Zeiss Nettar: only center is in focus

Theo Sulphate · Jan 14, 2018

The first 120-roll from my 515/16 has each frame in focus in the very center only, with extreme softness surrounding it. This is true even when focused at infinity and with apertures smaller than f/5.6.

The images look like those made by a Brownie Hawkeye where people reverse a lens element. Artsy effect, but not what I wanted.

Could someone have done something like this with the lens? My pressure plate seems fine (though less stronger than I'd expected).

Loading the camera seemed no different than other rollfilm cameras I've used for 50+ years: just pull the film from feed spool over to take-up spool, with film laying atop the thin rollers.

R.Gould · Jan 14, 2018

Must be a lens problem, stopped down to 11, which I find to be the best setting for the Nova's,my cameras with the Nova lenses, ( i have several) are fine performers and corner to corner sharpness, they are one of the best triplets around, in my opion

Nodda Duma · Jan 14, 2018

My Nova is awesome. I bet a previous owner took the lens apart and put it back wrong. Try reversing the front or back lens, starting with whichever is easiest to get to.

blockend · Jan 14, 2018

I have three Nettar cameras with Novar 4.5 triplets. Optically they're all similar, soft wide open with lots of "swirly bokeh" (or uncorrected astigmatism for the literally minded), before sharpening up between f8 and f11. They never get Hasselblad sharp, but plenty good enough to fill my large desktop monitor. Put your camera on a tripod to remove user error, shoot at f11-16, which is optimal on Novar lenses, and make a sequence, close, mid-distance and infinity. If it still looks too soft there's a problem with your camera, or your expectations are too high. I like the Novar look very much, never bitingly sharp like a modern lens, but way more resolution than toy or box cameras and meniscus lenses.

Yours is a nice early model, later ones only had shutter speeds down to 1/10 or 1/25. The pop-up sports finder is also preferable to the later glass viewfinder, which is a peephole.

Rick A · Jan 14, 2018

Mine is plenty sharp at f.11. I've never shot it wide open to see if there is any difference in quality. 1/100/11 Ilford FP4+

blockend · Jan 14, 2018

Rick A said:
Mine is plenty sharp at f.11.

Yes, that looks typical Nettar IQ at f11.

blockend · Jan 14, 2018

One thing all my Nettars do, and I believe is common - if you don't follow through when pressing your shutter, the camera assumes you've taken a shot and you'll need to wind on and waste a frame. This is true with all Nettar cameras with double exposure prevention. If this happens you can save the frame by pressing the sideways lever bottom right which actuates the shutter on the lens itself, bypassing the shutter button linkage on the camera. Then wind on next frame and cock shutter as usual.

We've become used to half pressing on modern cameras, which turns on light meters, locks exposure and whatnot, but the Netter requires a straight click.

bernard_L · Jan 14, 2018

If it's a lens reversed: the extreme lenses should have their convexity (bump) facing out from the lens. That is easy as a first check. If these look OK, try reversing the middle element; that is also the most likely to be inadvertently flipped in a previous intervention. Take notes and scribe marks in order not to lose infinity setting, or you'll have to re-calibrate. Good luck. Keep us posted.
https://www.spie.org/publications/pm92_101_triplets?SSO=1

Alan9940 · Jan 14, 2018

Theo,

My Zeiss Super Ikonta III had a similar issue, except my soft area was not where I expected it to be based on where I focused the lens. After much trial-n-error trying to resolve it myself, I sent it off to Ken Ruth at Bald Mountain and he determined that the front standard / lens combination was not aligned properly with the film plane. Took about 6 months to get it back, but it's perfect now! Too bad Ken has retired because he was magician with these old cameras. Sure hope you get the problem resolved as these old folders are great fun to shoot!

blockend · Jan 14, 2018

Alan9940 said:
Sure hope you get the problem resolved as these old folders are great fun to shoot!

I put a roll of Ektar 100 through my Nettar this afternoon.

bernard_L · Jan 14, 2018

Alan9940 said:
My Zeiss Super Ikonta III had a similar issue, except my soft area was not where I expected it to be based on where I focused the lens. (...) the front standard / lens combination was not aligned properly with the film plane.

Certainly a possibility. If such is the case, the OP should observe a zone of sharp imaging as band across the image, while the description of the problem (emphasis added)

Theo Sulphate said:
in focus in the very center only, with extreme softness surrounding it.

rather seems to imply a spot.
Theo, it might help resolve that ambiguity if you would post a problem image.

