14X17 Bausch & Lomb 11b Tessar

[sanking]

Can someone tell me the focal length of a 14X17 Bausch & Lomb 11b Tessar. I assume it would be around eighteen or nineteen inches but if anyone knows the exact nominal focal length of this lens I would appreciate the information.

Also, if anyone knows the actual circle of illumination of this lens I would also appreciate that information.

Sandy King

[Paul Fitzgerald]

the 1928 B&L catalog has it listed as 19 3/16" and will cover 15X20" stopped down.

[benrains]

According to the Bausch & Lomb 1912 catalog on Camera Eccentric, the 14x17 IIb Tessar covers a 14x17 plate at f/6.3, and a 16x20 at small stops. The focal length is listed as 19.25". Earlier in the catalog the angle of coverage for the IIb series is listed as 60º at f/6.3 and 66º at f/32 (I haven't cross-checked the math with the published coverage specs, but it's easy enough to do so.)

http://www.cameraeccentric.com/html/info/bauschlomb_8.html

[sanking]

According to the Bausch & Lomb 1912 catalog on Camera Eccentric, the 14x17 IIb Tessar covers a 14x17 plate at f/6.3, and a 16x20 at small stops. The focal length is listed as 19.25". Earlier in the catalog the angle of coverage for the IIb series is listed as 60º at f/6.3 and 66º at f/32 (I haven't cross-checked the math with the published coverage specs, but it's easy enough to do so.)

http://www.cameraeccentric.com/html/info/bauschlomb_8.html

Hi Paul and Benrains,

Thanks very much for the responses.

Just wondering out loud, but odd that the 1912 catalog gives coverage of 15X20" at small stops for the 14X17" 11b Tessar. Wonder why not 16X20? Was 15X20" ever a real plate size?

The information about the angle of coverage for the 11b series is very interesting. From the angle of coverage from the old catalog I calculate that a lens with a focal length of 19 3/16" (487.3mmm) would have an actual circle of illumination of 843mm at f/6.3 (60 degrees), and 1090mm at f/32 (66 degrees). To cover 20X24 requires a circle of illumination of about 32.25", or 790mm, so it sounds like the 14X17 11b would throw a large enough circle even at f/6.3, and plenty more at f/32.

I have one of these old lenses and was wondering if it would cover 20X24" stopped way down. The circle of illumination for this format is about 790mm. However, putting the lens on a camera and testing it would take a bit of work. It is currently mounted on a board with a Packard shutter and dismantling it would take some trouble, and I did not want to go to the effort if there was no possibility of coverage. However, if the angle of coverage is really a full 60 degrees at f/6.3 and 66 degrees at f/32it would be worth the effort to mount it on a board for the 20X24 and see how it actually performs.

Sandy King

[c.d.ewen]

Sandy:

I beleive I have one of these lenses, but I'm away for Easter, and can't be sure until tomorrow. I'll see if I can strap it on the 12x20. It may take a couple of days, though, if I have to make a flange for it.

Charley

[Dan Fromm]

Sandy, all of B&L's IIb Tessars were made to the same prescription. I just tried out an 85/6.3 on 2x3 and it covers from f/11 down. That's 60 degrees at f/11. f/8 is a little iffy, softer everywhere.

When I write cover I don't mean "illuminates," I mean "puts good image in the corners."

Cheers,

Dan

[EdWorkman]

I have one from Jim Galli
Having made a lensboard and waterhouse stops I have yet to make photos and verify the FL - yes I know the actual stops that I made are highly suspect, except for the relationship from stop to stop. I did try to calculate th FL from a closer focus by math, but i fear I failed, cuz I got just under 18". However, i digress, account i have searched the catalogs in vain to find the FL. Catalogs give the FL and the lens diam, none seem to match the diameter I have, but it's not stated WHERE the tabled dia is taken, barrel, front, glass, flange opening ?????- no correlation , so far.

[sanking]

Sandy:

I beleive I have one of these lenses, but I'm away for Easter, and can't be sure until tomorrow. I'll see if I can strap it on the 12x20. It may take a couple of days, though, if I have to make a flange for it.

Charley

Charley,

I was very curious so went ahead and removed the lens from the other board and mounted it on a board for the 20X24. I then focused on a fench about 150 feet from the camera and inspected the coverage by looking at the lens through the cut out corners at the four edges of the ground glass. You see an elipse at the corners from f/6.3 until f/22, then a round circle indicating full coverage at about mid-way between f/22-f/32. So there is full coverage at f/32 and f/45, with perhaps an inch of movement at the far corners when stopped down to f/45.

Unfortunately the aperture does not stop down any more than f/45. I wonder if this can be adjusted to stop down to f/64 and f/90?

Sandy

[Paul Fitzgerald]

"I wonder if this can be adjusted to stop down to f/64 and f/90?"

I have 1 1/2 of these, 1 is fine the other for parts. 1 is marked to f/64.

It's an easy barrel assembly and simple to lengthen the slot BUT you would run into the blade binding going smaller than f/64. Very simple to change to Waterhouse stops.

[c.d.ewen]

Sandy:

FYI: I do have one of these, S/N 3,225,xxx. I have a flange, and am fitting it to a lensboard tonight.

I'm not sure I'll be able to tell you anything more than you know already, as the Korona doesn't have shifts. I guess I'll just give it some rise and tilt and see what happens.

My exemplar also stops down to f/45 - about 9.5mm. I've meant to look at this lens to see if I can put it into an Ilex 5. The max opening then would only be f/8, but the shutter closes down a lot more than this barrel.

Paul:

My barrel has a 19-leaf iris. How many blades on your f/64?

Charley

[Paul Fitzgerald]

"My barrel has a 19-leaf iris. How many blades on your f/64?"

Each has 20 blades and everything is a direct match so change over would not be a problem.

[c.d.ewen]

Sandy:

I got the Tessar on the 12x20 today. With the max rise - four inches - I could see a perfect iris circle at f/11.

I took a picture with it, and should be able to determine the focal length when I get it processed.

Paul:

20 blades? Interesting. I counted mine again and again, and still come up short :) Is yours much older or younger than mine?

Charley

[Paul Fitzgerald]

I don't know B&L dates but serial #2,825,xxx and 2,789,xxx.

Coming up short??? Odd numbers of blades actually make a 'rounder' aperture than even numbers, the peaks are opposite the valleys not other peaks.

It seems to be low on contrast BUT with this much coverage I really should fit a lens shade for it, bellows flare and all that.

Have fun with it.