Author Topic: Possible emulation of CRT Nikkor?  (Read 1036 times)

Bruno Schroder

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Re: Possible emulation of CRT Nikkor?
« Reply #15 on: July 05, 2019, 14:23:37 »
Bruno, yes, exactly!
I did some quick handheld test shots on the DF (this sample of the 50/1.4 is not AI converted) with a 3T and a 4T and the results are quite good, particularly with the 4T. I'll do a direct comparison with the CRT on the D500 hopefully if I can find my other sample, which has been AI milled.

This has to wait till Monday however, the weekend being fully busy with friends and family.
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Akira

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Re: Possible emulation of CRT Nikkor?
« Reply #16 on: July 06, 2019, 04:15:21 »
Thank you, Bruno!  I'm looking forward to seeing your results, but please take your time.  No hurries!
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Michael Erlewine

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Re: Possible emulation of CRT Nikkor?
« Reply #17 on: July 06, 2019, 20:03:56 »
Let me get this right. Take a Nikon 50mm f/1.4 lens and put a Nikon #4 close-up lens on it and take photos, correct?

I tried this and here is what I got.
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JJChan

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Re: Possible emulation of CRT Nikkor?
« Reply #18 on: July 07, 2019, 13:39:19 »
I don't have a Nikkor-S 50mm but I used 4T with the Noct - these straight out of D850 resized only with no processing

Roland Vink

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Re: Possible emulation of CRT Nikkor?
« Reply #19 on: July 07, 2019, 23:07:19 »
Let me get this right. Take a Nikon 50mm f/1.4 lens and put a Nikon #4 close-up lens on it and take photos, correct?
To be precise: A pre-AI Nikkor-S 50/1.4 Auto, probably with serial 465011 and higher.  Earlier 50/1.4 lenses made between 1962 and 1966 had a slightly different optical design. In the mid 1960s the optics were revised with slightly different curvature and spacing, probably different glass materials too. The CRT Nikkor was made in the early 1970s so would have been based on the later version.

Also, the #4 close-up lens is a 2-element lens, to more closely replicate the CRT Nikkor you would need to use one of the single element close-up lenses #1, #2 or #3.

Actually, there is one thing which does not stack up. If you add a close-up lens, the focal length of the becomes shorter than the master lens alone (and the speed is correspondingly increased). The focal length of the CRT is 55mm, while the Nikkor-S 50/1.4 has a focal length of just 51.6mm - adding a close-up lens would shorten it to something like 45mm.

Maybe when the CRT Nikkor was designed, maybe Nikon used the optics of the Nikkor-S 50/1.4 but first scaled them up before adding the close-up lens??  Maybe someone who has both lenses can compare the size of the rear elements of both lenses.

Michael Erlewine

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Re: Possible emulation of CRT Nikkor?
« Reply #20 on: July 07, 2019, 23:36:33 »
To be precise: A pre-AI Nikkor-S 50/1.4 Auto, probably with serial 465011 and higher.  Earlier 50/1.4 lenses made between 1962 and 1966 had a slightly different optical design. In the mid 1960s the optics were revised with slightly different curvature and spacing, probably different glass materials too. The CRT Nikkor was made in the early 1970s so would have been based on the later version.

Also, the #4 close-up lens is a 2-element lens, to more closely replicate the CRT Nikkor you would need to use one of the single element close-up lenses #1, #2 or #3.

Actually, there is one thing which does not stack up. If you add a close-up lens, the focal length of the becomes shorter than the master lens alone (and the speed is correspondingly increased). The focal length of the CRT is 55mm, while the Nikkor-S 50/1.4 has a focal length of just 51.6mm - adding a close-up lens would shorten it to something like 45mm.

Maybe when the CRT Nikkor was designed, maybe Nikon used the optics of the Nikkor-S 50/1.4 but first scaled them up before adding the close-up lens??  Maybe someone who has both lenses can compare the size of the rear elements of both lenses.

I have a 50mm/1/4 with serial # 410167

I have a recent 50mm/1/4

I have an earlier NOCT

For this experiment what would the range of serial numbers be for the 50mm you folks are discusssing.  Between 465011 and ??

I am just curious.

