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==Improve Photos with digiKam’s Local Contrast Tool==

This originally appeared as a blog in [http://scribblesandsnaps.wordpress.com/category/software/open-source/ Scribbles and Snaps] and is reproduced by permission of Dmitri Popov.

'''digiKam''' offers several features that can improve photos containing under- or overexposed areas. For example, the [[Special:myLanguage/Digikam/Exposure_Blending| Exposure Blending]] tool lets you merge multiple shots with different exposures into one perfectly exposed photo. But what if you have just a single image? In this case, you might want to give the <menuchoice>Local Contrast</menuchoice> feature a try. It’s based on the [http://zynaddsubfx.sourceforge.net/other/tonemapping/ LDR Tonemapping utility] which is designed to improve the dynamic range of the photo by reducing its global contrast and increasing the local contrast. It does so by generating a desaturated and blurred version of the photo. It then combines the RGB channels of the original photo with the desaturated blurred image using either the <menuchoice>Linear</menuchoice> or <menuchoice>Power</menuchoice> function. Sounds complicated? Don’t worry, the <menuchoice>Local Contrast</menuchoice> tool is rather straightforward to use, so you don’t have to understand all its intricacies in order to achieve pleasing results.

[[Image:Digikam_localcontrast.png|thumb|300px|center|Copyright Dmitri Popov]]

Open the photo you want in the editor and choose <menuchoice>Enhance</menuchoice> -> <menuchoice>Local Contrast</menuchoice>. The tool lets you apply up to four tonemapping operations called ''stages''. Each stage offers two parameters for you to tweak: <menuchoice>Power</menuchoice> and <menuchoice>Blur</menuchoice>. The former allows you to specify the desaturation level, while the latter lets you adjust the affected areas on the photo. To preview the result, hit the <menuchoice>Try</menuchoice> button. Once you are satisfied with the result, press <keycap>OK</keycap> to apply the process to the photo.

While the <menuchoice>Local Constrast</menuchoice> tool may sound like an easy way to fix photos, you should use it with care: sometimes it can do more damage than good, producing unnaturally looking photos.

[[Category:Graphics]]
[[Category:Photography]]
[[Category:Tutorials]]