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data-event-name="pinnable-header.vector-toc.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-toc.unpin">hide</button> </div> <ul class="vector-toc-contents" id="mw-panel-toc-list"> <li id="toc-mw-content-text" class="vector-toc-list-item vector-toc-level-1"> <a href="#" class="vector-toc-link"> <div class="vector-toc-text">(Top)</div> </a> </li> <li id="toc-Photographic_darkroom_unsharp_masking" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Photographic_darkroom_unsharp_masking"> <div class="vector-toc-text"> <span class="vector-toc-numb">1</span> <span>Photographic darkroom unsharp masking</span> </div> </a> <ul id="toc-Photographic_darkroom_unsharp_masking-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Digital_unsharp_masking" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Digital_unsharp_masking"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Digital unsharp masking</span> </div> </a> <button aria-controls="toc-Digital_unsharp_masking-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Digital unsharp masking subsection</span> </button> <ul id="toc-Digital_unsharp_masking-sublist" class="vector-toc-list"> <li id="toc-Local_contrast_enhancement" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Local_contrast_enhancement"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.1</span> <span>Local contrast enhancement</span> </div> </a> <ul id="toc-Local_contrast_enhancement-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Comparison_with_deconvolution" class="vector-toc-list-item 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href="/wiki/File:Usm-unsharp-mask.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e6/Usm-unsharp-mask.png/220px-Usm-unsharp-mask.png" decoding="async" width="220" height="156" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e6/Usm-unsharp-mask.png/330px-Usm-unsharp-mask.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e6/Usm-unsharp-mask.png/440px-Usm-unsharp-mask.png 2x" data-file-width="3508" data-file-height="2480" /></a><figcaption>Unsharp masking applied to lower part of image</figcaption></figure> <p><b>Unsharp masking</b> (<b>USM</b>) is an <a href="/wiki/Image_sharpening" class="mw-redirect" title="Image sharpening">image sharpening</a> technique, first implemented in <a href="/wiki/Analog_photography" title="Analog photography">darkroom photography</a>, but now commonly used in <a href="/wiki/Digital_image_processing" title="Digital image processing">digital image processing</a> software. Its name derives from the fact that the technique uses a <a href="/wiki/Gaussian_blur" title="Gaussian blur">blurred</a>, or "unsharp", negative image to create a <a href="/wiki/Mask_(computing)" title="Mask (computing)">mask</a> of the original image. The unsharp mask is then combined with the original positive image, creating an image that is less blurry than the original. The resulting image, although clearer, may be a less accurate representation of the image's subject. </p><p>In the context of <a href="/wiki/Signal_processing" title="Signal processing">signal processing</a>, an unsharp mask is generally a <a href="/wiki/Linear_filter" title="Linear filter">linear</a> or <a href="/wiki/Nonlinear_filter" title="Nonlinear filter">nonlinear</a> filter that amplifies the high-frequency components of a signal. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Photographic_darkroom_unsharp_masking">Photographic darkroom unsharp masking</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Unsharp_masking&action=edit&section=1" title="Edit section: Photographic darkroom unsharp masking"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Unsharp_mask_principle.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Unsharp_mask_principle.svg/220px-Unsharp_mask_principle.svg.png" decoding="async" width="220" height="293" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Unsharp_mask_principle.svg/330px-Unsharp_mask_principle.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Unsharp_mask_principle.svg/440px-Unsharp_mask_principle.svg.png 2x" data-file-width="512" data-file-height="683" /></a><figcaption>Simplified principle of unsharp masking</figcaption></figure> <p>For the photographic darkroom process, a <a href="/wiki/Large_format_(photography)" class="mw-redirect" title="Large format (photography)">large-format</a> glass plate negative is contact-copied onto a low-contrast film or plate to create a positive image. However, the positive copy is made with the copy material in contact with the back of the original, rather than <a href="/wiki/Photographic_emulsion" title="Photographic emulsion">emulsion-to-emulsion</a>, so it is blurred. After processing this blurred positive is