Sirius Glass · Jan 14, 2018

I suggest that you send your camera to Carol at http://flutotscamerarepair.com/. She is near by and has done great work for me. I do not know if she can fix your problem if someone decided to become an amateur lens builder.

E. von Hoegh · Jan 14, 2018

I'd vote for the center biconcave glass being reversed.
Edit: not biconvex, biconcave.

Theo Sulphate · Jan 14, 2018

Thank you, everyone, for your replies.

Yes, it is just a central spot, less than 1cm in diameter on the negative, which is in focus. Everything surrounding that is wildly out of focus - extremely blurry.

Looking at the rear lens element, I do see marks around the retaining ring - so either improper reassembly is the culprit or someone wanted an artistic effect.

Sirius Glass · Jan 14, 2018

Theo Sulphate said:
Thank you, everyone, for your replies.

Yes, it is just a central spot, less than 1cm in diameter on the negative, which is in focus. Everything surrounding that is wildly out of focus - extremely blurry.

Looking at the rear lens element, I do see marks around the retaining ring - so either improper reassembly is the culprit or someone wanted an artistic effect.

More likely they did not know what they were doing and thought that they were cleaning the lens elements.

Theo Sulphate · Jan 14, 2018

bernard_L said:
If it's a lens reversed: the extreme lenses should have their convexity (bump) facing out from the lens. ...

Thank you for the reply and link.

Looking at it, the rear element seems to be reversed. Center might be reversed as well - I'll have to check that.

E. von Hoegh · Jan 14, 2018

Sirius Glass said:
More likely they did not know what they were doing and thought that they were cleaning the lens elements.

More likely they were watching yootoob.

shutterfinger · Jan 14, 2018

This is the only triplet lens layout for Zeiss in A Lens Collectors Vade Mecum.

The Vade does mention the camera/lens combo:
Novar f4.5 75mm This could be one of the high value ones, as it was fitted to the Zeiss
Super Ikonta 531/16 for 6x6cm, possibly as a low cost version for the UK, (B.J.A. 1955, p215) and this has
become a sought after folder. It had front cell focus, coupled R/F, and was said to 'produce excellent
negatives'.

Ste_S · Jan 15, 2018

blockend said:
shoot at f11-16, which is optimal on Novar lenses

What do folks get when shooting at f22 ? Just a loss of sharpness ?
I've been pushing 400ISO B&W film to 1600 to keep the lens stopped down with 1/100 or 1/200 shutter speed. Occasionally this means I'm shooting at f22 to not completely over expose the film.

At the other end of the scale, was quite surprised at shooting at f4.5, 1/50 hand held (I don't have steady hands) and guessing distance for portraits. Didn't turn out to be blurred out of focus mess, centre was sharp with some nice bokeh around the subject.

blockend · Jan 15, 2018

Ste_S said:
What do folks get when shooting at f22 ? Just a loss of sharpness ?
I've been pushing 400ISO B&W film to 1600 to keep the lens stopped down with 1/100 or 1/200 shutter speed. Occasionally this means I'm shooting at f22 to not completely over expose the film.

At the other end of the scale, was quite surprised at shooting at f4.5, 1/50 hand held (I don't have steady hands) and guessing distance for portraits. Didn't turn out to be blurred out of focus mess, centre was sharp with some nice bokeh around the subject.

Image quality drops at very small apertures due to diffraction: https://luminous-landscape.com/understanding-lens-diffraction/ In my experience definition drops off at smaller apertures (bigger f.numbers) with medium format compared to 35mm, but is still apparent if you stop right down.

I agree that at f4.5 the image is sharp enough in the centre to appear "sharp" on the Nettar, especially if the focus is spot on. Edge sharpness falls away pleasingly at wide apertures. In lens leaf shutters are easier to hand hold at longer shutter speeds than focal plain varieties, 1/50 is no problem and 1/25 doable with steady hands.

When I said f11-16 is optimal, I meant the point at which vignetting has disappeared, and sharpness is consistent across the frame. Obviously it's still very good a couple of stops either side of that point, and useable at all apertures.

Theo Sulphate · May 12, 2018

FINAL UPDATE: The problem has been resolved!

Nodda Duma said:
My Nova is awesome. I bet a previous owner took the lens apart and put it back wrong. Try reversing the front or back lens, starting with whichever is easiest to get to.

As you said, it was the rear element that was reversed - likely by some previous owner cleaning the elements. All is well now.

These Zeiss medium format folders are fun to use!

Nodda Duma · May 12, 2018

Awesome! Even a broken clock is right twice a day.

Zeiss Nettar: only center is in focus

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