Canonet central lens element removal

[Jon Goodman]

Removal of the Canonet central lens element often causes grief for the do-it-yourself repairer. You can see the two slots where a spanner would go, but you can't reach them. What is the answer? Here is how I do it:

First, you'll need two tools. (1) a pin vise. It doesn't have to be an expensive one. You can find them at hobby stores for $10 or so. Also pick up a drill bit with a diameter of about 1.2mm. (2) a pointed tip spanner...with fairly sharp points. I file mine to a tip of about 1mm.

Okay, step one. Place the drill bit on the outer perimeter of the lens collar and slowly turn the pinvise to start the bit in its work. Carefully turn the vise until you've made a hole about 1 to 1.5mm deep. Don't worry about breaking the glass. You will only damage the glass if you slip with the pin vise. You can't drill through it...the collar isn't designed that way.

Step two...diametrically opposed to the hole you've drilled, drill another. Basically, you're going to repeat step one.

Step three...on another note. I think I can only attach 5 images to each thread, right?

 

[Jon Goodman]

Canonet central lens element removal #2

Canonet central lens element removal #2

After step (1) and (2), you'll have some metal shavings in the cup of the lens shroud. Turn the camera over and shake them out. Don't worry that you've just defaced your lens. We'll take care of that later.

Step (3)...adjust your spanner so that the points fit into the holes you've drilled and unscrew the lens, turning in a counter-clockwise direction. You can see the element and its collar removed and on the back side you can see how the glass is held into its frame. You can also see why this element was removed to begin with...this twin element suffered breakdown of the cement holding it together. Repairing that is a project for another day...a good place to buy UV curable optical cement is S. LaRose & Co...I think www.slarose.com will get them. Something like that.

After you replace the lens element, get a tiny droplet of flat black paint on the tip of a toothpick or sharp bamboo skewer. Let it drop into the holes you've drilled. If you are careful, you can fill both holes up neatly with more than one droplet.

Did I forget something? I can't think of it right now, but it is a possibility.

Questions? Please let me know.
Jon

 

[laptoprob]

Hey Jon,
Just wondering, why do you need to replace the central element?

Good luck, Rob.

 

[Jon Goodman]

Well...the central element is actually two lenses glued together to make one lens. In this case the glue (probably Canadian balsam) has turned yellow and has begun to deteriorate at the edges. It will of course still work...the damage is limited to the perimeter at this point. But...it will detract from the value of the camera, and this one is in near perfect condition.

I can repair the lens, but I must first calibrate the thickness, soak it in a solvent, separate and clean the two elements and glue them back together creating the same thickness as original. For that, I will need a special UV cure optical quality glue. This glue remains soft until you expose it to UV light (sunlight will do it).

We can use this element for another post on repair issues after I get the glue.
Jon

 

[Jon Goodman]

But, another reason a person might want to remove this element could be to flush clean the shutter blades and/or the aperture blades, which can become gummed over time. The front and rear elements are not difficult to remove, as the retaining collars are accessible. The central one is...more challenging.
Jon

 

[matu]

Jon I find your post very usefull, it even may throw light on how to remove a central element on a similar camera.

Pablo