replaced in contact with the back of the original negative. When light is passed through both negative and in-register positive (in an <a href="/wiki/Enlarger" title="Enlarger">enlarger</a>, for example), the positive partially cancels some of the information in the negative. </p><p>Because the positive has been blurred intentionally, only the low-frequency (blurred) information is cancelled. In addition, the mask effectively reduces the <a href="/wiki/Dynamic_range#photography" title="Dynamic range">dynamic range</a> of the original negative. Thus, if the resulting enlarged image is recorded on <a href="/wiki/Photographic_paper#Contrast_control" title="Photographic paper">contrasty photographic paper</a>, the partial cancellation emphasizes the high-spatial-frequency information (fine detail) in the original, without loss of highlight or shadow detail. The resulting print appears more acute than one made without the unsharp mask: its <a href="/wiki/Acutance" title="Acutance">acutance</a> is increased. </p><p>In the photographic procedure, the amount of blurring can be controlled by changing the "softness" or "hardness" (from point source to fully diffuse) of the light source used for the initial unsharp mask exposure, while the strength of the effect can be controlled by changing the contrast and density (i.e., exposure and development) of the unsharp mask. </p><p>For traditional photography, unsharp masking is usually used on <a href="/wiki/Monochrome" title="Monochrome">monochrome</a> materials; special <a href="/wiki/Panchromatic" class="mw-redirect" title="Panchromatic">panchromatic</a> soft-working black-and-white films have been available for masking photographic colour transparencies. This has been especially useful to control the density range of a transparency intended for <a href="/wiki/Photomechanical_reproduction" class="mw-redirect" title="Photomechanical reproduction">photomechanical reproduction</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Digital_unsharp_masking">Digital unsharp masking</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Unsharp_masking&action=edit&section=2" title="Edit section: Digital unsharp masking"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Unsharped_eye.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/4/43/Unsharped_eye.jpg" decoding="async" width="250" height="565" class="mw-file-element" data-file-width="250" data-file-height="565" /></a><figcaption>Source image (top),<br />sharpened image (middle),<br />highly sharpened image (bottom)</figcaption></figure> <p>The same differencing principle is used in the unsharp-masking tool in many digital-imaging software packages, such as <a href="/wiki/Adobe_Photoshop" title="Adobe Photoshop">Adobe Photoshop</a> and <a href="/wiki/GIMP" title="GIMP">GIMP</a>.<sup id="cite_ref-gimp_1-0" class="reference"><a href="#cite_note-gimp-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> The software applies a <a href="/wiki/Gaussian_blur" title="Gaussian blur">Gaussian blur</a> to a copy of the original image and then compares it to the original. If the difference is greater than a user-specified threshold setting, the images are (in effect) subtracted. </p><p>Digital unsharp masking is a flexible and powerful way to increase sharpness, especially in <a href="/wiki/Scanned_images" class="mw-redirect" title="Scanned images">scanned images</a>. Unfortunately, it may create unwanted conspicuous edge effects or increase <a href="/wiki/Image_noise" title="Image noise">image noise</a>. However, these effects can be used creatively, especially if a single <a href="/wiki/Channel_(digital_image)" title="Channel (digital image)">channel</a> of an <a href="/wiki/RGB_color_model" title="RGB color model">RGB</a> or <a href="/wiki/CIELAB" class="mw-redirect" title="CIELAB">Lab</a> image is sharpened. Undesired effects can be reduced by using a mask—particularly one created by <a href="/wiki/Edge_detection" title="Edge detection">edge detection</a>—to only apply sharpening to desired regions, sometimes termed "smart sharpen". </p><p>Typically, digital unsharp masking is controlled via the amount, radius and threshold: </p> <ul><li>Amount is listed as a percentage and controls the magnitude of each <a href="/wiki/Overshoot_(signal)" title="Overshoot (signal)">overshoot</a> (how much darker and how much lighter the edge borders become). This can also be thought of as how much contrast is added at the edges. It does not affect the width of the edge rims.</li> <li>Radius affects the size of the edges to be enhanced or how wide the edge rims become, so a smaller radius enhances smaller-scale detail. Higher radius values can cause halos at the edges, a detectable faint light rim around objects. Fine detail needs a smaller radius. Radius and amount interact; reducing one allows more of the other.