Focus shift with the CV Nokton 35/1.4 MC?

[ArtZ]

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This morning I had some time to spend. I decided to test thoroughly my copy of the CV Nokton 35/1.4 MC

 

I’ve never detected focus shift on this lens (which is noticeable with my Summilux 35/1.4 ASPH from f/2 to f/5.6 between 1m to 10m).

 

I placed my M8 on a tripod and I’ve tested under natural light (in the street) the CV Nokton 35/1.4 at 3m, 5m, ≈10m, ≈15m, ≈30m and ≈50m. I’ve used the shutter timer (12 sec). I’ve tested from f/1.4 to f/8 (using all intermediate stops -11 pictures for every distance, 66 pictures for the whole test). I’ve done the same test with my second body.

 

RESULTS: No focus shift whatsoever. I really do not understand why some people keep on saying this lens suffers from focus shift. I agree this lens is soft from f/1.4 to f/1.8 (but more than usable), at f/2 sharpness is fairly good, at f/2.4 sharpness is good, at f/2.8 is very good and from there it's excellent. Considering this is a very compact f/1.4 lens with no aspherical elements and under 500€, I would define it as an excellent performer.

[giordano]

Can you tell us more about your methodology? Did your focus targets have distance scales (like the classic photo of a ruler at 45 degrees) so you could check the focus error at each aperture and each distance, or did you just use the rangefinder to focus on a subject at the relevant distance and decide by looking at the image whether it was adequately sharp?

 

If the latter, you can't know to what extent your observation of zero focus shift but increasing sharpness between f/1.4 and f/4 reflects the reality and to what extent it's the result of the way your lens and rangefinder(s) happen to be calibrated.

 

Sean Reid in his review of this lens found significant focus shift - visible in the test shots in the review as centre sharpness being less at f/2.8 than at f/1.4. But he uses "focus bracketing" to take multiple series of shots and then uses the series that was sharpest at f/1.4 to compare the results at differentapertures.

 

What your results do show is that for your purposes, at distances 3m and greater, focus shift with this lens is insignificant. Which is worth knowing!

[ArtZ]

Methodology:

 

I did the test at Place des Voges Place des Vosges - Wikipédia, just 200 metres away from my flat.

 

For those who don't know that place, Place des Vosges housefronts were all built using red brick with strips of stone quoins over vaulted arcades that stand on square pillars.

 

This construction helped me a lot to calculate distances. For 3 metes and 5 meters I used the lens scale. For the test with my first camera, I moved myself backwards keeping always focus on the same target. For the test with my second camera, the camera didn't moved (it was static) but I focused on different targets using the sames distances as in the first test.

 

For my first camera, I chosed a restaurant call "Ma Bourgogne" as subjet because they were enough tables, chairs, terrace gas heaters and other objets to get enough detail, contrast and get a scale; almost like using a printed target. A printed target at 45º is usuable from 1 to 3 meters (maybe a bit more) but at 10 meters is really useless: target point is too small.

 

For my second camera, I used different details with enough contrast in each pillar.

 

For both tests, targets were at the same level (high) than the camera, at the left side of the camera (next to the house wall while the camera was placed next to the pillars for the first test and the other way round for the second test), always on an angle from the center of the lens axis in order to be able to measure possible front or back focus.

 

I used together the Leica 1.25x magnifier + Megapearls 1.15x magnifier with diopter correction (which gives me 1.45x corrected to my presbytie).

 

Results: 121 pictures out 132 were perfectly in focus. Last set of 11 pictures taken (second camera -static camera at 50 meters) were slightly out of focus... but the problem it wasn't the lens but my eyes. I missed the focus from the first shot.

 

This test proves me that in real life use, my Nokton 35/1.4 is a reliable lens.

 

Two years ago my dad offered me for Christmas the latest Summilux 35 ASPH. I was very happy to use it but after a few hours using it, I realised focus shift. I've sent the lens to Solms a few times. Everytime I send it, they do something... but the focus shift is still there, only it moves backwards or forwards... Once, I was really excited because I thought they sorted out the problem... until I took a picture of a tower @ f/8. From f/8 to f/16, the lens was completely out.

[farnz]

... until I took a picture of a tower @ f/8. From f/8 to f/16, the lens was completely out.

