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17.5mm F0.95 Voigtlander topic
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    This shot I think shows the curvature of sharpness quite clearly. The centre in focus trees are fairly distant, the hedge top and fence is perpendicular and square to the lens. It is soft at the centre, sharp at the right edge, and even the top of the building on the right has some sharpness on its roof, even though this is really quite close to me.

    I've written more notes in the image description, but the amount of curvature on this "plane" of focus is rather extreme, I almost imagine visualising it like looking into a bowl, with perhaps quite steep walls.

    Dofmaster shows that lens at f1 on the gh2 is hyper focal at 20m, with sharpness from 10m to infinity. To get this degree of unfocusedness at the corner would need to have some serious curvature or other defect to overcome such a large wedge of what should be focused.

    Anyways, hopefully they're all the same in this respect, and let's face it we will be shooting 98% of stuff wide open and in that sweet spot of 0.5m to 2m where the shallow DOF is most noticeable and causes the subject to pop out of the scene in such a nice 3d way!!

  • Hmm, I don't see anything as extreme with mine. I did my fast test on a tiled roof opposite my house, I'll try another one with a large evaluation chart later.

  • @nomad - eek. If it's not normal i'm going to be pretty miffed. 2 lenses, i thought would imply that its pretty much just a feature of the lens.

    I don't think a large evaluation chart will let you test anything other than curvature up close.

    Did you try with the steps i outlined in my earlier post, just using live view and something 100m+ away, as close to actual infinity as possible... focussed centrally, out at the edges and fixed by focussing beyond infinity.

    You're making me question whether or not my GH2 could contribute. I have access to an olympus pen, i'll see if can try the same test on that to see if it has the same results.

    I'm also going to email Voigtlander directly. They should be able to say one way or the other whether this is "normal" for this lens. If not, i'll presume they could perhaps exchange it and test the replacement, or perform a fix. whatever. And get one that was much better or perfect.

    Thanks for trying Nomad, look forward to hearing any more results. Would ask that if you've not tried something v distant as outlined before that you could try.. the key is infinity... I don't know how far away a roof opposite your house is :) Use my shots as reference for what i'm talking about for real distant focussed subjects.


  • OK, I'll do another one. I followed your outline but the roof is about 80 meters away.

  • Thanks Nomad.

    Tbh you are pretty much distant enough at that i'd of thought. But perhaps the further you go the more noticeable it is. I'd appreciate it if you could upload some full res pics, though it is a real pain to keep track of what you're doing with no aperture in the EXIF. So you would say that fully zoomed in with the focus assist the subject is focussed (perhaps not quite as sharp, its at the edge of the lens after all) at the edge with the same focus setting as you had with central focussing. Centrally focussed seems to be pretty much on the money for the infinity lens marking for me. Edge focus achieved by going to the rotation stop of the lens past infinity.

    I've just had a quick go with the pen, and the issue is much less noticeable.. i'm just looking at the images i got now. I think the main thing though is the resolution difference may make the anomaly harder to see.

  • I just looked at google maps and the distance of my distant subject is getting on for 300m +, for the houses at the very top of the road.

    Just processed 4 shots and added them to the earlier flickr album, shot on the pen.

    It IS noticeable on the computer, i guess the pen's lack of EVF makes it really hard to see.. It's certainly a worse camera than the GH2. But reassuringly i see the same things going on in the images so i think i can exclude my camera from the equation.

    In my photos i've noticed that the neighbourhood watch sign is a nice thing to look at and see the sharpness difference between the two shots. It's probably more like 150m away.

    Another way to look at this is focus past infinity till the lens stops and take some photos or look around the edges, and as you can see in my shots the right and left 1/5 edge of the frame is sharp, regardless of its depth away from the lens.. the grass and driveway on the right of some of my shots is barely 5m away yet is sharp at the same time as the distant object. It's like its behaving like dofmaster predicts at this setting.

    It is strange! :-/

  • Yes, I found a much better location and I can confirm your observations now. What's annoying me is that my sample seems to be badly centered, since the effect is stronger on the right side than on the left.

    What some people perceive just as soft corners is more like a curved field on this lens.

    I'll investigate this further with a chart too.

  • @nomad. Sorry to say but i'm glad to hear that you have the same issue, not no issue at all. Would suck if its noticably off-centred. Though can't say whether mine is or isn't as all my testing has been a bit informal.

    If we all have the same issue then at least it becomes just a property of the lens. Will wait and see what Voigtlander have to say when they get back to me.