</li> <li>Threshold controls the minimal brightness change that will be sharpened or how far apart adjacent tonal values have to be before the filter does anything. This lack of action is important to prevent smooth areas from becoming speckled. The threshold setting can be used to sharpen more pronounced edges, while leaving subtler edges untouched. Low values should sharpen more because fewer areas are excluded. Higher threshold values exclude areas of lower contrast.</li></ul> <p>Various recommendations exist for starting values of these parameters,<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> and the meaning may differ between implementations. Generally a radius of 0.5 to 2 pixels and an amount of 50–150% is recommended. </p><p>It is also possible to implement USM manually, by creating a separate layer to act as the mask;<sup id="cite_ref-gimp_1-1" class="reference"><a href="#cite_note-gimp-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> this can be used to help understand how USM works or for fine customization. </p><p>The typical blending formula for unsharp masking is </p> <style data-mw-deduplicate="TemplateStyles:r996643573">.mw-parser-output .block-indent{padding-left:3em;padding-right:0;overflow:hidden}</style><div class="block-indent" style="padding-left: 1.5em;">sharpened = original + (original − blurred) × amount.</div> <div class="mw-heading mw-heading3"><h3 id="Local_contrast_enhancement">Local contrast enhancement</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Unsharp_masking&action=edit&section=3" title="Edit section: Local contrast enhancement"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Unsharp masking may also be used with a large radius and a small amount (such as 30–100 pixel radius and 5–20% amount<sup id="cite_ref-ciclce_3-0" class="reference"><a href="#cite_note-ciclce-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup>), which yields increased local contrast, a technique termed <i>local contrast enhancement</i>.<sup id="cite_ref-ciclce_3-1" class="reference"><a href="#cite_note-ciclce-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> USM can increase either sharpness or (local) contrast because these are both forms of increasing differences between values, increasing slope—sharpness referring to very small-scale (high-frequency) differences, and contrast referring to larger-scale (low-frequency) differences. More powerful techniques for improving tonality are referred to as <a href="/wiki/Tone_mapping" title="Tone mapping">tone mapping</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Comparison_with_deconvolution">Comparison with deconvolution</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Unsharp_masking&action=edit&section=4" title="Edit section: Comparison with deconvolution"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .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-Unreferenced_section plainlinks metadata ambox ambox-content ambox-Unreferenced" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><a href="/wiki/File:Question_book-new.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" decoding="async" width="50" height="39" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/75px-Question_book-new.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" data-file-width="512" data-file-height="399" /></a></span></div></td><td class="mbox-text"><div class="mbox-text-span">This section <b>does not <a href="/wiki/Wikipedia:Citing_sources" title="Wikipedia:Citing sources">cite</a> any <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">sources</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/Unsharp_masking" title="Special:EditPage/Unsharp masking">improve this section</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 <a href="/wiki/Wikipedia:Verifiability#Burden_of_evidence" title="Wikipedia:Verifiability">removed</a>.</span> <span class="date-container"><i>(<span class="date">December 2017</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> <p>For image processing, <a href="/wiki/Deconvolution" title="Deconvolution">deconvolution</a> is the process of approximately inverting the process that caused an image to be blurred. Specifically, unsharp masking is a simple linear image operation—a <a href="/wiki/Convolution" title="Convolution">convolution</a> by a <a href="/wiki/Kernel_(image_processing)" title="Kernel (image processing)">kernel</a> that is the <a href="/wiki/Dirac_delta" class="mw-redirect" title="Dirac delta">Dirac delta</a> minus a gaussian blur kernel. Deconvolution, on the other hand, is generally considered an <a href="/wiki/Ill-posed" class="mw-redirect" title="Ill-posed">ill-posed</a> <a