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#1
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Best Image -- Image Size vs Compression
I use a slide show package that will display images at full screen,
regardless of the size/resolution that the monitor is set at. Since the slide shows, which are run from a CD, contain many images, there is a need to keep the image file sizes below 600KB or so. The images are edited in PS, and stored using PS's jpg save. PS can save jpgs at MAX (levels 10, 11, and 12) or HIGH (7, 8, or 9). What I am seeking is to get the most sharpness in the images while keeping the file sizes below 600KB. The trade-off I am looking at is a larger image at higher compression, or slightly smaller image at lower compression. On my test image I came up with the following combinations that fall within my desired file size range: 1200 at 10 437KB 1000 at 11 476KB 800 at 12 494KB 1100 at 11 572KB where, for example, 1200 is size of longest side, and 10 is PS compression setting In closely examining the images on the screen, it appeared to me that the 1100 @ 11 was the best, while the 800 @ 12 was the least sharp. Is there some known truth about size vs compression in terms of jpg quality, or does one simply arrive at some general truth by this kind of testing. Does anyone have any alternatives to recommend? Thanks in advance. |
#2
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Best Image -- Image Size vs Compression
john chapman wrote:
I use a slide show package that will display images at full screen, regardless of the size/resolution that the monitor is set at. Since the slide shows, which are run from a CD, contain many images, there is a need to keep the image file sizes below 600KB or so. The images are edited in PS, and stored using PS's jpg save. PS can save jpgs at MAX (levels 10, 11, and 12) or HIGH (7, 8, or 9). What I am seeking is to get the most sharpness in the images while keeping the file sizes below 600KB. The trade-off I am looking at is a larger image at higher compression, or slightly smaller image at lower compression. On my test image I came up with the following combinations that fall within my desired file size range: 1200 at 10 437KB 1000 at 11 476KB 800 at 12 494KB 1100 at 11 572KB where, for example, 1200 is size of longest side, and 10 is PS compression setting In closely examining the images on the screen, it appeared to me that the 1100 @ 11 was the best, while the 800 @ 12 was the least sharp. Is there some known truth about size vs compression in terms of jpg quality, or does one simply arrive at some general truth by this kind of testing. Does anyone have any alternatives to recommend? Thanks in advance. You will find that compression ratios are strongly dependent on the actual image data. Try compressing a picture with a lot of grass and trees and you will see the effect. Unfortunately, there is no answer that will work for all pictures. You will just about have to do each one on its own merits to get the best results. Frankly, I would match the compression to the original image size, and compress less if the picture is filled with complex shapes, such as grass and trees, and more if it is large areas of color. You may see more artifacts, but they will be less distracting. |
#3
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Best Image -- Image Size vs Compression
john chapman wrote:
I use a slide show package that will display images at full screen, regardless of the size/resolution that the monitor is set at. Since the slide shows, which are run from a CD, contain many images, there is a need to keep the image file sizes below 600KB or so. The images are edited in PS, and stored using PS's jpg save. PS can save jpgs at MAX (levels 10, 11, and 12) or HIGH (7, 8, or 9). What I am seeking is to get the most sharpness in the images while keeping the file sizes below 600KB. The trade-off I am looking at is a larger image at higher compression, or slightly smaller image at lower compression. On my test image I came up with the following combinations that fall within my desired file size range: 1200 at 10 437KB 1000 at 11 476KB 800 at 12 494KB 1100 at 11 572KB where, for example, 1200 is size of longest side, and 10 is PS compression setting In closely examining the images on the screen, it appeared to me that the 1100 @ 11 was the best, while the 800 @ 12 was the least sharp. Is there some known truth about size vs compression in terms of jpg quality, or does one simply arrive at some general truth by this kind of testing. Does anyone have any alternatives to recommend? Thanks in advance. You will find that compression ratios are strongly dependent on the actual image data. Try compressing a picture with a lot of grass and trees and you will see the effect. Unfortunately, there is no answer that will work for all pictures. You will just about have to do each one on its own merits to get the best results. Frankly, I would match the compression to the original image size, and compress less if the picture is filled with complex shapes, such as grass and trees, and more if it is large areas of color. You may see more artifacts, but they will be less distracting. |
#4
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Best Image -- Image Size vs Compression
In message , john
