Adjusting aperture openings - synchro compur

[philldresser]

I have an old synchro compur shutter that I want to play with (had 150 lens attached) and just received a set of lens cells to put in to the shutter (Also 150mm).

In my estimations the aperture scale should be calibrated correctly as the focal length has not changed, but the full open aperture is faster (Was f9 now f5.6). So how do I open up the aperture to the correct diameter?

Phill

 

[Nick Zentena]

Maybe I'm just tired but Eh?

If you put a 150mm cells into a shutter that held 150mm cells the aperture markings should be very close. You can measure the apparent aperture seen from the front and then use that for your measurements.

Or are you saying the old shutter is marked to only f/9? And the lever doesn't move past that point?

 

[philldresser]

Or are you saying the old shutter is marked to only f/9? And the lever doesn't move past that point?

Nick

The aperture stops @ f9 and wont open wider. I assume this to be adjustable!

Phill

 

[David A. Goldfarb]

Ignoring the scale, does it seem like the iris is open as far as it will go? Usually these shutters don't have a stop, so it should open past whatever the maximum f:stop was for the previous lens. If there is a stop, it shouldn't be too hard to find.

 

[philldresser]

David

There is plenty of available iris left to open but the lever is restricted in some way. I can't see where the restriction is occurring (If my maths is right I should be able to open up to a diameter of 150/5.6=26.8mm, where as it stops at 150/9=16.7mm) The aperture in the Copal shutter will accomodate the 26.8 with a little to spare.

I dont particulary want to open up the shutter but as it is for 'playing' I will if necassary

Thanks

Phill

 

[medform-norm]

Phill,
check the back of the shutter - perhaps there is a small screw with which the f-stop setting is adjusted? This is just a guess, as I've not seen shutters that have that issue before. However, knowing 'regular' synchro-compur shutters from previous (tedious) disassemblies, it's hard to imagine there being enough room for some kind of aperture stopping mechanism. Maybe you can post some pics of the shutter back and front? It might help.
Norm

 

[David A. Goldfarb]

I'd also guess that the stop is either on the back of the shutter case, or just inside, depending on how the lever is designed. It should just be a matter of removing a screw once you find it.