Wrong infos about Apo-Nikkor 305mm in shutter

[Dan Fromm]

Is it possible there are two versions of the 305mm, one "unibody" and one separable?

- Leigh

Leigh, I doubt it but it is certainly possible. Go over to skgrimes site, take a look at the much-too-small image they've posted of one in a #1, and tell me what you think. http://www.skgrimes.com/lens-mountin...ed-to-shutters , towards the bottom of the second screen down.

I just compared mine with that image and the visible bits in the image look like it. Mine has a groove in front of a ~ 20 mm tube with slot for Waterhouse stops in front of the part of the barrel with the diaphragm. I think that groove is joint between front cell and tube. It matches what looks like a front cell in grimes' image. At the rear, mine has a threaded section with a slight lip that abuts the rear of the barrel just behind the diaphragm control ring. This matches what's visible as a rear cell in grimes' image.

Cheers,

Dan

Charley, thanks for the kind offer. I also have too many 300s. Apotal, Apo-Nikkor, Apo-Saphir, TTH Telephoto, ... I don't know about you, but although I don't have as much coming in as I did before I retired I can still afford the odd interesting and inexpensive lens. It seems to me that the supply of interesting inexpensive lenses has more or less dried up. And I say this even though I recently couldn't make myself pull the trigger on a couple of very inexpensive Zeiss Anastigmats and am ignoring some ancient and pretty Perigraphes. I have good enough lenses of those focal lengths, can't see the point of adding more.

The money is better spent on cookbooks, although, again, I just can't make myself pull the trigger on a $1,100 set that I'd somewhat like to have. I have all of the second edition, would like to compare with the first ($1,100 for 27 of 33 volumes) but not that badly. I've told my favorite library about the set on offer, hope they have enough acquisition budget and will to buy it.

[Leigh]

Leigh, I doubt it but it is certainly possible. Go over to skgrimes site, take a look at the much-too-small image they've posted of one in a #1, and tell me what you think.

One apparent difference is the lens at SKGrimes has a pair of holes in the front trim ring for a spanner wrench.
Those do not appear to be present in the OP's lens, but it might just be the lighting for the photo.

The SKGrimes lens in a Copal #1 have custom-made adapters fore and aft of the shutter.
The actual lens cells appear to be quite shallow at the mating diameter, perhaps 1/4".
The lens sub-assemblies may not be "cells" in the modern meaning of that term.

I'm unfamiliar with the design of the Apo-Nikkor. If it's just a symmetrical pair of cemented doublets,
as is/was common for apo lenses, you really only have two elements to deal with, one front and one rear,
so there's no need for "cells" in the sense that we see them in multi-element lenses. Just speculation.

If that's the case, then lens performance is critically dependent on proper "centering", which is just the
rotation of one element set relative to the other, to align the optical axes.

I just compared mine with that image and the visible bits in the image look like it. Mine has a groove in front of a ~ 20 mm tube with slot for Waterhouse stops in front of the part of the barrel with the diaphragm. I think that groove is joint between front cell and tube. It matches what looks like a front cell in grimes' image. At the rear, mine has a threaded section with a slight lip that abuts the rear of the barrel just behind the diaphragm control ring. This matches what's visible as a rear cell in grimes' image.

Now I'm seriously confused. Why would a lens have both Waterhouse stops and a variable diaphragm?

- Leigh

[Dan Fromm]

Leigh, process lenses use Waterhouse stops with non-round apertures to make half-tone dots that aren't round.

[Leigh]

OK. The original implementation of "bokeh".

I've only seen that done using halftone masks. It didn't occur to me that you could do it with a stop.

Thanks.

- Leigh

[Michael Jones]

The lens sub-assemblies may not be "cells" in the modern meaning of that term.

I'm unfamiliar with the design of the Apo-Nikkor. If it's just a symmetrical pair of cemented doublets,
as is/was common for apo lenses, you really only have two elements to deal with, one front and one rear,
so there's no need for "cells" in the sense that we see them in multi-element lenses. Just speculation.


- Leigh

Years ago I had Steve mount several RD Artars into shutters. When I got them back, the entire original barrels were in the box & the lens elements seemed to “look different.” I called him and he said these were so simple to mount he just made barrels en masse and just screwed the elements customers sent him into his barrels and then into the shutters.
I don’t ever recall hearing that about Apo Nikors from anyone.


Mike

[Sal Santamaura]

...Just before he passed away, Steve Grimes bought a collimator. I stopped by a year or two later, and Adam had put it up on a shelf, as no one knew how to use it. You might call again, as maybe by now someone has taken it down from the shelf...

Thanks for that tip. In the intervening decade, I've come to realize that a small spec of dust in my 305 is of no consequence, so I'll let it stay as is.

...Somewhere on the SKGrimes site there's a quote from Steve about how the Apo-Nikkor lenses were apparently "centered by God"...

I just performed an advanced search on the site and couldn't find that, so Adam probably took it down, but the quote is consistent with what Steve told me.

