{"id":3734,"date":"2013-02-22T10:58:49","date_gmt":"2013-02-22T16:58:49","guid":{"rendered":"http:\/\/apps.lib.ua.edu\/blogs\/digitalservices\/?p=1682"},"modified":"2013-02-22T10:58:49","modified_gmt":"2013-02-22T16:58:49","slug":"when-patterns-attack","status":"publish","type":"post","link":"https:\/\/apps.lib.ua.edu\/blogs\/coolathoole\/2013\/02\/22\/when-patterns-attack\/","title":{"rendered":"When patterns attack"},"content":{"rendered":"

Up until about a month ago, I\u2019d never heard the term moir\u00e9 pattern<\/i>, but I\u2019d definitely seen them in action. You probably have, too. It might\u2019ve looked something like this\u2026<\/p>\n

\"moire_color\"<\/a><\/p>\n

…or maybe this…<\/p>\n

\"moire_swirl\"<\/a><\/p>\n

A moir\u00e9 pattern, which may appear as shimmering lines or dots or even swirls, can manifest itself when two similar but not identical patterns are superimposed or two identical patterns are superimposed at an angle. (It\u2019s the visual equivalent of what happens when you\u2019re driving in the car, listening to music, and you hear the song\u2019s beat begin to sync up with your turn signal…but just for a moment.) In images, what causes the interference is not easy to spot — because one of the patterns in question comes from the workings of the camera itself.<\/p>\n

A digital camera has a particular pattern to how it senses color. Reds, greens, and blues are captured and translated into pixels in a grid-like Bayer<\/a> filter pattern. When that sensor grid in the camera lines up in a certain way with a pattern in the object you\u2019re photographing — the pattern on someone\u2019s shirt, for example, or simply the pattern of dots that manifest in offset printing — strange things can happen. <\/p>\n

The following images show a black grid partially laid over a Bayer filter pattern.<\/p>\n

Black grid of same scale as the Bayer pattern:<\/p>\n

\"bayer_and_1to1_offset_mask\"<\/a><\/p>\n

Black grid a bit larger in scale.<\/p>\n

\"bayer_and_off_interval_offset_mask\"<\/a><\/p>\n

We\u2019ve found that moir\u00e9 patterns don\u2019t creep into our camera-based digitization very often — they wouldn\u2019t show up in handwritten materials or photographs, the bulk of the archival material we capture — but when they do, they can be a real problem. <\/p>\n

We\u2019ve developed some methods of dealing with the psychedelic-looking color patterns intruding upon our workflow. There are actions we take during the capture process that normally combat the problem pretty well, but we also have a couple of tricks up our sleeves for correcting the problem in post-production. Full disclosure: we exclusively run into problems based in the color channel, rather than the brightness channel (we get dot patterns rather than swirls), so that\u2019s what these methods are designed to address.<\/p>\n

During Capture
\n<\/strong><\/p>\n

The front-line defense for making the pattern disappear while a digital image is being taken is to change the relationship of the object and camera. Hopefully, this will bring about a different relationship between the object\u2019s pattern and the camera\u2019s.<\/p>\n

1. Orientation: Rotate the object until a test shot or preview shows that the pattern disappears. Here are the grids from example one above, set at a 45 degree angle from each other. <\/p>\n

\"offset_rotation_45_degrees\"<\/a><\/p>\n

2. Distance: Move the camera or the object so that they are at least a few inches closer or further apart. <\/p>\n

After Capture<\/strong><\/p>\n

While it\u2019s better to nip the problem in the bud before you take the picture, there are a couple of ways to improve — but not entirely fix — the image after it\u2019s been made.<\/p>\n

1. Photo editor tools: Use a moir\u00e9 correction tool if your photo editor has one. We use Adobe Bridge\u2019s camera raw editor to crop and rotate images, and we found that it has a Moir\u00e9 Reduction tool suitable for dealing with minor cases.<\/p>\n

