3 ZM lenses reviewed

ferider said:
Let's assume the subject is 1.5m away, then this corresponds to a focus error of about 3cm. More than the focus shift of the lens, certainly. If the lens shifts in the right direction, it might even help :)
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Hmm . . . Especially when the lens has a curved field like the Sonnar instead of a flat field. Good point. :)

Huck
 
the thing i tend to do with digitial camera is "focusing bracketing", manually of course, all those auto focus SLR camera makers are too proud to admit any focus inaccuracy in their systems.

the M8 with motor is perhaps ideal for this method.

my original testing of the c sonnar on r-d1s at full aperture is very soft, i thought the lens is no good, but i bracket the focus a bit, the lens is very sharp at full aperture, you have to explore a bit in order to find out the full potential of the lens, and not trusting too much on the rangefinder mechanism itself.
 
Sean Reid recently posted an initial draft of his article "50 mm Rangefinder Lenses for the M8" on his Reid Reviews website. This is a "must read" for anyone interested in this thread. The difference in his approach to reviewing these lenses & that of the Luminous Landscape authors is just stunning . . . stunning. :eek:
 
Huck Finn said:
Sean Reid recently posted an initial draft of his article "50 mm Rangefinder Lenses for the M8" on his Reid Reviews website. This is a "must read" for anyone interested in this thread. The difference in his approach to reviewing these lenses & that of the Luminous Landscape authors is just stunning . . . stunning. :eek:
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agreed! totally!!

sean seems to have a user's/artist's appreciation and understanding of the gear he reviews.
reading this article i can see where the new zm sonnar is like having 2 lenses in one. most people only see the limitations of this lens instead of the freedoms.
well done sean but please don't forget about us film users.

joe
 
I really wanted the new sonnar, but the more I read about the shift on here the less I want it. I do in fact do a lot of low light shooting, I need my lens to focus correctly wide open and thats it, period. I cant be out wondering if my lens is actually doing what I need it to do. Zeiss saying they "designed" the lens to not focus right wide open for posterity's sake sounds more like trying to cover their ass. I and my customers would not be interested in such an excuse.

ps. I have used more then enough fast 50's to know that they will focus right wide open, including my very wonky canon 50 1.4 ef lens, autofocus, 1.4, no problem, always spot on.
 
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avotius, spring for the 30 bucks and read sean's review for a better understanding of the zm sonnar.
you might learn something.

if you need a sharp and fast 50 wide open then the zm sonnar is not for you. but that doesn't make it a bad lens - just one that won't work the way you want. no problem as there are many other 50's, including the 50 planar that will do what you ask.

bad mouthing a lens based on the fractured info you got here is just plain annoying.

joe
 
Ok, I don't want to bring this into controversy, but I read Sean's review and I found it great. That said, he did not mention anything about the focus shift in the Sonnar, which appears to be the deal breaker for most people. It is not so much that it is a softer lens wide open, it is that you cannot set the focal point accurately when its wide open. Sure, you can stop it down, but by 5.6 it is just like another modern lens. Lenses like the sonnar are designed to give a lovely soft character, but that does not do any good if you have blurry eyes and a lovely softly rendered ear. Or at least, that is how I understand it. It seems weird that a 50/1.5 Summarit gives a similar soft character, yet it focuses accurately wide open. Perhaps Sean can comment on that in his final review. Also, I think it is a bit problematic that his 50/1.4 ASPH appears to be damaged. Perhaps he can borrow a different one. Or even mine, depending on how long he needs it...
 
I've recently corresponded with Paul VanWalree on the subject of focus shift, or "wandering focus" as Zeiss termed it. He had an interesting comment:

"The only lens fault that can cause a wandering focus, i.e. unintended focus shifts, is spherical aberration. . . In the presence of spherical aberration, the depth of field is markedly asymmetrical. It is quite possible that front depth of field is much larger than the rear DOF. This creates an impression of a front focus."

