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Software-Corrected Barrel Distortion Revisted: Sony RX100

Discussion in 'Open Gear Talk' started by Amin Sabet, Oct 31, 2012.

  1. Amin Sabet

    Amin Sabet Administrator

    Jul 3, 2010
    We were the first to break the story about marked software-corrected barrel distortion with the Panasonic LX3, and since that time just about every small camera manufacturer has followed in Panasonic's footsteps. Using software to correct barrel distortion allows camera manufacturers to build fast lenses which are smaller and less expensive than they would be if optically corrected for distortion.

    Like other compact zoom cameras with fast lenses, the Sony RX100 has a lens which suffers from pretty severe barrel distortion which is then corrected by the camera. The leading RAW processing software Adobe Lightroom not only applies the same barrel distortion correction as the in-camera JPEG engine - it does so without any option to disable the distortion correction.

    The animated GIF below shows a resized version of the same RAW file processed in Adobe Lightroom (no barrel distortion) and Capture One 7 (barrel distortion left intact). As you can see, the distortion correction involves stretching out the edges and corners of the frame. The price to pay is a distinct loss of image sharpness at the edges/corners of the image.

    8143550438_b7ea415bd7_o.


    The default noise reduction and sharpening levels differ between Lightroom (LR) and Capture One (C1), so I tried to process them for reasonably similar center sharpness and noise.

    100% center crop:

    8143486137_ebedff0210_o.


    As soon as you move out to the right edge, the relative sharpness of the two files begins to vary significantly:

    8143485979_7e93199f8c_o.


    In the upper and lower right corners, respectively, the differences in sharpness are even more apparent:

    8143485839_a5d0a22228_o.

    8143516020_ab209d85aa_o.


    As you can see from the examples above, much of the reported edge softness of the RX100 lens is attributable to the effects of barrel distortion correction. The corner performance of the uncorrected lens is very decent. Moreover, LR seems to sacrifice more detail than necessary in the process of distortion correction. I can get better results processing with distortion intact and then correcting the distortion in a separate step in Photoshop.

    Many lenses which have less than optimal edge sharpness are much sharper without the mandatory corrections imposed by LR. The Panasonic 14mm f/2.5 Micro 4/3 pancake is such a lens, as are most Micro 4/3 wide angle lenses. For years I've been asking Adobe to turn on distortion correction by default by give us an option to disable it for those occasions where we can live with the distortion in order to gain either angle of view or edge sharpness. For the time being, I'll look to C1 when that need arises.

    A free trial of C1 Pro can be downloaded here.
     
    • Like Like x 9
  2. Luke

    Luke Super Moderator

    Nov 11, 2011
    Milwaukee, WI USA
    Luke
    software correction should ALWAYS be able to be turned off. I think people who would use advanced features like that know what they are doing. Nice write-up Amin. The pixel peepers thank you.
     
    • Like Like x 3
  3. wt21

    wt21 SC Hall of Famer

    Aug 15, 2010
    Thanks Amin. I know that now you have an RX100, we're going to learn a lot more about how the camera works! It's already become a main camera for me -- will be interested in hearing how it fits into your bag.

    It does show (continues to show) Sony's marvelous engineers. That's a nice lens packed in there! The softness is understandable when stretched (with the level of softness being the debatable part).

    For Halloween last night, I tried taking shots of my daughters and their friends with my 5D + 85/1.8 before they headed out. Not the right camera/lens (I don't have anything shorter than 85mm, and the light was too low for that focal length, so the pics were a bit blurred). Grabbed by 5n. Still not quite right (using legacy lenses, had to stop down a bit to get sharpness, then I again lost the light I needed). Ah. The RX100 did exactly what I needed. Fast aperture at wide angle and clean high ISO anyway, and all the girls were in focus from the inherent deep DOF. I love my RX100!
     
    • Like Like x 2
  4. Djarum

    Djarum SC All-Pro

    Jul 10, 2010
    Huntsville, AL
    Jason
    Interesting thread. I know that there is/has been lots of noise in regards to mFT lens corrections. I believe there are a couple of sites( I think lenstip) that really slam some of the more expensive mFT primes and zooms because they don't look at the corrected output. Obviously something is sacrificed when fixing distortion. Looking at the uncorrected files, the edges don't look that bad. However, I don't think the panny 14mm looks that bad after correction though. I know I'm comparing a prime to a zoom lens. I know the corrected output for the Olympus MkII zoom kit lens doesn't look this bad either. So, is it that the native distortion is just that bad, or is it that Sony/lightroom's correction algorithms are not very good?

    I've really thought about picking up this camera as strictly a nighttime/low light replacement for my mFT. Its smaller and has more flexibility than a panny 20mm stuck on a mFT. The lens decentering obviously still bothers me some.

    The more I think about it, I still am amazed at the lens quality of the XZ-1 wide open at 28mm. But wait, maybe olympus can take that design, scale it up, and slap it in front of the RX100 sensor now that they are both in cahoots. I'd pay 800 dollars for such a marvel.
     
    • Like Like x 1
  5. Amin Sabet

    Amin Sabet Administrator

    Jul 3, 2010
    Few things: 1) The Olympus and Panasonic lenses you mentioned have better edge performance than this Sony lens, so they hold up better after distortion correction; 2) The Sony has more megapixels, which gives a false penalty when viewing at 100%; 3) Lightroom doesn't seem to have a great correction algorithm. I get better results using distortion correction in PTLens or C1.
     
