Mister E
Well-known
I don't buy all the hype about copy variation in the VM 21/4 or any CV for that matter. All of mine have performed as expected. I made the following comparison for my friend considering which lens to buy the other day:
ZM 21/4.5: Bigger, Slower, more expensive, a ton of fall-off, almost no distortion, maybe sharper in the corners wide open, character and no flare
VM 21/4: Smaller, cheaper, faster, better handling, less fall-off, very minor distortion, sharp, no character and a lot of flare
ZM 21/4.5: Bigger, Slower, more expensive, a ton of fall-off, almost no distortion, maybe sharper in the corners wide open, character and no flare
VM 21/4: Smaller, cheaper, faster, better handling, less fall-off, very minor distortion, sharp, no character and a lot of flare
Bob Michaels
nobody special
Roger Hicks recently made the excellent observation that there is a very low threshold with modern optics where our personal vision passes any difference in optical quality. (Roger please correct me if my paraphrasing was not what you meant.)
I have the CV 21mm and it certainly does not impact the quality of the photos I make. For comparison, I also own the Zeiss 21mm Biogon 2.8 in ContaxG mount, probably the highest rated 21mm lens of all time.
I have the CV 21mm and it certainly does not impact the quality of the photos I make. For comparison, I also own the Zeiss 21mm Biogon 2.8 in ContaxG mount, probably the highest rated 21mm lens of all time.
Turtle
Veteran
So because yours have been fine, you think the many others out there saying they have had issues are 'hype?' Its very real I am afraid. I love CV lenses and am a particular fan of the CV 35 2.5 Pancake, but there is not the same optical consistency as there is with ZM lenses for example. Try see how many people report ZMs that are decentered.
Sean Reid very clearly documents 3 out of 4 CV 21s being decentered with the 4th copy, loaned by a reader, putting in spectacular corner performance (all four corners). The point here is that when the lens is performing up to its potential it is spectacular, but the cost of perfectly centering each and every lens is very high and cannot be done reliably for the cost of CV lenses.
A lot depends on how demanding you are too. There is an epic difference between blowing up a shot wide open to 20x16 and printing shots take an f11 to 10x8 in terms of what you will see. A lens visibly decentered at f4 might look very good at f8.
Sean Reid very clearly documents 3 out of 4 CV 21s being decentered with the 4th copy, loaned by a reader, putting in spectacular corner performance (all four corners). The point here is that when the lens is performing up to its potential it is spectacular, but the cost of perfectly centering each and every lens is very high and cannot be done reliably for the cost of CV lenses.
A lot depends on how demanding you are too. There is an epic difference between blowing up a shot wide open to 20x16 and printing shots take an f11 to 10x8 in terms of what you will see. A lens visibly decentered at f4 might look very good at f8.
Mister E
Well-known
There's no need to get grumpy. Having had decentered lenses I know that they don't look good at any aperture. Wide open, f/11 they look the same: lousy. I think Mr. K would have to argue with you about not being able to afford quality control at his prices. Don't forget who makes all but two of the Zeiss branded lenses. I think Cosina's quality control is just as strict as Leica, but people don't make excuses for Cosina like they gladly make for Leica. Both companies are probably members of the ISO which dictates quality control and other guidelines.
Krosya
Konicaze
I have had 2 CV 21mm lenses in the past. Both were very good as far as I could tell. However, since I really like to use 21mm I opted for a better (and more expensive) options. Tried 2 different Kobalux 21's and finally ended up with ZM 21/2.8. What a fantastic lens, I have to say. I never did try ZM 21/4.5 - it's just way too slow for my taste, but the 2.8 version - sooooo goooood. Great flare control, great bokeh, great sharpness - it does all I need, really, - good for all sorts of use in this FL.
Having said that - I still like the CV 21 a lot and if I didnt want a faster lens, I'd be very happy with a CV21.
Having said that - I still like the CV 21 a lot and if I didnt want a faster lens, I'd be very happy with a CV21.
kossi008
Photon Counter
Well, I have to side with Turtle here, even though I started this thing, kinda. It's not about what Cosina CAN do, but what they DO. I have no doubt that they CAN apply the same stringency in QC as Leica, but I don't think they will do it for the money of a CV lens.
Thus I believe that one would find less decentered ZM than CV lenses. I have no proof, of course.
Tim Gray
Well-known
For an extra $600 over the CV lens, I got the ZM 21/4.5, finder, and hood used. Seemed like a good deal to me. I just developed the first roll from it last night - haven't scanned yet.
My take on the differences:
- the 1/3 of a stop difference is meaningless, especially with the vignetting these lenses have.
- the optical formulas look pretty similar
- the ZM has a 46mm filter, the CV has a 39mm. I can only imagine that the CV vignettes more with a filter attached because of this given the focal length and the similarity in formulas, but I have no evidence of this. I have other lenses with 46mm filters so this was a plus for me.
