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Thread: Moiré pattern blues...

  1. #1

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    Moiré pattern blues...

    Hi everyone. I am having a bad time dealing with a Moiré pattern in one of my photographs, shown below, and not for the first time! The problem is the corrugated steel roof. Although I have dealt with it in a fashion, I have sacrificed the original look, which can be seen on the smaller roof of the building extension lower to the left, which is untouched -- you need to look at the larger version to see it adequately.

    I have tried a number of recommended solutions, mostly originating as treatment for scanned images. None of these have worked out for this image.

    Any advice? All comments are very much welcome and appreciated.

    PS: The camera used is a Canon 350D w/8 mp sensor. My 7D does not have this problem, which tells me something. Oh, I am using Photoshop CS5. And, as some of you know by now, I like dramatic skies and bold colors. This photo is one of those. I am thinking about starting a "How was it done" thread open to everyone -- if there is enough interest.

    Moiré pattern blues...

    Larger version here.
    Last edited by David deSousa; 12th November 2010 at 08:32 PM.

  2. #2
    Moderator Dave Humphries's Avatar
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    Re: Moiré pattern blues...

    Hi David,

    I don't see any (of what I would call) moire patterning*, but I do see significant jaggies on the angled lines, is that what you are concerned about? I suppose you could call it a moire effect.

    Yes, that will be more obvious with lower resolution sensors, especially if you crop significantly.

    I also think it looks worse because (in my opinion) it is rather over sharpened at a radius that is an unfortunate choice.

    Have you tried a small rotation to see whether that improves it?

    Cheers,

  3. #3

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    Re: Moiré pattern blues...

    Quote Originally Posted by Dave Humphries View Post
    Hi David,

    I don't see any (of what I would call) moire patterning*, but I do see significant jaggies on the angled lines, is that what you are concerned about? I suppose you could call it a moire effect.

    Yes, that will be more obvious with lower resolution sensors, especially if you crop significantly.

    I also think it looks worse because (in my opinion) it is rather over sharpened at a radius that is an unfortunate choice.

    Have you tried a small rotation to see whether that improves it?

    Cheers,
    Hi Dave,

    Yes, the dreaded jaggies, another artifact of few sensor pixels and editing, although this one was not cropped at all. I have included the original frame for comparison.
    Moiré pattern blues...

    It is interesting that you tell me it is over sharpened, which is a big deal to me. I go to some trouble to avoid it. Mostly I avoid USM for that reason and sharpen in three stages, and I also use a unsharpening (selective blur) trick or two most of the time when uploading. When I do use USM or Smart sharpen, I usually use the Fade USM feature now in PS5. Will you tell me exactly what you see that makes you say it is over sharpened?

    Frankly, to my eye, most uploaded pictures look UNDER sharpened, with lower acuity than I know is possible for both camera and post. But then there are those that are clearly (even to my old eyes) over sharpened, with halos and unnatural infinite depth of field. Maybe that's just me, but I don't like the soft "out of focus" sensation. I am wondering if I need new glasses or something or perhaps I am still too heavily influenced by my old sheet film days.

    It would be a big help to me for anyone inclined to point out exactly what makes my photos(s) give rise to the "over sharpened" comment.

    BTW, there seems to be a phenomenon regarding the Moiré pattern relevant to picture size. The reduction show here has very little Moiré, where the same picture in Photoshop show significant Moiré on the roof -- more mysteries to solve!

    Thanks,
    David

    Oh, and BTW, I did try a -0.5 to -1 degree rotation previously without success.
    Last edited by David deSousa; 12th November 2010 at 09:18 PM.

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    Moderator Dave Humphries's Avatar
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    Re: Moiré pattern blues...

    Hi David,

    OK, heres a screen snip off the larger version
    Moiré pattern blues... I am seeing a large dark halo
    There are additionally some jpg artefacts

    Here at 400%
    Moiré pattern blues...

    Similarly, the grass looks very speckly to me
    Moiré pattern blues...

    and the timber rail against the sky, at 200%
    Moiré pattern blues...

    I believe USM gives far greater control than smart sharpen, what sort of amounts and radii are you using with Smart Sharpen?

    Some more questions;
    a) what sort of monitor are you viewing on; CRT or LCD?
    b) exactly how did you down size for the larger version? (which method)
    c) what jpg quality are you using?

    I am thinking that at least some of this is happening after your editing - e.g. while you are producing the smaller image for web publication.

    Moiré pattern blues...

    For the record, I don't trust the last option, despite what it says!

    Might be worth doing a Sendthisfile and letting me have a look at the fullsize RAW image and see if I can avoid some of the issues.

    But I have to say, some images do just seem more prone to the effect than others - I have had it too
    Last edited by Dave Humphries; 12th November 2010 at 11:26 PM.

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    Re: Moiré pattern blues...

