advice on Cooke with stuck Soft focus

gandolfi

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(I have posed at LF forum as well, so if you are overthere too, then skip this...)

I have a really beautiful 14.5" (370mm) Cooke Series II portrait lens.

the condition on the lens is really fantastic, with a deep warm glow to it - it looks like a lens that havn't been used much..

However, the soft focus mecanism is stuck - as firmly as it can be.. which obviously is a shame..

I have tried to soak the soft focus with oil, but it is atill stuck.

The condition of the lense is so fine, that I actually don't think old dust or something similar would cause this problem.

on the back of the lens ther is a little plate with what it seems like two screws screwed into the glass (the moving part of the lense?)

I am tempted to try and remove these screws, but I think I have read somewhere, that they are there for a reason to begin with..
That Cooke did this , as the moving lense had to be placed with much precision...

So, my question to you is: would there be a way to make the soft focus work, without destroying the lense all together?

(I have another, slightly smaller Cooke, I can use.. so I won't risk too much..)

I have taken some pictures of the stuff mentioned above..
 

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archphoto

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My first impression: this lens had a major overhoal, has been cleaned and repainted.
The 2 screws are not the original ones and are too long .... maybe.

It looks like those 2 screws interfere with the movement you want.

Peter
 
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gandolfi

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I agree that the screews (looking at the last image) looks to modern (my other Cooke has the same screws, but they look different).

so your "maybe" is my concern...

what would happen if the screws were to be unscrewed..?
 

archphoto

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These srews go through 4 surfaces:

Chrome plate
outer shell
??? maybe a guide
shell that has to move
glass

What I would do is to take one screw out and have a verry good look at the hole.
File that screw down a bit and measure its lengh.
Than do the other screw to the same lengh

You will have to doe this a couple of times to get to the right lengh.

Otherwise: you have an other Cook lens: take one screw out and measure,
file the screws of the problem lens down to that lengh replace and see what happens.

Good luck !
Peter
 

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my uneducated guess is the same as peter's more educated guess.
the screws are the wrong length and obstruct the mechanism that
separates the groups that soften the image. maybe it was done this way
on purpose because the mechanism was "loose" and defocused to soft
all the time by itself, especially when s/he wanted to image to be stopped down and sharp ...

i think jim galli used this same lens to shoot his now famous cowboy wedding ..
maybe he has disassembled his lens and knows what size the screws should be ..
or can suggest a remedy for your problem.
 
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gandolfi

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I think/fear you're right.
The problem for me now is, that I still think I have read, that the screws has to be there (to hold the moving lens part in place).

Bu unscrewing one at a time seems like one way to go...

I took ar couple of snaps of my other Cooke, so you can see the plate with the screws (this looks original) and the markings in the glass inside..

Thanks for your help so far..
 

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archphoto

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Im talking as a repairman now.

There is a possibility that the former owner did put new screws in that were wider/thicker than the original ones.
It is (verry much) posible that there are 2 slits in the barrel that should move.
If that is the case you will need to file down the thickness of the two screws at the end part of the screw, just the thread, so they will fit into the two sits without locking the front barrel up.

I wish I had the lens in my hands in Holland, then the problem would be solved in an hour or so, maybe less.

Peter
 
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gandolfi

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hi Peter..

So if I sent the lens to you, you could fix it?

If so, how costly would you think it would be?
 

archphoto

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I would love to, BUT: I am in Brazil right now and will not be back in Holland before July this year.

Cost: shipping cost only.

On the other hand: if you can measure the one screw of your older Cook and one from this lens and send them to me, if posible pic's of them.
I have quite a bit of tiny screws here in Brazil, I could send you some by mail at no cost.

Peter
 

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another problem might be that, since the former owner used winder/thicker screws,
thinner diameter screw shafts will now work -
the thread size is now tapped out for a larger screw ...
MAYBE if some of the turns/threads are filed down/ removed, on the areas
that the lens needs to have these bigger threads be not bind it / make it
seized-up .. that might work .. but i don't think thinner screws will actually hold
since the holes are bigger now than they were before ...

maybe find a machinist in denmark who might be able to take the screws out, put
a threaded shaft in the holes and re-tap it out to fit thinner screws, and the shafts would have slots in them
to allow the lens to rotate as it was designed to do ...
or maybe find a tapered screw that looks like a golf tee / threaded peg
so it holds onto the top of the lens, but is smooth just takes up space in the bottom .. .

it sounds like a fun project ( kind of )
 
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gandolfi

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Hi Peter.
I am in no hurry, so we can get back to it...

Thanks for all the suggestions.
 

Ian Grant

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You could try asking Cooke, they are still in business (although now split from taylor Hobson), but they are now heavily involved with making cine camera lenses. There may well be a retired employee who could tell you what the problem is likely to be. Those lenses were still made in the 60's and possibly 70's.

Ian
 
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