href="/wiki/Inverse_problem" title="Inverse problem">inverse problem</a> that is best solved by nonlinear approaches. While unsharp masking increases the apparent sharpness of an image in ignorance of the manner in which the image was acquired, deconvolution increases the apparent sharpness of an image, but is based on information describing some of the likely origins of the distortions of the light path used in capturing the image; it may therefore sometimes be preferred, where the cost in preparation time and per-image computation time are offset by the increase in image clarity. </p><p>With deconvolution, "lost" image detail may be approximately recovered, although it generally is impossible to verify that any recovered detail is accurate. Statistically, some level of correspondence between the sharpened images and the actual scenes being imaged can be attained. If the scenes to be captured in the future are similar enough to validated image scenes, then one can assess the degree to which recovered detail may be accurate. The improvement to image quality is often attractive, since the same validation issues are present even for un-enhanced images. </p><p>For deconvolution to be effective, all variables in the image scene and capturing device need to be modeled, including <a href="/wiki/Aperture" title="Aperture">aperture</a>, <a href="/wiki/Focal_length" title="Focal length">focal length</a>, distance to subject, lens, and media <a href="/wiki/Refractive_index" title="Refractive index">refractive indices</a> and geometries. Applying deconvolution successfully to general-purpose camera images is usually not feasible, because the geometries of the scene are not set. However, deconvolution is applied in reality to microscopy and astronomical imaging, where the value of gained sharpness is high, imaging devices and the relative subject positions are both well defined, and optimization of the imaging devices to improve sharpness physically would cost significantly more. In cases where a stable, well-defined aberration is present, such as the lens defect in early <a href="/wiki/Hubble_Space_Telescope" title="Hubble Space Telescope">Hubble Space Telescope</a> images, <a href="/wiki/Deconvolution" title="Deconvolution">deconvolution</a> is an especially effective technique. </p> <div class="mw-heading mw-heading2"><h2 id="Implementation">Implementation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Unsharp_masking&action=edit&section=5" title="Edit section: Implementation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In the example below, the image is convolved with the following sharpening filter: </p><p><b>Sharpen filter</b> <span class="mwe-math-element"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\begin{bmatrix}\ \ 0&-1&\ \ 0\\-1&\ \ 5&-1\\\ \ 0&-1&\ \ 0\end{bmatrix}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mrow> <mo>[</mo> <mtable rowspacing="4pt" columnspacing="1em"> <mtr> <mtd> <mtext> </mtext> <mtext> </mtext> <mn>0</mn> </mtd> <mtd> <mo>−</mo> <mn>1</mn> </mtd> <mtd> <mtext> </mtext> <mtext> </mtext> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mo>−</mo> <mn>1</mn> </mtd> <mtd> <mtext> </mtext> <mtext> </mtext> <mn>5</mn> </mtd> <mtd> <mo>−</mo> <mn>1</mn> </mtd> </mtr> <mtr> <mtd> <mtext> </mtext> <mtext> </mtext> <mn>0</mn> </mtd> <mtd> <mo>−</mo> <mn>1</mn> </mtd> <mtd> <mtext> </mtext> <mtext> </mtext> <mn>0</mn> </mtd> </mtr> </mtable> <mo>]</mo> </mrow> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\begin{bmatrix}\ \ 0&-1&\ \ 0\\-1&\ \ 5&-1\\\ \ 0&-1&\ \ 0\end{bmatrix}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/beb8b9a493e8b9cf5deccd61bd845a59ea2e62cc" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -4.005ex; width:17.409ex; height:9.176ex;" alt="{\displaystyle {\begin{bmatrix}\ \ 0&-1&\ \ 0\\-1&\ \ 5&-1\\\ \ 0&-1&\ \ 0\end{bmatrix}}}"></span> </p><p>This matrix is obtained using the equation shown above under <a href="#Digital_unsharp_masking">#Digital unsharp masking</a>, using a uniform kernel with 5 pixels for the "blurred" image, and 5 for the "amount" multiplier: </p><p><span class="mwe-math-element"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\begin{bmatrix}0&0&0\\0&1&0\\0&0&0\end{bmatrix}}+\left({\begin{bmatrix}0&0&0\\0&1&0\\0&0&0\end{bmatrix}}-{\begin{bmatrix}0&1&0\\1&1&1\\0&1&0\end{bmatrix}}/5\right)5={\begin{bmatrix}\ \ 0&-1&\ \ 0\\-1&\ \ 5&-1\\\ \ 0&-1&\ \ 0\end{bmatrix}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mrow> <mo>[</mo> <mtable rowspacing="4pt" columnspacing="1em"> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>1</mn> </mtd> <mtd> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> </mtd> </mtr> </mtable> <mo>]</mo> </mrow> </mrow> <mo>+</mo> <mrow> <mo>(</mo> <mrow> <mrow