Lens aberrations explained – Part 1

Introduction

jupiter-3 zenith sonnar sony a7s bokeh

In many of our lens reviews we talk about certain kinds of aberrations, so this article shall give you an overview of typical lens aberrations, tell you in what lenses to encounter them and how to cope with them.
We may publish another article in the future that will go further into detail, not only naming the aberrations, but talking about what causes them.

Distortion

 

Description: Straight lines in the picture are not straight but curved or bent.

Common problem in: zoom lenses and wide angle primes

Solution: “uniform” barrel or pincushion distortion can be easily corrected. For complex/wavy distortion though, lens correction profiles are mandatory, but not every correction profile works perfectly at every focusing distance.

Trivia: for today’s digital photography many lens manufacturers decided to correct this in post processing

 

Field curvature

ttartisan 7artisans 21mm 1.5 m-mount leica m10 sony a7rII a7rIII a7rIV sharpness resolution review performance bokeh

Description: When you shoot a flat scene there is a dip in resolution/contrast in a part of the frame, e.g. the midframe area or the corners. In the example above you can see a lens that has higher corner resolution than midframe resolution.

Common problem in: wide angle lenses, some fast lenses

Solution: stopping down will usually reduce the field curvature. With some lenses focusing on the midframe instead of the center can also improve results.

Trivia: usually a big problem when using small rangefinder wide angle lenses on a Sony camera.

 

Vignetting

Light Falloff

nikon af-s 58mm 1.4g n nano high resolution bokeh portrait sony a7rII a7rIII a7rIV vignetting light fall off

Description: Lower exposure in the corners compared to the center of the frame.

Common problem in: wide angle lenses, fast lenses

Solution: with most lenses stopping down will reduce the light falloff (with very small lenses there are sometimes only minor improvements)
Corner exposure can be lifted in post processing e.g. in Lightroom. For common lenses there are profiles available. C
orrecting this in post can lead to increased noise in the corners!

Trivia: back in the film days you could buy center filters to reduce the light falloff of your wide angle lenses.

 

Optical Vignetting

Sony FE 85mm 1.4 GM gmaster portrait bokeh sharpness a7rII a7rm3 a7riii 42mp review
Left: center, right: extreme corner

Description: the shape of out of focus light circles deteoriates towards the corners of the frame, so instead of circles you see shapes that resemble cat’s eyes.

Common problem in: (small) fast lenses

Solution: none (except for maybe buying a lens where this is less pronounced)
Stopping down you will eventually get a perfect circle at some point, but then you are shooting at e.g. f/2.8 instead of f/1.4.

Trivia: also often referred to as “mechanical vignetting”

 

Color Cast

 

Description: The corners of the frame take on a different color than the rest of the frame.

Common problem in: small wide angle lenses, especially mirrorless/rangefinder designs

Solution: correct it with the third party software “corner fix” or use gradients in Lightroom

Trivia: this is not exactly a lens aberration but rather the inability of digital sensors to capture light that hits them at a very acute angle.

 

Spherical Aberration

 

Description:
undercorrection: loss of contrast and resolution (“glow”) across the whole frame
overcorrection: harsh bokeh with severe outlining

Common problem in: fast lenses (especially old ones) at maximum aperture

Solution: stopping the lens down by 1 stop usually makes a big difference

Trivia: for portraits a bit of undercorrected spherical aberration can be beneficial to give a smoother look

 

Chromatic Aberrations

Lateral CA


Crop from corner region of the frame

 

Description: the different color channels show different distortion patterns. Usually this leads to outlining on edges of high contrast that gets stronger the farther you move away from the center.

Common problem in: wide angle lenses, older tele lenses without ED elements, most zoom lenses.

Solution: in most cases this can be losslessly corrected in post. Stopping down does not make a difference to this aberration.

Trivia: Some symmetrical lenses show zero lateral CA.

 

Longitudinal CA

 

Description: Longitudinal chromatic aberrations come in different forms where the most common are purple fringing (it shows up close to the plane in focus) and the “bokeh-CA” or “bokeh fringing” which you will see in the out of focus areas.

