How to remove holos in a easy way,please?

Discussion in 'Digital Darkroom' started by x_wang, Nov 13, 2011.

  1. When I take photos against light, I get holos at the edge(of buildings). It is easier to remove them by using clone tool when there are only a few lines. Last month, I took a photo of a big wheel. The holos are massive. Because the back lihgts are all in different colours, I couldn't make a single coloured background layer to find way out or as a copy to do clone...eventually I had to try some clone work in a very small space between lines. It was tedious and difficult.:-D . I also tried CS5's Layer>matting>defringe (or remove white matte), it didn't work effectively.I wonder if there are some easier ways to get rid of the holos.Thank you
    Jasmine
    00ZbNk-415415584.jpg
     
  2. Sorry, bad English...:-D "AN easy way"...
     
  3. I think you mean "halos" - but it would really help if you cropped out a 100%-zoomed-in section of one of the photos that show the problem, and post that (make a 700x700 pixel section of the full-resolution image, without any repairs done to it, and post it here).

    It's possible that there are some better ways to approach this, including not getting the artifacts in the first place - which may involve changing how you're using your camera/lens under some shooting conditions, or perhaps considering a different lens when shooting high contrast items like the one in your example above. I suspect that you're talking about CA (chromatic abberations), and you may be able to correct for some of that with a couple of mouseclicks in the right software, fixing the whole image in one step.

    But it will be easier to comment if you can show us a close-up example of the problem.
     
  4. Thank you Matt. You spotted on both matters. Yes, it is the lens and CA.
    I only take photos when I travel, I don't use tripod and I only have one lens which is EF-S18-200mm f/3.5-5.6 IS. Down to CA matter, it's rather poor. After I corrected CA, the coloured part became white.
    I can't get exactly 700x700, 600 something here for you to have a look... thanks again.
    00ZbR9-415459584.jpg
     
  5. Photoshop, Lightroom and perhaps others have software to mitigate chromatic aberation.
     
  6. the chromatic aberation in Lightroom will get rid of that in less time it take you to read this... welcome to digital..; ) this halo can also be red / purple depending of the color where the problem stand out (beside blonde hairs, beside windows...
     
  7. As noted-LR3 will help with some of this. One of the handy little tools in the C/A slider group is something called "defringe"- it has the effect of slightly color blurring (lack of better term) the chosen edges (highlight or all).
    Another issue which appears to be presenting itself here is oversharpening, or rather possibly the wrong type of sharpening. Note the horizontal bars and the white edges on them. I'm not sure what software you are using, or if you are even starting with a RAW file.
    If these are camera produced JPEGS, there's not much you can do with the sharpening halos except tedious removal methods already mentioned.
    IF you are working with a RAW file, I highly suggest that you zero the camera settings out before transferring the file to Photoshop, LR3 or any other editing software as the sharpening tools in DPP are at times akin to using a mallet on a finishing nail. Proper sharpening techniques will also by default reduce a fair amount of the offensive C/A.
     
  8. First, thank you all:).
    Matt was right, I knew that it was CA and the lens(Canon EF-S18-200mm f/3.5-5.6 IS) . It is not that I can't get rid of CA. When I correct the CA, sometimes, I get rid of the coloured lines but it leaves a white colour line. It is still easier to deal with them when there are only a few lines. The problem is that on this kind of the photo, I have 'massive' lines to deal with. I just wonder if there is an easy way to get rid of the white lines after CA correction. I'd tried CS5's Layer>matting>defringe (or remove white matte), but it was not effective enough. I don't think that the original cropped image (above) was sharpened in the camera and CS5, I'd set the settings back to default.
    What else can I do? :) Not shooting against the sun? But I like that:-D
    Thanks again.
    Jasmine
     
  9. White color line you mention could be from over sharpening
     
  10. If you are a masochist you go in close to the white lines with a small clone tool of perhaps 2 pixel size and clone across adjacent pixels to cover the white :) I did it a couple of times to prove to myself it works but try now to avoid over sharpening. The white line comes when adjacent tones have big difference. Hi-pass sharpening is less prone to the problem than USM.
     
