HDR Cookbook - Correcting Chromatic Aberration -  featured - 01

HDR Cookbook – Correcting Chromatic Aberration

ZigZag (HDR)Chromatic aberration (in short “CA”, sometimes also referred to as “color fringing”) is an effect caused by a lot of lenses, in particular cheaper models and wide-angle lenses. It is caused by the failure of a lens to focus all colors to the same convergence point. The effects are color fringes particularly at high-contrast edges and a generally more blurry image. The fringes tend to get worse towards the edges of the image.

Photomatix is not very good at removing these artefacts and the usual HDR workflow tends to amplify the fringing effect, creating visible strange-looking fringes and blur in the final image. In this recipe, you will learn how to fix this problem before feeding your images into Photomatix (or any other HDR software).

Requirements and Assumptions

I assume that you have produced the source files in RAW format and that you have Adobe Camera RAW (ACR) or a similar RAW converter.

Overview

Instead of feeding the RAW files directly to Photomatix, we will develop TIFF files from our RAW source files using ACR. This is the very first step in the entire HDR workflow. One essential part of developing the RAW files in ACR is the CA correction. The resulting TIFF files are then loaded into Photomatix to produce the HDR image and do the tone-mapping.

Illustrating the Effect of CA

Before we take a look at the rather simple procedure of correcting CA, we will first look at an example and show what CA is and what its detrimental effects are on the tone-mapped image. Below, you see a sample image. This is the 0ev JPEG straight out of the camera. I was using a Nikon D90 with a Sigma 10-20mm F3,5 EX DC HSM lens at 10mm focal length. CA is particularly apparent with wide-angle lenses.

JPEG file straight out of the camera – crop area is marked

Below, you see a series of 200% crops of the area marked in the image above. The first crop shows the original RAW file without any adjustments applied to it in ACR’s default settings. The purple/red and cyan fringes are quite obvious.

Chromatic Aberration – Original RAW file

The Nikon D90 has a good CA correction mechanism built into the camera. Below, you see the same crop from the corresponding JPEG produced by the D90. You can see that the fringes are greatly reduced. However, there are still some visible blue fringes. Moreover, we would rather not want to use the JPEG output of the camera for our HDR image because using the RAW images leads to a higher quality of the final image. So, the bad news is that the in-camera CA reduction does not help us. The good news is that we can do better than that!

Chromatic Aberration – JPEG produced by a Nikon D90

The next image is the same crop from the image developed in ACR. You can see that the CA has disappeared almost completely.

Chromatic Aberration – Fixed using ACR

Ok, now we know that we can reduce the CA using Adobe Camera RAW. But why should we bother? The following crop shows the result of creating the HDR image and tone-mapping it using Photomatix Pro 4.0 without any CA correction. One could argue that the color fringes have gotten worse to a point where they are noticeable at normal zoom settings. Moreover, the image looks somewhat blurry.

Chromatic Aberration – Result of tone-mapping w/o CA correction

Of course, we could use the built-in CA correction feature of Photomatix to cure the problem. Below, you see the result of feeding the RAW files directly into Photomatix and turning on the “Reduce chromatic aberrations” option in the Preprocessing Options dialog. Yes, the CA is reduced – kind of. But what becomes apparent is that the image still looks blurry. More importantly though, ugly fringes occur on the edges replacing the former color fringes – not a very satisfying result. Photomatix has never been very good at removing CA and this continues into the newest version of the software.

Chromatic Aberration – fixed by Photomatix

Finally, below you see the image resulting from the workflow I will sketch in a moment. Notice that the any fringes are almost gone and the image is noticeably sharper than any of the versions above.

Chromatic Aberration – fixed in ACR before tone-mapping

It is obvious that this is the way to go in order to obtain the highest output quality of the HDR process.

Detailed Process

  1. Start Photoshop
  2. Mark the RAW files in your preferred image browser and drag them onto the Photophop window (If you use Adobe Bridge, you can also use the menu to open them in ACR). Photoshop will automatically open the files in ACR.

