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Archive 2014 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

levi.hammett
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p.1 #1 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

I recently purchased the Zeiss C Sonnar 50 1.5 ZM and wanted to run some tests to investigate what the much discussed 'sonnar character' looks like compared to some other lenses. I thought this would be a good place to share my results. Hope you enjoy them.

The lenses I included in the comparison were:
Zeiss C Sonnar 50 1.5 ZM
Canon FD 55 1.2 SSC
Canon FDn 50 1.2
Voigtlander 35 1.2 (For fun)

I meant to test a Leica Summilux 50 1.4 R but the adapter I ordered turned out to be a dud, and my copy of the Voigtlander Nokton 50 1.1 developed a very loose interior element that was binding up the aperture blades which I could not fix until I came back home (test was done while traveling). I'll probably do a larger comparison when I get some time. For now it is what it is...

I'll start with a near infinity sharpness and corner test. Below is the test shot. This one from the ZM Sonnar @ 1.5.

DSC00638 by lalalevi, on Flickr

Here are the 100% center crops.
No surprise that the Zeiss is not the sharpest of the bunch. I also had some trouble with the FDn 50 1.2. The last shot @ 5.6 had a bit of camera shake. I didn't want to reshoot the test. Lazy.

Lens Test, 50mm, Center by lalalevi, on Flickr

Here are the 100% corner crops pulled from very near the upper right corner of the image. With this one can see the relative corner shading of the different lenses at max aperture. The big surprise for me was the seeming performance decrease of the Zeiss in the corners moving from f2.8 to f5.6. At first I thought I was seeing camera shake. But after reshooting a number of different tests with different scenes over multiple days, I eventually realized that it is something else. My best guess is that it is corner smearing due to the short distance and steep angles of light from the rear element to the sensor. Much discussed with rangefinder lenses (especially on this board), but I was under the impression that the problem was mostly with 35mm and below.

Lens Test, 50mm, Corners 2 by lalalevi, on Flickr

Here is another corner test. Actually the first one I conducted. Same result with the Zeiss corners.

Lens Test, 50mm, Corners by lalalevi, on Flickr

Now to look at some of the more fun attributes that contribute to that thing called lens 'character'. This was my bokeh test. The shots were hand held, and the light may have been changing subtly, so take the comparison for what it is worth. This first one is a comparison of the entire shot. The 35mm voigtlander is cropped to match the 50mm field of view. Don't flame me for it, I just wanted to compare the bokeh at about the same size, for fun.

Lens Test, 50mm, Bokeh by lalalevi, on Flickr

Here is a detail near the center of the frame. These are not pixel accurate, probably like a 50% or something. Very subjective preferences here, but the Zeiss seems to maintain 'nicer' shapes to the out of focus highlights, the circles are much more 'full' and consistent than the other lenses in the group.

Lens Test, 50mm, Bokeh Detail 1 by lalalevi, on Flickr

Crops from the upper right.

Lens Test, 50mm, Bokeh Detail 2 by lalalevi, on Flickr

Here are the shots I took for contrast and fringing. There is also a nice comparison of more bokeh in the upper left corner (detail further below). With these one can really see the Zeiss step ahead of the pack in terms of retaining good contrast with such an extreme back-lit subject and strong light source in frame. There is also no real evidence of any flare induced artifacts, which is impressive. Now the Voigtlander is cropped again, which hides some of the flare induced artifacts from that lens, so it is not a fair comparison for that lens.

Lens Test, 50mm, Flare by lalalevi, on Flickr

Here are two details to look at contrast.

Lens Test, 50mm, Flare Detail 2 by lalalevi, on Flickr

Lens Test, 50mm, Flare Detail 3 by lalalevi, on Flickr

And an interesting crop from the upper left of the image that shows the some of the bokeh character. The Zeiss is able to maintain nice circular out of focus highlights, while the two canon lenses have dart shaped highlights. The voigtlander bokeh is just sort of messy, but again this is a crop so not fully representative of the 'real' corner of that lens.

Lens Test, 50mm, Flare Detail 1 by lalalevi, on Flickr

And lastly another sharpness test. This time close focus, not infinity. Here is the test shot.

