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As noted here focus breathing can be problematic, especially for macro focus stacking.

Are there lenses that exhibit absolutely no focus breathing?

Is there some way to find lenses that minimize focus breathing without actually testing them? (E.g., is it an advertised characteristic, or can it be deduced from some other lens specification?)

  • You already got the suggestion for using focus reels, what's the problem using those? – null Jul 1 '15 at 15:21
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    @null One small problem with rails for focus stacking is that they create perspective shift. Granted, they are one solution to the problem mentioned in the preamble. But this question is about lenses. – feetwet Jul 1 '15 at 15:27
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+50

If you are looking for a macro lens that does not noticeably breathe, the best one that I know of is the $1800 Zeiss 100mm f/2 Makro-Planar. The Canon 100L and non-L are both quite bad for this, and the Nikkor is worse. I am not sure about the Tamron non-VC or the Sigma, Tokina, etc., lenses. The Zeiss 100/2 only provides 1:2 magnification so you will need tubes or diopters to get to 1:1.

The Zeiss 135mm f/2 is also very good and provides up to 1:4. It is shorter than the fully-extended 100/2, so perhaps with tubes you could get greater working distance out of it.

In terms of deducing it from specs: if you can find a lens diagram, more symmetrical lenses will be better.

In the following example, a Sigma 150mm macro, the first several elements have a great deal of optical power (a very short focal length). Everything after the last ED element in the front is negative. In the back there is some positive stuff and then a couple of negative elements. This is a highly asymmetrical design, so it probably breathes quite intensely.

Sigma #106 lens diagram

In contrast to the Sigma's autofocus-optimized design is a bit of a relic: the Zeiss 100mm Makro-Planar. The design dates from the 1980s but is a truly stunning design with perhaps decades of performance on par with or higher than its peers still up its sleeve. Its design is classic and simple, so it is a good choice with which to identify design elements.

Zeiss lens diagram

From the front, we have a split doublet made of a low dispersion glass. This helps with the axial chromatic aberration, though in this lens model that aberration still needs some work. Both elements have strong curvature on their front side and weak curvature in the same direction on back side. From the equation for the optical power of a surface, φ=C(n-n') where C or curvature is the inverse of radius of curvature (i.e., 1/R), n is the refractive index of the ambient medium, and n' is the refractive index of the second medium. At the first surface the ambient is air, at the second it is the glass.

Since the front curvature is greater than the rear curvature, it provides more optical power and these are net positive elements. Likewise with the third. The fourth has a greater back or rear curvature, so it is negative. This particular shape helps to flatten the image plane as well, and the meniscus third element helps to correct spherical aberration and coma. The first two have little spherical and coma, but the greater bend on the third provides more correction.

Elements 5 and 6 are cemented to correct color and have a strong negative power. If you cut the lens off after that doublet it would have a very long negative focal length, perhaps -500mm or something. Then there is a thin biconvex lens which provides more positive power, another biconcave, and another biconvex to finally focus the light to the sensor.

In front of the stop we have two "medium positive" elements, a strong positive, and a very strong negative. Behind the stop we have a strong negative, a mild negative, and two "medium" positive elements. The stop sits close to the more negative rear member increasing the relative power of the front group. If you imagine a magnifying glass, you get greater and greater magnification (more power) as you move from being very close to one focal length away. At one focal length you get no image, and beyond that you will get an inverted one. We are within one focal length, so the power increases the further back you go.

As you focus this symmetrical design closer it will approach unity imaging, e.g., an object 10" in front of it will be projected 10" behind it at life size. There may be issues in terms of aberrations, or mechanical issues that caused Zeiss not to pursue 1:1 magnification with it.

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    Can you explain what you mean by "symmetrical lenses?" Or perhaps if you explain it here just link to your answer. – feetwet Jul 2 '15 at 18:52
  • @feetwet a symmetrical lens has equal and opposite optical power on both sides of the aperture stop. They are very stable across a long range of focusing distances and only the back focal length changes significantly as it focuses. – Brandon Dube Jul 2 '15 at 22:26
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    You will never get a diagram with any lens data on it from a manufacture =) That is their secret to protect. The element shapes tell us what we need to know. The first several elements have a great deal of optical power (a very short focal length). Everything after the last ED element in the front is negative. In the back there is some positive stuff and then a couple of negative elements. This is a highly asymmetrical design, so it probably breathes quite intensely. – Brandon Dube Jul 3 '15 at 14:55
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    here is the second piece of a recent article I wrote for Photozone.de. The lens layout there is the output from Code V. It shows three ray bundles - the red one is the marginal ray, which makes it easy to see positive and negative "flow" in the lens. If the beam is shrinking, it is interacting with positive elements. The inverse is true of negative elements. – Brandon Dube Jul 3 '15 at 15:00
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    Hmm, I wouldn't post a dedicated question for how to read a lens diagram. If you go in the photozone articles you can find this which is the first of the series - it talks about optical power of singlets quite a bit. Doublets are fairly similar. I'll update my answer with details on the 100mm MP. – Brandon Dube Jul 3 '15 at 16:23
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Cine lenses are designed to minimise focus breathing so that directors can perform large focus pulls quickly without viewers becoming disoriented by the field of view changing.

However you can expect to pay five figures for a genuine cine lens (don't be fooled by Samyang/SLRmagic etc. "cine" lenses, they are just DSLR designs with stepless apertures and followfocus gearing).

  • So would you say minimal focus breathing is a characteristic unique to "true" cine lenses? I.e., you wouldn't expect to find it on non-cine lenses? And do you know whether it can be technically reduced to zero on a lens with variable focus? – feetwet Jul 2 '15 at 13:11
  • @feetwet it's more that case that cine lenses are specifically optimised for focus breathing whereas other lenses aren't, that doesn't mean there aren't SLR lenses with little focus breathing, though. I imagine it could be reduced to zero, but with everything in lens design it's a compromise so it's never going to be zero in a real lens. – Matt Grum Jul 2 '15 at 16:16
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    @feetwet It is a desirable characteristic for proper cinema lenses. It can be optimized to zero quite easily though that may have adverse effects on image quality, often pushing the design towards a more modular lens layout which in turn increases the size. The same is true of making the lens zoom in a parfocal manner. If you post the question I can provide an answer longer than the comment box allows. Never is a very strong word, many exotic cinema lenses are optimized until the point where it is appreciably zero. Many simpler lenses may have zero breathing out of coincidence too. – Brandon Dube Jul 2 '15 at 18:30
  • @BrandonDube: Please do tell! photo.stackexchange.com/q/65100/27832 – feetwet Jul 2 '15 at 18:50

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