class="MJX-TeXAtom-ORD"> <mrow> <mo>[</mo> <mtable rowspacing="4pt" columnspacing="1em"> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>1</mn> </mtd> <mtd> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> </mtd> <mtd> <mn>0</mn> </mtd> </mtr> </mtable> <mo>]</mo> </mrow> </mrow> <mo>−</mo> <mrow class="MJX-TeXAtom-ORD"> <mrow> <mo>[</mo> <mtable rowspacing="4pt" columnspacing="1em"> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>1</mn> </mtd> <mtd> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mn>1</mn> </mtd> <mtd> <mn>1</mn> </mtd> <mtd> <mn>1</mn> </mtd> </mtr> <mtr> <mtd> <mn>0</mn> </mtd> <mtd> <mn>1</mn> </mtd> <mtd> <mn>0</mn> </mtd> </mtr> </mtable> <mo>]</mo> </mrow> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mo>/</mo> </mrow> <mn>5</mn> </mrow> <mo>)</mo> </mrow> <mn>5</mn> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mrow> <mo>[</mo> <mtable rowspacing="4pt" columnspacing="1em"> <mtr> <mtd> <mtext> </mtext> <mtext> </mtext> <mn>0</mn> </mtd> <mtd> <mo>−</mo> <mn>1</mn> </mtd> <mtd> <mtext> </mtext> <mtext> </mtext> <mn>0</mn> </mtd> </mtr> <mtr> <mtd> <mo>−</mo> <mn>1</mn> </mtd> <mtd> <mtext> </mtext> <mtext> </mtext> <mn>5</mn> </mtd> <mtd> <mo>−</mo> <mn>1</mn> </mtd> </mtr> <mtr> <mtd> <mtext> </mtext> <mtext> </mtext> <mn>0</mn> </mtd> <mtd> <mo>−</mo> <mn>1</mn> </mtd> <mtd> <mtext> </mtext> <mtext> </mtext> <mn>0</mn> </mtd> </mtr> </mtable> <mo>]</mo> </mrow> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\begin{bmatrix}0&0&0\\0&1&0\\0&0&0\end{bmatrix}}+\left({\begin{bmatrix}0&0&0\\0&1&0\\0&0&0\end{bmatrix}}-{\begin{bmatrix}0&1&0\\1&1&1\\0&1&0\end{bmatrix}}/5\right)5={\begin{bmatrix}\ \ 0&-1&\ \ 0\\-1&\ \ 5&-1\\\ \ 0&-1&\ \ 0\end{bmatrix}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e2c62dcc8ceafd14d261fad619e065f4230b5dc9" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -4.005ex; width:70.084ex; height:9.176ex;" alt="{\displaystyle {\begin{bmatrix}0&0&0\\0&1&0\\0&0&0\end{bmatrix}}+\left({\begin{bmatrix}0&0&0\\0&1&0\\0&0&0\end{bmatrix}}-{\begin{bmatrix}0&1&0\\1&1&1\\0&1&0\end{bmatrix}}/5\right)5={\begin{bmatrix}\ \ 0&-1&\ \ 0\\-1&\ \ 5&-1\\\ \ 0&-1&\ \ 0\end{bmatrix}}}"></span> </p><p>The sharpening effect can be controlled by varying the multiplier. The value of 5 was chosen here to yield a kernel with integer values, but this is not a requirement for the operation. </p> <ul class="gallery mw-gallery-traditional" style="max-width: 886px;"> <li class="gallerybox" style="width: 435px"> <div class="thumb" style="width: 430px; height: 293px;"><span typeof="mw:File"><a href="/wiki/File:SharpenCarExample.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5e/SharpenCarExample.png/400px-SharpenCarExample.png" decoding="async" width="400" height="263" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/5e/SharpenCarExample.png/600px-SharpenCarExample.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/5e/SharpenCarExample.png/800px-SharpenCarExample.png 2x" data-file-width="1504" data-file-height="987" /></a></span></div> <div class="gallerytext"></div> </li> <li class="gallerybox" style="width: 435px"> <div class="thumb" style="width: 430px; height: 293px;"><span typeof="mw:File"><a href="/wiki/File:SharpenCarExample2.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/23/SharpenCarExample2.png/398px-SharpenCarExample2.png" decoding="async" width="398" height="263" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/23/SharpenCarExample2.png/597px-SharpenCarExample2.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/23/SharpenCarExample2.png/795px-SharpenCarExample2.png 2x" data-file-width="1506" data-file-height="997" /></a></span></div> <div class="gallerytext"></div> </li> </ul> <p>The second image has been sharpened twice as much as the first. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Unsharp_masking&action=edit&section=6" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Edge_enhancement" title="Edge enhancement">Edge enhancement</a></li> <li><a href="/wiki/Cornsweet_illusion" title="Cornsweet illusion">Cornsweet illusion</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Unsharp_masking&action=edit&section=7" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <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-gimp-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-gimp_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-gimp_1-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://docs.gimp.org/2.10/en/gimp-filter-unsharp-mask.html">4.9. Unsharp Mask</a>, esp. 4.9.4. How does an unsharp mask work?, Gimp documentation.</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"><a rel="nofollow" class="external text" href="http://www.cambridgeincolour.com/techniques/image-sharpening.htm">Guide to Image Sharpening</a>, Cambridge in Color.