DSC00390 by lalalevi, on Flickr

100% center crops wide open.

Lens Test, 50mm, Sharpness Wide Open by lalalevi, on Flickr

100% center crops @ f2.0

Lens Test, 50mm, Sharpness F2 by lalalevi, on Flickr

Overall, I am very happy with the Zeiss lens. It handles beautifully. Great images. Lovely soft renderings and vibrant colors. Here are a few real shots with the Zeiss. All wide open.

DSC00433 by lalalevi, on Flickr

DSC00428 by lalalevi, on Flickr

DSC00422-2 by lalalevi, on Flickr

DSC00607 by lalalevi, on Flickr

_levi

Jan 07, 2014 at 05:39 AM

levi.hammett
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p.1 #2 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

The other bit of information that I should have included: All of these shots are with the Sony A7R.

Jan 07, 2014 at 05:47 AM

waterden
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p.1 #3 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

Nice work, Levi, thank you. The C Sonnar is indeed a classic and a natural fit for this camera. I really like the snap in its images. It would be interesting to compare it with the FE 55/1.8.

Jan 07, 2014 at 06:10 PM

darrellc
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p.1 #4 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

See bmupix.com for his comparison of C Sonnar and FE 55/1.8. He's selling the Sonnar.

I'm liking the C Sonnar on my A7, but may pick up the FE 55 and do my own comparison.

Jan 07, 2014 at 06:17 PM

Jabberwockt
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p.1 #5 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

I have mix feelings about the A7/A7r as a testing platform due to the sensor toppings issues. But I'm not surprised that the corners never get that sharp, the design has loads of field curvature and is a bit of a specialty lens IMO.

Jan 07, 2014 at 06:57 PM

philip_pj
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p.1 #6 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

Thanks for these well-prepared images, they illustrate so much about the need for good corner MTF in lenses for the a7r, if corner resolution is needed or wanted.

I can provide a long answer, it is tedious for lay observers, but the short answer is this: this lens, the C Sonnar has very poor long edge/corner performance, consisting of strong sag data and very low tan data. Wide open both are low and very low contrast with good shaping results.

At f5.6 sag data has skyrocketed over 60% tan is still around 20%. The result is rampant CA in a radial direction, good contrast radially but very poor contrast tengentially. Compare and contrast the Canon FD image crop immediately below this one. See how branches look equally good in both directions?

Now here is the relevant MTF chart for the C Sonnar ZM:

http://lenses.zeiss.com/content/dam/Photography/new/pdf/en/downloadcenter/datasheets_zm/csonnar_1-5_50_zm_en.pdf

You can read my comments and see the chart reflects them - f4 in the chart is close enough to f5.6 for this exercise.

Zeiss will tell you to look for flat near to parallel lines or slowly declining lines in MTF charts if you desire good image object shaping and low CA, quite the opposite of what the C Sonnar shows us. Of course it is not ideal as an all of frame landscape lens but has other fine attributes, which I thank you for pointing out and showing here. It's a fast lens and like so many of them designed for wide open work.

The a7r works extremely well for lenses with good overall design parameters, like the amazing FE 55mm and as seen above in the FD lenses. For a look at this, see the blur index diagram here for the FE 55mm:

http://slrgear.com/reviews/showproduct.php/product/1656/cat/82

That chart is from an a7r. Note the corners at all but widest apertures. It is a real bargain at $1000, and as good as it gets most likely, short of an Otus.

Jan 07, 2014 at 07:48 PM

BrianVS
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p.1 #7 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

The 55/1.8 is "Sonnar" in name only, 7 elements in 5 groups with 3 aspheric surfaces.

The Sonnar gets much of it's character from high spherical aberration - a result of asymmetric design and resulting short optical path. If you ever take one apart, the front section is a telephoto lens with a focal length about 2.5x the focal length of the complete lens. The rear group is about the same focal length of the complete lens. The groups are spaced relatively close. "Short, Stout lens, depth of field is "spread out" for a softer focus when used wide-open. Stopped down a little, quite sharp.

