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Thread: Which CV 35 2.5

  1. #1
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    Which CV 35 2.5

    I've read good things about the CV 35 2.8.
    I see there are 2 versions, the threaded and the M mount.
    Are these lenses the same optically?
    Can the M mount be 6 bit coded, or am I better off going with the thread and adaptor for this lens?
    Thanks
    Shaun O'Boyle
    new.oboylephoto.com

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    Member Bébèrt's Avatar
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    Re: Which CV 35 2.5

    Here you can find the coding for this Skopar

    http://whimster-photography.com/leic...des/index.html
    Enjoy living, live to enjoy

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    Member Bébèrt's Avatar
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    Re: Which CV 35 2.5

    Some info on this lens here:

    http://www.cameraquest.com/voigtlen.htm

    If you count the extra LTM adaptor, the price is about the same. Altough I haven't got this lens, I would go for the smaller pancake type.
    Enjoy living, live to enjoy

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    Senior Member Braeside's Avatar
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    Re: Which CV 35 2.5

    I have the classic version with the Voigtlander LTM to M adaptor ring. The ring is easily hand coded and as it is recessed it does not rub off.

    One word of caution, there are sample varitions with this lens, the first copy I got was quite poor. The replacement is excellent.

    I also bought the optional LH hood which obscures a bit of the VF but does help reduce flare compared to the almost useless ring that is supplied with the lens which only serves to mount the lens cap.
    David Anderson

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    Senior Member Braeside's Avatar
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    Re: Which CV 35 2.5

    This is the Classic Skopar with optional LH-2 hood attached.

    Attachment 25313
    David Anderson

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    Senior Member Braeside's Avatar
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    Re: Which CV 35 2.5

    Some photos taken of the misty weather with the classic Skopar at the weekend. [Processed to change colour balance quite a bit.]
    Attachment 25321

    Attachment 25320

    Attachment 25322

    Attachment 25319
    David Anderson

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    Re: Which CV 35 2.5

    It looks like the classic version is teh right choice. I wonder what changes have been made to the lens in version PI and PII.
    Beautiful images made with that lens. What light!
    Shaun O'Boyle
    new.oboylephoto.com

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    Re: Which CV 35 2.5

    according to CameraQuest, the CV dealer, the differences are:

    "Same Glass as Screw Mount 35/2.5C but now Rangefinder Coupled Leica M mount"

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    Re: Which CV 35 2.5

    as you might be aware, you can also get the "coding kit", which I'm assuming would work with the M mount version, but be aware that the pen marks will eventually wear off. No big deal, you just have to re do it every so often.

    http://www.popflash.com/index.php?p=...=4352&parent=0

  10. #10
    Mango
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    Re: Which CV 35 2.5

    You can get a coding kit for $5 (paypal, shipped). It works perfectly on all my lenses.

    http://bophoto.typepad.com/bophoto/2...-m-lenses.html

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    Re: Which CV 35 2.5

    Thanks, I ordered one of the kits from Bo today. Can't beat that deal.
    Shaun O'Boyle
    new.oboylephoto.com

  12. #12
    wilsonlaidlaw
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    Re: Which CV 35 2.5

    To give the other side of the picture, I have a horrible 35/2.5 Skopar classic. It back focuses and even if you focus bracket, it is as soft as putty with very low contrast. I recently put it on my M4 when it went for its first service (not bad after 40 years), just so that it would have a lens on it for anything that needed checking with a lens. Kelvin, who does my camera servicing, said what a poor lens it was and said just out of interest, he had tried to improve it for me. He commented further that it was a pretty crudely made thing and it is not really possible to move the lens cell relative to the RF cam, so no real progress possible. I did not pay a lot for it second hand, so I am not too worried.

    My record with CV lenses has been poor. I have bought three and have yet to get a decent one. My best record has been with Zeiss lenses, where I have bought three and got three great ones. My Leica record is somewhere in the middle. However, normally Leica lenses are correctable, if they are not good. My only failure has been a recent 11826 50mm Summicron, where the back focus ran from nil at infinity to dramatic at 2 meters. The two lens guys I took it to, went "arghhh - take it back to the seller", which I did.