    I'm happy to have the lens with that issue, though it does sting a little that your £800 lens can't focus reliably at infinity!!! It's perhaps just a quirk and once you know it you can work around it. Some of my stopped down tests last night seem pretty good... if you pixel peep you can see a difference at the edge, but its very close. More testing on this front is key perhaps... the best way to test that would perhaps be to do some true landscape photography with it, where EVERYTHING from edge to edge is relatively at infinity. I think this lens' resolution peaks about f5.6 before diffraction takes its toll... it'll be around here and f8 where perhaps you have to be for infinity shots.

    I'm about to go shoot a wedding reception with the lens this evening, the subjects will all be much closer, but if there is any nice shots of the setting i'll either stop down and take my chances or change lenses! :)

    One test i'd like to try now is a formal measurement of just how curved it is. My thinking is perhaps to get something bowl shaped, relatively close focussed (where DOF is shallow... and see if i can get anything at the extents of the bowl in focus where it's obviously MUCH closer and can only be explained by this curvature... if you were lucky you may be able to get a lot in focus in this odd shape, a bit like that Rokkor lens mentioned earlier in the thread... Obviously this lens is just missing the afore mentioned ring to control curvature :)

    I look forward to further testing results nomad... i still love the lens, but notably my copy of the 25mm doesn't exhibit anywhere near this level of curvature, if any. I've googled and found some people saying their 25mm did, and hoping the 17.5mm would be better... i think we can pretty safely say its worse! As I said before though, its never really what the lens is for, and i do still love it... let's see what more we can find out. Cheers.

  • Well, I googled around a bit and found that the Canon 24mm 1.4 which got positive reviews otherwise, is plagued by field curvature too. Maybe it's inherent to wide designs with fast speed. BTW, the 1.4 by Canon is about 4 times the price of the 2.8. One remark "The 24 f/1.4 II does have some field curvature which I think is its only notable weakness when stopped down."

    Other users complain about field curvature with the Samyang 24mm 1.4 too.

    I don't think such lenses are made for landscape, they are made for interior scenes at very low light. Every lens is a very complex compromise, and if you shift it to one side (like very wide and very fast) other parameters suffer. But some seem to like it, like Bjorn Utpott: "Field curvature can be a problem for those who spend most of their time photographing test charts and brick walls; the corners will look worse than on a lens with a flat focal plane. But it's also possible to take advantage of field curvature. In the real, 3-dimensional world, field curvature can be used to increase the apparent depth of field or to isolate a subject. I think Zeiss specifically designed the Sonnar with these 3D effects in mind." See here:

    After all, he's talking about a Zeiss Sonnar!

    I like your idea about testing with a curved target, should be possible to print a test chart on stiff paper and place it on a table bent to varying degrees. I won't have the time, though, for the next week, we are preparing a huge workshop right now – including lenses ;-)

  • @jimtreats

    Got it. You're right. That is very significant field curvature. I was seriously considering this lens, but now, I don't think so. Thanks for the test.

  • @nomad

    What he said.


  • @nomad, nice research. I will have a go at testing on something bowl shaped next week. If this is just how the lens is then its fine. Hardly noticeable in normal use, focus on your subject and go. Would prefer to not have it perhaps but if it's just the way it is then ill still take it as the FOV is lovely, the shallow DOF nice, nearly as pronounced as the 25mm, footage handheld is steadier due to the added wideness, the stepless aperture is really nice!

    @Ralph_b, @RBD glad to give you info on this lens, fair enough if it's not for you though genuinely in the typical usage of this lens, up close and wide open it's a non-issue.

    I think the review I linked to earlier nailed it best, and it's the ONLY review I've found so far that mentions this curvature and that this lens can punish the hell out of you if you try to use it against what it's good at. Use it in harmony with its strengths though and there is little like it.

    I just wanted to know if my copy was a bad one, once I know it's just how it is ill move on and just learn to work around it.

    To be continued...

  • Add my name to the list of those for whom it's a non-issue.

    I paid a lot of money for manual focus fast glass, and used mine for the first time this morning shooting interior video at the local cafe, @ 160.

    A really great match to the GH-2.

    I'm ecstatic.


  • Read something about Gh2 that 1 of the downsides is that it need alot of colorgrading in post... if I see this "Drewnet"Stills it does look good to my eyes!

  • colour me unimpressed but i've had no reply from Voigtlander about this problem.. I'll leave it a little longer before trying again. Not exactly great treatment when you've thrown this much money at a lens!

    Still not overly worried about the issue, but would appreciate and official comment on it.

    To be continued...

  • @jimtreats- Perhaps they feel they have more important things to do with their time?