  11. Thank you Chris. Over sharpening does have white lines sometimes. But I'm not sure about this one. I'll upload an unsharpened image which was after CA correction. You may see the white lines. It's an old problem for me, and also that's why I agreed with Matt as soon as he mentioned CA and lens.
    Thank you JC. That's exactly what I do most of the time, using clone tool.. but it was too tedious and difficult to do clone work on this kind of image.I just wonder if there is an easy way on PS when there are 'Massive' lines..
    There is no high pass sharpening on PS, but I do remember it was on Corel that I used to use. Could you tell me which sharpening tool equivalent to hi-pass sharpening on PS?
    Another thing, as you said "masochist, ...when you check the detail of the image I wonder if there is a standard or we say acceptable level, eg. if I zoom it up to 440.76%( as the image I'll upload), I can see the white lines clearly,but if I zoom it at 100%, I can hardly see the lines. How far should I go? I'm a bit on chasing perfection side.;-)
    Thank you all again..
    Jasmine
    00ZbaM-415629584.jpg
     
  12. theres a high pass filter in ps, under filter / other / highpass... but the smart sharpen is far better and more refine than
    highpass.

    100% is the correct size at what u should inspect your file on screen, anything bigger than this is... well, over the top... so
    looking at it at 400% mean that u might need medecine : )
     
  13. I'm with Pat-Smart sharpen @100% ensures it won't show up in prints 99% of the time. Workflow aside, while it's fun to view images at 100% or more (pixel peeping), it's not "real world" unless you're cropping ~50% or enlarging beyond 20x30.
    As to your last posted image- as you've already noted and confirmed, it's primarily the lens and the high contrast backlit nature of the scene creating the C/A. -I slid my chair back 3 feet from my screen and those halos dissapeared altogether. Proper viewing distance for a given image size/magnification also has to be considered.
     
  14. One method I use for white or dark contrast halos that result from oversharpening or blending exposures is to set the clone stamp tool's blend mode to darken or lighten. If I have a white halo that is between a bright sky and a dark mountain, I will set the blend mode to darken. Then I will paint along the edge without worrying about cloning the darker object because the darken blend mode will only darken pixels that are lighter than the source, in this case the source being the sky. On the flip side, I can also lighten dark outline halos with lighten, just making sure I source the darker object. The clone stamp will lighten the dark line but will not affect the brighter areas because it can't lighten something that is lighter than the source. Takes some practice and it is certainly much easier when using a digital tablet, but because you are using the blend modes, it doesn't require such preciseness!
     
  15. Thank you Patrick for telling me about the location of high pass..I use unsharp mask a lot, because it's easy to control... I only used smart sharpen once to correct the blur which caused by camera shaken in low lights.It looked slightly better, but I have no idea how to control it..
    Thank you Randall. I might push it too far... :-D, as I said that I only take photo when I travel, mainly museums, churches and very bright day light, two kind of extreme conditions,because I don't use tripod, so it seems that I'm chasing sharp image that you guys take that is difficult for me to get...
    Thank you Mark. I do use darken and clone both and work on tablet., but I haven't tried lighten yet. It's a good idea that I have never thought of before, because most of the time I've been battling with the light colour. It's easier when it is pure white, when CA correction can't get rid all colours as the edge showed above, darken can only change colour, normal clone is needed.
    I'm still thinking if there is any other way to get rid of them easily on such massive lines:)
    Thank you all again very much, I learned something else from all of you. A very good morning to you all.
    Jasmine
     