    RAW files opened in ACR

  3. Go to the “Lens Correction” Tab on the right side of the window.

    ACR – Lens Correction tab

    At the top, you will see three controls: two sliders for correcting different fringes and a general “Defringe” drop-down list.

  4. Open the drop-down list and select “All Edges”.
  5. Zoom into a suspicious part of the image using a zoom factor of 200-300%.
  6. Use the sliders to remove the visible fringes. The specific setting is highly dependent on the lens you were using. You have to experiment. You can observe how the fringes increase or decrease as you move the sliders. Finding the optimal settings should be a matter of a couple of minutes. Note that the same lens used at the same focal length and aperture produces very similar CA across all photos. Consequently, also your setting will be similar for different photos. In our case, settings of -30 and +10 turned out to by the best.

    ACR – Lens Correction – Settings

  7. When you are satisfied with the result, press the “Select All” button at the upper left corner of the window and then Alt-click the “Synchronize…” button to apply your settings to all loaded images. Note that before doing this, you may want apply any other adjustment in ACR.

    ACR – Apply setting to all images

  8. Finally, click the “Save Images…” button at the lower left of the ACR window and save your files to some destination folder. Be sure to select all files before doing this. Save the files in TIFF format.
  9. Navigate to the destination folder and open your files in Photomatix. You can now continue your normal workflow in Photomatix. However, please uncheck the “Reduce chromatic aberrations” option. We do not need this anymore and we do not want Photomatix to degrade the quality of our image in a desperate attempt to remove any CA that is not there (any more).
  10. Done!

Detailed Process

35 replies
  1. PapaDunes
    PapaDunes says:

    Thanks for the excellent tutorial! All this time I’ve been running each of the RAWS through ACR one at a time never knowing that I could click on “Select Rated” and “Synchronize”!!! Thanks for the time-saver!

    PapaDunes

    Reply
  2. Bryan B Hernandez
    Bryan B Hernandez says:

    Hello there my friend, I always ask myself how do you get the crip -refreshing look in you images and I’m hoping this is why –I will try this as soon as I get home, thank you very much for sharing this great article…

    Bryan Hernandez

    Reply
  3. Victor C
    Victor C says:

    I just wanted to take a minute of your time and thank you for all your hard work and dedication.

    Your tutorials and techniques have really made a HUGE difference on my approach to HDRi and my post processing as well, without a doubt the best tutorials I’ve come across so far .

    Sharing is caring, thanks!

    -Vic

    Reply
    • farbspiel
      farbspiel says:

      Thanks a lot for taking the time to give me feedback, Victor. I greatly appreciate that. It is nice to hear that you found the information useful.

      Cheers

      Reply
  4. Julie in Jeans
    Julie in Jeans says:

    Thanks for the tutorial. I didn’t understand what CA was until I read through this. I took some photos last evening of bicycles and other very shiny stuff. I have CA all over. When I correct it in one area, I get it in another area. Can this be completely corrected in more than one pass? Could I correct it on one set of surfaces, save it as a Tiff and go back into ACR and correct another set of surfaces? I’m kicking myself now that I have such a cheap lens.

    Reply
    • farbspiel
      farbspiel says:

      Hi Julie,

      normally, programs like Adobe Camera Raw should be able to remove the CA in on pass. Since the raw converter is shifting the whole color channels relative to another in order to cure the CA, it is not possible to work on different areas in consecutive passes. But you should really play around with the controls, and I am pretty sure that you can remove it. All of my lenses produce CA (in fact all lenses do), and I can remove 95% of it in ACR. I guess your lens should not be that much different.

      Best of luck!

      Cheers
      __________________________________
      Visit me at facebook.com/farbspiel

      Reply
  5. stefan
    stefan says:

    Thanks for the wonderful tutorials, they are always so thorough and helpful.
    Its very generous of you to take so much time to share your knowledge with all of us.

