muju79 Posted November 28, 2022 Share #1 Posted November 28, 2022 Advertisement (gone after registration) Hi all, I've recently got a ZM 50/1.5, the lens is brand new so it should be optimised for focusing at f/1.5...and as a matter of fact, close focus at f/1.5 and f/2 does not disappoint and it's spot on. However, when testing the lens at f/4 and focusing at middle distance I've got some wild back-focusing. In the 2 examples below the RF was focused on the statue: Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! 100% crop: 100% crop: I I hope it's visible enough that in both example the focus ended up on the building behind the statue. I am sure that the RF split image was on the statue so this is puzzling me, especially since the lens performs well at the same aperture (f/4) at closer distance, like in the example below: The lens is indeed capable of precise focusing at wider aperture settings, for example the photo below is f/2.8 and the focus was on the tiny white flower in the center of the frame: I have no digital bodies to test the lens, and more testing is indeed in order as soon as I'll have time, but in the meanwhile I wanted to ask here whether this kind of massive back-focusing at middle distance and mid aperture values is an already known behaviour for this lens, or if there's something else wrong here and what could it be. The lens is from Amazon, so luckily I'd be able to return it without any issue. Cheers! Quote Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! 100% crop: 100% crop: I I hope it's visible enough that in both example the focus ended up on the building behind the statue. I am sure that the RF split image was on the statue so this is puzzling me, especially since the lens performs well at the same aperture (f/4) at closer distance, like in the example below: The lens is indeed capable of precise focusing at wider aperture settings, for example the photo below is f/2.8 and the focus was on the tiny white flower in the center of the frame: I have no digital bodies to test the lens, and more testing is indeed in order as soon as I'll have time, but in the meanwhile I wanted to ask here whether this kind of massive back-focusing at middle distance and mid aperture values is an already known behaviour for this lens, or if there's something else wrong here and what could it be. The lens is from Amazon, so luckily I'd be able to return it without any issue. Cheers! ' data-webShareUrl='https://www.l-camera-forum.com/topic/350998-zeiss-zm-5015-is-this-focus-shift-or-something-else-going-on/?do=findComment&comment=4580879'>More sharing options...
Advertisement Posted November 28, 2022 Posted November 28, 2022 Hi muju79, Take a look here Zeiss ZM 50/1.5: is this focus shift or something else going on?. I'm sure you'll find what you were looking for!
SiggiGun Posted November 28, 2022 Share #2 Posted November 28, 2022 This lens is very sensitive to focus shift wide open. The lens is by Zeiss optimized for f/2.8 Quote Link to post Share on other sites More sharing options...
tom.w.bn Posted November 28, 2022 Share #3 Posted November 28, 2022 vor 14 Minuten schrieb SiggiGun: This lens is very sensitive to focus shift wide open. The lens is by Zeiss optimized for f/2.8 Except for those lenses which were optimized for 1.5 later. Don't know how many there are though. Quote Link to post Share on other sites More sharing options...
mheine Posted November 28, 2022 Share #4 Posted November 28, 2022 As far as I know most of them are now optimized for around f2 like mine. I have front-focus below f2 and back-focus at anything higher than f2 - so, your lens looks normal to me. 3 Quote Link to post Share on other sites More sharing options...
tom.w.bn Posted November 28, 2022 Share #5 Posted November 28, 2022 I had the lens and liked some results really much but mostly had a hard time working around the focus shift. Sold it. Quote Link to post Share on other sites More sharing options...
lct Posted November 28, 2022 Share #6 Posted November 28, 2022 (edited) Your pics show too many variables to be self explanatory. You may wish to put your camera on a tripod and keep the exact same settings but one, apertures that you would test from f/1.5 to f/16. Focusing at f/1.5 and no refocus afterwards. f/1.5 click, f/2 click, f/2.8 click etc and nothing else should change to be sure. Painful? I confirm . Edited November 28, 2022 by lct 1 Quote Link to post Share on other sites More sharing options...
SiggiGun Posted November 28, 2022 Share #7 Posted November 28, 2022 Advertisement (gone after registration) vor 1 Stunde schrieb tom.w.bn: Except for those lenses which were optimized for 1.5 later. Don't know how many there are though. Yes, this is correct. Quote Link to post Share on other sites More sharing options...
haikos Posted November 28, 2022 Share #8 Posted November 28, 2022 I normally use mine at f2. I don't think I've ever used f4. I'm usually at 2, 2.8, or 5.6 on that lens. Maybe 1.5 here and there just because. How does it do at 1.5/2/2.8? Quote Link to post Share on other sites More sharing options...
lct Posted November 28, 2022 Share #9 Posted November 28, 2022 If the lens is optimized for f/1.5, as is mine, it should be normally sharp at f/1.5 and f/2, then more or less soft due to focus shift from f/2.8 to f/5.6 and again sharp due to DoF at f/8 and on. 1 Quote Link to post Share on other sites More sharing options...