  16. OP may find this thread helpful:
    http://www.photo.net/casual-conversations-forum/00Zad3
     
  17. The previous posters who suggested avoiding the problem in the first place were right on the mark. Doing so is vastly preferable to trying to fix it after the fact. Fixing chromatic aberration in your raw converter, using smart sharpening in moderation instead of USM or HPF are both excellent ways to minimize the problem.
    That being said, for various reasons, one is occasionally given an image with halos, and there is no possibility of going back and re-shooting or re-processing it. In such a a case, if the geometry is not too complex, the previous suggestions to do manual cloning with the blend mode set to darken (to reduce the bright halos) is reasonable. However, if the geometry is complex (eg, oversharpened leaves) that approach can be infeasible and an automated approach is needed. Below is one way I use to reduce bright halos in such cases. The method is trivially modified to work on dark halos.
    Let's start with the following image.
    00Zbjd-415769584.jpg
     
  18. Next, let's oversharpen it to generate lots of bright halos.
    00Zbjg-415769784.jpg
     
  19. Run the image through the high pass filter. I used a radius of about 0.5 for this image, but you will have to adjust this based on the size of the halos.
    00Zbjl-415771584.jpg
     
  20. Whoops. In the previous message, I forgot to mention that I desaturated the image before passing it through the HPF.
    The high pass filter compares a give pixel to its neighbors and if it's different, it displays the difference with no difference displayed as an intensity value of 128. To remove bright halos, we want to select them. In other words, we only want to process edge pixels that are substantially brighter than their neighbors. An easy way to do this is to run the high pass filtered version of the image through a curve which is zero up to an intensity of 128 and then jumps to 50% and rises linearly from there to full brightness. Here is such a curve.
    00Zbjp-415773584.jpg
     
  21. And here is the result of passing the HPF version of the image through that curve.
    00Zbjt-415775584.jpg
     
  22. Make a copy of the original image, and then use the above mask to remove the bright halo pixels, leaving transparency in their place. Transparency does not reproduce well, so, only for the purpose of this demo, I'm going to show the transparent regions by placing a solid red layer under the layer with transparent halo pixels.
    00Zbjx-415777584.jpg
     
  23. You next want to use the pixels surrounding each transparent (ie, halo) pixel to fill in for each transparent pixel. There are several ways to do this, but probably the easiest way is simply to blur the layer with transparency that we just generated. I used an radius of about 2 pixels to do this. Too small, and it won't fill in wide halos, and too large, and it will be picking up color and luminosity info from too far away.
    Below is the result of blurring. It looks horrible because we blurred everything, but don't worry, that will go away in a moment.
    00Zbk7-415779684.jpg
     
  24. Next, use the mask we generated early in this process to select out only the areas of the above image that were originally bright halos, and place these replacement pixels on their own layer at the top of the layer stack. Set the "blend-if" sliders for this layer to only allow these pixels to be seen where the underlying layer is fairly bright (ie, where there were bright halos).
    As the final step, make another copy of the starting, over-sharpened image, and place this on a new layer immediately under the layer described in the previous paragraph.
    The result of this process is shown below. As you can see, the huge number of geometrically intricate halos generated by the intentional oversharpening have been greatly reduced by the procedure I just described, and the loss of sharpness is reasonable ... hopefully acceptable for most applications, and a lot more successful and less work than trying to remove the halos manually with the clone or similar tools.
    00ZbkF-415781584.jpg
     
  25. And, once again, for immediate comparison with the previous image, here is the original image before the intentional oversharpening.
    I know this method sounds complicated, but once you have done it a couple of times, it is very fast and easy to implement, and produces much better results than one could possibly do with the clone brush, particularly in situations with very intricate halos.
    HTH,
    Tom M
    00ZbkR-415783584.jpg
     
  26. Hi Tom,
    I'm so pleased that you've come to rescue...:-D.Thank you so,so... much!
    As you know, I don't know much about photoshop, but I wondered that if there was a way.. here we are...
    Just to say thanks first, and I'm going to follow your steps to see how it works..it is really great!
    My best wishes to you, and have a great afternoon:)
    jasmine
     
  27. Thank you Robert for the link.:)
    Jasmine
     
  28. So, I just came back into this thread on a whim, and man am I glad I did. Tom, that is pure genuis, I'll have to try it out.
    And X Wang, don't feel bad about being a novice in Photoshop, I am decently well versed, but there is always a new trick to any problem to learn. I don't think anyone knows every technique.
     