- Zeiss touts the lack of distortion on the ZM. Again, I'm guessing it's better than the CV, since it's better than most lenses out there. On the other hand, even though the CV has no published spec on distortion, it's probably better than a lot of lenses too in this case. Unless you want ZERO distortion, the CV is probably fine in this dept., and might even be better than any other lens you have.
- We can guess that the ZM has better and more effective coatings.
- I'm guessing the ZM is a bit better in the corners. This is a guess though based solely on cost. The CV looks to be very sharp, and could very well be as sharp as the Zeiss. End result is that this point might be meaningless.
- The ZM protrudes into the finders (internal on an M and external). With the square hood attached, the top of the hood lies directly on the bottom bright line of the external finder, which is actually nice for framing purposes. I think the CV is a hair smaller, but practically the same.
- the CV lenses I've owned have all been very good and well made, but I've never done any formal testing.
- the ZM certainly has the cachet with the name and all. There is something kind of cool knowing that this is as close as you'll get to having an SWC lens on your RF. On the other hand, practically, this is meaningless.
I say if you love 21mm, really want a Zeiss lens, want zero distortion, and have the money to burn, get the ZM. Otherwise the CV looks to be a great buy. And probably the smart buy every time.
My take on the differences:
- the 1/3 of a stop difference is meaningless, especially with the vignetting these lenses have.
- the optical formulas look pretty similar
- the ZM has a 46mm filter, the CV has a 39mm. I can only imagine that the CV vignettes more with a filter attached because of this given the focal length and the similarity in formulas, but I have no evidence of this. I have other lenses with 46mm filters so this was a plus for me.
- Zeiss touts the lack of distortion on the ZM. Again, I'm guessing it's better than the CV, since it's better than most lenses out there. On the other hand, even though the CV has no published spec on distortion, it's probably better than a lot of lenses too in this case. Unless you want ZERO distortion, the CV is probably fine in this dept., and might even be better than any other lens you have.
- We can guess that the ZM has better and more effective coatings.
- I'm guessing the ZM is a bit better in the corners. This is a guess though based solely on cost. The CV looks to be very sharp, and could very well be as sharp as the Zeiss. End result is that this point might be meaningless.
- The ZM protrudes into the finders (internal on an M and external). With the square hood attached, the top of the hood lies directly on the bottom bright line of the external finder, which is actually nice for framing purposes. I think the CV is a hair smaller, but practically the same.
- the CV lenses I've owned have all been very good and well made, but I've never done any formal testing.
- the ZM certainly has the cachet with the name and all. There is something kind of cool knowing that this is as close as you'll get to having an SWC lens on your RF. On the other hand, practically, this is meaningless.
I say if you love 21mm, really want a Zeiss lens, want zero distortion, and have the money to burn, get the ZM. Otherwise the CV looks to be a great buy. And probably the smart buy every time.
kossi008
Photon Counter
The ZM *is* better, I've tried. Distortion is practically invisible at 0.7 m, and does show up with the Skopar at that distance. Look at the attached shots (left C-Biogon, right Skopar). Having said that, the distortion of the Skopar never bothered me at larger distances, because then it's not nearly as extreme as shown here.
That's exactly what I fell for
, and in the end I drew exactly the same conclusion. And I *did* have the money to burn...Attachments
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Mister E
Well-known
Tim, there's a lot of anecdotal information in your post. I wouldn't call half the size a hair larger:
ZM 21/4.5: 56mm long and 210g
VM 21/4: 25.4mm long and 132g
The Zeiss was measured with caps so that make sit longer, but the lenses are noticeably different in size.
Mister E
Well-known
The ZM *is* better, I've tried. Distortion is practically invisible at 0.7 m, and does show up with the Skopar at that distance. Look at the attached shots (left C-Biogon, right Skopar). Having said that, the distortion of the Skopar never bothered me at larger distances, because then it's not nearly as extreme as shown here.
That's exactly what I fell for
After squinting at your tiny shots I still see nearly no difference. For example shots you could have at lest leveled the camera.
ampguy
Veteran
What you need to compare distortion with wides, is a camera with a bracket and fixed mount.
Otherwise the motion of changing lenses or removing the camera can move the angle a fraction of a degree which will affect the image.
Otherwise the motion of changing lenses or removing the camera can move the angle a fraction of a degree which will affect the image.
Tim Gray
Well-known
Absolutely a lot of anecdotal information. I wasn't trying to claim otherwise. In fact I was trying to say a lot of the things that people (including me) suppose are mostly based on 2nd hand info or guesses based on pricing.
Sorry about the sizes - but the Zeiss pdf says the ZM is 31mm long and 190g... that's not that much longer. Just measured it. It is indeed 31mm from flange to the front edge. But you are right. To me, that's a hair larger (6 mm). To others, that might be a big difference.
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kg4nih
Established
My first (attempts) at using the CV 21/4. For me a great lens. The shots below all from the same first roll of film.
ZI, CV21/4, Ektar 100 (home developed)
ZI, CV21/4, Ektar 100 (home developed)