Reid Review: 28 2.0 Ultron focus shift

P. Lynn Miller said:
Sean,

Thanks for your detailed reply. While I have not noticed any focus shift in my Ultron 28/2, maybe I do not know what to look for. I have simply been very impressed with the photographs that I have taken with this lens and that was good enough for me.

Couple of questions...

How much does the focus shift... are we talking a few millimetres or a couple of centimetres?

There seems to be a correlation between aspherical designs and lack of focus shift, so am I right to assume the Zeiss ZM series would also display some focus shift since the lens are traditional spherical designs or are the Zeiss designs 'better' than the less expensive CV designs?

Thanks,
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The degree of the focus shift will depend on the aperture and its "apparent" degree will also depend on subject distance. But if you're happy with the lens as is, I wouldn't bother testing.

There are various non-aspherical lenses that show little focus shift. But I think it's a challenge to design to design a fast lens, F/1.4 for example, that does not use aspherical elements and which also does not shift focus.

*But* I'm not a lens designer and I can only look at the results. It's interesting that the CV 35/1.2, for example, is so fast yet is not prone to focus shift.

Some of the ZMs show some focus shift but it is usually quite mild. Zeiss has, if memory serves, made a point of noting that the ZMs are designed to avoid this.

The Leica 35/1.4 ASPH shows focus shift and its still one of my favorite lenses.

Cheers,

Sean
 
First of all, I must say that this discussion is much more even-keeled that I had feared. I'm pleasantly surprised.
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Hi Sean, I am glad to agree.

First off, though not included in the original post, obviously your review contains a lot more than just the statement that the lens suffers from focus shift. Fortunately other posters were able to add more of what you found in your tests. And we benefited from Marty's great contributions which greatly helped my understandings of your findings, and the facts behind lens design and focus shift.

I am happy you have been able to join in and add more to the discussion.
 
Sean,

I am a subscriber to your site and very happy with all of your reviews–I think you do an excellent job. I have one question... in the past you did some focus shift tests using a 3-dimensional subject: some bottles. I know you've developed your test board for resolution, but I wonder if it might be helpful to do that kind of a test on a lens that does exhibit some focus shift, to see more clearly how pronounced the issue is. I'm just curious about your process.

Thanks,
Ben
 
rover said:
Hi Sean, I am glad to agree.

First off, though not included in the original post, obviously your review contains a lot more than just the statement that the lens suffers from focus shift. Fortunately other posters were able to add more of what you found in your tests. And we benefited from Marty's great contributions which greatly helped my understandings of your findings, and the facts behind lens design and focus shift.

I am happy you have been able to join in and add more to the discussion.
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Thank you sir.

Cheers,

Sean
 
benkelley said:
Sean,

I am a subscriber to your site and very happy with all of your reviews–I think you do an excellent job. I have one question... in the past you did some focus shift tests using a 3-dimensional subject: some bottles. I know you've developed your test board for resolution, but I wonder if it might be helpful to do that kind of a test on a lens that does exhibit some focus shift, to see more clearly how pronounced the issue is. I'm just curious about your process.

Thanks,
Ben
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Hi Ben,

Thanks.

It's a good question for sure. The res. board test tells me how much res. is being lost (as one stops down) at the point of intended focus (ie: the distance giving highest res. wide open). But maybe I'll do the bottle tests when I check the other two samples of the 28/2.0.

Cheers,

Sean
 
mabelsound said:
I do fear that an internet culture has developed, of pixel-peeping fussiness among people who are preoccupied with the idea of perfection, at the expense of seeing the big picture. (Sean, I certainly don't think you're one of these people.)

A good example is the new Pentax DA35 f/2.8, which was widely regarded as a miracle lens on the forums, until a couple of sharpness tests came out, saying it was actually a weak performer as a "standard" lens. But I bought it anyway, and it's freaking stunning. Every picture, when you look at the whole, is wonderful, at all apertures, with superb contrast, dynamic range, and color. In other words, it takes great pictures.

I'm sure there are many photographers for whom absolute sharpness at all apertures is a necessity, and these photographers should consider Sean a fantastic resource. But it bothers me that there also seem to be so many photographers who will turn their noses up at a useful tool because they read somewhere that it's soft at f/4, when such a "problem" would never affect their work in any significant way.
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I agree with the spirit of what you're saying and I try to keep it in mind as I write about a lens or camera.

A. To be sure, photography is more important than technical performance per se.

B. A lens with technical weaknesses can still be a wonderful lens.

With any luck, RR has *also* been a resource to a lot of photographers who are concerned about much more than sharpness. If you ever decide to read the site, check out the "Myths" article. My favorite articles on that site aren't specifically about lenses or cameras.

Cheers,
 
Could anyone care to explain a bit more about why film will mask the focus shift as compared with digital? I know film is thicker than digital sensors, but still don't quote get it. Is it related to why I've been told that scratches on the rear element of a lens are much worse than on the front, especially with wide angle lenses? I had a brief read of the vanwalree site linked (actually I've read it before, very interesting, and there's much more on the site of interest too), but hope someone here could shed some more light!

EDIT: Is this a case for an autofocus digital rf? Dante Stella I think mentions that the Hexar AF automatically corrects for focus shift (spherical aberation), at each aperture, so the lens can be left uncorrected, allowing for an arguably nicer oof redition?
 
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I just posted an extreme close up of the license plate of the old Packard on our flickr site. This was shot with 400asa film and @f2 and 1/60. I can not see any focus shift at all in this lens, at least with film.
 