    Wilson

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    Senior Member Braeside's Avatar
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    Re: Which CV 35 2.5

    It is a bit of a lottery with CV lenses certainly, the first CV35/2.5 Skopar Classic I had was very bad on the left side, so was replaced by the retailer with a copy that is fine as far as IQ goes, however the infinity stop was not correct, though the RF agreed. I just shimmed the lensmount with foil and that fixed that.

    The ebay bought CV 75/2.5 Heliar screwmount also had a problem with front focus, I had to lap the RF coupling ring on the lens to correct that. IQ is very nice on that copy too.

    I think I can accept this given the price compared to Zeiss and Leica, but it would be nicer if CV's QC was a little better.
    David Anderson

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    Re: Which CV 35 2.5

    yes, agreed. But for the price, it's worth the hassle. Don't you think? That being said, the day I win the lottery, all of my glass is going to have a red dot on it....

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    Senior Member Braeside's Avatar
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    Re: Which CV 35 2.5

    I would agree, if the price is right. Best to buy from somebody that will exchange if the copy is poor though. I got lucky with my eBay CV75/2.5 as I could fix it myself.
    David Anderson

  16. #16
    wilsonlaidlaw
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    Re: Which CV 35 2.5

    Quote Originally Posted by Braeside View Post
    I would agree, if the price is right. Best to buy from somebody that will exchange if the copy is poor though. I got lucky with my eBay CV75/2.5 as I could fix it myself.
    David,

    Out of interest, how did you lap the RF cam to equalise the amount removed for all distances. I might give this a go on my 35/2.5, as there is little to lose. Otherwise it is just a paperweight. It is never going to be much good for digital but it might be OK for use on my M4.

    Wilson

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    Senior Member Braeside's Avatar
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    Re: Which CV 35 2.5

    Quote Originally Posted by wilsonlaidlaw View Post
    David,

    Out of interest, how did you lap the RF cam to equalise the amount removed for all distances. I might give this a go on my 35/2.5, as there is little to lose. Otherwise it is just a paperweight. It is never going to be much good for digital but it might be OK for use on my M4.

    Wilson
    Hi Wilson,

    On the CV75/2.5 the end of the RF coupling tube is not angled to any great degree (if at all), and I only had to take the smallest bit off, just really the thickness of the black paint on the end of the tube.

    I took advice of a friend who recommended starting with 600 grit wet and dry paper glued onto a really flat surface, I used a piece of old kitchen laminate, but glass plate would do. Then I wet the paper and carefully rubbed the end of the RF tube in a figure of eight motion a couple of times. I then cleaned the end of the tube and refitted to camera, tested and found I had reduced the RF error by about half already.

    I repeated this with finer grade of wet and dry (1200 grit) again just a couple of gentle figure of eight turns. Checked again and very close to perfect.

    Finally I used a bit of "Brasso" metal polish on the back of a piece of wet and dry stuck down to do the final bit. Cleaned all up and checked again, it seems almost perfect, perhaps a fraction short of where it should be, but I am stopping there as I do not want to go to far, as there is no way to easily lengthen the tube!
    David Anderson

  18. #18
    Senior Member Braeside's Avatar
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    Re: Which CV 35 2.5

    Quote Originally Posted by wilsonlaidlaw View Post
    David,

    Out of interest, how did you lap the RF cam to equalise the amount removed for all distances. I might give this a go on my 35/2.5, as there is little to lose. Otherwise it is just a paperweight. It is never going to be much good for digital but it might be OK for use on my M4.

    Wilson
    Wilson I note that your copy of CV35 BACK focuses in that case you need to lengthen the RF tube?
    David Anderson

  19. #19
    wilsonlaidlaw
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    Re: Which CV 35 2.5

    Quote Originally Posted by Braeside View Post
    Wilson I note that your copy of CV35 BACK focuses in that case you need to lengthen the RF tube?
    Agreed David. I was going to put a shim under the mount and then do the fine adjustment by lapping the RF cam. I also have a John Milich mount which is .01 mm thicker than the Voigtlander one. I don't think the RF cam slope is quite right as well. The back focus is worse at infinity than at 2 meters.