    Read a little between the lines: "...for those who spend most of their time photographing test charts and brick walls...."

    What do you think the implication is here?


    Not only is it an extremely fast lens, it's a macro.

    And you're concerned about infinity?

    Use the lens for the purpose for which it was intended.

    It's a really wonderful tool.

    Let it go, Jim.

    The folks at Cosina think you're rowing with one oar out of the water.


  • @jimtreats Character versus technical perfection. It seems the two are, more often than not, mutually exclusive.

  • It was not my intent to offend @jimtreats-

    Here's my view:

    We all know Thoroughbred horses?

    Long legs, high strung, not really good for anything. You can't, for instance, heard cattle with them, a little too twitchy for pleasure riding, etc.

    But with a light rider over a distance of about a mile, a little more, they can't be beat.

    They're absolutely amazing.

    The Nokton is a Thoroughbred.

    If you ask it to do something it wasn't designed for, that's your shortcoming, not not the lens's.


  • So true!

    Get a Voigtländer Heliar 15mm 1:3.5 if you want incredible sharpness on a plane and low distortion in a wide lens.

    It won't shoot in the dark, though ;-)

  • Rather buy some contax zeiss lenses, i am not impressed but these voightlanders.

  • I had the Voigtländer Heliar 3.5/15 and sold it again. Now I have the Nokton 17.5 and am quite happy with it. Here is why: The Heliar does distort significantly more than the Nokton, despite various claims on the net that it has next to zero distortion. My copy, shot on a GH2, distorted a lot. Secondly the lens is tough for mounting any filters. Version 1 has no filter thread, so you need to manufacture something to mount filters to it. Secondly the controls, though smooth and nice, are very small. For video work it gets fiddly. Thirdly you need to get an adapter. The M39 to m43 adapter that I got on ebay did not allow me to get infinity focus. The new version requires a Leica M to m43 adapter which costs more. It has a 52mm filter thread but with a build in lens shade. So forget about mounting any filter adapter with a larger diameter so you can use any of your larger diameter filters. The Nokton 17.5 does have the flaws as described, but it has less distortion, beautiful bokeh, step-less aperture ring and a normal filter thread. The only thing I find a cumbersome is the very short focus ring travel from infinity to one meter. I am not using the lens for macro, and I think it is not designed as a macro lens which would deliver its best performance in close range. The Nokton just offers the short focal length as a bonus that may come in handy. Last but not least you get an aperture of 0.95 (which is closer to a T 1.2 in reality). This is about three stops faster than the Heliar. f 3.5 is not enough for indoor work, at least on a GH2 due to the noise. The downside is the higher price. If you can't afford the Nokton, get a Panasonic 2.5/14. Or get the cheap 14-42 kit lens. Negligible distortion at 17mm at essentially the same f stop as the Heliar and for the cost of the m43 adapter that you will need for the Heliar. If you don't need the lens now than wait for Photokina for new lens announcements. As for Zeiss lenses I have no personal experience with them but reading about their very high contrast I would be cautious. The GH2 has a very limited dynamic range, so high contrast lenses can cause blown out highlights or lack of shadow detail. For the GH2 lenses with less contrast are better as one can boost contrast in post, unlike recovering blown out highlights.

  • I found the time to do some more testing with professional resolution charts at close distances and a building about 80m away at a carefully measured rectangular position. This is what I found:

    It seems to be normal that such a lens has a curved field of sharpest focus, but the effect is much stronger at long distances. You'll need to take this into account if you want to do landscapes with it and you can even use it to your advantage if you learn to tame this behavior.

    The effect is far less pronounced at close distances, you can only see it wide open with serious pixel peeping. I can just barely see it at 1 meter when shooting full rez photos, I doubt it can be seen in video at that distance. IMHO, this lens is perfect for low-light interiors!

    BTW, it breathes far less than my wider vintage lenses, like a Rokkor or a Takumar at 28mm.

    P.S. Did I tell you that I love this lens?

  • Cheers nomad.

    Voigtlander never bothered to get back to me, but i think its settled that this lens has more quirks than its longer brother. I've got busy with my day job since so will have to wait to do anymore significant shooting with mine.


    "On the Voigtländer 17.5mm, this exhibits itself rather severely when focused near infinity.  If you focus using the center of the frame, the curvature is such that objects between 5 and 20 feet on the edges will be sharp, but further objects get soft."

    Bang on, and a good review. Nice to see more reviews being clear about its quirks, yet still loving it!

  • It's the sharpest at f/4 or f/5.6. That's my preferred f-number at infinity focus.