    Stefan Bekker

    Reply
  6. Bobbi Mercouri
    Bobbi Mercouri says:

    OMG! This is such a great tutorial – I’ve thought that something was wrong with my camera. So glad to find out I can fix this. You’re a wonderful person to take the time to help us newbies out. Thanks again.

    Reply
  7. Michael Hatten
    Michael Hatten says:

    After all these years of being self taught through trial and error. I appreciate this resource you provide. Thank you!
    I may finally be able to take my photography to the next level…
    I have one question.
    Is Lightroom’s CA feature as good as Photoshop CS5? You would think that it is since they are both an Adobe product.. What is your take?

    Michael…

    Reply
    • farbspiel
      farbspiel says:

      Hi Michael,

      you’re welcome! Taking it to the next level is really only about hard work and an open mind. You can do it, man! Just go for it!

      I don’t own Lightroom, so I cannot comment first-hand. But I too would suspect that the RAW converters should be the same.

      Cheers

      Reply
  8. Lewis Mann
    Lewis Mann says:

    Great tutorials. However, I have Photoshop Elements 10. It does not apparently offer the CA tools you show in your video. Maybe only the full Photoshop does?

    Lew

    Reply
    • Ryan
      Ryan says:

      Anyone try this yet? I read this after having imported a couple CR2s at home (into PSE 10) and I can’t remember if all those options are present in the version of ACR included with PSE 10 or not. I know with PSE 7 all we got was the initial color slider tab and the sharpening/NR tab. But I can’t remember what it looks like with the latest version that comes with PSE. I’m tempted to say we don’t have those options.

      Reply
  9. TJ
    TJ says:

    Thank you for this information. I am working on my first photo using your method and have already run into a problem. I have ACR 6.6 and when I click “Lens Corrections” I do not get the same Chromatic Abberation sliders that you show. Also, when I look at my 3 images, I don’t see any CA. Is this normal?

    Reply
    • farbspiel
      farbspiel says:

      Hi TJ,

      in ACR 6.6, there should be a ‘Lens profile’ tab with a check box to remove CA. CA removal is now done automatically. Just ckeck the box and verify that the CA is gone.

      Cheers
      Klaus

      Reply
      • TJ
        TJ says:

        Hi Klaus,

        Thanks for your reply. I don’t see that checkbox. But I do see a “Chromatic Aberration” slider whose values range from 0 – 200. http://flic.kr/p/buurmh I don’t see any CA in my images anyway so I’ll play with this slider in future images. Thanks for all your information. Your website is great.

        TJ

        Reply
  10. Ed
    Ed says:

    You take things that have been bothering me for ages and make them so easy to fix! And you share all your amazing knowledge freely. If only everyone were as generous with their knowledge. Here’s a heartfelt thank you!

    Reply
    • farbspiel
      farbspiel says:

      Thanks a lot for your kind words, Ed! They mean a lot to me.

      I am glad you’ve had a revelation while reading this recipe. Have fun applying it!

      Reply
  11. Seiz Agaz
    Seiz Agaz says:

    Just wanted to know which TIFF format, 32 or 16 bits, you are going to save the RAW after ACR?

    I REALLY love this site!

    Thanks.

    Reply
    • farbspiel
      farbspiel says:

      Hi Seiz,

      to my knowledge, there are only 8-bit and 16-bit TIFF images. ACR only lets you save to 8-bit images, at least in CS4. I have to check in CS5. So, to answer your question: I save the image as 8-bit TIFFs.

      Cheers
      Klaus

      Reply
  12. Brandon Velasco
    Brandon Velasco says:

    I was reading on one of your images that you turn your photos to tiff format i was just wondering if you can help me step by step to put them into photomatix. I get stuck after getting the two additional exposure from the over exposed and the under exposed image. I dont know what to do next after that. Please help.

    Reply

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