a 10x loupe) at infinity, so maybe the optimization is not too extreme. I’ll test this more carefully later. When I was setting up the test image above, using white light did give me colorful halos around bright objects.

All scientific lens designs take into account the thickness of the sensor filter pack or, in the case of these x-ray lenses, the thickness of the screen in front of the phosphors. Unfortunately there is no easy way to know this thickness once the lens has been separated from its host device, so experimentation may be necessary to see what thickness of optical glass works best. I think the best way to discover the designed expectation is to aim the front element at the moon or stars, and place different thicknesses of optical glass behind the rear element, and then examine the aerial image of the stars. The glass thickness that gives the sharpest stars can then be determined. We should shoot through glass of that thickness for best results. Rodenstock gave data about their 68mm X-Ray Heligon’s “cover glass” thickness: it is 4.2mm (https://www.photo.net/discuss/threads/alright-what-the-heck-is-this-also-recommendations.482530/), which happens to be the same as the sensor filter pack of MFT cameras. This will unfortunately take up much of the working distance!

This fits perfectly with my intended use of these lenses, though. I often image specimens in alcohol or water. The liquid acts like a sensor filter pack. A lens designed to shoot through thick glass will also be pretty good at shooting through a layer of liquid.

Important drawbacks

Mounting them reversed involves fitting them with the right male-male coupling ring, or step-down rings and smaller male-male coupling rings, but some of these lenses have such large diameters that it is hard to find appropriate step-down rings. On top of that, some of these lenses have no front threads. It is fairly easy to epoxy rings onto their front flanges.Luckily the commonly-available Rodenstock X-Ray Heligon 100mm has ordinary 72mm filter threads which fit standard 72mm male-male coupler rings.

I’ve already mentioned that these lenses are probably best used with blue or green monochromatic light.

Working distance of these lenses is not very good. All of mine seem to have a working distance (when reversed) that I measure to be about 5-6 mm (with no filter in place). The internet says the exact distance is 6-7 mm.; one source says that the X-Ray Heligons have slightly longer working distances than the TV Heligons. Luckily the rear element (now the front element since the lens is reversed) is quite small and comes in a narrow housing, so lighting is not impossible.

For the specific purpose of making monochrome images of (preferably transilluminated) subjects at low to moderate magnifications, these lenses are extremely good and extremely cheap. I have yet to test the non-Rodenstock versions though.
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Last edited by Lou Jost on Tue Oct 31, 2017 11:00 am; edited 1 time in total
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harisA



Joined: 03 Jul 2011
Posts: 442
Location: Greece

PostPosted: Tue Oct 31, 2017 6:51 am    Post subject: Reply with quote

You have a nice collection of really exotic glass here. I 'm also a fan of x-rays lenses and I have done several attempts to adapt them to various cameras:

https://petapixel.com/2016/02/13/50mm-f0-75-x-ray-lens-into-worlds-fastest-e-mount-glass/



It is difficult to impossible due to very short working distance and the very small image circle.Your best bet will be sony aps cameras. Olympus is not suitable due to lack of adequate space. Of course you can use them as pairs -the way they were designed in the first place-but with but with common telephoto lens as tube lens.If you give me permission I can post some images to your thread taken with an ''improved'' x-ray lens

Finaly I'm looking forward to read your impression from the stepper lens you have bought.
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Lou Jost



Joined: 04 Sep 2015
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PostPosted: Tue Oct 31, 2017 9:55 am    Post subject: Reply with quote

Quote:
"Of course you can use them as pairs -the way they were designed in the first place-but with but with common telephoto lens as tube lens."


Yes, that's the main point of my post, and the method I used to take the example picture of the butterfly wing.

Quote:
"If you give me permission I can post some images to your thread taken with an ''improved'' x-ray lens"


Yes, by all means, you (and anyone else) are welcome to post images on this thread, and to post any information about specific "x-ray" lenses. I would love to see this thread become a central repository for everything we can learn about these seductive lenses.