Tom A said:
I just posted an extreme close up of the license plate of the old Packard on our flickr site. This was shot with 400asa film and @f2 and 1/60. I can not see any focus shift at all in this lens, at least with film.
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Tom,
There shouldn't be any focus shift wide open - this is not the C-Sonnar "optimised" for 2.8. ;)
And from my experience, centre sharpness of the Ultron wide open is very good, however, it appears that there are some other issues with this lens which makes it unusable for me.

Cheers,
Uwe
 
sreidvt said:
A. To be sure, photography is more important than technical performance per se.

B. A lens with technical weaknesses can still be a wonderful lens.

With any luck, RR has *also* been a resource to a lot of photographers who are concerned about much more than sharpness. If you ever decide to read the site, check out the "Myths" article. My favorite articles on that site aren't specifically about lenses or cameras.

Cheers,
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Thanks, Sean, perhaps I will! I can tell you that your evenhanded R-D1 review on LL (and presumably on your own site as well) is what convinced me I would like that camera, and I was right. In that case, the camera's shortcomings are not only not problematic for me, they are part of its personality, and part of what I like about it.
 
What I dont understand here is that there has been no complains about focus shifts with the older, non asph lenses from Konica,Leica and Zeiss/CV.
If this theory about asph is correct, your 35f2 III and IV would be useless on the M8!
 
Tom, I think digital (M8 and computer screens) has a lot to do with the higher expectations.

Edit: I should say, enlargements both on a computer screen and with an inkjet.
 
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Tom A said:
What I dont understand here is that there has been no complains about focus shifts with the older, non asph lenses from Konica,Leica and Zeiss/CV.
If this theory about asph is correct, your 35f2 III and IV would be useless on the M8!
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I don't know the 35/2 III and IV, but as far as I understand, it's not a theory about asph, but rather a theory about controlling spherical aberrations. Being a brickie, I however don't have a clue whether this can be only achieved with asph lenses.

Cheers,
Uwe
 
Tom A said:
What I dont understand here is that there has been no complains about focus shifts with the older, non asph lenses from Konica,Leica and Zeiss/CV.
If this theory about asph is correct, your 35f2 III and IV would be useless on the M8!
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Hi Tom,

Like the Zeiss ZM lenses, the Summicrons are of only moderate speed for their focal length. The relevant spherical aberrations become more difficult to control with increasing speed. Aspherical element use is not a 'theory' about focus shift - designers definitely include them to reduce spherical aberrations in camera lenses. The pre-asph Summicrons are conservative enough designs that the spherical aberrations are well enough controlled to prevent significant focus shift. The pre-asph 35/1.4 Summilux shows some focus shift - but with this lens it was hard for me to measure because it is so soft wide open (at least the sample I tested was - it was from the first type 35/1.4). The f1 Noctilux and 75/1.4 Summilux show a lot of focus shift. I haven't tested other Leica lenses. But don't think that any lens with aspherical elements has no focus shift - because many do (including the 35/1.4 asph and aspherical) or that all spherical designs have a lot - because they don't.

Marty



Marty
 
Marty, thanks for the reply. What bugs me here is that a lot of "chatter" about a percieved focus shift in lenses were I can not discern it! I have used Noctiluxes and Summilux 75's extensively and they suffered from, in some cases, massive focus shift! My stash of VC/Zeiss lenses doesn't have any major problem with it, in fact some of those lenses are far better than the Leica products in this aspect.
The 90'2 Apo-Asph would shift quite noticably at f2.8 and f4 and really wasen't that good until you hit 5.6! Heresy, I know, but that was my experience. I suspect that the floating element technology of the 50f1.4 Asph and 75f2 Apo does correct for this, particularly in the close range.
All of this is based on using film of course as I refuse to go digital until my 35mm lens is a 35mm lens on the camera, not a 42.3 mm or something like that.
Focus shift or not - the 28f2.0 Ultron is one of the best 28's I have ever used (and I have used a lot of different ones) - and it is particularly impressive in close up.
 
All of this is based on using film...
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The solution seems simple: Use the 28/1.9 on your R-D1/M8; the 28/2.0 on your film body.

That's probably not an answer that will make Mr. K very happy, though.
 
I dont think that's is a problem. Mr K is happy for the simple reason that tthere are only about 16000 M8"s out there and 8-9000 RD1's - And several 100 000's of M-bodies still being used! With film doing a albeit slow but significant come back, the future is rosier for "digital back focussing" lenses than we think.
I also think we approach this from the wrong end! IF the M8 and the RD1 (though less chatter about that) does induce backfocussing in certain lenses, be it Zeiss/VC or Leica - the flaw is in the camera, not the lenses. We should petition Leica to fix the problem with the camera instead!
Most everybody that I know that has M8's have had to go through the procedure of having the cameras"recalibrated" to accept lenses like the Noctilux, the Summilyx 75 and even the 35f1.4 Asphs and diminish the focussing problems. We are talking a $6000 camera and lenses ranging from $3500 to $6000+ having to go back to work properly!
The new lenses,$3000 to $11000 obviously work fine - at least judging from inital reports and at that price they should.
As the LOMO stand proudly proclaimed "The Future Is Analog".
 
I often wonder why we (as shooters ourselves) put so much weight into the words, web images, and styles of a handful (on one hand even) of "reviewers" (be they Sean, Phil Askey or others).

Go out, snag a lens for yourself and decide for yourself if it suits your style/camera.

I've had the Ultron f2 for quite some time and am perfectly happy with it - just as I am with the CV 35mm f1.4 Nokton - the benefits, for the money, far outweigh any detrimental affects that may be a result of the lens - both are used on the M8 regularly and I'll be happy to use them both on the M7 as well.

If I had listened to everyone else who said that the CV 35mm f1.4 Nokton was a dog of a lens I would never have tried one and then I would have never realized just how wonderful a lens it truly is.

Dave
 
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