Getting a Voigtlander lens "re-centered"?

[agoglanian]

Hi guys,

I bought another CV 21mm f/4 (not on this forum) as I wanted to try one again and I was hopeful I would be able to locate a copy that had even performance across the frame (Note: I'm not expecting nit-picky perfection, just usability). The copy I had in the past definitely struggled on digital, as in the left and right edges (thirds really) of the frame were never "sharp" meaning, they were basically always blurry.

This new copy is in pretty decent shape overall, clean glass, typical helicoid grease on the back (every CV and Zeiss lens I've owned / tried has exhibited this). And when I did a quick test on my M240 I saw that the center was wonderfully sharp, the right side was also very decent from wide open but the left side is clearly "off". It's mostly ok by f/11 but still not even performance even at that point. I'm mostly going to be using this lens on film, so who knows maybe it won't even show up on film, but it would be nice to be able to use it on digital when the need arises.

I'm sure the lens will still be usable in its current state, but my question is this:

Is it possible to have the lens reassembled to correct this problem? If so, who would be the person to send it to? My concern would be that having this done would likely cost as much as the lens itself, but the end result would hopefully be a perfectly functioning lens that would easily meet my ultra wide angle needs indefinitely.

At $300 I think this lens is a total bargain, but at $600+ I'd have saved up a little more for a Super Angulon. (Just being honest)

Any thoughts?

 

[sevo]

Forget it. Most alignment issues happen when cementing groups - if undoing and re-cementing them was economically feasible, the makers would do it themselves...

 

[Huss]

all these wide CV lenses smear on the corners due to the rear nodal point being too close for the sensor. It's only the latest generations like the CV 15 Asph III that work properly on digital.

My CV 21 smears on my M240, but is fine on film.

 

[agoglanian]

Well my concern was the unevenness. The center and right sides are great, but the left is off, to me that says something's off internally.

Not trying to be a complainer, just looking for creative solutions 🙂

It's mildly frustrating as the seller was "too busy" to send me sample images when I requested them, I took a chance and bought the lens anyway. As you mentioned Huss I'm hopeful it'll be fine on film because that's where I primarily intend to use it, so this could wind up a non-issue! Haha

 

[Huss]

Abram, you can come down to my gallery in San Pedro and try out my CV 21 4 to see if it is any different. I'm there most weekends.

 

[Rico]

Your C/V may shimming, a simple adjustment performed at the lens mount. Since bayonet-mount lenses are secured against the camera mount with spring force, you can just wedge a bit of paper on one side, and confirm symmetric performance across the frame. As noted, the chance of getting w/o sharpness across a digital sensor with an UWA is about zero: the sensor cover induces field curvature. Your best option for sharpness is a retrofocus lens but, then, you lose that compact rig.

 

[agoglanian]

I appreciate the responses guys, I guess I just won't expect too much and make the most of it! I imagine it'll work fine on film and I'll find out when I get my film back.

 

[Ronald M]

My CV25 does the same. I use it for a paperweight.

I have two 24 3.8 ASPH in the family and both work from 3.8 in the corners. You get what you pay for.

 

[agoglanian]

Naturally this is always the case. All my other lenses are from Leica and I agree they work incredibly well, but 21mm is not a focal length I use more than maybe 5-10% of the time so I figured the CV 21 was sufficient enough.

If I happen to come across a Super Angulon for a fair price in the future though I'd definitely consider that.

 

[rfaspen]

Whew! I actually almost bought this lens.

Sorry Abram for the difficulty. FWIW, my LTM version of this lens also has a little unevenness. I only see it on the M9 (didn't see it on the M8 or film bodies).

Larger picture: I'd also like to have an M-mount 21 for those times it would be the "right" focal length. The lens to get: Leica 21/3.4 SEM but......it runs a bit higher in price. I think SAs have come down a bit in price on the used market, and seem a good deal again? I use the LTM CV for now, but dislike the little focus post.

 

[agoglanian]

Of course, the Super Elmar is an optical marvel, and if I frequently shot 21mm I'd most certainly be considering that instead. The reality is that I live in the 28-50 range and occasionally step out to 21 or 90 when the need arises.

I'm looking forward to seeing the film results, I'm optimistic now that it'll look just fine there.

 

[Livesteamer]

If anyone could do it, John Van Steltan at Focal Point in Colorado would be the one. It would be costly. Joe