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.mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}</style><table class="box-More_citations_needed plainlinks metadata ambox ambox-content ambox-Refimprove" role="presentation"><tbody><tr><td class="mbox-text"><div class="mbox-text-span">This article <b>needs additional citations for <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verification</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/Purple_fringing" title="Special:EditPage/Purple fringing">improve this article</a> by <a href="/wiki/Help:Referencing_for_beginners" title="Help:Referencing for beginners">adding citations to reliable sources</a>. Unsourced material may be challenged and removed.<br><small><span class="plainlinks"><i>Find sources:</i> <a rel="nofollow" class="external text" href="https://www.google.com/search?as_eq=wikipedia&q=%22Purple+fringing%22">"Purple fringing"</a> – <a rel="nofollow" class="external text" href="https://www.google.com/search?tbm=nws&q=%22Purple+fringing%22+-wikipedia&tbs=ar:1">news</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?&q=%22Purple+fringing%22&tbs=bkt:s&tbm=bks">newspapers</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?tbs=bks:1&q=%22Purple+fringing%22+-wikipedia">books</a> <b>·</b> <a rel="nofollow" class="external text" href="https://scholar.google.com/scholar?q=%22Purple+fringing%22">scholar</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.jstor.org/action/doBasicSearch?Query=%22Purple+fringing%22&acc=on&wc=on">JSTOR</a></span></small></span> <span class="date-container"><i>(<span class="date">July 2023</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <style data-mw-deduplicate="TemplateStyles:r1237032888/mw-parser-output/.tmulti">.mw-parser-output .tmulti .multiimageinner{display:flex;flex-direction:column}.mw-parser-output .tmulti .trow{display:flex;flex-direction:row;clear:left;flex-wrap:wrap;width:100%;box-sizing:border-box}.mw-parser-output .tmulti .tsingle{margin:1px;float:left}.mw-parser-output .tmulti .theader{clear:both;font-weight:bold;text-align:center;align-self:center;background-color:transparent;width:100%}.mw-parser-output .tmulti .thumbcaption{background-color:transparent}.mw-parser-output .tmulti .text-align-left{text-align:left}.mw-parser-output .tmulti .text-align-right{text-align:right}.mw-parser-output .tmulti .text-align-center{text-align:center}@media all and (max-width:720px){.mw-parser-output .tmulti .thumbinner{width:100%!important;box-sizing:border-box;max-width:none!important;align-items:center}.mw-parser-output .tmulti .trow{justify-content:center}.mw-parser-output .tmulti .tsingle{float:none!important;max-width:100%!important;box-sizing:border-box;text-align:center}.mw-parser-output .tmulti .tsingle .thumbcaption{text-align:left}.mw-parser-output .tmulti .trow>.thumbcaption{text-align:center}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .tmulti .multiimageinner img{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .tmulti .multiimageinner img{background-color:white}}</style><p>In <a href="/wiki/Photography" title="Photography">photography</a> (particularly <a href="/wiki/Digital_photography" title="Digital photography">digital photography</a>), <b>purple fringing</b> (sometimes called <b>PF</b>) is the term for an <a href="/wiki/Defocus_aberration" title="Defocus aberration">unfocused</a> purple or <a href="/wiki/Magenta" title="Magenta">magenta</a> "ghost" image on a <a href="/wiki/Photograph" title="Photograph">photograph</a>. This <a href="/wiki/Optical_aberration" title="Optical aberration">optical aberration</a> is generally most visible as a coloring and lightening of dark edges adjacent to bright areas of broad-<a href="/wiki/Electromagnetic_spectrum" title="Electromagnetic spectrum">spectrum</a> illumination, such as <a href="/wiki/Daylight" title="Daylight">daylight</a> or various types of <a href="/wiki/Gas-discharge_lamp" title="Gas-discharge lamp">gas-discharge lamps</a>. </p><div class="thumb tmulti tright"><div class="thumbinner multiimageinner" style="width:204px;max-width:204px"><div class="trow"><div class="tsingle" style="width:202px;max-width:202px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Purple_fringing.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Purple_fringing.jpg/200px-Purple_fringing.jpg" decoding="async" width="200" height="135" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Purple_fringing.jpg/300px-Purple_fringing.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Purple_fringing.jpg/400px-Purple_fringing.jpg 2x" data-file-width="874" data-file-height="589"></a></span></div><div class="thumbcaption">Severe purple fringing can be seen at the edges of the <a href="/wiki/Horse" title="Horse">horse</a>'s forelock, mane, and ear.</div></div></div><div class="trow"><div class="tsingle" style="width:202px;max-width:202px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:FeralHorse044.JPG" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/9/94/FeralHorse044.JPG/200px-FeralHorse044.JPG" decoding="async" width="200" height="150" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/94/FeralHorse044.JPG/300px-FeralHorse044.