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What would you use to rotate this ring?
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PostPosted: Tue Jul 14, 2009 1:08 pm    Post subject: What would you use to rotate this ring? Reply with quote



My question is about the sleeve / ring / flange that screws into the shutter, and the front elements I'm holding screw into it.

As this is not a front cell focusing lens, I figure the only way I can adjust infinity is by rotating this sleeve / ring / flange in or out. It has three scallops pointed to by the arrows - so a regular spanner will not work. Maybe I have to use a screwdriver or pilers, if there's not a three-legged thingamabob for the job.


PostPosted: Tue Jul 14, 2009 3:12 pm    Post subject: Reply with quote
It would be something I'd probably make out of brass or copper tubing.
Brass would be stronger, tho. Try a place that repairs band instruments
and see if they have a junker trombone bell or a section out of an old
sousaphone. I use a jeweler's saw frame with #2 blade in my work for cutting
but a hacksaw would do as well, just not as neatly. Somewhere
there's a supplier for spanner wrenches, will look in my huge list of favorites
and see if I can find it. Don't recall seeing a 3-point wrench when I was
perusing it, tho.


PostPosted: Tue Jul 14, 2009 3:34 pm    Post subject: Reply with quote
something like a 3-jaw chuck for a metal lathe would be best.

possibly a jar lid remover, the clamp-pliers kind, with vinyl coated jaws.

make a tool: drill hole into flat aluminum stock, size of outside of ring, flathead-screw three small pieces of aluminum inside to fit scallops...


PostPosted: Tue Jul 14, 2009 4:19 pm    Post subject: Reply with quote
Maybe you could use a rubberband wrench like this one:

http://forum.mflenses.com/the-boa-constrictor-a-useful-tool-t14600,highlight,boa+constrictor.html

Regards,

Jes.


PostPosted: Tue Jul 14, 2009 4:21 pm    Post subject: Reply with quote
Excellent ideas!

Perhaps I should ask the underlying question:

This is a rail-focus set up, ie. the front element isn't used to focus, but rather the whole assembly moves forward.

I'd like to set a more accurate infinity focus - which I figure I can do by moveing the front elements forward or back slightly. This sleeve is the only thing I can see that might allow me to go backwards (short of doing something with the infinity stop screw on the rail itself) and forwards (short of putting a gasket of the right size between lens and this thing it screws into.

How else might I correct infinity with this kind of set up?
thanks, ness


PostPosted: Tue Jul 14, 2009 7:58 pm    Post subject: Reply with quote
Well, if it only has afront element, it may work - but if there is a rear element you would be changing the lens spacing and that would degrade the optical quality considerably.


PostPosted: Tue Jul 14, 2009 9:16 pm    Post subject: Reply with quote
Gotcha, Klaus. I will try the following to figure out what direction I need to go:
- move the entire assembly back slightly on the rails
- move the focus sled forward
- unscrew the front element assembly slightly

The Skopar is a 4 element design, but on this camera the two groups seem to be cemented into two units, so I can't see a way to change the distance between the front and second elements.

It is capable of sharpness, only when I set it to the factory infinity, it's not quite in focus. Probably it was enough so for the small prints they made at the time from cameras like these.

I'm having a lot of fun!


PostPosted: Tue Jul 14, 2009 11:08 pm    Post subject: Reply with quote
Nesster wrote:
Excellent ideas!

Perhaps I should ask the underlying question:

This is a rail-focus set up, ie. the front element isn't used to focus, but rather the whole assembly moves forward.

I'd like to set a more accurate infinity focus - which I figure I can do by moveing the front elements forward or back slightly. This sleeve is the only thing I can see that might allow me to go backwards (short of doing something with the infinity stop screw on the rail itself) and forwards (short of putting a gasket of the right size between lens and this thing it screws into.

How else might I correct infinity with this kind of set up?
thanks, ness

I've just had a look on my Welta 9x12 with rail focus and the focus scale is mounted on a hidden sliding tab secured by a flat head screw in a slot. Shine a torch under the focus scale mount and you might see yours is the same. If yours has one, that is.


PostPosted: Fri Jul 17, 2009 1:25 am    Post subject: Re: What would you use to rotate this ring? Reply with quote
Nesster wrote:
My question is about the sleeve / ring / flange that screws into the shutter, and the front elements I'm holding screw into it.
If you're wanting to unscrew/adjust that ring, and if it is threaded, I'd suggest first trying one of Alex's firm rubber tools for the job. If it works for the application, it will cause no physical damage to anything on the camera, while lathe chucks and pliers probably will.
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