[cyberjunkie]

After a quick browsing of the thread i started, i think i might add a few consideration about my lens and what i believe about the subject.

1) i don't think there were two revisions of the 305mm. Simply there were two different "families" of Apo-Nikkors, one of the Apo-Tessar type (older) and one dialyte (newer). Time ago Dan kindly posted a nice list of both types, as far as i remember there were very few overlapping focals, if any. Going by memory, one was 300mm and the other 305mm.
A research on this forum would bring up that list (which i religiously saved on my HD).
The other Apo-Nikkor i own is a 480mm, coming from a reprocamera, complete with A very large round flange and a giant Copal electrically actuated shutter (which would be perfect for giant brass lenses, if only i could win my lazyness and assemble some sort of trigger). The 480mm is also a dialyte, and looks to be made the same way.

2) How are they made, and how can you disassemble the optics?
I can't remember very well, cause i have worked with other lenses afterwards, but i will tell you something:
there is a small set screw, then you remove a ring, then there is a very wide "beauty ring", but after you start to unscrew it, you feel that the glass element sitting behind it is starting to rattle! Normally there would be another thin ring which keeps the glass centered and with the right spacing.
At that point i stopped, as it was already sure that there were no "cells" that would go in a shutter, and also because i understood that after i had taken out all the bits, the alignment could well be screwed for good...
Of course i didn't remove the set screw at the back, i had already enough of it.

3) When it comes to adapting lenses with no conventional cells to shutters, i think that most works were done cutting the original barrel in the middle. I have seen Zeiss Jena (DDR) and a B&L 20" tele adapted the same way.
It would be quite complicate and risky (albeit possible) to do it with the optics in place. Though i find it hard to believe, with a lens the size of the 305mm Nikkor.
It would be very difficult to protect the glasses from damage and dirt, so i guess that in the shown example the glasses were removed during machine work.
Considering the way the barrel is made, i believe that they had a special tool at the factory, to ensure correct centering; probably you could near that perfection if you are careful and fortunate enough during reassembly, but it's a hit/miss affair.
The vast majority of LF lenses can be disassebled, cleaned, and then reassembled, with a few tools and good care, with no adverse consequences. Others, like the Apo-Ronar CL, are better left alone: the elements are centered and glued in place with a technology available only at the factory (or maybe a few authorized center... but really, i don't think so).

A quick side (sad?) note:
it's a true pity that any skilled mechanical work has got so expensive in the recent years. It's no marvel that the best adaptations were made some time ago. Now it's even difficult to find an experienced photo-mechanic. The old masters retire and nobody take their place.
As an admirer of precision mechanic and vintage LF optics, i find it quite depressing.

have fun

CJ

[Dan Fromm]

CJ,

Thanks for the kind word. The current version of my Apo- and Proces-Nikkor list is here: http://www.galerie-photo.com/apo-pro...ikkors-en.html (in English) and here: http://www.galerie-photo.com/apo-pro...ikkors-fr.html (in French).

Re your point (2), it sounds as though you started to open the lens from the front. This isn't the same as unscrewing the front cell from its barrel.

Re your point (3), I have a 38/4.5 Biogon in Copal #0. Steve Grimes extracted it from its native shutter, for an AGI/Williamson F135 aerial camera, and remounted it in the #0. When he started the job he wasn't sure whether the elements were in conventional cells so he cut the AGI shutter off with a hacksaw. My lens has a shallow cut in its front cell; Steve did it. Turns out that F135 Biogons' elements are in conventional cells. I sold several of those lenses and a few of them were remounted by Steve's successors. They, having the benefit of Steve's experience with my lens, just unscrewed the cells.

Steve's successors, Adam and Joel Dau, still look quite young. If we want them to stick around, we should keep them busy.

Centering lens elements has been mentioned in this discussion. In my limited understanding of lens making, centering has to do with trimming the elements, after their surfaces have been ground to the desired shape so that when they are glued together or simply put in the barrel their apices will be collinear.

[Leigh]

In my limited understanding of lens making, centering has to do with trimming the elements...

Lens elements are already fully figured with the perimeter ground to size before the centering step.

It may also be done following repair procedures that disturb the centering.
This is why I always laugh when people say they took a lens apart to clean it and put it back together.

Centering involves aligning the optical axes of the various elements to eliminate any tilt,
and shifting individual elements to make the axes colinear with the axis of the assembly.

Googling "lens centering" gets hundreds of hits, including instructions for performing the operation.

- Leigh

[Dan Fromm]

Leigh, thanks for the suggestion. You're right, Google returned many hits. Some of them refer to techniques for positioning what seem to be defective elements in a lens barrel to eliminate tilt and make the element's optical axis coincide with the barrel's axis.

I also looked in S. F. Ray's Applied Photographic Optics, 3d ed. See p. 173, where he says:

A vital final stage is that of centering, where the optical and mechanical axes are brought into alignment. The element is aligned on a centring [sic] device and the edge-ground to a specified diameter. Alignment aids for later assembly, such as bevels or flats on the rim, can also be added.