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/94/FeralHorse044.JPG/400px-FeralHorse044.JPG 2x" data-file-width="2592" data-file-height="1944"></a></span></div><div class="thumbcaption">A wider-view context of the above cropped image, from a <a href="/wiki/Fujifilm_FinePix_S5200" title="Fujifilm FinePix S5200">Fujifilm FinePix S5200</a> camera.</div></div></div></div></div> <p><a href="/wiki/Lens_(optics)" class="mw-redirect" title="Lens (optics)">Lenses</a> in general exhibit axial <a href="/wiki/Chromatic_aberration" title="Chromatic aberration">chromatic aberration</a>, in which different colors of light do not <a href="/wiki/Focus_(optics)" title="Focus (optics)">focus</a> in the same <a href="/wiki/Focal_plane" class="mw-redirect" title="Focal plane">plane</a>. Normally, lens designs are optimized so that two or more (at least three for <a href="/wiki/Apochromatic" class="mw-redirect" title="Apochromatic">apochromatic</a> lenses) wavelengths of light in the <a href="/wiki/Visible_spectrum" title="Visible spectrum">visible spectrum</a> focus at the same plane. Wavelengths very different from those optimized in the design process may be severely out of focus while the reference colors are in focus; this <a href="/wiki/Optical_axis" title="Optical axis">axial</a> chromatic aberration is usually severe at short wavelengths (violet). Lens performance may be poor for such wavelengths in other ways too, including an increase in <a href="/wiki/Lens_flare" title="Lens flare">flare</a> due to anti-reflective <a href="/wiki/Optical_coating" title="Optical coating">coatings</a> also being optimized for the expected wavelengths. </p><p>Most film has relatively low sensitivity to colors outside the visible range, so light spread in the near <a href="/wiki/Ultraviolet" title="Ultraviolet">ultraviolet</a> (UV) or near <a href="/wiki/Infrared" title="Infrared">infrared</a> (IR) rarely has a significant impact on the image recorded. However, <a href="/wiki/Image_sensor" title="Image sensor">image sensors</a> used in digital cameras commonly are sensitive to a wider range of wavelengths.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="sensitivity range compared to visible light? (July 2020)">citation needed</span></a></i>]</sup> Although the lens glass itself filters out much of the UV light, and all digital cameras designed for color photography incorporate <a href="/wiki/Photographic_filter" title="Photographic filter">filters</a> to reduce red and IR sensitivity,<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="camera's internal filters need more explanation (July 2020)">citation needed</span></a></i>]</sup> the chromatic aberration can be sufficient for unfocused violet light to tint nearby dark regions of the image.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="why violet, all wavelength outside lens' optimized range may cause that (July 2020)">citation needed</span></a></i>]</sup> Bright cloudy or hazy skies are strong sources of <a href="/wiki/Light_scattering_by_particles" title="Light scattering by particles">scattered</a> violet and UV light,<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="Comparison to other wavelengths needed, especially infrared (July 2020)">citation needed</span></a></i>]</sup> so they tend to cause the problem. </p><p>The term <i>purple fringe</i> used to describe one aspect of chromatic aberration dates back to at least 1833.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> However, Brewster's description with a purple fringe on one edge and a green fringe on the other is a <i>lateral</i> chromatic aberration. A general defocus of the shortest wavelengths resulting in a purple fringe on all sides of a bright object is the result of an <i>axial</i> or <i>longitudinal</i> chromatic aberration. Quite often, these effects are mixed in an image. Axial chromatic aberration is more subject to reduction by stopping down the lens than lateral chromatic aberration is, so the purple fringing can be very dependent on <a href="/wiki/F-number" title="F-number">f-number</a>: a larger f-number (smaller <a href="/wiki/Aperture" title="Aperture">aperture</a>) reduces axial aberration. </p> </section><div class="mw-heading mw-heading2 section-heading" onclick="mfTempOpenSection(1)"><span class="indicator mf-icon mf-icon-expand mf-icon--small"></span><h2 id="Other_explanations">Other explanations</h2><span class="mw-editsection"> <a role="button" href="/w/index.php?title=Purple_fringing&action=edit&section=1" title="Edit section: Other explanations" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet "> <span class="minerva-icon minerva-icon--edit"></span> <span>edit</span> </a> </span> </div><section class="mf-section-1 collapsible-block" id="mf-section-1"> <p>Purple fringing is usually attributed to <a href="/wiki/Chromatic_aberration" title="Chromatic aberration">chromatic aberration</a> as described above. Other attributed causes of purple fringing in digital photography include many hypothesized sensor effects: </p> <ul><li>Digital noise in dark areas</li> <li>Image processing and <a href="/wiki/Interpolation" title="Interpolation">interpolation</a> artifacts (almost all CCDs and CMOS require considerable processing)</li> <li><a