Is this the type of lens and within range:

https://www.ebay.com/itm/Near-Mint-Nikon-NIKKOR-S-Auto-50mm-F1-4-Lens-Japan-Kovaku-Nippon-Beautiful/133098245647?hash=item1efd460e0f:g:UDMAAOSw5ipdFxOG


Here is one that says it is converted. Let me know if this is still the correct type and I might just get it to experiment.
https://www.ebay.com/itm/EXC-5-Nikon-Ai-Converted-Nikkor-S-Auto-50mm-f-1-4-MF-Prime-Lens-from-JAPAN/392305831819?hash=item5b573fef8b:g:CBEAAOSwj61cswyS


Would any of the 55mm Nikkors work for this of which there are many?
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Roland Vink

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Re: Possible emulation of CRT Nikkor?
« Reply #21 on: July 08, 2019, 01:24:14 »
The CRT Nikkor came out in the early 1970s, so if it was based on the Nikkor-S 50/1.4 it would have been based on the then-current optical design. This is the time-line of the original Nikkor-S 50/1.4 (see http://photosynthesis.co.nz/nikon/lenses.html#50fast):
  • Nikkor-S nos.314111 - 454670 from 9162 - 1966
  • Nikkor-S nos.465011 - 1256578 from 1966 - 1973. Revised optics - Optical drawings show noticeable differences in curvature in the cemented convex/concave doublets near the centre of the lens. CRT Nikkor made during this period so probably based on this design.
  • Nikkor-S.C no.1280001 - 1613735 from 1973 - 1974. Same as before but now multicoated.
  • New Nikkor no.2797021 - 3004000 from 1974 - 1976. Final revision with modern style barrel. Lens focuses to 0.45m (vs 0.6m for previous versions) so optics probably tweaked to improve close range performance.
Your lens no.410167 would be from the original series - I assume it is the old metal hill-and-dale focus ring (if you missed a digit from the serial number then no.410xxxxx would correspond to the AI 50/1.4 which has a different optical design). All the lenses above are pre-AI so would need modification for use on a D850, but are fine on the Z cameras.

We can probably get a close approximation of the CRT Nikkor by adding a close-up lens to the 2nd Nikkor-S 50/1.4. I'd suggest the single-element No.0, 1 or 2 (in increasing strength) as the best candidates. Be aware there is probably more to it than that. The 50/1.4 optics would have been scaled up to something like 60mm with the extra convex front element bringing the entire focal length back to 55mm. The curvature, spacing, glass materials and coatings of individual elements may be been changed to optimise the lens for its intended purpose. The extra element added at the front also won't be the same as any of the screw-in close-up lenses that Nikon made for general photography. Given that it's always going to be an approximation, it probably does not matter which of your standard lenses you use - try out various combinations and see what works.

Note that none of the 50mm Nikkors (with the possible exception of the Noct) are anything like the highly corrected APO lenses that you usually work with. If you do want to explore this area further, I'd consider a multicoated Nikkor-S.C or the "New Nikkor" as they will give better colours and contrast, unless you prefer the more muted rendition. The "New Nikkor" also has a greater focus range and may be better optimised at close range, but that is just a guess - some lens / close-up lens combinations work better than others.

It's also worth mentioning that single-element close-up lenses are by definition uncorrected for spherical aberrations (I haven't come across any aspherical close-up lenses!) Most 50/1.4 Nikkors are a little over-corrected, so adding a close-up lens this should make the background bokeh smoother.


Michael Erlewine

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Re: Possible emulation of CRT Nikkor?
« Reply #22 on: July 08, 2019, 02:30:10 »
Roland Vink: You are indeed a treasure!

I bought one of the New versions SN 2936443 converted

Thanks so much. I have all the close-up set, so I will play around with it.

Thanks so much for clarifying this.
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Akira

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Re: Possible emulation of CRT Nikkor?
« Reply #23 on: July 08, 2019, 04:08:34 »
Let me get this right. Take a Nikon 50mm f/1.4 lens and put a Nikon #4 close-up lens on it and take photos, correct?

I tried this and here is what I got.

Michael, thank you for taking time for the clumsy experiment.  At least on my screen, your combo appears to live quite well up to the task.  The achromatic element of #4 may help here.
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Akira

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Re: Possible emulation of CRT Nikkor?
« Reply #24 on: July 08, 2019, 04:10:10 »
I don't have a Nikkor-S 50mm but I used 4T with the Noct - these straight out of D850 resized only with no processing

JJ, thank you for chiming in.  The rendition of the combo looks lovely.
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Akira

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Re: Possible emulation of CRT Nikkor?
« Reply #25 on: July 08, 2019, 04:12:35 »
Roland, thank you for the further analysis of what is happening optically.  Indeed, the focal length is one of the remaining enigmas.
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Michael Erlewine

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Re: Possible emulation of CRT Nikkor?
« Reply #26 on: July 08, 2019, 07:16:20 »
Roland, thank you for the further analysis of what is happening optically.  Indeed, the focal length is one of the remaining enigmas.

