19" Artar element spacing

Whiteymorange · Nov 7, 2011

I bought a lovely 19" red dot APO Artar at the Photographica show yesterday and I need to check something. It came mounted in a shutter, using aluminum spacers that were obviously professionally made. The rear element, however, does not screw all the way down to seat cleanly in the spacer. Before I redo the spacer, or the threads in the element, which seem to be very slightly out of round (they don't fit the front spacer either, even though the front element screws cleanly into either front or back) I thought I'd ask someone who has this lens in a barrel to measure the barrel length and tell me what the proper spacing on this should be. Neither the element nor the spacer barrel show any signs of abuse or damage.

Anyone got one of these things and a good measuring device - or a spec sheet?

Thanks,
Whitey

c.d.ewen · Nov 7, 2011

Whitey:

My notes say:

C. P. Goerz Am Opt Co Apochromat [RD] Artar 19 In F:11 No 801033

Barrel: 1.865"
Front to Iris: 1.133"
Front Thread: 2.310 - 2.339" x 36 TPI
Rear Thread: 2.322 - 2.351" x 36 TPI
Flange: 2.482 - 2.514" x 26 TPI

As you can see, in my example, the rear thread is about a hundredth of an inch larger than the front.

Charley

ps: which shutter?

ic-racer · Nov 7, 2011

Whiteymorange said:
I bought a lovely 19" red dot APO Artar at the Photographica show yesterday and I need to check something. It came mounted in a shutter, using aluminum spacers that were obviously professionally made. The rear element, however, does not screw all the way down to seat cleanly in the spacer. Before I redo the spacer, or the threads in the element, which seem to be very slightly out of round (they don't fit the front spacer either, even though the front element screws cleanly into either front or back) I thought I'd ask someone who has this lens in a barrel to measure the barrel length and tell me what the proper spacing on this should be. Neither the element nor the spacer barrel show any signs of abuse or damage.

Anyone got one of these things and a good measuring device - or a spec sheet?

Thanks,
Whitey

From what I understand the red dots came mounted in shutters, but were not set up for infinity focus. The lens spacing will affect the film flatness at a particular reproduction ratio. So, someone may have adjusted the spacing to use it on a field camera or it could be set up as it came from the factory. If you have a way of checking field flatness (mounting it on a camera) you can play with the spacing and see what works best for your intended reproduction ration or shooting distance.

Mark Crabtree · Nov 7, 2011

I'm not sure I have an Artar in that FL around at the moment (will look), but I think posting a picture of yours would be wise to make sure everybody is talking about the same exact lens.

BTW, I've found some thread incompatibility even on originals. Seems to be a tolerance issue over the years, not a spec change.

E. von Hoegh · Nov 7, 2011

ic-racer said:
From what I understand the red dots came mounted in shutters, but were not set up for infinity focus. The lens spacing will affect the film flatness at a particular reproduction ratio. So, someone may have adjusted the spacing to use it on a field camera or it could be set up as it came from the factory. If you have a way of checking field flatness (mounting it on a camera) you can play with the spacing and see what works best for your intended reproduction ration or shooting distance.

Red dots came in BBL or shutter. The ones factory mounted in shutter were supposedly set up for infinity.

Whiteymorange · Nov 7, 2011

Thanks, everyone.
Here are some quick pics. The shutter it's in is an Alphax, probably #4, I haven't checked the measurements and it's not tagged as to model number. The difference in the thread size could be the problem, though as I said, it seems to have been a professional job, and I can't imagine the machinist simply saying, "oh, well... good enough."

Then again, maybe it's not a pro-job, at least not a purpose-made set of spacer rings. Maybe the guy had them made for another lens and faked it after something went south on that one. It was originally from an estate sale, so the owner was not available for comment. I got a very good price on some nice glass and a good, if limited, shutter. I'm going to make it work. I have a retired tool designer/engineer/machinist for a brother-in law. He'll help me now that I have the specs.

ic-racer · Nov 7, 2011

A 'pro' job would probably have included a better aperture scale

Whiteymorange · Nov 7, 2011

ic-racer said:
A 'pro' job would probably have included a better aperture scale

Good point. I have actually measured the various parts at this point, and the guess of a professional adaptation was wrong on many points. Since my calipers measured the threads exactly as they were specified in Charley's post, I am making the assumption (there I go again!) that the spacing should be the same as the barrel length. If so, the rear element is not too far back, but too close... by over .05". If this is right, I can jury-rig the spacing quite easily with washers. More testing necessary maybe even some real photography! As I said, good glass, decent shutter, good price I'll live with it.

Thanks again everybody.

Mark Crabtree · Nov 7, 2011

Charley's seems to be very similar vintage to yours, so that sure seems like a good reference point.

My impression has been that precise spacing on these symmetrical process lenses isn't all that critical. I think it will mostly affect field curvature (anybody know more). I talked to Ron Wisner about this years ago and wish I could remember which way curvature shifted with more cell spacing. I hate to guess. Some process lenses sold for general use (Computar?) had a thin spacer. Maybe someone here can remember whether you put it in, or took it out, for infinity.

Nonetheless, I've used process lenses (mostly on Cirkut Cameras) at long distances for years without noticing any issues. My 16.5" Repro-Clarons (Artar design) have had some pretty varied spacing. I'd put a loupe on some ground glass and see what yours looks like. If you have some cheap film, give it a go. You can try unscrewing cells partially as an experiment.

BTW here's an Artar:
http://en.wikipedia.org/wiki/File:Artar.png
I would assume spacing from the diaphragm is symmetrical for 1:1.

Whiteymorange · Nov 8, 2011

Thanks Mark. As they say, the proof of the pudding is in the tasting. We'll see what it shoots like as soon as I have a minute to make a lensboard. Darn work keeps getting in the way!

Whiteymorange · Nov 10, 2011

OK. Now that I have had a chance to do a couple of test shots wide open at f11, Tmax 320, Sprint dev. 5 copies of a test pattern pinned to the wall in a cross pattern, so that the papers fill the frame. I can say that any difference between how the elements were spaced when I bought the lens and the specified distance from the above post is invisible on the negative using an 8x loupe - right to the corners. Since I will be contact printing anything I shoot with this lens, that's more than good enough for me.

Damn, this thing is sharp! I'm used to shooting with old brassies and the occasional magnifying glass and such. I might have to up my game in terms of focusing... . The thing is that I bought it on a whim, being flush with the money from selling off some 35mm gear. It doesn't fit my "travel" 8x10- needs too much bellows draw for the Korona Home Portrait. I may put it up for trade for something in the 12-14 inch range in shutter, but it is amazing at long portrait range on the Studio Master.

19" Artar element spacing

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