href="/wiki/Stray_light" title="Stray light">Stray</a> <a href="/wiki/Ultraviolet" title="Ultraviolet">ultraviolet</a> and/or <a href="/wiki/Infrared" title="Infrared">infrared</a> light</li> <li>Image bloom from overexposure of CCD sensor (not applied to CMOS)</li></ul> </section><div class="mw-heading mw-heading2 section-heading" onclick="mfTempOpenSection(2)"><span class="indicator mf-icon mf-icon-expand mf-icon--small"></span><h2 id="Mitigations">Mitigations</h2><span class="mw-editsection"> <a role="button" href="/w/index.php?title=Purple_fringing&action=edit&section=2" title="Edit section: Mitigations" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet "> <span class="minerva-icon minerva-icon--edit"></span> <span>edit</span> </a> </span> </div><section class="mf-section-2 collapsible-block" id="mf-section-2"> <p>Commonly advocated methods of avoiding purple fringing include: </p> <ul><li>Avoid shooting with a lens at fast apertures in high contrast scenes</li> <li>Avoid overexposing highlights (e.g. specular reflections and bright sky behind dark objects)</li> <li>Shoot with a strong UV-cut filter<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup></li></ul> <p>Post-processing to remove purple fringing (or chromatic aberration in general) usually involves scaling the fringed colour channel, or subtracting some of a scaled version of the blue channel, or other blue-channel tricks.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p> </section><div class="mw-heading mw-heading2 section-heading" onclick="mfTempOpenSection(3)"><span class="indicator mf-icon mf-icon-expand mf-icon--small"></span><h2 id="References">References</h2><span class="mw-editsection"> <a role="button" href="/w/index.php?title=Purple_fringing&action=edit&section=3" title="Edit section: References" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet "> <span class="minerva-icon minerva-icon--edit"></span> <span>edit</span> </a> </span> </div><section class="mf-section-3 collapsible-block" id="mf-section-3"> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFBrewster1833" class="citation book cs1">Brewster, Sir David (1833). <a rel="nofollow" class="external text" href="https://archive.org/details/atreatiseonopti01brewgoog"><i>A Treatise on Optics</i></a> (First American ed.). Philadelphia: <a href="/w/index.php?title=Carey,_Lee,_and_Blanchard&action=edit&redlink=1" class="new" title="Carey, Lee, and Blanchard (page does not exist)">Carey, Lee, and Blanchard</a>. p. <a rel="nofollow" class="external text" href="https://archive.org/details/atreatiseonopti01brewgoog/page/n82">76</a>. <q>purple fringe chromatic.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=A+Treatise+on+Optics&rft.place=Philadelphia&rft.pages=76&rft.edition=First+American&rft.pub=Carey%2C+Lee%2C+and+Blanchard&rft.date=1833&rft.aulast=Brewster&rft.aufirst=Sir+David&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fatreatiseonopti01brewgoog&rfr_id=info%3Asid%2Fen.wikipedia.org%3APurple+fringing" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGary_Nugent2013" class="citation web cs1">Gary Nugent (14 June 2013). <a rel="nofollow" class="external text" href="http://www.great-landscape-photography.com/ultraviolet-filter.html">"The Ultraviolet Filter"</a>. <i>great-landscape-photography.com</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=great-landscape-photography.com&rft.atitle=The+Ultraviolet+Filter&rft.date=2013-06-14&rft.au=Gary+Nugent&rft_id=http%3A%2F%2Fwww.great-landscape-photography.com%2Fultraviolet-filter.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APurple+fringing" class="Z3988"></span></span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGary_Nugent2013" class="citation web cs1">Gary Nugent (14 June 2013). <a rel="nofollow" class="external text" href="http://www.great-landscape-photography.com/remove-purple-fringing.html">"Photoshop Technique: Remove Purple Fringing"</a>. <i>great-landscape-photography.com</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=great-landscape-photography.com&rft.atitle=Photoshop+Technique%3A+Remove+Purple+Fringing&rft.date=2013-06-14&rft.au=Gary+Nugent&rft_id=http%3A%2F%2Fwww.great-landscape-photography.com%2Fremove-purple-fringing.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3APurple+fringing" class="Z3988"></span></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFScott_Mendham2004" class="citation web cs1">Scott Mendham (29 January 2004). <a rel="nofollow" class="external text" href="http://www.pcworld.idg.com.au/article/75955/removing_purple_fringing/?fp=2&fpid=1585691688">"Removing Purple Fringing"</a>. <i>PC World Australia</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=PC+World+Australia&rft.atitle=Removing+Purple+Fringing&rft.date=2004-01-29&rft.au=Scott+Mendham&rft_id=http%3A%2F%2Fwww.pcworld.idg.com.au%2Farticle%2F75955%2Fremoving_purple_fringing%2F%3Ffp%3D2%26fpid%3D1585691688&rfr_id=info%3Asid%2Fen.wikipedia.org%3APurple+fringing" class="Z3988"></span></span> </li> </ol></div></div>    </section></div> <noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?useformat=mobile&type=1x1&usesul3=0" alt="" width="1" height="1" style="border: none; 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