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One of the common "criticisms" of the Zeiss ZM C-Sonnar 50 mm/1.5 is its pronounced focus shift. That got me curious if the similar-design Zeiss Sonnars for the Hasselblad V-system (e.g. 150 mm/4 and 250 mm/5.6) also displays any focus shifting when stopping down.

I know that focus shift isn't such a big issue on an SLR (but can still be) since you "see the focus" of the image. However, due to the already dark standard focusing screen, I rarely use the DoF preview on my 'blad. So would focus shift still be noticeable if I take closeup shots (possibly with an extension tube) with my 150 mm Sonnar slightly stopped down at, for instance, f/5.6? Or does perhaps the slow speed of the hassie lenses, compared to the f/1.5 ZM, mean that the spherical aberrations that cause the focus shift are already negligible?

Edit

I just wanted to clarify that this question was more of an academic curiosity about lens designs. That is, if the general Sonnar design itself suffers more from focus shift than others, or if it is the specific design of the 50 mm/1.5 ZM which gave that lens a more pronounced focus shift (besides the fact that it's way faster than the f/4 or f/5.6 'blad lenses).

Andréas Sundström
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1 Answers1

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Take some pictures and determine if the phenomenon occurs and if it occurs decide if it does or does not matter. If it does matter think about possible work arounds.

There is variation among individual lenses, even the best, when they leave the factory. After a few decades, and these are often old and perhaps hard used lenses at this point, there can be substantial differences between copies of the same lens.

If you don’t yet own one or more of the lenses, rent them to test. Testing is the only way to match your needs to your options.

Bob Macaroni McStevens
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  • Thanks! Although the reason why I asked was to see if anyone had any experience or knew about the issue so that I wouldn't have to burn a roll of film on test shots. Also, I'm not sure how focus shift could vary that much between individual lenses without also seeing (much larger?) effects on image quality. – Andréas Sundström Dec 06 '21 at 09:55
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    @AndréasSundström The sources of the information that sparks your concerns probably did something where the optical trade offs could be seen on inspection. Test charts are designed to reveal everything. Even things that don’t matter except when shooting test charts. What matters is if it destroys your pictures. No one looks at a landscape and weeps because the corners are pin sharp. – Bob Macaroni McStevens Dec 06 '21 at 18:18
  • @AndréasSundström Lenses get dropped. Some more and/or harder than others. The variations among lenses increases over the years with use. In the same way some lenses have fungus and others don’t. Even in the factory, all the glass may meet the optical specifications but some exceeds the specifications and some of that exceeds further than other batches. All of it is good enough. Some is better. – Bob Macaroni McStevens Dec 06 '21 at 18:27
  • "All of it is good enough..." [*good enough as defined by the manufacturer.] That may or may not meet the definition of good enough for a specific user and use case. YMMV. – Michael C Dec 08 '21 at 00:21
  • Obviously that is why I mentioned specifications and set the context of my comment to the manufacturing process. It is also why the theme of my answer is test and see if it matters. That that’s not good enough for some people is just Billy goats over the bridge. – Bob Macaroni McStevens Dec 08 '21 at 01:35
  • @BobMacaroniMcStevens I'm all onboard with "what matter is if it destroys your image", and it hasn't so far for me. So all is well and good for that. It was perhaps poorly conveyed by me, but the question was more academic in nature than practical. A probably better formation of my intended question would be "Is focus shift inherent to the Zeiss Sonnar lens designs (more than in other designs)?" – Andréas Sundström Dec 08 '21 at 08:20
  • @BobMacaroniMcStevens I still doubt that focus shift would be one of the first thing to appear if a lens is off calibration (at least due to wear and tear). I'm not an expert in optical design, but my suspicion is that image quality (resolution, micro-contrast) is more severely affected by bad calibration than focus shift, since that seems to be the most sensitive aspects of an optical system. Focus shift is more due to spherical aberrations present in the lens elements, which I wouldn't think should vary that much over the years of wear (unless you're polishing you lens with a grinder). – Andréas Sundström Dec 08 '21 at 08:34