</span> </li> <li id="cite_note-ciclce-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-ciclce_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-ciclce_3-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://www.cambridgeincolour.com/techniques/local-contrast-enhancement.htm">Local Contrast Enhancement</a>, Cambridge in Color.</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"><a rel="nofollow" class="external text" href="http://www.luminous-landscape.com/tutorials/contrast-enhancement.shtml">Understanding Local Contrast Enhancement</a>, The Luminous Landscape.</span> </li> </ol></div></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1251242444"><table class="box-More_citations_needed plainlinks metadata ambox ambox-content ambox-Refimprove" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><a href="/wiki/File:Question_book-new.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" decoding="async" width="50" height="39" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/75px-Question_book-new.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" data-file-width="512" data-file-height="399" /></a></span></div></td><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/Unsharp_masking" title="Special:EditPage/Unsharp masking">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=%22Unsharp+masking%22">"Unsharp masking"</a> – <a rel="nofollow" class="external text" href="https://www.google.com/search?tbm=nws&q=%22Unsharp+masking%22+-wikipedia&tbs=ar:1">news</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?&q=%22Unsharp+masking%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=%22Unsharp+masking%22+-wikipedia">books</a> <b>·</b> <a rel="nofollow" class="external text" href="https://scholar.google.com/scholar?q=%22Unsharp+masking%22">scholar</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.jstor.org/action/doBasicSearch?Query=%22Unsharp+masking%22&acc=on&wc=on">JSTOR</a></span></small></span> <span class="date-container"><i>(<span class="date">May 2010</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:r1239549316">.mw-parser-output .refbegin{margin-bottom:0.5em}.mw-parser-output .refbegin-hanging-indents>ul{margin-left:0}.mw-parser-output .refbegin-hanging-indents>ul>li{margin-left:0;padding-left:3.2em;text-indent:-3.2em}.mw-parser-output .refbegin-hanging-indents ul,.mw-parser-output .refbegin-hanging-indents ul li{list-style:none}@media(max-width:720px){.mw-parser-output .refbegin-hanging-indents>ul>li{padding-left:1.6em;text-indent:-1.6em}}.mw-parser-output .refbegin-columns{margin-top:0.3em}.mw-parser-output .refbegin-columns ul{margin-top:0}.mw-parser-output .refbegin-columns li{page-break-inside:avoid;break-inside:avoid-column}@media screen{.mw-parser-output .refbegin{font-size:90%}}</style><div class="refbegin" style=""> <div class="mw-heading mw-heading2"><h2 id="General_references">General references</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Unsharp_masking&action=edit&section=8" title="Edit section: General references"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="http://www.ledet.com/margulis/Makeready/MA27-Sharpening_With_Stiletto.pdf">Sharpening With a Stiletto</a>, <a href="/wiki/Dan_Margulis" title="Dan Margulis">Dan Margulis</a>, February, 1998</li> <li><a rel="nofollow" class="external text" href="http://www.ledet.com/margulis/Makeready/MA69-Life_on_the_Edge.pdf">Life on the Edge</a>, <a href="/wiki/Dan_Margulis" title="Dan Margulis">Dan Margulis</a>, January, 2005</li></ul> </div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Unsharp_masking&action=edit&section=9" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>Excel spreadsheet that calculates an <a rel="nofollow" class="external text" href="https://rlatour.com/av4w/help/help_1_4_1_0.html#MaskSpreadsheet">Unsharp Mask</a></li> <li><a rel="nofollow" class="external text" href="https://micro.magnet.fsu.edu/primer/java/digitalimaging/processing/unsharpmask/index.html">Interactive Example of Unsharp Mask</a></li> <li><a rel="nofollow" class="external text" href="http://www.pixelgenius.com/sharpener/manual.html">PhotoKit Sharpener User Guide</a></li> <li><a rel="nofollow" class="external text" href="http://cschu.redirectme.net/mirrored/bythom/www.bythom.com/sharpening.htm">Sharpening 101</a>, mirror of <a rel="nofollow" class="external text" href="http://www.bythom.com/">by thom</a>, Aug 1, 2003</li> <li><a rel="nofollow" class="external text" href="http://stanstudio.com/Boston_Photo_Blog/the-unsharp-mask-analog-photoshop">The Unsharp Mask: Analog Photoshop</a>, Sample of unsharp masking in the darkroom, before digital</li></ul>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; 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