C-Sonnar on the M8, F2.8 (or so)

Jan 07, 2014 at 08:19 PM

philip_pj
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p.1 #8 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

Brian, thanks for that information. Zeiss are now seemingly treating their fine lens titles as marketing tools, sad but true.

I am presuming you are referring to the C Sonnar 1.5/50 in your main para. I thought readers might like to see what the talk is about. Here are lens design schema for the C Sonnar 1.5/50 and the FE 1.8/55 along with Zeiss own (measured at infinity) optical bench actual lens data for the C Sonnar at f4 and the 'calculated' MTF for the FE 1.8/55.

The bottom scale shows in mms the image height - distance away from the image centre; the left side scale is percentage of contrast - more is better. The take home message is that calculated MTF is a probably reliable guide to the profile of lens performance, but is optimistic by an unknown degree, perhaps by around 5-10% for the lower spatial frequencies (5 lpmm and 10 lpmm) and by 20% for the higher spatial frequencies - 40 lpmm. That is an 'educated guess'. These are still useful because they indicate the general behaviour of the lens.

Obviously designs are very different, and as you say the C Sonnar is close to the appearance of a traditional 'real' Sonnar. The FE 1.8/55 is something again...Maybe Zeiss can start new names for new designs they feel have passed the test. Perhaps they are making what is needed on a case-by-case basis though; who knows?

The MTF data chart for the C Sonnar 1.5/50 shows the huge departure from ideal from image height (IH) of 16mm to the very corner of 21mm. This is the fly in the ointment described in my above post.

The MTF data chart for the FE 1.8/55, in the left side 'Max. Aperture' diagram shows the ideal characteristics of near to parallel gently declining line pairs. We look at this kind of chart with great satisfaction, as it indicates very good handling of aberrations across the board, with very little curvature of field (no rapid departure from steady decline) and excellent and high data across the entire frame. You can see performance is high from image centre and stays at that level almost to the long edge at IH of 18mm.

The main point I wish to make is that the main issue is that the *shape of the lines as they move across the frame strongly influences perceived performance* and perceived image quality. It does not hurt that the new FE no doubt has very high measured MTF, from early on in the aperture range, say f2.8. The great additional benefit is it is still very good indeed at f11.

Some people are saying they feel it produces 'cold, soul less images', but they remind me of the 135/2 APO Sonnar in some ways. Some liken the bokeh to medium format. That of course is down to opinions, which vary for all kinds of reasons. The richness of life.

C Sonnar lens design - 6 elements in 4 groups

FE 55 lens design - 7 elements in 5 groups

C Sonnar 1.5/50mm - Zeiss Actual Lens MTF at f4

FE 1.8/55 - Sony Calculated MTF at f1.8 and f8

Jan 08, 2014 at 02:11 AM

BrianVS
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p.1 #9 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

I did a write-up on the C-Sonnar for "Theme" a few months ago. The C-Sonnar is Bertele's late Ernostar design. With the "Sonnar", Bertele basically filled in the air gap between the 2nd and 3rd element to increase transmission of light. With multi-coated optics, it's not necessary.

http://www.the.me/lesson-in-history-the-magic-of-the-value-for-money-zeiss-c-sonnar-50mm-f1-5/

I've collected Sonnar formula lenses for several years now, love the ones from the 1930s.

http://www.the.me/unique-blend-of-compactness-super-speed-and-perfect-imperfections-1930s-sonnar-lenses-on-the-leica-m9-and-m-monochrom/

Jan 08, 2014 at 05:54 AM

waterden
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p.1 #10 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

Quality thread. Excellent links too.

Jan 08, 2014 at 09:59 AM

Makten
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p.1 #11 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

philip_pj wrote:
Obviously designs are very different...

It depends. If you exclude the frontmost group with two cemented elements of the new Sonnar, the rest is not that far from the old one.