Common problem in: fast lenses

Solution: stopping the lens down will reduce this. You can also try to correct it in post, but this will not always work well enough.

Trivia: Some lenses that carry an “APO”-tag are perfectly corrected for this aberration and won’t show any colorful outlining at all.

 

Coma

ttartisan 7artisans 21mm 1.5 m-mount leica m10 sony a7rII a7rIII a7rIV sharpness resolution review performance bokeh coma astro milky way koma

Description: small point light sources in the corners of the frame are not rendered as points but take on weird shapes instead.

Common problem in: fast wide angle lenses

Solution: stopping the lens down will reduce this

Trivia: if you are into astrophotography you should care about good coma correction.

 

Astigmatism

Description: away from the center structures show double edges which are either radially or tangentially oriented.

Common problem in: fast lenses, wide angle lenses

Solution: usually improves on stopping down.

Trivia: it can be difficult to distinguish between astigmatism and coma.

 

Focus Shift

 

Description: When you stop a lens down the plane of optimal focus shifts to the front or the back.

Common problem in: fast lenses

Solution: first stop the lens down and then focus. Often it also helps to just use f/8.0 to f/11 for this not to be a problem anymore.

Trivia: classic Sonnar lenses are known to show a notorious amount of focus shift.

 

Onion ring bokeh

 

Description: out of focus light circles show onion-ring-like patterns.

Common problem in: some fast lenses with aspherical elements

Solution: none except for buying a lens without these issues.

 

Flare resistance

Ghosting

voigtlander 35mm 1.4 nokton e classic review sony e-mount emount sharpness bokeh rendering vignetting

Sony_FE_50mmf1.8-7

Description: colorful artifacts (circles, crescents) in the frame

Common problem in: wide angle lenses, zoom lenses, lenses with high element count and big front elements

Solution: stopping down may change the shape and size of the artifacts. Slight reframing can sometimes help as well.

 

Internal reflections

tokina macro makro 35mm 2.8 sony a7 a7rII a7rm2 close backlit flare sharpness

Description: ring-like aberration (see picture)

Common problem in: a few very fast wide to normal lenses

Solution: stopping down can sometimes help here

 

Veiling flare

ttartisan 7artisans 35mm 1.4 asph sharpness mirrorless spiegellos review flare resistance veiling ghost ghosts

Description: almost the whole frame is covered by a veil of light that takes away most of the contrast

Common problem in: most severe in tele lenses

Solution: sometimes using the hood can help a bit

Further Reading

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My name is Bastian and I am your expert here when it comes to ultra wide angle lenses, super fast portrait lenses (ranging from a 50mm f/0.95 to a 200mm f/1.8) and I also have reviewed way too many 35mm lenses. Don't ask me anything about macro or wildlife shooting though.

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32 thoughts on “Lens aberrations explained – Part 1”

  1. Great roundup. I think you’ve covered everything.

    Few notes:

    • Most of the aberrations (CA, astigmatism, coma, vignetting) are often non-uniform and greatly increase towards the corners. At least for web sized pics cropped (relative to lens image circle) sensors might care less.
    • Color cast can cover the whole frame. I think several people on the team have Canon FDn 50/1.4 which wide open often gives uniform purple cast over the whole frame. I think the physics behind it is different from the corner cast, but it is still a thing.
    • Veiling flare for adapted lenses depends on adapter and sensor behind the lens.

      1. So is the article wrong? Or am I misunderstanding it?
        Under LaCA: “This kind of aberration does not lead to colored areas, but to fringes that occur around objects of high contrast as the magnification is dependent on the wavelength.”

          1. Yes, that’s right.
            I’d like to post another link:
            https://photographylife.com/what-is-chromatic-aberration

            If you compare the tree image under LoCA and the test chart image under LaCA, you can see that both types of CA can look similar. Maybe that’s why I was confused about it. The only way to find out, which CA is present, is to stop down, because LaCA will stay.

            That’s also what you wrote in your article. So sorry for the hassle, your didn’t mix it up. 🙂

  2. Very useful compendium. Thanks.

    I have paid careful attention over the years to reviews like those you post to ensure that I avoid lenses that have built in problems that are difficult to correct (LOCA, a tendency to veiling flare and reflections, field curvature).