I would imagine the focal length depends on the use of the lens, which is to monitor CRT screens. That focal distance must have something to do with it.  I am constantly trying all kinds of extension to all kinds of lenses to see if I can get the particular kind of range I would like, knowing that  in some cases it works well enough and in others it destroys the quality of the lens.. To me, the curvature of the the CRT screen gives the lens that odd (psychedelic) like aspect.  I would think that Birna or Erik might know how this was put together. I can only experiment.
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Bruno Schroder

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Re: Possible emulation of CRT Nikkor?
« Reply #27 on: July 08, 2019, 19:05:19 »
Maybe when the CRT Nikkor was designed, maybe Nikon used the optics of the Nikkor-S 50/1.4 but first scaled them up before adding the close-up lens??  Maybe someone who has both lenses can compare the size of the rear elements of both lenses.

measuring the lens element itself is not easy. The caliper is very sharp and I don't want to scratch the lens. My measure of the inner brass diameter around the rear element of the CRT is 36.45mm but the lens is chamfered and the element itself appears to be 34.3mm. The 50/1.4 S Auto nr 794265 has a light baffle of 36.5mm and the rear element itself is 34.1mm. My 2nd sample, the 50/1.4 S Auto nr 1187713, has a light baffle of 36.2mm and the rear element is also 34.1mm.

Roland, is 0.2mm the difference you would expect between the CRT and the 50/1.4 or is it within the margins of the measurement error?

Now, I only need to retrieve the 0, 1 and 2 close up lenses. When I got the 3T and 4T I thought I would never use them anymore, stored them somewhere and forgot about them. I don't have the faintest idea of where they are …. That said, I would always trust Michael's test over mine :)

Anyone else measuring either the CRT or the 50/1.4?
Bruno Schröder

Roland Vink

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Re: Possible emulation of CRT Nikkor?
« Reply #28 on: July 09, 2019, 03:59:28 »
I would imagine the focal length depends on the use of the lens, which is to monitor CRT screens. That focal distance must have something to do with it.  I am constantly trying all kinds of extension to all kinds of lenses to see if I can get the particular kind of range I would like, knowing that  in some cases it works well enough and in others it destroys the quality of the lens..
As you know, some lenses work well (optically) with extension, others are not so good. All will suffer to some degree when extended beyond the range for which they were designed. Field curvature, astigmatism and other aberrations are likely to become worse, especially away from the centre of the image.

In many cases, a better way to increase magnification is to use a close-up lens instead. The CRT lens seems to be a good example of this. The master lens can remain within it's optimum range, and if the close-up lens is well matched, the results can be very good. In special cases the closeup lens could even correct aberrations in the master lens resulting in improved performance. Some lenses work better with the close-up lens reversed. Generally the two-element close-up lenses work better since they are better corrected. But as always, there are no firm rules, you have to experiment with each lens/close-up combination and find what works best.

Roland Vink

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Re: Possible emulation of CRT Nikkor?
« Reply #29 on: July 09, 2019, 05:25:43 »
measuring the lens element itself is not easy. The caliper is very sharp and I don't want to scratch the lens. My measure of the inner brass diameter around the rear element of the CRT is 36.45mm but the lens is chamfered and the element itself appears to be 34.3mm. The 50/1.4 S Auto nr 794265 has a light baffle of 36.5mm and the rear element itself is 34.1mm. My 2nd sample, the 50/1.4 S Auto nr 1187713, has a light baffle of 36.2mm and the rear element is also 34.1mm.

Roland, is 0.2mm the difference you would expect between the CRT and the 50/1.4 or is it within the margins of the measurement error?
Nikkor-S 50/1.4 has a true focal length of 51.6mm. If the CRT Nikkor is a scaled up Nikkor-S 50/1.4, I would guess the focal length to be around 60mm (with the extra convex lens at the front bringing the total focal length to 55mm). My assumption was that the diameter of each lens element would be scaled up accordingly. However that may not be the case, so my earlier suggestion is probably not much help.

A good example is the Medical-Nikkor 200/5.6. The optics are borrowed from the Nikkor-Q and set into the barrel with a small amount of extension giving 1/15x magnification. The diameter of the elements was reduced (the 200/4 permanently stopped down to f/5.6), probably to give more room for the built-in ring-light and to improve performance for closeup photography.