Jan 08, 2014 at 12:30 PM

Beni
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p.1 #12 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

BrianVS wrote:
I did a write-up on the C-Sonnar for "Theme" a few months ago. The C-Sonnar is Bertele's late Ernostar design. With the "Sonnar", Bertele basically filled in the air gap between the 2nd and 3rd element to increase transmission of light. With multi-coated optics, it's not necessary.

http://www.the.me/lesson-in-history-the-magic-of-the-value-for-money-zeiss-c-sonnar-50mm-f1-5/

I've collected Sonnar formula lenses for several years now, love the ones from the 1930s.

http://www.the.me/unique-blend-of-compactness-super-speed-and-perfect-imperfections-1930s-sonnar-lenses-on-the-leica-m9-and-m-monochrom/

I read that article recently actually when thinking of the C-Sonnar for my A7r. Thanks for your work.

Jan 08, 2014 at 01:23 PM

philip_pj
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p.1 #13 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

thanks for the links Brian, much appreciated.

Jan 08, 2014 at 09:11 PM

Jeff Kott
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p.1 #14 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

If anyone's interested, Bjorn Utpott posted a comparison of the ZM 50/1.5 to the FE 55 on his A7r.

http://bmupix.com/home/2014/1/7/end-of-the-road-for-a-classic-lens

Jan 09, 2014 at 12:46 AM

BrianVS
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p.1 #15 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

The new 55/1.8 looks like a retrofocus design, large negative group up front. This is to cope with the digital sensor of the A7. The C-Sonnar was made for the Zeiss Ikon film camera, light exits the lens at a higher angles. The Leica sensors are design to cope with light coming in at these steep angles. So- a real Sonnar formula lens is not going to do as well at the corners on an A7 as it will on the Leica or with a film camera.

Just to add- the Canon 50/1.4 FL mount, later version, has a "long drawn out" optical path, has very low spherical aberration, and can be had "cheap". I ended up converting one to Leica mount. It should be great on the A7.

Jan 09, 2014 at 05:50 AM

aleksanderpolo
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p.1 #16 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

For sharpness the ZM Planar has been available for a long time, I don't think that's the point of the C-Sonnar. Similarly, I won't be comparing the 55/1.8 with a macro lens and complain about the former's lack of macro capability. YMMV

Jan 09, 2014 at 12:00 PM

BrianVS
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p.1 #17 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

I have sharp lenses. Almost never use them, prefer the rendering of the Sonnars.

Field Curvature with an A7r means never having to worry about aliasing.

It's a feature, not a flaw.

Jan 09, 2014 at 03:39 PM

briantho
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p.1 #18 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

I love the character of the C Sonnar, the OOF areas renders beutifully. What I don't like is its resolution at infinity, it's awful, useless actually. The C Sonnar is a superb lens to use for portraits or close (1-2 meters away) objects, but for landscape use it's the worst lens I've owned.

I decided to sell my C Sonnar to get the FE55 instead, because after all, with the A7R I want to get all the resolution it's capable of, and unfortunately the C Sonnar doesn't deliver. If I could afford to have both, I would have kept the C Sonnar for portraits and indoor events, but from what I've seen, the FE55 is a pretty good all rounder on A7R.

Jan 09, 2014 at 06:56 PM

BrianVS
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p.1 #19 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

The focus shift is the problem. Most people stop down for infinity- and on the C-Sonnar, that pushes the focus past infinity. When stopped down, I focus slightly closer than infinity and let the shift bring things into focus.

With a Jupiter-3, the focal length is longer. Wide-Open/Close-up and F4/Infinity is typical.

Jan 09, 2014 at 08:42 PM

redisburning
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p.1 #20 · Testing the ZM C Sonnar 50 1.5 & 3 other lenses

Brian I am a fan of your work and expertise. Additionally, I agree that lens choice is personal and one lens winning along a few objective measures does not make it better per se.

But the C-Sonnar is not a sharp lens. Older Sonnars really aren't sharp lenses. And especially not to some of the stuff we use around here.

Some of us really are into sharpness. I sold my ZM 50 Planar to switch systems to Nikon so I could shoot the 50 Makro-Planar just because my most expensive lens HAD to be the sharpest one I could afford.

Some people will chase "character". I get that. Sometimes I wished I could have an E46 Summilix so much I considered a serious sell off of my cherished Olympus gear. But liking a lens like the C-Sonnar will never be enough to make up for what is frankly an insurmountable difference in contrast.

Jan 09, 2014 at 08:57 PM

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