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#1
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best compression for saving photos in jpeg?
What is the best compression (1 - 100%) to use when saving a scanned
colour photo in jpeg? I was to be able to display the photo on the computer screen and also be able to print the saved photo on a inkjet printer. If I have very little compression then the saved photo file size is too big in size. Is there a general rule I can use to decide the best compression to use? Regards Brian |
#2
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On Thu, 23 Dec 2004 01:51:56 +1300, Brian wrote:
What is the best compression (1 - 100%) to use when saving a scanned colour photo in jpeg? I was to be able to display the photo on the computer screen and also be able to print the saved photo on a inkjet printer. If I have very little compression then the saved photo file size is too big in size. Is there a general rule I can use to decide the best compression to use? 0% .. :-) jpg being a "lossy" compression every compression factor applied will degrade picture quality ... so you will have to balance between picture size and stored/needed/expected quality .. (Paintshop pro 9 has a nice (save_as/optimizer) feature that will show you picture deterioration versus compression factor applied ... ) FWIW |
#3
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Brian wrote:
What is the best compression (1 - 100%) to use when saving a scanned colour photo in jpeg? I was to be able to display the photo on the computer screen and also be able to print the saved photo on a inkjet printer. If I have very little compression then the saved photo file size is too big in size. Is there a general rule I can use to decide the best compression to use? You need to determine this for yourself - what is acceptable to one person may not be to another. Printing is likely to require a higher quality of image than display on the computer screen (as the screen is limited to about 1MP and your scan is likely to be more than that). You also need to be sure that you are scanning to a sufficient number of pixels per inch. David |
#4
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I tend to use:
For best quality printing or editting later 1 to 5% (assuming you need to save space and do not want to use TIFF etc) For viewing on PC or 'general' printing 10% For internet 15 to 25 % "Brian" wrote in message ... What is the best compression (1 - 100%) to use when saving a scanned colour photo in jpeg? I was to be able to display the photo on the computer screen and also be able to print the saved photo on a inkjet printer. If I have very little compression then the saved photo file size is too big in size. Is there a general rule I can use to decide the best compression to use? Regards Brian |
#5
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Brian writes:
What is the best compression (1 - 100%) to use when saving a scanned colour photo in jpeg? It sounds like the compression factor in the program you're using is reversed from the -quality switch in the cjpeg program I use, so switch 0% and 100% in the information below, from cjpeg's manual page. I personally find quality 75 to work well even with photos that have lots of high-contrast transitions. The -quality switch lets you trade off compressed file size against quality of the reconstructed image: the higher the quality setting, the larger the JPEG file, and the closer the output image will be to the original input. Normally you want to use the lowest quality setting (smallest file) that decompresses into something visually indistin- guishable from the original image. For this purpose the quality set- ting should be between 50 and 95; the default of 75 is often about right. If you see defects at -quality 75, then go up 5 or 10 counts at a time until you are happy with the output image. (The optimal setting will vary from one image to another.) -quality 100 will generate a quantization table of all 1's, minimizing loss in the quantization step (but there is still information loss in subsampling, as well as roundoff error). This setting is mainly of interest for experimental purposes. Quality values above about 95 are not recommended for normal use; the compressed file size goes up dra- matically for hardly any gain in output image quality. In the other direction, quality values below 50 will produce very small files of low image quality. Settings around 5 to 10 might be useful in preparing an index of a large image library, for example. Try -quality 2 (or so) for some amusing Cubist effects. (Note: quality values below about 25 generate 2-byte quantization tables, which are considered optional in the JPEG standard. cjpeg emits a warning message when you give such a quality value, because some other JPEG programs may be unable to decode the resulting file. Use -baseline if you need to ensure compatibility at low quality values.) -- http://ourdoings.com/ Let your digital photos organize themselves. Sign up today for a 7-day free trial. |
#6
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My figures are from PSP where 1 is highest quality and goes down to 100
which is highest compression. "dylan" wrote in message ... I tend to use: For best quality printing or editting later 1 to 5% (assuming you need to save space and do not want to use TIFF etc) For viewing on PC or 'general' printing 10% For internet 15 to 25 % "Brian" wrote in message ... What is the best compression (1 - 100%) to use when saving a scanned colour photo in jpeg? I was to be able to display the photo on the computer screen and also be able to print the saved photo on a inkjet printer. If I have very little compression then the saved photo file size is too big in size. Is there a general rule I can use to decide the best compression to use? Regards Brian |
#7
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"Brian" wrote in message ... What is the best compression (1 - 100%) to use when saving a scanned colour photo in jpeg? "Best" with respect to what? "Best quality" = least amount of compression "Best size" = most amount of compression. Most people select a medium compression value, and that might be OK for you provided that you do not edit the image very many times. Jim |
#8
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Brian wrote:
What is the best compression (1 - 100%) to use when saving a scanned colour photo in jpeg? I was to be able to display the photo on the computer screen and also be able to print the saved photo on a inkjet printer. If I have very little compression then the saved photo file size is too big in size. Is there a general rule I can use to decide the best compression to use? Regards Brian Use the minimum compression that will give you the file size you need for your purpose. The more you compress, the more data you lose. Always save the original. Remember, HD space is something like $.50US a gigabyte these days, so adding HD space is a pretty cheap alternative. -- Ron Hunter |
#9
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"Ron Hunter" schrieb
Brian wrote: What is the best compression (1 - 100%) to use when saving a scanned colour photo in jpeg? Use the minimum compression that will give you the file size you need for your purpose. The more you compress, the more data you lose. Always save the original. Remember, HD space is something like $.50US a gigabyte these days, so adding HD space is a pretty cheap alternative. I can second that. And 95% quality level really gives you the optimal value to start with. A 100% doesn't scale to the gain you get for quality and everything less is covered by the 50 cent/GB (nice value BTW ) -- Regards Jürgen http://cpicture.de/en |
#10
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"Ron Hunter" schrieb
Brian wrote: What is the best compression (1 - 100%) to use when saving a scanned colour photo in jpeg? Use the minimum compression that will give you the file size you need for your purpose. The more you compress, the more data you lose. Always save the original. Remember, HD space is something like $.50US a gigabyte these days, so adding HD space is a pretty cheap alternative. I can second that. And 95% quality level really gives you the optimal value to start with. A 100% doesn't scale to the gain you get for quality and everything less is covered by the 50 cent/GB (nice value BTW ) -- Regards Jürgen http://cpicture.de/en |
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