Taylor Hobson 10.16" 'Copying' - freebie ... coverage ?

[Mark J]

One of my now-retired colleagues, a good friend who used to be my line-manager and worked at Dallmeyer too, many years ago, left a lens on my desk when he was clearing out.
I must admit I didn't think too much about it and regarded it as a paperweight.
However, now that I'm gearing up to use my Gandolfi 5x7 a bit more before my joints give out, I took a closer look today and did some searching.
It's a lens that Dan Fromm has spoken about quite a lot, the Taylor Hobson 10.16" f/9 Copying.
Serial number is 586800
My initial plans would be to use it for IR, where I can get 3-4 sec exposures routinely at f/22.
Maybe I could get an external shutter later.

On searching, all I can really find are Dan's comments that it covers 2x3" fine.
That's a good start .... !
For IR I'll be looking at 4x5 , for general B&W 5x7.

Now obviously I can lash it up to some sort of board with blu-tack and gaffer tape, to test, but ahead of this, does anyone have any existing hands-on experience ?
I'd be interested in how it performs in the 2m to infinity range at 'working' apertures.

[Dan Fromm]

Mark, as always, since you have the lens, ask the lens.

The 10.16"/9 Cooke Copying Lens is an Apotal, i.e., an Apo-Tessar with radioactive glass(es). Arne Croell thinks that Apo-Tessars cover 43 degrees. 203 mm circle, then.

[Mark J]

Thanks, that sounds encouraging. I will 'release' the lens tomorrow.
It could be radioactive, it looks a bit yellow.
However that doesn't mean it is an Apotal from a design point of view. Maybe Arne did not imply that these properties were connected though.
The radioactive glasses were in the upper left part of the Abbe chart, in the LaK and LaSF regions. These glasses were not anomalous in any useful way, certainly not as the crowns in a Tessar. They were just high index with relatively low dispersion.
I think this has become one of those internet myths.

There's a chance I could get the old design for this lens, I have asked Dr. Jon Maxwell who worked for Cooke for many years.

[Dan Fromm]

Thanks, that sounds encouraging. I will 'release' the lens tomorrow.
It could be radioactive, it looks a bit yellow.
However that doesn't mean it is an Apotal from a design point of view. Maybe Arne did not imply that these properties were connected though.
The radioactive glasses were in the upper left part of the Abbe chart, in the LaK and LaSF regions. These glasses were not anomalous in any useful way, certainly not as the crowns in a Tessar. They were just high index with relatively low dispersion.
I think this has become one of those internet myths.

There's a chance I could get the old design for this lens, I have asked Dr. Jon Maxwell who worked for Cooke for many years.

Mark, when I counted reflections the lens came out a tessar type. So are Apotals. As for radioactive glasses, on the one hand I never measured my lens' emissions, on the other after basking for a while under a UV lamp it came clear.

Arne wrote about CZJ Apo-Tessars, not about TTH Apotals.

[Mark J]

Thanks for the extra info. I did see that you had 'cured' the colouration with UV. In my case it's not so important because I'll only shoot it in B&W.
It does indeed look like a Tessar, the front lens unscrews, it is positive, and then the next lens in front of the stop looks negative.
It will be interesting if I can find out anything from Jon on the Apotal design. My guess is that they could have used a lead-borate flint in the second element.

[arri]

I use a 140mm Apo Tessar in 4x5" and a 300mm in 8x10" and I know that the angle of view is larger than the 43°
It is a Tessar design, the different is only that between the both lenses in the rear is an air gab.
So why should the angle of view smaller than the other Tessar lenses?
It is a myth as well.
A Tessar can cover 75°. The f/6.3 Tessar lenses has nearly 70°.
The f/8 28mm for the Contax rangefinder has 75°.
The Apo Tessar is a low speed lens but in the consequence it has a larger angle of view.
I use my Apo Tessar lenses with shift and swing and it has a very good quality up to the corners.

The lens is apochromatic corrected and this is maybe limited to the 43° but I have no equipment to test it. I only make B&W pictures and here I can´t see any quality limitation.
I can say it only for this two mentioned focus length, maybe longer A.T. lenses have smaller image circles and smaller angle of view.

The Apotal is a clone of the Apotessar and I think is has the similar data.

[Mark J]

I'm not convinced this is like the Apotal. It looks nothing like it on the pictures. This lens is the same as the ones labelled '10.16" f/9 Xerox'.
I haven't looked at any wide angle Tessar's construction, have you got a good example with a cross-section ?
Most Tessars field curves fly apart quickly after their design field of eg. 55° , unlike Dagors and Plasmat which have a slow deterioration.
I would guess that any wide-field Tessar would need a more curved front 2 elements with the +ve and -ve close together ?

[Dan Fromm]

I'm not convinced this is like the Apotal. It looks nothing like it on the pictures. This lens is the same as the ones labelled '10.16" f/9 Xerox'.
I haven't looked at any wide angle Tessar's construction, have you got a good example with a cross-section ?
Most Tessars field curves fly apart quickly after their design field of eg. 55° , unlike Dagors and Plasmat which have a slow deterioration.
I would guess that any wide-field Tessar would need a more curved front 2 elements with the +ve and -ve close together ?

The 10.16"/9 copying lens has a brother, 6"/9, also a tessar type. I have a 30 cm/9 Apotal, have seen pictures of focal lengths of lenses sold as Apotals. Most are in similar barrels that are nothing like those of the 10.16" and 6". Different mechanical designs don't always mean different optical designs.

There were only two wide angle Tessars, both by CZJ. 28/8 for Contax, 55/8 for VP Exakta.

Re coverage, f/4.5 and faster tessar types' coverage grew after the Tessar was first released. Newer glasses, possibly improved design. f/6.3 tessar types always had more coverage than fast ones of the same vintage. At least 60 degrees, some claim 70 degrees. Asymmetrical type Apo-Nikkors are Apo-Tessar clones. All have narrow claimed coverage, none greater than 45 degrees.