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Thread: Urban Aliasing

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    Urban Aliasing

    A question for anyone who uses MF digital in urban / industrial environments: do you ever find the lack of an anti-aliasing filter to cause problems? If so, can you describe?

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    Re: Urban Aliasing

    Quote Originally Posted by paulraphael View Post
    A question for anyone who uses MF digital in urban / industrial environments: do you ever find the lack of an anti-aliasing filter to cause problems? If so, can you describe?
    I use my P30+ for urban / industrial photography almost exclusively and the only time I have ever experienced any issues with moire have been with the fins on the housing of an air conditioner captured at some distance. But this was easily addressed in post-processing, so I wouldn't call it a problem...

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    Re: Urban Aliasing

    I have seen moire a very few times in urban scenes and usually only on objects like air conditioner fins. Most of the times when moire was an issue is while shooting fabrics in-studio.
    -bob

    edit: Looks like our posts crossed and yes, it seems we have the same experience

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    Subscriber and Workshop Member MGrayson's Avatar
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    Re: Urban Aliasing

    Aliasing doesn't have to come from a repeating pattern. A single thin line has a lot of high frequency information, and there are a lot of very thin lines in a cityscape. If you look for them, you'll see that some of those lines have interesting colors. (Disclaimer: My personal experience is with M9 pictures). Some of the published Pentax 645D samples also have delicately multicolored window frames on buildings. It's not the horrible distraction of fabric Moire, but it's fairly common.

    --Matt

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    Workshop Member Woody Campbell's Avatar
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    Re: Urban Aliasing

    I shoot a lot of stuff in urban environments and see minor aliasing all of the time - its somewhere in almost every image. If it's minor, which it usually is, I ignore it.

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    Re: Urban Aliasing

    Quote Originally Posted by Woody Campbell View Post
    I shoot a lot of stuff in urban environments and see minor aliasing all of the time - its somewhere in almost every image. If it's minor, which it usually is, I ignore it.
    For many buildings, it's an improvement.
    Likes 1 Member(s) liked this post

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    Re: Urban Aliasing

    That's good to hear. I was concerned about brick walls, fences, and iron bars, which abound in my neck of the woods.

    What sorts of post-processing most easily deals with the air conditioner finns?

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    Re: Urban Aliasing

    Quote Originally Posted by paulraphael View Post
    That's good to hear. I was concerned about brick walls, fences, and iron bars, which abound in my neck of the woods.

    What sorts of post-processing most easily deals with the air conditioner finns?
    In precisely that sort of environment my Aptus 22 generates moire that ranges from the mildly irritating to the simply unremovable.

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    Re: Urban Aliasing

    My subjects have a lot of thin and bright reflective edges. If your lens resolves thin lines well, CCD color aliasing is a problem. Because of Bayer artefacts you get single pixels showing primary colors instead of white. I think this is what Matt was talking about, and I am really bothered by it.

    Factors are lens MTF, sensor pixel pitch and subject spatial frequency. With current generation MF lenses (very sharp) I had much more of this problem at a 6 um pixel pitch than at 5.2 um. Very difficult to correct.

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