Copal shutter aperture problem (?)

[Tom J McDonald]

Hi guys,
I bought a lens in a copal 0 shutter recently. The lever to select the aperture moves beyond both minimum and maximum openings. When the selector is showing max. aperture, the actual opening is not wide open. And when it goes past it opens more. Same on the other extreme, the aperture is not at its smallest until it goes past f/64.
Any idea how to fix this at home?

[Leigh]

If that's the factory shutter, it's correct as marked. What lens do you have?

The maximum and minimum physical aperture diameters of the shutter may not correspond with commonly-used f-numbers for your particular lens.

This is one reason (presumably) that modern lenses use standardized focal lengths, rather than the random assortment that's common with vintage lenses.

Most likely your shutter does not need to be "fixed".

- Leigh

[Tom J McDonald]

Leigh,
I'm not sure if it's the factory shutter as it's second-hand and quite well-used.
It's a Nikkor-W 135mm f/5.6.

Is there a way to physically measure what the f numbers are so I can get more accurate exposures?

[Leigh]

It's a Nikkor-W 135mm f/5.6.
That shutter should have marked apertures from 5.6 to 64, inclusive. If yours does not have that range, there's a problem.

If it does, I would just use it as is. Even an error of a fraction of a stop won't affect your photos. Our type of photography is just not that precise.

Modern Nikon shutters have the Nikon name on the shutter itself, along with the focal length and aperture of the lens.
I don't know when they started doing this, so an original shutter of earlier vintage may not have this information.

That's a nice lens.

- Leigh

[Tom J McDonald]

Leigh, apertures are marked that way.

The problem is it looks to me to be a whole stop.

I have been using it as though 5.6 is 8, 8 is 11 etc... but I haven't developed any sheets yet.

Tom

[Leigh]

The problem is it looks to me to be a whole stop.
That's quite possible. Remember, the shutter was not designed for that specific lens.

My database shows Copal 0 shutters used on f/5.6 lenses from 65mm to 150mm focal length.

Since the f-number is (roughly) the ratio of focal length to aperture diameter, obviously the shutter has more range than required for a 135mm lens.

- Leigh

[Tom J McDonald]

OK, thanks Leigh. makes sense. I suppose I won't know for sure until I make some prints.
Thanks for your help.
Tom.

[Leigh]

You're welcome. Certainly the film is the final arbiter of such things.

I have 15 LF lenses here, and the aperture control goes beyond at least one end of the scale on most of them.

Good luck with it.

- Leigh

[Tom J McDonald]

OK thanks Leigh, that's alot of lenses.

[Leigh]

Yeah, I have every standard focal length from 65mm through 360mm, except 105mm.

There's some FL duplication, like a Nikkor M 300/9 for the 4x5 and a Nikkor W 300/5.6 for the 8x10.

- Leigh

[John Koehrer]

Is there a way to physically measure what the f numbers are so I can get more accurate exposures?
Measure from the front of the lens with the group in place. 1:3.5=38.6mm, 1:5.6=24mm etc.

[Leigh]

1:5.6=24mm etc.
Would I believe 24.1mm???

- Leigh

[Tom J McDonald]

Measure from the front of the lens with the group in place. 1:3.5=38.6mm, 1:5.6=24mm etc.

Cheers John.

[Jon Shiu]

I don't know if it helps, but the actual size of the max and min openings in a copal 0 are 24mm and 1.5mm

Jon

[Tom J McDonald]

Thanks Jon, I'm at work, but when I get home I will have to measure to see.

When the dial indicates f/5.6 though, the iris is definitely not wide open.

[Leigh]

the actual size of the max and min openings in a copal 0 are 24mm and 1.5mm
Thanks Jon,

I couldn't find the minimum.

- Leigh