    I had the same recently but the other way round on an otherwise mint 11826 current model coded 50mm Summicron I had bought. It was spot on focus at infinity albeit with the RF cam needing a small amount of adjustment, as the images had not quite reached coincidence (on the Summicron, the RF cam tube can be adjusted relative to the optical cell). By 2 meters, the lens was back focusing by between 75 and 85 mm on scale and even worse on RF. My usual lens guy said he had never seen anything like it on an external focusing Leica lens. He also spoke to one of the top Leica lens people in the UK, who said that it was unlikely that a lens behaving like this could ever be got right and I should ask for a refund, which I did and got.

    Wilson

  20. #20
    Senior Member Braeside's Avatar
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    Re: Which CV 35 2.5

    Quote Originally Posted by wilsonlaidlaw View Post
    Agreed David. I was going to put a shim under the mount and then do the fine adjustment by lapping the RF cam. I also have a John Milich mount which is .01 mm thicker than the Voigtlander one. I don't think the RF cam slope is quite right as well. The back focus is worse at infinity than at 2 meters.
    Wilson
    Hi Wilson,

    I am not sure that would work - because adding thickness to the lens mount will only shift the scale focus of the lens and the offset between the RF and the actual focus will remain the same. If the lens is back focussing then the RF cam needs to be made longer with respect to the optical cell.

    Think I have got that right.
    David Anderson

  21. #21
    wilsonlaidlaw
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    Re: Which CV 35 2.5

    Quote Originally Posted by Braeside View Post
    Hi Wilson,

    I am not sure that would work - because adding thickness to the lens mount will only shift the scale focus of the lens and the offset between the RF and the actual focus will remain the same. If the lens is back focussing then the RF cam needs to be made longer with respect to the optical cell.

    Think I have got that right.
    David,

    I am not sure you have this right.

    Let's say for argument that it is back focusing by 10cm at 2 meters. That means that the point of most accurate focus is at 2.10 meters, when the lens is set on scale to 2 M or focusing on the RF to 2 meters, assuming that the scale and RF cam are in sync. So in order to get the lens to focus at 2 meters, you would have to focus on scale to 1.90 meters. This would involve moving the lens cell (and RF cam) forward, so that adding a shim between lens and mount would have the same correcting effect.

    Now has my brain become scrambled (not unlikely with the new anti arthritis regime I have been put on) or is this correct?

    The above was why I could not get my Summicron 50 corrected, because the sync between the RF cam and optical cell seemed to vary between infinity and 2 meters and the extent of back focus varied as well. In theory if a lens is correct at 2 meters, as long as the focus thread is the correct pitch, the lens should be correct at infinity.

    Wilson

  22. #22
    Senior Member Braeside's Avatar
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    Re: Which CV 35 2.5

    Wilson, This is hurting my brain too. But perhaps we are slightly at cross purposes.

    In the 2 cases I have dealt with, I had 2 different problems to fix.

    I felt the M8's RF was adjusted fine as it worked well with other Leica lenses.

    1. CV 75/2.5 Front focus at infinity and other distances - when the rangefinder patch was aligned, the lens was focussed slightly in front of where it should be. This I could cure by shortening the RF cam length relative to the optical cell, by lapping. NOTE: This lens was accurate on the scale - infinity marking on lens was actually infinity OK, before and after the RF cam length was reduced.

    2. CV 35/2.5 Infinity marking on lens not infinity focus, but Rangefinder focus accurate. In my case infinity was a little bit short of the infinity end stop, so I shimmed the lens mount which moves both RF and optical cell forward by the same amount. This brought the scale into agreement with the actual distance and the rangefinder still focussed accurately.

    Hopefully from the above you can work out which of the two problems you have, it may you have both - the lens needs shimmed to bring the scale into alignment and the length of the RF cam needs adjusted to get the RF to agree with true focus.
    David Anderson

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