    I especially like the Zeiss Batis 135mm in particular, though I like the Sony 28mm f/2 as well. I that I had been more savvy before buying the 55mm f/1.8, though (I failed to read your review in that instance).

    It is competent and light and okay with my A7R2, but the onion rings grate (and the bokeh, while generally pleasing, is often busy.

  3. Great informative article for newcomers, thank you!

    Does the infamous reflection from the sensor in older Sony designs fall into this category?

  4. Wonderful explanation to learn about various issues that we encountered, but do not know its terminology and meaning.

  5. Really appreciate this article. It clarifies a lot of things that I see in my Takumars and other film-era lenses and makes it clear what can be corrected for and what we just have to live with. Looking forward to a follow-up article or two.

  6. Clear, easy-to-digest article, should clear up a few users’ misunderstandings. I like that first photo of the pinetreeling and the lit funky bokeh behind it. Looks pretty stellar, like the MC 28/2’s : )

    1. That was one of the main reasons to put it together: to have an easy to understand resource that can be linked to to clear up confusion 😊
      Title picture has been taken with the Jupiter-3 50mm 1.5 @ f/1.5. I think every aberration is there 🤣

  7. I always though that Color cast comes from coatings of the lens. And one of the quickest ways to fix it is shifting WB setting.

    1. Also, the lenses with old designs usually have this color cast issue, because those designs were developed for film cameras, so glass coatings were different. Most of the time you will see harsh yellow/green color cast, compared to the modern lenses.
      I do believe that the glass elements with different coatings are at fault here.

      1. The color cast you are talking about is visible across the whole frame, not only in the corners.
        Often (but not always) Auto White Balance will already take care of this.

  8. A nice roundup, thank you!
    Noted that different color renderings are not included in the list. I don’t see that as a serious omission though.
    There is no disagreement about some lenses producing warmer colors than some others. Sometimes however there are strong opinions about the color characteristics of a specific lens, but I think those are mostly subjective opinions without rigorous research.
    Scientifically thinking, it can be assumed that different glass types can act as filters, blocking certain wavelengths more than others. But I don’t know how the lens could change the wavelengths of the light going through it. The colors in an images are the result of a complex phenomenon that depends on many things, including the spectrum of the light, the reflective spectrum of the object, and the sensor. So, a few sample photos really can’t tell everything about how a lens handles colors.

    1. indeed lenses could be blocking some of the colors also there is sensor/processor programming and it also effects the colors greatly, so if the lens is different the sensor gets different amounts of different colors, there fore sending different kind of information to the processor and processor makes the image according to the information that it got, the sequence is something like that. Depending on how it is programmed and how it “understands” the colors we get the results, that`s why modern lenses got the “color profiles” even in cameras so the images looks stunning with proper contrast, colors and clarity, but if we could adapt them to the early cameras that can not understand those color profiles, I wonder how the images would look on them 🙂

  9. a. I would like to add mine to all previous expressions of gratitude to you all. This and FM are reliably and always the 2 most interesting photo-related sites in all of history. Thank you!

    b. Not to complain, but when might we expect as comprehensive an article on “Lens-reviewers’ aberrations”?

    Best wishes from Texas.

  10. I can appreciate the work on explaining. I am optical engineer myself and I tend to explain such concepts from time to time .
    Well put together, and pretty complete collection!

    One of the most common aberrations that help with is the “finger oil” on lenses. Especially for cellphones or small diameter lenses. The images are less sharp especially with incoming light source (at night). That’s easy to fix by wiping the smudges from the lens.

    Will you talk of the affect of mold/fogged lens on images?

    1. Indeed that is a major issue with smartphone lenses, it may also lead to a plethora of lens flares.
      For foggy/hazy lenes I would like to have 2 perfect examples lenses: one with and one without.
      Unfortunately this is not the case so far.
      It might also better fit a “common issues in used lenses” articles, together with loose mechanics
      and too slow aperture blades.

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