I will soon start a similar thread for stepper lenses, which are even more exciting. I have nine of them now, including Russian, German, Japanese, and US versions. Some are amazing, some are dogs. Working distance when reversed is almost as bad as with "x-ray" lenses, unfortunately. Immense image circles though, up to 150mm diameter at 5x or 10x!!
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Beatsy



Joined: 05 Jul 2013
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Location: Malvern, UK

PostPosted: Tue Oct 31, 2017 10:57 am    Post subject: Reply with quote

Lou, you are a 'tinkerer extraordinaire'! Love posts like this, and I'm very much looking forward to more installments. Top banana!
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harisA



Joined: 03 Jul 2011
Posts: 442
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PostPosted: Tue Oct 31, 2017 11:23 am    Post subject: Reply with quote

Lou Jost wrote:
Yes, by all means, you (and anyone else) are welcome to post images on this thread, and to post any information about specific "x-ray" lenses. I would love to see this thread become a central repository for everything we can learn about these seductive lenses.

Thank you Lou. These lens are actually medical lenses and have saved the lives of thousands of people.They were the perfect solution to the following problem.''How to project a small fluorescent screen on a camera ccd with the minimum light losses.''

These are not for the faint of the heart. I used to call them ''vampire lenses'' since they hate light and always seeking for the shadows. During the day is difficult to take pics since it will require shutter speeds over 1/4000 at 100iso. If you manage to use them according to their specifications they can be very rewarding.






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Lou Jost



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PostPosted: Tue Oct 31, 2017 11:29 am    Post subject: Reply with quote

Thanks Beatsy, I think there has got to be a gem or two in this set of lenses!!!!
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Lou Jost



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PostPosted: Tue Oct 31, 2017 11:35 am    Post subject: Reply with quote

HarisA, those are nice! Thanks for posting them. You are using the lens with the fat side outward, so you get these nice soft images reminiscent of a Nikkor CRT lens used outside its designed parameters.

I think most people associate these lenses with that soft look. I think it is important that people discover that these lenses also have an exquisitely sharp side, when used as they were designed to be used.
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Lou Jost



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PostPosted: Tue Oct 31, 2017 5:44 pm    Post subject: Reply with quote

HarisA, your second shot shows very nice color, at least at this reduced magnification. What lens is that taken with? Maybe some of these lenses are color-corrected. Maybe the TV versions? If you blow up the sharp part of that image (the lips, it seems), are color aberrations visible?
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rjlittlefield
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Joined: 01 Aug 2006
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PostPosted: Tue Oct 31, 2017 6:57 pm    Post subject: Reply with quote

In case it's interesting:

"The Mesolens: a giant colour-corrected optical microscope objective for sub-cellular 3D resolution within 118 mm^3 of tissue"

www.coolled.com/wp-content/uploads/2017/06/IVSLA-gmcconnell-2017.pdf

4X NA 0.47

But only rated for a 6mm x 6 mm field. And not likely to have hit eBay yet...

--Rik
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Lou Jost



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PostPosted: Tue Oct 31, 2017 7:06 pm    Post subject: Reply with quote

Interesting! I note the working distance is as bad as that of these x-ray lenses though.
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RobertOToole



Joined: 17 Jan 2013
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PostPosted: Tue Oct 31, 2017 7:31 pm    Post subject: Reply with quote

I want to hear more about your microlithography lenses Lou Very Happy

Robert
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Lou Jost



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PostPosted: Tue Oct 31, 2017 7:48 pm    Post subject: Reply with quote

Robert, I am waiting to do more tests on them, but some of them look very promising apart from the short working distances and restriction to monochrome imaging. Optically they have NA as high or higher than typical microscope objectives. One 5x photolithography lens has an NA of 0.30, which would be hard to beat with any a 5x objective, and it has a gigantic image circle that is perfectly sharp corner to corner, far larger than the image circle of any microscope lens. One of my 10x lenses also beats most 10x objectives in every spec and has a giant image circle. I will use that huge image circle. My plan is to stitch by moving the camera through that single gigantic aerial image, holding lens and subject stationary, rather than typical stitching by shifting the objective or subject. I've already been doing that on a smaller scale with my current optics, but I will be able to get much bigger images with these lithography lenses.
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harisA



Joined: 03 Jul 2011
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PostPosted: Wed Nov 01, 2017 12:30 am    Post subject: Reply with quote

Lou Jost wrote:
HarisA, your second shot shows very nice color, at least at this reduced magnification. What lens is that taken with? Maybe some of these lenses are color-corrected. Maybe the TV versions? If you blow up the sharp part of that image (the lips, it seems), are color aberrations visible?