That doesn't sound like focus shift because by f/8 any focus shift will be obscured by the lens's depth of field and more so for f/11 and f/16 of course.

 

Pete.

[matlep]

Please redo the test on 0.7-1m on all apertures instead. Then you will see a significant shift.

 

I have tried three different copies and they all had focusshift at close distances. So the lens did not fit my type of shooting. Also it was extremely soft on 1.4.

[ArtZ]

That doesn't sound like focus shift because by f/8 any focus shift will be obscured by the lens's depth of field and more so for f/11 and f/16 of course.

 

Pete.

 

Of course not! It was a problem after Solms tried to fix it. I send it back and now I have again focus shift from f/2 to f/4 (even @ f/5.6 but really difficult to see) between 1 and 10 meters (depending on the f stop used). The worst is between 2-5 meters.

 

 

Please redo the test on 0.7-1m on all apertures instead. Then you will see a significant shift.

 

I have tried three different copies and they all had focusshift at close distances. So the lens did not fit my type of shooting. Also it was extremely soft on 1.4.

 

I'll try to do this week. It's true I haven't really used this lens at 0.7 - 1m. The most common use for me is from 2m to 5m and from 10m to infinite

 

EDIT: I agree with you about softness though I wouldn't say 'extremely soft' but pretty soft at f/1.4 - f/1.8 (and still usable). At f/2 there's a great improvement and from f/2.8 is very good.

 

In fact, what I love about this lens is its size and its price. I use quite a lot this lens just for convenience: I can take it everywhere and it's nice to have the possibility to use f/1.4 if needed (even when it's soft). I don't chose this lens when I need a good low light performer.

[matlep]

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In fact, what I love about this lens is its size and its price. I use quite a lot this lens just for convenience: I can take it everywhere and it's nice to have the possibility to use f/1.4 if needed (even when it's soft). I don't chose this lens when I need a good low light performer.

 

I agree! It is a nice competitor to the original Summilux 35 pre ASPH. But with a slightly more modern look.

[ArtZ]

Please redo the test on 0.7-1m on all apertures instead. Then you will see a significant shift.

 

I have tried three different copies and they all had focusshift at close distances. So the lens did not fit my type of shooting. Also it was extremely soft on 1.4.

 

@matlep

 

I have re-tested my Nokton this morning for 0.7m - 1m - 1.5m and 2m. Tis time I've done indoors using a Focusing Test Chart.

 

Yes, you're right. I've found some focus shift (about 1.5 -2 cm front focus) from f/1.8 to f/2.4 at 0.7m and 1m. There's also some focus shift (about 0.5 cm - 1 cm back focus this time) at f/2 at 1.5m.

 

In fact, it looks very much like my Summicron 28/2 ASPH ! My cron 28 front focus about 1 cm at f/2.4 at 0.7m while is spot on at f/2. I have also some back focus (about 1.5 cm at 1m at f/2) while is spot on at f/2 and 1m.

 

My cron 28 has been recalibrated twice since 2007 at Solms for focus shift. I have no problem with the actual settings. I really don't notice it.

 

Even if I had never felt focus shift with this lens in real life use, I'm pleasantly surprised by these results. I think the only weak point of this lens is softness at f/1.4 (but more than acceptable for a non aspherical lens with a price under 500€). From f/2.8, the CV Nokton is an excellent performer.

[ArtZ]

In fact, it looks very much like my Summicron 28/2 ASPH ! My cron 28 front focus about 1 cm at f/2.4 at 0.7m while is spot on at f/2. I have also some back focus (about 1.5 cm at 1m at f/2) while is spot on at f/2 and 1m.

 

Correction:

 

I have also some back focus (about 1cm at 1.5m at f/2) while is spot on at f/2 and 1m (but also at 0.7m)

[johnwolf]

I have the SC version and just tested it at about 30". It focus shifts about 1/2" backwards at each full stop up to about f4.

 

I don't see it as a problem for the way I shoot -- mostly street and landscape. Like your first test showed, at 3m it's not evident, even at large apertures. And I usually settle on an aperture and then focus.

 

I do agree the jump is sharpness between 1.4 and 2.0 is pretty striking.

 

John