It seems that there may be a significant learning curve for how to use this lens to best effect when shooting in certain circumstances.
 
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who is this paul vanwalree?

i have only shot a few rolls through this lens so far but i was pleased enough with it to sell the planar.
 
back alley said:
who is this paul vanwalree?
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His site was linked earlier in this thread, Joe, but it's been weeks - www.vanwalree.com. The section on spherical aberration is what''s relevant to the discussion of the C-Sonnar.

I've had the opportunity to borrow a C-Sonnar & for the kind of shooting I like to do - people & cityscapes - I'm with you, Joe. I don't see what all the complaints have been about. I ran some tests & didn't see much of a focus shift. I'm getting another roll back tomorrow, so I'll take a second look. So far, I like the look & I'm considering getting one.

As someone said, it's just a tool that you put between your subject & the film. If it gives you a look you like, use it. If it doesn't, move on.
 
thanks huck.

looking at sean's review and photos show that after 5.6 the lens looks like most any really sharp 50 and from 1.5 to 5.6 it looks like a sonnar, sharp but not surgical, more rounded, 3 dimensional.
like having 2 different lenses as far as i can see.
 
Oddly enough, my Zeiss Softar and Hoya Softener don't seem to introduce focus shifts (and certainly none as bad as what has been reported about the C-Sonnar.) Their subtle effects also remain even at f/5.6 on any lens I choose to use. :p
 
I think these soft filters produce their soft effect through means other than spherical aberrations, so it makes some sense there'd be no focus shift.

On the other hand, I have the Pentax-67 120mm Soft that I believe introduces spherical aberration as the lens is opened toward its f/3.5 max. It's virtually normal by f/8 or so, but the instructions are to focus this manual-diaphragm lens at the aperture that you expect to shoot and that otherwise focus errors could occur.
 
There seems to be another option for those that want a high speed M free of focus shift, a sharp central zone wide open, great OOF rendering, excellent flare resistance and freedom from secondary reflections. It's the pre-asph. 50 Summilux that shows up in classifieds evey few weeks fo what the C-Sonnar costs new or LN used as seen here: http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00K9V8&tag=for example. My question for those who have used both is this: how are the fingerprints different? It would especially be interesting to hear from those that are very happy with the C-Sonnar and have owned the Summilux in the past. I know the CV Nokton is as sharp or sharper the the Summilux but I'm not sure if the bokeh is as good which is typically the case once aspherics are introduced.
 
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Just to reinforce what Huck related: what people are calling a focus shift could very well be an antisymmetry in the DOF. The C-Sonnar DOF range (not the focus point) may be shifted further forward than we expect. This means one would have to focus further behind the point one typically uses. In my experience, this putative and unexpected DOF symmetry is consistent with the results I've obtained to date.

An asymmetric DOF is also consistent with the reports in this forum. Some experienced Rf users can achieve focus, some can't. This does not mean those who didn't get focused results are inept. It means they did not expect the DOF symmetry to be different than their other lenses. It may also mean some rangefinder calibrations at close-in distances are more compatible with the the C-Sonnar than others.

So, if photographer A uses a camera with an small but inherent RF focusing error that is back shifted, they will think the C-Sonnar focuses like their other 50mm lenses. If photographer B uses a camera with an inherent to RF focusing error that is front shifted, they will think the same lens is impossible to focus.

Now we know RF mechanisms are relatively imprecise. As the subject-to-lens distance increases and as the f-stop number increases, the focusing uncertainties in our RF cameras becomes less of a problem. The symmetry of the DOF is becomes important as well.

In my view, there are three reasons not to buy a C-Sonnar.

1/ it is tricky to focus wide open at close distances (less than 8-10 feet). It is tricky because the DOF does not have the expected 1/3 – 2/3 field we are used to. It's a challenge to focus any 50mm lens wide open at short distances with a RF camera. The C-Sonnar is more challenging because its DOF symmetry is unexpected.

2/ It is soft wide open.

3/ It is relatively expensive.

