B&L Tessar IIb "6-1/2 x 8-1/2" barrel lens

Greetings,

I just purchased a B&L Tessar IIb "6-1/2 x 8-1/2" size barrel lens. (The lens has not yet arrived.)

Its appearance is that shown in the 1906 B&L lens catalog (all-brass finish except for the "shade", notations engraved on the side of the barrel), as distinguished from the appearance shown for that lens series in the 1920 B&L catalog (black finish, notations engraved on the front of the lens).

In the 1906 catalog, the No. 8 size of the Tessar IIb lens is shown as suitable for 6-1/2" x 8-1/2" plates at full aperture (f/6.3).

In the 1920 catalog, the No. 8 size of the Tessar IIb lens is shown as suitable for 8" x 10" plates at full aperture (f/6.3) and for 10" x 12" plates at "smaller stops".

The diameter specification (which turns out to the the overall actual glass diameter of the front element ), and the focal length (12") is the same in both catalogs for the No. 8 size, suggesting that the "Number" designations had not changed.

Note that in these lenses the "size number" is not usually marked on the lens, just the "coverage rating" (full aperture).

Do we know what (if anything) changed in the design of this lens between the 1906 catalog version and the 1920 catalog version, or is the difference in "coverage" specification just an advance in marketing engineering?

For reference, here are links to the catalog pages on which I have relied:

B&L 1906 lens catalog - Tessar IIb (f/6.3):

http://www.cameraeccentric.com/html/...hcata/p11.html
http://www.cameraeccentric.com/html/...hcata/p13.html

B&L 1906 lens catalog - Tessar IIb (f/6.3):

http://www.cameraeccentric.com/html/...t/lensesg.html
http://www.cameraeccentric.com/html/...coveraged.html

Perhaps nothing changed. Maybe they rated the coverage conservatively in the 1906 catalog and then re-rated it either less conservatively (or more properly) in the 1920 catalog. It could be that competitors were rating the coverage les conservatively than B&L was and they changed their measurement specs to compete.

I really doubt that they improved the lens that much without changing design and without changing maximum stop.

Hi, Christopher,

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Originally Posted by Christopher D. Keth

Perhaps nothing changed. Maybe they rated the coverage conservatively in the 1906 catalog and then re-rated it either less conservatively (or more properly) in the 1920 catalog. It could be that competitors were rating the coverage les conservatively than B&L was and they changed their measurement specs to compete.

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That was certainly my first thought.

Thanks for your insight.

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Originally Posted by Doug Kerr

Hi, Christopher,

That was certainly my first thought.

Thanks for your insight.

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No problem, though I'm certainly no old lens expert. Many of the people here who shoot anything bigger than 8x10 have often noted that lenses actually can cover quite a bit more than old tables like those state.

Since one (maybe both, I forget) of those catalogs state coverage angles, you could do a bit of trig and figure out the actual coverage circle. It may even be different than they say in both catalogs. I have no idea how coverage circle are determined sometimes. They often seem misleading at best, completely inaccurate at worst.

Quote:

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Originally Posted by Christopher D. Keth

Many of the people here who shoot anything bigger than 8x10 have often noted that lenses actually can cover quite a bit more than old tables like those state.

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I have a modest collection of B&L Tessars - 3.25x4.25, 5x7, 5x8 and 6.5x8.5. In my experience tinkering with the three shorter ones in the field, they offer coverage that's adequate for the stated format, but not really more than that.

The 6.5x8.5 is a recent acquisition. Conveniently, it came mounted on a 6" Eastman board that fits my 6.5x8.5 Eastman No. 2, so I'm hoping to give that combination a try soon as well.

UPDATE: Just checked mine - the 3.25x4.25, 5x7 and 6.5x8.5 are Ic's, the 5x8 is a IIb. The latter doesn't seem to do any better relative to its specified format than do the shorter Ic's.

Hi Doug,

I have B&L 6 1/2 X 8 1/2 #1086779 in a Compound shutter. It is 10 inch length and shows a clear, round aperture to the corners at f/32 so it JUST covers 8x10. A 12 inch would easily cover 8x10.

I also have a B&L 8x10 IIb tessar in a Volute shutter (pat applied, really old) #737793 which is 14 inch length. Somewhere along the line B&L changed to shorter lengths, their 8x10 Ic tessars are 11 3/4 inch.

Hope it's a help.

Hi, Paul,

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Originally Posted by Paul Fitzgerald

I have B&L 6 1/2 X 8 1/2 #1086779 in a Compound shutter. It is 10 inch length and shows a clear, round aperture to the corners at f/32 so it JUST covers 8x10. A 12 inch would easily cover 8x10.

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I assume you mean this is a IIb. It is probably a No. 7 size of the "newer" style, which would have (then) been designated 6-1/2 x 8-1/2.

[QOUTE]I also have a B&L 8x10 IIb tessar in a Volute shutter (pat applied, really old) #737793 which is 14 inch length.[/QUOTE]

This is probably a "No. 9" size of the "older" type (although the 1906 B&L catalog does not list one that big). In 1920, it would have been rated to cover 10 x 12 at full aperture.

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Somewhere along the line B&L changed to shorter lengths, their 8x10 Ic tessars are 11 3/4 inch.

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The change in "coverage rating" for any given size (focal length) for the IIb seemed to have happened sometime between the 1906 and 1920 catalogs, probably when the appearance design of the lens changed.

The same thing happened for the Ic between the 1907 catalog (Zeiss) and the 1920 catalog (B&L).

(The Ic series was introduced by Zeiss in 1907; the IIb in 1902.)

Thanks for the serial number info, I don't yet know the s/n of my new IIb.