There is therefore no global setting you can use, if you want files of a certain size you have to tune the quality for each image.Īlternatively you might want to use a higher setting for images with more fine detail (or noise - noise doesn't compress well so can result in more artifacts). Therefore quality merely determines what proportion of image information will be lost, if an image that contains more information to begin with (in terms of high frequency details) you will get a larger JPEG file even with the same quality settings. The important thing to note is that there is no direct correspondence between "quality" and final size. Without going into too much detail this determines the degree to which the frequencies contained in an image are approximated to achieve compression. The "quality" parameter determines the quantization matrix used to compress the data. Different classes of images will regularly fall into certain JPEG compression levels (the site linked above can help learning what fall where).so it can quickly become second nature to know what compression level to use when saving various images for the web.ĭisks are still pretty cheap these days so there are advantages to JPEG files, even if they are as big as the original RAW, instant image preview, being able to display on computers without RAW software. When saving for web, compress as much as you can without introducing visible compression artifacts. as a wallpaper for a 30" 2560x1600 screen), there is no reason not to use the best quality setting available. You can clearly see, by observing each image at each compression level, why a higher setting such as 90-100 may be required in some cases, and a lower setting such as 40-60 is entirely acceptable for others.Īs a side note, if you are saving a JPEG for any kind of print purpose, or for viewing on-screen at a large size (i.e. This site demonstrates JPEG compression from the lowest to highest settings in discrete ranges for a series of sample images of differing content. There is no single "best" JPEG compression setting, and depending on the type and complexity of detail (or lack of complexity and detail), you may find yourself using 40-60, 70-80, or 90-100 as appropriate for the photo(s) you are exporting.Īn excellent visual resource for how JPEG compression affects IQ can be found here:Īn Analysis of Lightroom JPEG Export Quality Settings An image that contains nothing but complex detail could probably get away with a quality setting of 50-60, possibly even lower. An image of a smooth blue sky or a sunset sky with large areas of orange gradient should probably use a high quality setting, 90-100. The quality level one should choose when exporting an image to JPEG is highly dependent upon the kind of detail contained within the image. The amount of JPEG compression should really depend on the usage purpose for the JPEG, and the contents of the JPEG. To be frank, it is entirely anecdotal that a JPEG image should be exported at a certain compression level all the time.
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