If the hassle and uncertainty implied by item #1 is a deal killer, that's fine. It is hard enough to focus a 50mm lens at f 1.5 at short distances, why use a lens that operates differently than the lenses we're used to?

However this lens can be focused at apertures wider than f 2.8.

I have not experienced a focus shift wide open. But I have mis-focused with this lens as well as several other designs (Canonet f 1.7, Nikkor AI 50/1.4 and Canon 50.1.2 LSM) wide-open, at distances of 8 feet or less.


willie
 
Great points Willie! I wonder if the DOF asymmetry is somehow linked to the C-Sonnar's asymmetrical optical layout vs. the more symmetrical Gaussian designs in other high speed 50's?
 
awilder said:
I know the CV Nokton is as sharp or sharper the the Summilux but I'm not sure if the bokeh is as good which is typically the case once aspherics are introduced.
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Here are some of my wide open shots with CV Nokton 50/1.5, if you are interested.
 
awilder said:
Great points Willie! I wonder if the DOF asymmetry is somehow linked to the C-Sonnar's asymmetrical optical layout vs. the more symmetrical Gaussian designs in other high speed 50's?
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according to the author that huck quoted, it's caused by the spherical abberation.

joe
 
fgb2 said:
This is actually an easy experiment to do. So I thought I would prove to myself that my ZM C-Sonnar (which I like) did not have this problem.

I put the lens on an R-D1 on a tripod angled down toward a spread-out newspaper. Camera was 9 inches above the table, focusing distance 0.9 m set on the lens. I used the Leica 1.25x magnifier held up to the viewfinder to position the paper so I knew just where the rangefinder plane of focus was. Then I took a sequence of images at apertures 1.5, 2, 2.8, 4, 5.6 without touching anything but the aperture ring.

Yes, the lens focuses about 2 cm closer to the camera at aperture 1.5 than at 2.8. You can see the answers right on the camera’s LCD. There seems to be little movement in the plane of focus after that, but it’s hard to estimate since so much of the paper is in focus at the smaller apertures.

A Zeiss pre-war Contax mount 50mm Sonnar at 0.9 m had about the same amount of focus shift. Incidentally, the plane of focus for the lens differed from the rangefinder plane by about 3 inches with this adapter, made from a Contax helicoid. I think Roland made a similar observation on one of these adapters.

Canon 50/1.2, at 3.5 feet, about the same focus shift between apertures 1.4 and 2.8. I think I remember this is a double Gauss design and not a Sonnar.

Noctilux 50/1.0 at 1.0 m, similar focus shift from 1.4 to 2.8. Puts confirms this for this lens in his Lens Compendium.

Summilux 75/1.4 at 0.9 m, aperture 1.4 to 2.8, about the same shift as for the other lenses.

I don’t have the lenses you would think would be corrected for this (modern 50 Summilux ASPH, Summicron, ZM Planar, etc) and would urge people to try this with their own lenses. It takes about 3 minutes.

For my own R-D1 + ZM C-Sonnar combination the rangefinder and lens agreed on the same plane of focus at aperture 2.8 or 4. I wouldn’t trust my uncalibrated refurb rangefinder as a gold standard here. But comments on Zeiss’ bulletin seem to indicate Zeiss has calibrated the lens for correct focus at smaller apertures. Puts says the Noctilux cam is calibrated for the wider apertures, which would be my choice. But it’s clear one has to make a choice, because by aperture f/2 the line of newsprint that was in focus at f/1.5 is no longer sharp for me with this lens – which I still like a lot.
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I'm quoting fgb2 in the quote above in repsonse to Mazurka's comment ". . . focus shifts (and certainly none as bad as what has been reported about the C-Sonnar)" just to make the point that the reports have not been consistent. I think we're still getting to know this lens. Fgb2's report is consistent with the small focus shifts that I observed in the early returns with the sample that I have borrowed. I have just not gotten anything dramatic . . . & I've tried.
 
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