  6. wt21

    wt21 SC Hall of Famer

    Aug 15, 2010
    Amin, did you test Sony jpg distortion correction vs. LR distortion correction on RAW for the RX100? Of course, I could test this myself, but I thought I'd ask first :)
     
  7. Alan Brown

    Alan Brown New to SC

    1
    May 14, 2011
    Two questions. First, are there any raw converters for macs that don't auto correct, or at least give the option not to?
    Secondly, has anyone compared the Nex 7 with 16mm 2.8 with and without auto distortion, and does the 16 give better corner sharpness when uncorrected?

    Thanks,
    Alan
     
  8. Amin Sabet

    Amin Sabet Administrator

    Jul 3, 2010
    Haven't tried that. I have a somewhat serious allergy to in-camera JPEGs - hives, tongue swelling...


    C1 is Mac/Windows and gives the option to disable distortion correction. There is a free 60 day trial which I linked in the first post. Raw Developer is Mac only and doesn't do distortion correction. Terrific app.

    I haven't tried NEX 7 with 16/2.8, but my understanding is that the 16 has little distortion to begin with.
     
    • Like Like x 1
  9. wt21

    wt21 SC Hall of Famer

    Aug 15, 2010
    You're a doctor. Can't you take something for that :p
     
    • Like Like x 2
  10. bartjeej

    bartjeej SC Hall of Famer

    Nov 12, 2010
    bart
    off-topic, but I never knew that. Somehow it makes perfect sense though, I guess your online appearance is still one of a doctory type :tongue:
     
  11. Asha

    Asha New to SC

    4
    Nov 1, 2012
    Amin, does Adobe Camera Raw also do the auto correction? I can open raw RX100 images without applying the Sony lens profile, but I do not see much corner difference between RAW and the in-camera JPG.

    ETA: OK, I downloaded the Capture One Pro 7 trial version and did my own check. ACR (same engine as LR) does indeed add distortion correction, even when I do not select a lens profile from within Camera Raw. Thanks so much for the info--very helpful!
     
  12. Luckypenguin

    Luckypenguin SC Hall of Famer

    Dec 24, 2010
    Brisbane, Australia
    Nic
    Hey, Amin It might be that the example image is deceiving me, but does the RX100 have complex distortion (partially optically corrected) or pure barrel distortion at wide angle?
     
  13. Asha

    Asha New to SC

    4
    Nov 1, 2012
    I'll add my 2cents and say that most wide angle lens designs have quite a bit of edge aberration, usually coma or astigmatism. Plus, there is generally some rather severe vignetting. For lens design, the term "distortion" literally means a difference in magnification from the center to the edge, so is specific to barrel or pincushion effects.

    What I noticed in the test images is that the chromatic aberration at the edge was made worse by the distortion correction. That seems counterproductive!
     
  14. petemasty

    petemasty SC Regular

    90
    May 24, 2011
    wiltshire, UK
    Ever so glad this thread is here. I was wondering why the corners of my shots are badly distorted and full of CA. particularly the bottom right hand corner.

    I may have to resort to the Sony raw converter and convert to tiff before opening up in LR, and see if this makes a difference.

    Any chance of a LR update to sort out? Lets hope.
     
  15. tdp

    tdp Guest

    Amin,

    Thanks for taking the time to research/shoot/draft and post this. I fully agree with you, RAW files should be presented in their unaltered form to allow the photographer the options of what to lens imperfections correct and how much. Any professional editing software should facilitate this, unfortunately Adobe doesn't agree.

    Thanks for the Capture One link - I'm off to the downloads!

    - tdp
     
  16. Smabbage

    Smabbage New to SC

    5
    Oct 28, 2012
    The beta version of Aftershot Pro I've been running (1.1.0.30), which has support for the RX100, has the ability to turn off lens correction. However, the RX100 lens is not calibrated in their database as yet. I spent the last two days scouring the net for lens correction parameters and found some that work quite nicely posted on pastebin. I had to modify the profile_sony.txt file but once I did they worked beautifully. Not sure how much they soften the edge of the image in comparison to LR4 but at least you can turn the feature off if you desire.
     
  17. BJPhoto

    BJPhoto New to SC

    2
    Nov 21, 2012
    I saw the comparison of distortion correction comparing LR4 and Capture One and thought I would offer another.
    DxO offers lens distortion correction for the RX100 and claims to do Lens Softness Correction progressively from the centre to the edges. I thought I would check it out.
    Here's a comparison of Lightroom 4 on the left and DxO 8 on the right. DxO also does vignette correction which is why it's a bit brighter. No other alterations were made to the image.
    It appears that the DxO image is sharper.

    Comparison.
     
  18. BJPhoto

    BJPhoto New to SC

    2
    Nov 21, 2012
    I forgot to mention in my previous post that the sample comparison was a 100% crop of the bottom left corner of the image.
     
  19. Armanius

    Armanius Bring Jack back!

    Jan 11, 2011
    Houston, Texas
    Jack
    Off topic on the RX100, but still on the distortion topic. The edges in the iPhone 5 camera have horrible distortion!!! Got that out of my chest!
     
  20. Asha

    Asha New to SC

    4
    Nov 1, 2012
    Wow, the DxO is really nice--none of the corner "smear" that I see in ACR/LR! Thanks BJPhoto!