KEH and the "Copal BT" shutter

[gmed]

Can someone explain Copal BT? Im thinking of buying a fujinon lens, which KEH states it has a Copal BT (35mm). Im assuming this is a Copal 0 (34.6mm)?

does the BT stand for Bulb/time?

[IanG]

There's no explaining, you've guessed right. BT does mean Bulb & Time and 35mm is the hole needed for a Copal/Compur/Protor etc #0

Ian

[Swami]

I've got a question that I'm surprised I've not found a quick answer for.

I'm looking at a lens on KEH that mentions it has a Copal BT shutter. I believe BT stands for Bulb and Timer.

Does it also have other shutter speeds? Or is BT used to indicate that it only has Bulb and Timer?

Thanks

[Jimi]

I know there was a Sinar Norma "simple" behind-the-lens shutter that only had B and T settings. I have never seen one, only know this from a catalogue listing.

I found an earlier post on here, confirming what you already assumed: https://www.largeformatphotography.info/forum/showthread.php?113854-Copal-BT

[roscoetuff-Skip Mersereau]

I believe KEH uses that designation for Copal 0 shutters.

[Dan Fromm]

I just did two searches on keh.com. The first for Copal BT. It got 596 hits. The first page was lenses in Copal #0 and #1 shutters. All fully speeded. Note, one Copal Press, top speed 1/125. The second for Copal. It got 711 hits, including fixed lens cameras with Copal shutters and Copal #3 shutters.

OP, if you want the lens get it. If the lens isn't fully speeded return it.

[Greg]

GITZO once made and distributed a B & T shutter which was rebranded by other brands. Just a guess on my part...

[Oren Grad]

Threads merged.

[reddesert]

KEH's designations are a little cryptic but I'm pretty sure that many of their LF lenses are listed as "BT," meaning "this shutter has B and T in addition to the normal timed speeds." There are some shutters that don't have both B and T. For example here is a listing for a Schneider lens that says "SCHNEIDER 90MM F/8 SUPER ANGULON MC COPAL PRESS B (32 MT)." This means a standard Copal Press #0 shutter that has B, but no T setting, and a 32mm diameter mounting thread. https://www.keh.com/shop/90-f8-sup-ang-mc-copal-press-b-32-mt-4x5-lens-1.html (No endorsement implied.)

[europanorama]

KEH's designations are a little cryptic but I'm pretty sure that many of their LF lenses are listed as "BT," meaning "this shutter has B and T in addition to the normal timed speeds." There are some shutters that don't have both B and T. For example here is a listing for a Schneider lens that says "SCHNEIDER 90MM F/8 SUPER ANGULON MC COPAL PRESS B (32 MT)." This means a standard Copal Press #0 shutter that has B, but no T setting, and a 32mm diameter mounting thread. https://www.keh.com/shop/90-f8-sup-ang-mc-copal-press-b-32-mt-4x5-lens-1.html (No endorsement implied.)
M32.5-0.5 mount thread copal 0 not 32
see skgrimes table
he has also explenation how to measure threads outside(rounding) and inside(adding pitch).
and has best spanner wrench.