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Software Chromatic Aberration Correction

Discussion in 'Photography, Art & Design' started by Gareth Halfacree, 9 Sep 2020.

  1. Gareth Halfacree

    Gareth Halfacree WIIGII! Staff Administrator Super Moderator Moderator

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    I've got a cheapy 35mm f1.8 Nikon lens here, which I strap to my D3200 for product photography work. It's fine, except there's a fair amount of chromatic aberration at the edges.

    I've been using GIMP's built-in correction tool, which works fine but can be a little fiddly - you've got a relatively small preview window and no way I can see to zoom in past 1:1 for more detail.

    Now I've discovered that Darktable, the RAW processor I use, has its own chromatic aberration correction tool - and there's nowt to adjust, you just tick the box and yer done.

    Decided to put 'em head-to-head:

    upload_2020-9-9_14-0-24.png

    Darktable's correction isn't as good as the manual version to my eyes, but a distinct improvement on the original. The GIMP's version is maybe a little too far the other way on the red channel, but that's not its fault - I could have spent a bit more time twiddling the twiddles for a better result.

    I've got to say, though, Darktable gets me most of the way there for very little effort - and once the image is scaled to web resolution or printed in a mag I doubt you'd be able to spot the difference between it and the manual version.

    Scaled final image - the P is from "Production." (GIMP's processing, not Darktable - I only discovered the feature after I'd finished!):

    upload_2020-9-9_14-3-34.png
     
  2. Gareth Halfacree

    Gareth Halfacree WIIGII! Staff Administrator Super Moderator Moderator

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    Fiddling with some new post-processing... err, processes, too. Click to embiggen:

    upload_2020-9-9_22-5-14.png
     
  3. Gareth Halfacree

    Gareth Halfacree WIIGII! Staff Administrator Super Moderator Moderator

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    Also also, I can't believe how much stuff I've been doing manually in The GIMP can be done near-automatically in Darktable. Like perspective correction on the above image: that'd traditionally involve dragging a bunch of gridlines around the image and figuring it by eye. In Darktable, I just click the "find lines in this image please" button followed by the "make as many of those lines you found as straight as you can" button. Bosh. Done. How many flamin' hours have I wasted doing it by hand over the last decade and a half?!
     
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  4. veato

    veato I should be working

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    I remember the first time I used the current version of Lightroom when editing some wedding photos. As a starting point I pressed the auto button (or whatever it's called, I cancelled my sub so can't check) and thought "that's that then, job done." Some photos still needed tweaking but as a starting point it was amazing. Made me feel a bit redundant to be fair.
     
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  5. wyx087

    wyx087 Homeworld 3 is happening!!

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    That Pi computer photo, is it me or the shinny bits look double vision? The connector to the top right of the image, next to the capacitor looks fuzzy and strange.

    Personally, I think I prefer to leave it natural. Chromatic aberration gives the photo certain character that reflects the lens used. It's only an issue when zoomed in. The Pi computer looks perfectly fine as whole image on my 1440p.

    With Lightroom, for some reason, whenever I click auto adjust, LR always tries to save brightest area and make my photos really dark. My standard is (from RAW): set camera colour profile (I prefer Fujifilm Astia), click auto, reset brightness and it's very good, most of the time don't need extra adjustment.
     
  6. Gareth Halfacree

    Gareth Halfacree WIIGII! Staff Administrator Super Moderator Moderator

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    That could be the result of:

    1) There's an ND (UV? I forget) filter in front of the lens, 'cos I'd rather scratch a £5 filter than a £100 (or whatever it was) lens. Sometimes if things are REALLY bright, you get reflections from that.
    B) The lens is not one of Nikon's professional-type ones.
    iii) The camera is also not one of Nikon's professional-type ones, and has a pretty severe crop factor.
    d) It's handheld, 'cos I can't be faffed setting the tripod up all the time.
    5) The full-size image is not massively smaller than the raw capture in terms of resolution - I think the cropped full-size image was about 5,500 wide, and this is 4,000 - so there's not much room to hide.
    VI) I don't really know what I'm doing.
    G) All of the above.

    Like I say though, none of this has to be perfect - hell, a lot of my fellow freelancers either submit cameraphone photos on a messy bench or just rely on stock imagery from the vendor. I don't get extra for the photography, neither, so there's a limit to how much time and money I'm willing to sink into it - though I have to admit, I've been wondering about an upgrade from my D3200. Hard to justify when it's still fully operational, tho'!

    EDIT:
    Looking at it again, I think it's just lens distortion: the centre's pin-sharp, but the further you get towards the edge of the image the softer things look. Again, it was not an expensive lens. I could compensate by backing off and putting more of the subject in the sharp centre, but then that's a tradeoff in resolution - and I ain't got that much resolution to spare on a D3200!
     
    Last edited: 10 Sep 2020
  7. wyx087

    wyx087 Homeworld 3 is happening!!

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    Fair enough. To be honest, no one needs to zoom in to look in such detail, I only did because you asked us to do this and we are talking about computer correcting CA. I thought those fuzzy bright parts are result of CA correction.

    D3200 is standard APS-C isn't it? Should be able to offer excellent image quality.
    I downsized from full frame to APS-C because after a few years with a second hand 5D2, I felt it didn't really offer as much as I wanted, at expense of excess weight. Sold off 3 red ring lenses for much cheaper Fujifilm APS-C lenses and I'm happy ever since.

    Nowadays, I rarely take my camera system out. It's mostly phone snaps. Their processing is amazing and I'm happy with the result most of the time, again, as long as I don't zoom in!
     

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