CV25/4 adjustment of mount

pvdhaar · 12-07-2005

Ever since I've had the CV25/4, I wasn't able to screw it in so that the focus mark lined up at the top. It always sat a little sideways. At first I thought it was the LTM-M adapter that caused it, but when I put it on another adapter the other day, the situation remained unchanged.

Yesterday I took the mount off and repositioned it, so that the focus mark is right where it should be. I took a couple of pictures of the process for those interested.

Picture 1: CV25/4 mounted, focus mark is to left of top position

Picture 2: Rear side of mount, there are four screws holding the mount

Picture 3: Removing the screw mount reveals a couple of shims

Picture 4: Removing the shims shows three possible positions for each of the four screws.

After this, the shims can be placed back, but positioned differently. There are four orientations that the screw mount itself can be attached now. I didn't think of this beforehand, so I had to try twice..

Picture 5: After placing the screw mount back, the lens can be screwed in so that the focus mark is at the top

It's definately easier to read the DOF scale like this

Toby · 12-08-2005

Well done Peter! You are much braver than I am

ducttape · 12-08-2005

OMGosh, I always thught it was all the CV lens only I bought! Way to go guy! And thanks for sharing too.

Brian Sweeney · 12-08-2005

This is very good information.

I would like to see it in the Repair Section, I'll bet a lot of lenses are made like this one.

dcsang · 12-08-2005

Whoa..

Just an FYI - this also happens with the CV 15mm when mounted. It's just a tad to the left of center.

As a fiddler (one that tinkers, not one that plays on the roof

) I'd be willing to take a look at this

Thanks for the tip
Dave

Nick R. · 12-08-2005

Good job, Peter. I see this question come up here and on other forums. Now people can point them to your post.

FPjohn · 12-08-2005

Hello:

I used to be disturbed by the offset 'till I realized we are assumed to be viewing from the side; the eyepiece being on the far left. A very Leitz centric view. I still wonder about a Staeble-Telexon 135mm f3.8 which mounts with its well delineated and legible depth of field scale and focus mark facing the floor. What were they thinking?

yours
Frank

pvdhaar · 12-08-2005

Quote:

Originally Posted by FPjohn

I used to be disturbed by the offset 'till I realized we are assumed to be viewing from the side; the eyepiece being on the far left. A very Leitz centric view.

Could be, but in this case the lens was oriented away from where the viewfinder is on any of the Bessa-R/R2/R2a/R3a/HexarRF/LeicaM/..

FPjohn · 12-09-2005

Hello:

So much for a logic to it! and my powers of observation.

yours
Frank

Theo-Prof · 12-19-2005

I noticed the same thing with my 15.4.5. It would not quite screw in tight enouth for the index mark to be straight up, and thus the possibility that the built in lens shade would show up in the corners. My fix was more simple. There is actually a fair amout of room around the screw heads on the mount. I just loosened the screws, turned the mount slightly and retightened the screws. I did the same with the mount on the camera body. The slight change in both mounts allowed the 15/4.5 to line-up properly.

Kevin

oscroft · 02-01-2007

Quote:

I used to be disturbed by the offset 'till I realized we are assumed to be viewing from the side; the eyepiece being on the far left

No, I'm pretty sure it's not intended to be like that - the hood on the 15 isn't square if the focus indicator isn't vertical.

Bébèrt · 02-06-2007

Dank je wel pvdhaar,
it realy works. I just adjusted my new heliar 15mm/4.5 and 4 screws later the lens was perfectly mounted on my R2M. Thanks for this usefull info.
you are an

mike goldberg · 02-06-2007

Hi... I just got the CV 25/4, and the little black dot is 1mm to the left of the groove of the CV adapter, as I look down from the top. Since this does not affect functionality in any way, I shall leave well enough alone. "If it ain't broke, don't fix it." mike

wyk_penguin · 05-20-2007

Quote:

Originally Posted by oscroft

No, I'm pretty sure it's not intended to be like that - the hood on the 15 isn't square if the focus indicator isn't vertical.

That would be a likely cause of uneven vignetting.

My Heliar is one of the stuborn type, no tinkering left it "exactly" straight. It was always a bit to the left or a bit to the right

and now I have to go return it and get another one. I Hate Voigtlander for this, but the Heliar is too good a lens to miss becuase of a misaligned mount. Why can't they get it right the first time? The Russians (and everyone else) make their mounting threads and then align them with the lens by drilling the appropriate holes. Why does Voigtlander drill 3 holes, none of which give the correct alignment (as with mine)?

pvdhaar · 05-20-2007

Quote:

Originally Posted by wyk_penguin

That would be a likely cause of uneven vignetting.

My Heliar is one of the stuborn type, no tinkering left it "exactly" straight. It was always a bit to the left or a bit to the right

and now I have to go return it and get another one. I Hate Voigtlander for this, but the Heliar is too good a lens to miss becuase of a misaligned mount. Why can't they get it right the first time? The Russians (and everyone else) make their mounting threads and then align them with the lens by drilling the appropriate holes. Why does Voigtlander drill 3 holes, none of which give the correct alignment (as with mine)?

The three screw positions can get rid of coarse problems like the one that prompted me to do this reseating of the mount on my CV25/4. But for the final mm of turn, the problem may not lie in the lens at all.

I've two CV adapters (28/90 and 35/135) and the same lens aligns differently in them. One a fraction to the left of vertical, the other dead center. You can even see that in the top picture #5, where the lens remains a bit skewed to the left..

winoto · 05-20-2007

i had the same problem with cv21 mounted without adapter on bessa L and with m adaptor onto bessa r2. however, when mounted on my leica IIIc, no alignment problems. since i use the cv21 more on my bessa L more than the leica, i did the adjustment as you have done, peter. thanks

varjag · 05-21-2007

Quote:

Originally Posted by wyk_penguin

The Russians (and everyone else) make their mounting threads and then align them with the lens by drilling the appropriate holes. Why does Voigtlander drill 3 holes, none of which give the correct alignment (as with mine)?

Because drilling apropirate holes involves relatively qualified human labor, while drilling the 3 holes can be easily automated and the approximate matching can be done by anyone.

wyk_penguin · 05-21-2007

Oh well enough ranting on the qualities of mass produced products. Eventually I swapped it with one that fits without tinkering at the shop.

chdiliproy · 06-16-2011

Hi, can anybody tell me where the pictures (1 through 4) are? I might have ruined my CV 35. I opened the base plate, and went beyond that. I also opened the little black screws holding the helicoid. After assembly, the whole focusing mechanism is a mess.

jamesmck · 06-16-2011

Ummm.... Anyone know why I don't see any of Peter's pictures (with either Firefox or Chrome)?