Lou these are with a 0.75 lens. They are soft but comparison with a normal photography lens is not fair because there isn't a no such a lens (with the exception of zeiss planar 50mm 0.7 which is another story). Tv heligons have smaller image circles than xr heligons.All these lenses are optimized to work with parallel light rays (focus at infinity) so it won't suprize me if they are color corrected when used like this.At least at the center of the image I can't notice any chromatic aberrations but the edges have various problems (APS SENSOR).I will like to see a color image from your setup maybe with a lower focal distance tube lens .I think that Your 100mm heligon has the biggest image circle and is more corrected than the others since is not an extreme design in terms of physical aperture.
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typestar



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PostPosted: Wed Nov 01, 2017 3:41 am    Post subject: Zeiss Stepper lenses Reply with quote

Lou,

if I count it correctly, on your first image that shows your new collection -
I see 4 (?) Zeiss Stepper lenses --
could you- please specify the specs of the lenses for us, then ? the more "little" lenses will be of interest -- or will only the super large S-Planar give that huge image circle.

As far as I could catch this - I do not know of anyone, that could mount these for "normal" (what a word!) macrography use.
For now, I am exited to see your further testing -- but I believe -- all in all -- this extended resolution, if, will be of the cost of a HUGE setup, finally.

All the best,

Christian
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Lou Jost



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PostPosted: Wed Nov 01, 2017 6:58 am    Post subject: Reply with quote

Quote:
Lou these are with a 0.75 lens.


harisA, could you tell us which 0.75 lens? There are big differences among them, as you know.

I will test more of mine over time, but I need some new giant step-down rings for some that have threads (the Canon ones). For the ones without threads, I am epoxying rings onto them but I'm nervous since these lenses are so big and heavy.

Quote:
All these lenses are optimized to work with parallel light rays (focus at infinity) so it won't suprize me if they are color corrected when used like this.


I'll make some photos at my next opportunity, but I have lots of other work and travel in the next two weeks, so it may take a while. I saw lots of purple/yellow LoCA on the Live View screen.

Quote:
I see 4 (?) Zeiss Stepper lenses --
could you- please specify the specs of the lenses for us, then ? the more "little" lenses will be of interest -- or will only the super large S-Planar give that huge image circle.


Christian, there are some not in the picture. All the larger, newer Zeiss have giant image circles. So do some of the off-brand ones. Russian ones seem to have only about a 50mm image circle. Older Nikon ones have quite modest image circles. All these refer to the image size when used in reverse, as enlarging rather than reducing lenses; that's the opposite of their designed use, which was to project a reduced image of a larger mask. I will put more information about the stepper lenses on a separate page dedicated to them, in the coming weeks, after I have tested them more. Also, I have a few that may be either missing essential front lens elements or simply have other designed uses, as they do not behave like the genuine stepper lenses.

Quote:
I do not know of anyone, that could mount these for "normal" (what a word!) macrography use.
For now, I am exited to see your further testing -- but I believe -- all in all -- this extended resolution, if, will be of the cost of a HUGE setup, finally.


Yes, that is certainly the consensus, but I think they are wrong. Certainly the older lenses, especially the Russian ones, don't need huge setups. However, the more modern the lens, the bigger. Some weigh hundreds of pounds!!! The most recent may weigh a few tons. But no problem, we can stack by moving the subject and lighting rather than the lens!! Laughing

By the way I was over-weight with my luggage and some stepper lenses had to be left behind....will bring them during my next trip. Also, one was destroyed in shipping due to stupid packing job by the vendor-- I got a full refund-- and one has a loose element inside that rattles around---not noticed until too late for a refund.

I will add here that I bought one of the two Nikon Engineering "5x" lenses that were recently on eBay, and they appear to be stepper lenses. I suspect they may come from a Nikon 'Mini-stepper" and if so, they use the mercury i-line (405 nm). Mine has a longer working distance than most of the other steppers and has a moderate image circle. I'll write more about it later after more tests. My initial experience is that they need to be stopped down a stop or two (or three) for best results and may not be as good as the older Ultra-Micro-Nikkors (which, however, I do not own--too expensive-- so can't compare directly).

Thanks both of you for your interest in these weird lenses!!
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