I am puzzled by the Nex 7 and CV 15 user reports. Some say it produces blurry corners but opposite reports pop up.
Here is one statement from LL
"Re: Voigtlander 15mm f/4.5, can it be easily mounted on a Sony NEX-7?
« Reply #5 on: January 18, 2012, 08:41:06 AM »
Reply
For what it is worth, I've had very sharp results so far with the CV 15mm on a NEX-7. For this particular field of view, this lens produces results as good as any other lens and camera combo that I had tried. Fine detail is rendered with remarkable clarity across the image. Others have observed a marked drop in sharpness as the edges are approached. My particular copy seems to be much better than those other lenses tested. The results from this one easily make the extra processing with Cornerfix (to remove the magenta cast and vignetting) worthwhile. My copy happens to be one of the older Leica-thread (M39) mount versions. Adapters are readily available. If you go this route, may you find an excellent copy.
Regards, Rick"
I have a LTM mount CV15 that never produced blurry corners on my old Nex 3, just some correctable corner shift. Others reported problems with this combination.
It would be really interesting to get some first hand information especially from the CV15 LTM version on the Nex 7.
Exactly my question as well. Some conflicting info out there. No rush though. While I've got a CV15 LTM sitting here, the NEX-7 that I pre-ordered in August probably won't get here until April, if I'm lucky.
I have the CV15 and don't experience any corner blurring issues with the NEX-5N. The increased pixel pitch of the NEX-7 could mean a different result though.
I'd really like someone who has the NEX-7 to do a more a comprehensive study of corner color shift and blurring issues of the NEX-7 as COMPARED to a NEX-5N.
i suspect that the per-pixel sharpness of the cv 15 is more noticeably degraded on the NEX-7 versus 5N compared to the central sharpness on the same camera. BUT, that it is still decently sharp even in the corners on the 7. in the LL article you link he says it is equal to the minolta 20/2.8 on the a900, but i've seen crops from the corners of that lens and it's not what i'd call particularly sharp itself in the corners. outside of the Z*21mm and the latest leica m not much is blistering sharp in the corners at that angle of view.
sadly i don't have a NEX-7 or a cv15, so i'm really just talking out my ass.
Well, the only 'review' I looked at was Steve Huff's and from the one NEX-7 & CV15 sample at the pond, it doesn't seem to suffer from lack of corner sharpness. Rather, the problem is the strong color shift.
In theory there shouldn't be a difference between the LTM & M versions of this lens because they're optically identical. I don't know.. I have the M mount version and it was stellar on the 5N and is excellent on the GXR.
There could be copy to copy variation that causes problems. While my CV15 appears to be excellent, my CV12 appears to be slightly decentered. On the M9 this is visible as slight drop in sharpness in a vertical band between the left side and center of the frame from 5.6 to f/8. On the 5N the lens looked quite smeared along the left side until f/11. With the GXR I can also see this, though it doesn't seem to be as bad. Anyway, I tried another copy at the store where I bought it and that one was considerably worse, with severe corner softness and extremely strong CA on the M9... IIRC I've read about copy variation with the CV lenses...
What I'm also finding, having now tried a number of M mount lenses on both the 5N and GXR, is that slight optical issues that could be excused on FF, seem to be much more exaggerated on the APS-C croppers. Maybe because the APS-C sensors are effectively 'zooming in' on a small part of the image circle at a higher resolution than the FF sensor does at an equivalent crop, therefore revealing undesirable characteristics. This doesn't necessarily explain why the NEX-7 doesn't work well with some rangefinder lenses, but could be a factor in different experiences by different reviewers with certain lenses.
Again from my own experience, I got poor results with the ZM21 f/2.8 on the 5N, but samples I've seen from another copy on a different 5N looked better than mine... It's possible my lens is slightly imperfect compared to the other person's copy.
Could be a difference in expectation, needs and if people are judging the corner sharpness when the lens is focused at Infinity (where the lens to sensor distance will be at its closest). If I remember correctly the examples I've seen of the GXR vs 5N with this lens shows that there is slight corner smearing with the 5N but its only really noticeable when images of the 5N with this lens are placed against the ones taken with the GXR. I'd expect the 7 to perform worse than the 5N in this regard.
A combination of the infinity setting significantly increasing the beam angle from the rear element to the sensor toppings, and the extra resolution working the lens corners harder seems a plausible explanation.
Re internet pundits, its is not their fault as we all have personal preferences and usage patterns. I think you really need to get one yourself, carefully shoot a series of RAWs, then Crtl+Alt+0 into each to see what is really going on...
From what I can tell, Pete, while the 7 is unquestionably more succeptible to colour shift than the 5N, there is no indication at all that it is worse than the 3/5, rather the reverse. My 5 objected to anything wider than a 35mm, whereas the 7 seems to accomodate wider lenses, with exceptions. So if you were OK with your 3, my guess is that you will be all right with your 7.
I'm not so sure. If Bjorn Utpott's edge samples of the ZM 35/2 on the Nex-7 are to be believed, I don't think they're better than my 5's edge performance with that lens.
Ultimately, it's all about perspective and comparison. Until we see more direct comparisons between the 5N and 7, like Bjorn's or Herb's, we're relying too much on user perspective, I'd imagine. The CV 15 may very well be fine at the edges on the 7, but possibly even better on the 5N. I've seen quite a few comparisons showing the 5N's edges to be superior the 7's, but I've seen none of the opposite with rangefinder lenses wider than around 35mm, so far.
I just got my NEX-7 today and was planning on posting a investigation with crops this weekend after I get a chance to go out and shoot some with the combo. Mine is the CV 15 M mount version. I have been lookin forward to seeing how the lens performs... Stay tuned.
pdmphoto wrote:
^ that helps confirm the lens is decent at (very) close distance. How about infinity?
Don't get me started on this lens with the N7 If your talking an improvement in corner color smearing between 2.5 feet and infinity, we're talking .015" max focus travel. The story hardly changes. Expose & focus for the corners, and Cornerfix (what a hassle) is required!
Add to that, field curvature, but that is another chapter.
Question to Corner fix,
How good is the workflow?
Does it take a lot of time to correct every picture?
are there presets for every situation/aperture ...?
furthermore, does some color information get lost?
If your talking an improvement in corner color smearing between 2.5 feet and infinity, we're talking .015" max focus travel. The story hardly changes. Expose & focus for the corners, and Cornerfix (what a hassle) is required!