2. Manual RGB manipulation in Photoshop: I won\u2019t pretend to describe this process here, but it involves manipulating the values of the RGB channels, and it must be done on a case-by-case basis. It\u2019s not something that makes sense for the average digitization project\u2019s workflow. <\/p>\n

There is no one simple fix for moir\u00e9 interference patterns. As you photograph things with a digital camera, be on the lookout for that tell-tale shimmer of color, and see what you can do to re-position the object as you\u2019re shooting it. Hopefully, you won\u2019t have to bring out the big, complicated guns. Avoiding combat in this case really is half the battle.<\/p>\n","protected":false},"excerpt":{"rendered":"

Up until about a month ago, I\u2019d never heard the term moir\u00e9 pattern, but I\u2019d definitely seen them in action. You probably have, too. It might\u2019ve looked something like this\u2026 …or maybe this… A moir\u00e9 pattern, which may appear as … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":426,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3736,3737],"tags":[3738,5878],"class_list":["post-3734","post","type-post","status-publish","format-standard","hentry","category-digitization","category-work-flow","tag-digitization-2","tag-image-capture"],"yoast_head":"\nWhen patterns attack - What's Cool at Hoole<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/apps.lib.ua.edu\/blogs\/coolathoole\/2013\/02\/22\/when-patterns-attack\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"When patterns attack - What's Cool at Hoole\" \/>\n<meta property=\"og:description\" content=\"Up until about a month ago, I\u2019d never heard the term moir\u00e9 pattern, but I\u2019d definitely seen them in action. 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It might\u2019ve looked something like this\u2026 …or maybe this… A moir\u00e9 pattern, which may appear as … Continue reading →\" \/>\n<meta property=\"og:url\" content=\"https:\/\/apps.lib.ua.edu\/blogs\/coolathoole\/2013\/02\/22\/when-patterns-attack\/\" \/>\n<meta property=\"og:site_name\" content=\"What's Cool at Hoole\" \/>\n<meta property=\"article:published_time\" content=\"2013-02-22T16:58:49+00:00\" \/>\n<meta property=\"og:image\" content=\"http:\/\/apps.lib.ua.edu\/blogs\/digitalservices\/files\/2013\/02\/moire_color.jpg\" \/>\n<meta name=\"author\" content=\"kgmatheny\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"kgmatheny\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"3 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/apps.lib.ua.edu\/blogs\/coolathoole\/2013\/02\/22\/when-patterns-attack\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/apps.lib.ua.edu\/blogs\/coolathoole\/2013\/02\/22\/when-patterns-attack\/\"},\"author\":{\"name\":\"kgmatheny\",\"@id\":\"https:\/\/apps.lib.ua.edu\/blogs\/coolathoole\/#\/schema\/person\/d5f5cd65eb2797de0df24a1b16a348d1\"},\"headline\":\"When patterns attack\",\"datePublished\":\"2013-02-22T16:58:49+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/apps.lib.ua.edu\/blogs\/coolathoole\/2013\/02\/22\/when-patterns-attack\/\"},\"wordCount\":661,\"commentCount\":0,\"image\":{\"@id\":\"https:\/\/apps.lib.ua.edu\/blogs\/coolathoole\/2013\/02\/22\/when-patterns-attack\/#primaryimage\"},\"thumbnailUrl\":\"http:\/\/apps.lib.ua.edu\/blogs\/digitalservices\/files\/2013\/02\/moire_color.jpg\",\"keywords\":[\"digitization\",\"image capture\"],\"articleSection\":[\"Digitization\",\"Work Flow\"],\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"CommentAction\",\"name\":\"Comment\",\"target\":[\"https:\/\/apps.lib.ua.edu\/blogs\/coolathoole\/2013\/02\/22\/when-patterns-attack\/#respond\"]}]},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/apps.lib.ua.edu\/blogs\/coolathoole\/2013\/02\/22\/when-patterns-attack\/\",\"url\":\"https:\/\/apps.lib.ua.edu\/blogs\/coolathoole\/2013\/02\/22\/when-patterns-attack\/\",\"name\":\"When patterns attack - 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