Huss Posted November 28, 2022 Share #10 Posted November 28, 2022 The lens is behaving like all ZM 50 1.5s do. The only way to avoid that focus shift is to guestimate, or use a camera with an EVF. Which is not going to be a film camera! 2 Quote Link to post Share on other sites More sharing options...
muju79 Posted November 28, 2022 Author Share #11 Posted November 28, 2022 Thanks for all your replies! I'll do more controlled and reproducible testing, I like the lens and I'd like to keep it. Cheers! Quote Link to post Share on other sites More sharing options...
gotium Posted November 28, 2022 Share #12 Posted November 28, 2022 That's normal for that lens. I used to own it, had it optimized by Zeiss at 1.5 and basically only used it at f/1.5 and f/5.6 or above. Everything in between was just guesswork and it was rare for me to get anything in-focus. 1 Quote Link to post Share on other sites More sharing options...
mheine Posted November 28, 2022 Share #13 Posted November 28, 2022 vor 1 Stunde schrieb muju79: Thanks for all your replies! I'll do more controlled and reproducible testing, I like the lens and I'd like to keep it. Cheers! I have tested several 50mm for the M and only the Sonnar made the click for me. Yes, it's hard at the beginning but you'll get used to it. I didn't use it very often (50mm is not my favorite focal length) but whenever I took it with me, I felt in love with the look. 3 Quote Link to post Share on other sites More sharing options...
muju79 Posted November 29, 2022 Author Share #14 Posted November 29, 2022 8 hours ago, haikos said: I normally use mine at f2. I don't think I've ever used f4. I'm usually at 2, 2.8, or 5.6 on that lens. Maybe 1.5 here and there just because. How does it do at 1.5/2/2.8? Very well indeed (see the 3rd photo posted). Thanks for the input! 1 Quote Link to post Share on other sites More sharing options...
Ouroboros Posted November 29, 2022 Share #15 Posted November 29, 2022 (edited) There still seems to be a lot of confusion about how the ZM c-sonnar aperture is optimised as supplied. Mine seems to be fine at f2 whilst f1.5 does have some front focus with portraits at 4-5' distance, so it seems to conform to the general internet wisdom of being optimised at f2 as standard. I rarely use it at smaller apertures, for my purposes it's primarily a portrait lens to be used at, or near, full aperture. In defence of the c-sonnar, it has a rendering character that makes persevering with it worthwhile. I rate it equally with the Voigtlander 50mm f1.5 Heliar Classic (which I also have) as a lens that you can explore your creativity with but would not have either of them as my only 50mm. Both these lenses make you work a little harder to get to know them but the rewards are worth the effort. Edited November 29, 2022 by Ouroboros 3 Quote Link to post Share on other sites More sharing options...
lct Posted November 29, 2022 Share #16 Posted November 29, 2022 The Sonnar 50/1.5 is my favorite portrait lens on APS-C (digital CL) and does very well full frame on electronic Visoflex too. Same in RF mode at f/1.5 or f/2. At f/2.8 and on, i prefer a Planar 50/2 to keep the Zeiss look w/o focusing issues. YMMV. 2 Quote Link to post Share on other sites More sharing options...
muju79 Posted November 30, 2022 Author Share #17 Posted November 30, 2022 (edited) On 11/29/2022 at 8:14 PM, Rabunmoss said: Hello there. Unfortunately you chose the lens notorious for horrendous constant focus shift. If this bothers you choose the Voigtlander 50f1.5 Nokton II. Well I am not entirely clueless, I knew perfectly about focus shift before buying this lens. I just did not expect the shift to be so massive and so visible at middle distances. But again, I have to test more carefully to exclude focusing errors on my part and define the issue more clearly. Most if not all reviews of this lens available online test focus shift only at close distance. I'll post again once I'll have the results. Cheers. Edited November 30, 2022 by muju79 Quote Link to post Share on other sites More sharing options...
sinjun Posted November 30, 2022 Share #18 Posted November 30, 2022 I use this lens without problem on a rangefinder. I think mine's optimised at f2.8 and I don't have issues at this aperture and smaller. At f1.5 - 2 I compensate by turning the focus slightly - something I've practised with an EVF attached. I find in the same way that other non focus-shift lenses (some Leica) require some compensation through the range due to less than perfect calibration. I get a pretty good hit rate but for absolute reliability would use an EVF. 1 Quote Link to post Share on other sites More sharing options...
Kl@usW. Posted November 30, 2022 Share #19 Posted November 30, 2022 Since this discussion is still going on, here my 2-pence: As Steve already said, Zeiss seems to adjust the lens for F 2 at 1m. Quote: The out-of-factory adjustment of the 50mm C Sonnar when combined with a perfectly adjusted camera rangefinder will show about 1.5cm front focus at f/1.5 and 1m focusing distance, perfect focus at f/2 and 1m focusing distance, and about 2-3cm back focus at f/2.8 and 1m focusing distance." I took this from an extensive report by Hamish Gill, who seems to have done a PhD on the Sonnars; the complete article is here: https://www.35mmc.com/22/11/2015/zeiss-50mm-1-5-zm-c-sonnar-review/ I own the lens among some other 50´s and after a short learning curve it´s a very ! pleasant lens to use. 2 Quote Link to post Share on other sites More sharing options...
Pyrogallol Posted November 30, 2022 Share #20 Posted November 30, 2022 Does that mean that they expect the majority of users will be using the lens at f2 and 1 metre ? Quote Link to post Share on other sites More sharing options...
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