Advice on Rokkor 40mm requested

[pfogle]

Hi, after my adventures with the Canon f1.2, I'm temped to have a go at fixing the front focus on the Rokkor CLE 40mm f2.

I imagine I'll have to get the lens module out of the focusing mechanism, and sand a bit off the shim/spacer.

Anyone taken one of these things apart and have any words of wisdom/warnings?

Any advice welcome!

thanks
Phil

 

[back alley]

i have not done any work on the 40 but the canon 1.2 is very easy lens to work on.
not trying to rain on your parade but it might not be as easy with the 40.

 

[ferider]

The 40/2 CL Rokkor that I have was (slanted RF ring) real easy to disassemble, much like the 40/2 Summicron-C.
Just take the retaining ring off the back and the barrel will come off the focus mount. You will see a brass collimation
shim on the barrel, much like with your Canon 50/1.2.

However: the Leitz lenses and clones are typically very well collimated. If your Rokkor focuses badly I would really
check the RD1 RF adjustment, first. Take a tape measure, focus on an object 1m away, and compare the 1m tape
measurement with what it says on the lens scale. Repeat this focusing from left and right, to see if there
is back-lash. The two numbers have to match (within one inch or so), and are independent of the lens collimation.

Good luck,

Roland.

 

[pfogle]

The 40/2 CL Rokkor that I have was (slanted RF ring) real easy to disassemble, much like the 40/2 Summicron-C.
Just take the retaining ring off the back and the barrel will come off the focus mount. You will see a brass collimation
shim on the barrel, much like with your Canon 50/1.2.

However: the Leitz lenses and clones are typically very well collimated. If your Rokkor focuses badly I would really
check the RD1 RF adjustment, first. Take a tape measure, focus on an object 1m away, and compare the 1m tape
measurement with what it says on the lens scale. Repeat this focusing from left and right, to see if there
is back-lash. The two numbers have to match (within one inch or so), and are independent of the lens collimation.

Good luck,

Roland.

thank, Roland, I have the later lens with a complete ring on its own helicoid. My other lenses focus OK, particularly the collapsible summicron and the (no longer mine!) 50/1.5 Nokton. I'm hesitant to change the camera and then have the other lenses go out. Now the Canon seems to be good as well. It's all a bit of a black art

I've checked the RF as you suggested, and it gives the same (correct) distance with both the Canon 50 and the Rokkor. However, the Canon is now focusing correctly and the Rokkor focuses about 3cm nearer at f2.

What I need to get is the tool to get the ring off the back. Anyone know where you can get these? The ring has two round holes, so I guess it's some sort of needle-nose pliers?

thanks
Phil

edit - just rechecked, and the focusing scales of both lenses are exact at 4 feet, but now both lenses are front-focusing by about 3cm - I knew I shouldn't have taken the Canon off the bl**dy camera :bang:

 

[ferider]

It does sound like the camera is ok and the lens is off.

However, 3cm is not a lot off for a 40/2, close-up. The total DOF of the 40/2, .8m distance,
and for 35mm film format is 5cm. 7cm at 1m distance. If the lens back-focuses, 3cm is almost
OK, using the 1/3rd, 2/3rd rule ...

If you want to go for it, I suggest buying some needle nose pliers and modifying/grinding
their front, if necessary.

Good luck,

Roland.

 

[mwooten]

...
What I need to get is the tool to get the ring off the back. Anyone know where you can get these? The ring has two round holes, so I guess it's some sort of needle-nose pliers?

Phil,
Have you tried Micro-Tools? Here is a link to their Euro site (LINK).

Michael

 

[pfogle]

thanks, guys...

Ron - the main issue I have with the front focus is not so much close up, but that the lenses are noticeably soft for subjects at 'infinity' when used at f2 or (for the Canon) above. There's no way round this except to adjust the lens, as you can't compensate by deliberately back-focusing.

Michael - great link, thanks!

ps - I've decided to shoot every day with these lenses for a week, and then decide if I really do have a problem, or whether I'm just being neurotic about this

 

[pfogle]

Update...

I went and spent more money today - bought a very nice clean tab-focus summicron with hood.

Anyway, it also focuses a tiny bit in front, so when I got home I decided to have a fiddle with the rangefinder. I didn't want to take the top off, so I limited myself to screws 1 and 3 in the howto on RichC's sticky. That brought all the lenses pretty close to acceptible except the Rokkor which still was madly front focusing.

So, armed with a swiss army pocket knife and some emery paper, off came the back of the lens and I found the relevant spacer and ground it down. From 1.6mm to about 1.5mm. Problem solved

Now I just have to work out if I can afford to keep all these lenses

 

[ferider]

Cool. Thanks for the update ... The M-Rokkor is a great lens. Mine is very sharp, see:

Cheers,

Roland.

 

[pfogle]

Great shot, Roland.

the new summicron is making all my other lenses look sick, except the 40mm and the 28mm Ultron.

I'll keep the 'cron, the Rokkor (I don't have a 35mm any more) and the big Canon. Might let the collapsible summicron go...

things are looking good

 

[tmessenger]

You can make a tool out of needle nose pliers, just file down the ends, handy to have. I have the 40/2 CLE and it's the best lens I've ever owned. Photo with this lens at f2.

Tim

 

[pfogle]

You can make a tool out of needle nose pliers, just file down the ends, handy to have. I have the 40/2 CLE and it's the best lens I've ever owned. Photo with this lens at f2.

Tim

I think I'll do that - this time I used the scissors from my pocket knife, but it has burred the edges of the holes a bit - oh well, now it's a 'user' lens!

(but a great one anyway )