  29. Hi Jasmine - Good to hear from you again. It sounds like you are making great progress.
    Zach - Thanks for the kind words, but the truth be told, my algorithm works in a similar way to Photoshop's "dust and scratches" filter. There are many significant differences, but probably the most important one is that with my filter, you can get "under the hood" and optimize all of the intermediate steps and parameters to give you the best result for halos. In contrast, with D&S, you only have two sliders, and IMHO, D&S always looks crude when applied to halos.
    Cheers,
    Tom M
     
  30. Tom, I'm totally lost after your HPF version. I need more detailed help from you...I don't know how the masks, layers work.Maybe this is not kind of question for an entrance level to ask, but I'm going to follow you through...
    First, I don't know how you "placing a solid red layer under the layer with transparent halo pixels." If you think that is only for demo, not import, we could omit it.
    Second, I've got the blured image. But How to "use the mask we generated early in this process to select out only the areas of the above image that were originally bright halos, and place these replacement pixels on their own layer at the top of the layer stack".
    Did you mean to select on that HPF version of the image, by using select tool? And I don't know how to put one layer on the top of another..
    Could you leave a few quick notes, like " 1. click ... 2...."?
    or links ( layer related) for me to have an idea about how to move them around.
    or a short video, like a kind of tutorial, for me to have a look the procedure performed on PS. I just learned where the high pass was from Patrick today.:-D
    If the file is too large or anything, could you send me an email,please? Whatever, if it suits you..I really want to learn your method, I've been searching for the answers for days,so glad that you came to help again.
    I'll be back tomorrow at GMT Time :). Many, many thanks Tom, and all of you.
    Good night.
    Jasmine
     
  31. Hi Jasmine - I would love to help you, but, as they say, you have to walk before you can run, and the method I described is fairly advanced and presupposes considerable knowledge of PS.
    So, if, for example, you don't know how to put one layer on top of another, you undoubtedly have many other really fundamental and critically important gaps in your knowledge of photoshop that unfortunately just can't be rectified in a few forum postings - it takes a book and substantial experience, not just a few postings, or even a video tutorial. As an example of this, one of the main benefits of my approach is that it gives the user many, many adjustments. However, if, for example, you have little experience with setting the radii for the HPFor the blur, or using the blend-if sliders, there is no way you can get this to work. In this case, I suggest relying on preventative measures instead of an after-the-fact procedure like mine.
    Cheers,
    Tom M
    PS - BTW, for comparison, this procedure requires vastly more knowledge than needed in our previous discussions.
     
  32. Hi Tom,
    Sure, I know that you'd love to help me and us, that's why you'd spent such time and efforts to show us how to do so. I'm very grateful. I believe that all of us who are interested in this subject are grateful as well...
    I also know that there is a lot of catch up work needed to be done, but I have to start from somewhere, even I'm not technical, and knowing very little about PS. Yes, I have NO "experience with setting the radii for the HPFor the blur, or using the blend-if sliders"..actually I've never heard of them. but it's a great start to learn. So far, I'm very please that you've supplied me an answer. This method is very important to me, it IS pure genuis. As I said that I'd been searching for the answer for days... That means it can be done in your way,it's not my 'wild' imagination. I don't want to give up at the starting point, it's not finished yet. I'll try to find out little by little to fill up 'the book'. Prevention is one thing, I aslo have to learn how to solve the problem..
    Again, thank you so,so much.
    Jasmine
     
  33. Tom, awesome example. Thanks.
     

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