chapman writes I use a slide show package that will display images at full screen, regardless of the size/resolution that the monitor is set at. Since the slide shows, which are run from a CD, contain many images, there is a need to keep the image file sizes below 600KB or so. The images are edited in PS, and stored using PS's jpg save. PS can save jpgs at MAX (levels 10, 11, and 12) or HIGH (7, 8, or 9). What I am seeking is to get the most sharpness in the images while keeping the file sizes below 600KB. The trade-off I am looking at is a larger image at higher compression, or slightly smaller image at lower compression. On my test image I came up with the following combinations that fall within my desired file size range: 1200 at 10 437KB 1000 at 11 476KB 800 at 12 494KB 1100 at 11 572KB where, for example, 1200 is size of longest side, and 10 is PS compression setting A single test image will lead you seriously astray unless by chance you happened to have picked an unusually representative one. Do the test on a directory of about 100 images and you will get a better idea of how the size quality trade off works with a range of images. The ones to inspect really carefully are a couple of typical ones and the two with the most extreme smallest and largest file sizes after compression. In closely examining the images on the screen, it appeared to me that the 1100 @ 11 was the best, while the 800 @ 12 was the least sharp. Is there some known truth about size vs compression in terms of jpg quality, or does one simply arrive at some general truth by this kind of testing. You would be well advised to chose a size that is nicely commensurate with typical screen sizes of 800x600, 1024x768, 1280x960, 1440x1080, 1600x1200. Some display drivers can be relied upon to make a hash of displaying an image full screen with unusual sizes like e.g. 1100x825. Does anyone have any alternatives to recommend? Thanks in advance. You would have a lot more control of the compression settings with something based on the JIG codec. IrfanView springs to mind as reasonable quality free software with excellent batch rescaling and JPEG encoding functions. In addition it will not store a small essay on PhotoShop and various assorted colour management dross which will probably save you around 50kb per file. Regards, -- Martin Brown |
#5
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Best Image -- Image Size vs Compression
In message , john
chapman writes I use a slide show package that will display images at full screen, regardless of the size/resolution that the monitor is set at. Since the slide shows, which are run from a CD, contain many images, there is a need to keep the image file sizes below 600KB or so. The images are edited in PS, and stored using PS's jpg save. PS can save jpgs at MAX (levels 10, 11, and 12) or HIGH (7, 8, or 9). What I am seeking is to get the most sharpness in the images while keeping the file sizes below 600KB. The trade-off I am looking at is a larger image at higher compression, or slightly smaller image at lower compression. On my test image I came up with the following combinations that fall within my desired file size range: 1200 at 10 437KB 1000 at 11 476KB 800 at 12 494KB 1100 at 11 572KB where, for example, 1200 is size of longest side, and 10 is PS compression setting A single test image will lead you seriously astray unless by chance you happened to have picked an unusually representative one. Do the test on a directory of about 100 images and you will get a better idea of how the size quality trade off works with a range of images. The ones to inspect really carefully are a couple of typical ones and the two with the most extreme smallest and largest file sizes after compression. In closely examining the images on the screen, it appeared to me that the 1100 @ 11 was the best, while the 800 @ 12 was the least sharp. Is there some known truth about size vs compression in terms of jpg quality, or does one simply arrive at some general truth by this kind of testing. You would be well advised to chose a size that is nicely commensurate with typical screen sizes of 800x600, 1024x768, 1280x960, 1440x1080, 1600x1200. Some display drivers can be relied upon to make a hash of displaying an image full screen with unusual sizes like e.g. 1100x825. Does anyone have any alternatives to recommend? Thanks in advance. You would have a lot more control of the compression settings with something based on the JIG codec. IrfanView springs to mind as reasonable quality free software with excellent batch rescaling and JPEG encoding functions. In addition it will not store a small essay on PhotoShop and various assorted colour management dross which will probably save you around 50kb per file. Regards, -- Martin Brown |
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Best Image -- Image Size vs Compression
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Best Image -- Image Size vs Compression
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#8
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Best Image -- Image Size vs Compression
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#9
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Best Image -- Image Size vs Compression
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