35/1.8 W-Nikkor C & 35/2 Summicron-M comparison tests

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awilder

Alan Wilder
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Posted here: http://www.photo.net/photodb/photo?photo_id=5729855 are some comparison shots of the two lenses. Film was ISO 100 color neg. Reala for the Nikkor and Kodak Gold 100 for the Summicron. Sorry but these were taken at different dates as I sold the 'cron years ago. The 'cron is the pre-asph (version 4) and the Nikkor is the latest version from the SP 2005. Both have similarilarities in that central resolution wide open is better than stopped down to f/4 but the 'cron starts at a much higher level of resolution. Resolution tests at the right intermediate zone for example, shows greater detail wide open with the 'cron but by f/4 both lenses are close with the 'cron having slightly better contrast. Non-resolution pictures of the figurines show similar performance with both lenses at the same openings for off axis images although corner performance looks better with the 'cron to me.
 
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That's interesting. I haven't noticed that kind of softness. I used to do a lot of b&w printing, where I would have noticed softness in the negative. On the other hand, I don't think that would have shown up in my shooting style, either. I don't center my subject, and as your tests showed with the statuettes, the off-axis performance of the lenses are nearly identical. If you compose with rule of thirds, the lenses are very close.

Still, I can understand awilder's concerns.
 
No, not at all Mike. I double checked rf and lens coupling accuracy by bracketing focus in small increments and reviewed the resolution charts. The factory adjustment gave the best overall result. Defocus in one direction may help center resolution but everything else got worse. Defocus in the opposite direction worsens the center but improves the outer field.
 
>> Defocus in one direction may help center resolution but everything else got worse. Defocus in the opposite direction worsens the center but improves the outer field.<<

A wide-angle lens focuses on an arc (actually a section of a sphere), not a plane (unless it's a flat-field lens). The arc radiates from the camera lens.

If you focus on a point 36 inches away, the edge of the field of view is 41 inches away on the long axis (usually horizontal axis), even further in the corner. That's a difference of 5 inches. The depth of field for a 35mm lens at f/2 focused at 36 inches covers only about 2 inches behind the point of focus.

When the lens is focused at 6 feet (72 inches), the long/horizontal axis is 82 inches away (a difference of 10 inches), whereas depth of field covers just 7 inches behind the point of focus.

You have to focus to 12 feet (144 inches) before depth of field covers the difference, which as that point is 20 inches (edge is 164 inches away).

This is all basic triangulation.

You solve it by focusing on the subject, then composing.

I don't know much about aspherical lenses. Do they correct the arc of focus into a plane? If so, that would make it difficult to compose using rule-of-thirds.
 
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Vince is absolutely correct about focus and I should have been more precise but I didn't want to go into too much detail because other factors like spherical aberration can also come into play especially with an early high speed wide angle design that's over 55 yrs old. "Minus" defocusing this lens very slightly in the direction of 0.9 meters and well within the f/1.8 dof marks does in fact sharpen the center resolution target at f/4 from 44+ lp/mm to 56+ lp/mm but nothing significant changes at f/2 where dof is much shallower and resolution goes from 36- lp/mm to 32+ lp/mm. My guess is that the improvement at f/4 is probably due to spherical aberration induced focus shift from f/2 to f/4 and the camera's rf or lens seating is calibrated to give best focus at the widest aperture where dof is shallowest. Further "minus" defocus (still within the f/1.8 dof marks) improves f/4 central resolution to 64- lp/mm but now f/2 central resolution drops down to 28+ lp/mm. It's just a guess, but maybe Nikon has tried to balance rf focus accuracy with aberration control to give a best compromise thoughout the aperture range.
 
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>>an early high speed wide angle design that's over 55 yrs old.<<

Actually, I believe it just turned 50 last September. The original release date was September 1956. I wonder if the reissued lens also used radioactive Lanthanum? Half-life is 60,000 years, so these lenses will be around for a long time to come.
 
Thanks Vince and awilder for the info. On the plus side, my 35mm 1.8 was not radioactive or at least similar to background. Still looking for a user out there.....
 
I was wondering too if the new Nikkor 35 has the Lanthanum glass element. Glass catalogues change and to have the exact glass in the new lens that was in the 50s original would be unusual it seems, but I would think that they made the new lens, if not equal in performance, maybe even better with more recent glass. (Maybe one of the reasons the SP/35 was only officially sold in Japan was because of European safety regulations, which a slightly radioactive Lanthanum glass may not pass.)

I understand that the 1.8/35 Nikkor was designed to be a very flat field optics - at least at longer distances which most lenses are optimized at. Sometimes with curvature of field (not the same as 'distortion'; pincushion / barrel) this can work as an advantage, in real world photography we rarely make photos of objects that are 'flat' and they have depth - and usually more than a few centimeters.
 
I reviewed my negs at f/4 and indeed the rf focus appears very accurate as I'll demonstrate. The 1st image is the figurine (shown in the earlier link) focused using the center resolution chart. Since the figurine is actually located a few inches in front of the plane of the chart, it's in accurate focus as it falls within the curved arc of focus described earlier by Vince and confimed when I swung the camera in position to focus on it. The next image is the same shot but the lens is slightly "minus" defocused by moving a point on the distance scale 1/4 of the length between the f/1.8 dof marks on the lens barrels dof scale. Note how the first image is sharper than the second defocused one.
 

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Usually, Nikon/Nikkor lenses have had minimal sample variation. It's been one of their strengths from the beginning.

On the other hand, the SP-5000 and new 35/1.8 are very unusual cameras in that they are actually custom-built. It is weird for a camera and lens to both be so out of whack, especially when the new S3/SP production runs have been so high-quality.
 
I wonder if mine sample was a lemon? My test shots were at about 1.8 meters (1:51 repo ratio) but it's hard to believe it would make that much difference. I probably would have kept the kit if the lens was as sharp as shown above and simply serviced the shutter under warranty from the dealer.
 
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