    Well, Dave, I did not notice the jpg artifacts or the dark halos until you showed them to me. I must remind you that the first image is a composite, as you now must realize from my original of the barn. I wasn't happy with the original clouds so I just popped in a sky image from my archives -- but didn't look very closely at it. I was more focused on the Moiré problem.

    I believe USM gives far greater control than smart sharpen, what sort of amounts and radii are you using with Smart Sharpen?

    Some more questions;
    a) what sort of monitor are you viewing on; CRT or LCD?
    b) exactly how did you down size for the larger version? (which method)
    c) what jpg quality are you using?

    I am thinking that at least some of this is happening after your editing - e.g. while you are producing the smaller image for web publication.
    I agree with you about USM vs Smart Sharpen in terms of control. I use them both for different reasons, however. I use USM often to boost "local" contrast with relatively large numbers, but much smaller numbers when I want to use it to actually sharpen. Most of the time I use a formula of high-pass, or one of a half-dozen 3rd party plug-ins, depending on the stage or phase of my workflow. I use the sharpening brush sometimes, or a selection with all the above as well. I almost never sharpen globally except at the very end of my workflow.

    My monitor is an old but very good Sony Pro LCD that is regularly calibrated with a Spider Pro 3.

    My downsizing is done in most cases with PhotoZoom Pro 3 using either the Lanczos algorithm or the very good but proprietary S-Spline Max algorithm -- which I use most of the time to down size. I make a copy of my PSD or Tiff, flatten the layers, downsize to either 640 for CiC or 920 for others. I then check the image, but rarely apply any sharpening. Then I save the file as jpg with either a quality of 10 or 12, depending on the original file size and the website requirements.

    Lately, however, esp for CiC, I have been using Flicker, who is reportedly using Lanczos as a resizing algorithm. In that case I upload the full sized PSD directly from Bridge and let Flicker take over from there. All of my images on CiC have been done that way. It is just so much easier to post an embedded image or a link, as you can see here. Using that method I don't see objectionable degradation as I often do with the native Photoshop method. I must admit (as you are no doubt aware) the down size /upload process is tricky and variable and must be watched carefully if you care about what others ultimately see.

    So, the black halos around the clouds are my fault, I know how to fix that, but other things like grainy grass I think are resize /upload artifacts because I don't see them here on my computer. As for the overall sort of 'shocking' qualities of the image, that is my style, as you will or have seen already. I don't aim for true-to-life pictures because 1) Photographs aren't true-to-life anyway by a long shot in my opinion; so I don't previsualize them that way, and 2) I studied with Ansel Adams for years in person -- he taught me to see the unseen and represent the scene as only manipulated photographic media can. That's the difference between art and snapshot in my view. But I have to contend with those who don't like my style -- N'est-ce pas?

    In any case, there are some aspects to post processing that I don't do so well with yet (I bought my first digital camera in 2006) and often it takes new eyes on the problem to dial in on them to grok the remedies -- which I appreciate very much your doing for me here.

    Thanks,
    David

    Oh, BTW, bicubic is NOT the best for any resizing task, which is not my lone opinion.

  6. #6
    Moderator Dave Humphries's Avatar
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    Re: Moiré pattern blues...

    Hmmm,

    Looks like you have most things under control, it may be just 'one of those' images then.

    We do have different ideas on PP and how to achieve things, but there's nothing wrong with that and I'm certainly not saying what I do is better. Of course, I always do things the best way I can, until someone shows me an even better way all part of learning and I hope I never stop.

    As a small example - I rarely use a sharpen brush, as I do often find it too coarse (in Elements, that is). I almost always do globally sharpen, but in several stages with conservative values and as low a threshold as I can. I prefer a more natural look, but then my subjects are different too, being mostly wildlife.

    I certainly don't see your monitor having any bearing on the matter, given what you say.
    I'd be suspicious of Flickr, do you really upload a PSD (not a jpg)? That seems odd, but then I don't use them.

    It is the free and constructive exchange of views and methods here at CiC that do enable us all to learn from each other - and long may it last,

  7. #7

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    Re: Moiré pattern blues...

    Thank you Dave, it is the chase we like best I perceive, and learning, learning, learning. It is very difficult to embrace all of the post processing techniques we come across. Since they impact the look we want to achieve, then no stone should be left unturned in my book. The problem is time and the fact that I for one do not like to skip around with experimentation to far off the track I am following at any given time. I am not unwilling to abandon certain procedures but it is also my style to pursue them to a conclusive end.

    I know that Moiré patterns can be the devil incarnate when they strike, this from experience -- what little I have -- and from others who know more than me. It puts another demand on knowing your equipment even before you press the shutter button. The old art class admonition, "Artist, know thy medium," rings true all the time even when you don't expect it.

    I appreciate your saying that you use your tools conservatively. I admire that and am not ashamed to admit it is harder to do than it sounds, or is to say. With film I never had the problem of over sharpening but now I do. At this stage of growth with digital I see that getting feedback from others, such as yourself, is invaluable because as I said, I don't really know what "over sharpening" means when observed by someone who does.

    D.

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