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#21
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rafe b wrote:
. . . . . . I keep tabs on eBay auctions of drum scanners, hoping to find one selling at a decent price and within driving distance. For some odd reason I can't bring myself to buy an Epson 4990. The Microtek (for which I paid $1K) just wasn't up to the job. A good source for used drum scanners and service: http://genesis-equipment.com They have a few Howtek models at reasonable prices. The downside of many older drum scanners is a lack of modern software. That can mean a need to run a dedicated older computer and OS just for scanning. Ciao! Gordon Moat A G Studio http://www.allgstudio.com |
#22
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On Wed, 07 Dec 2005 13:10:07 -0800, Gordon Moat
wrote: Perhaps if you read a bit closer to what I stated; I don't print from JPEGs, and my concern with image files is their printing quality. Obviously, storing TIFF files would take up a huge amount of space, and is not practical for websites. The JPEG algorithm also functions with a sharpening effect, even at the least compressed settings. I stand by what I stated: "a JPEG is a poor way to judge how a printed item will turn out". That has nothing to do with "fear", and I highly disagree in your assertion that my "concerns" are "unfounded". If you want to believe otherwise, you are entitled to your opinion. Hmm.. Your words we "I have been mostly opposed to these internet challenges mostly due to the degradation of images by posting and viewing JPEGs." That's the statement I was refering to. Also, you're dead wrong about sharpening being implicit in "the JPG algorithm." My contention is that, in a fair test, you would not be able to distinguish between the same image as TIF vs. high- quality (low-compression) JPG. Whether you view it on screen or print it -- makes no difference. rafe b www.terrapinphoto.com |
#23
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rafe b wrote: On Wed, 07 Dec 2005 13:10:07 -0800, Gordon Moat wrote: Perhaps if you read a bit closer to what I stated; I don't print from JPEGs, and my concern with image files is their printing quality. Obviously, storing TIFF files would take up a huge amount of space, and is not practical for websites. The JPEG algorithm also functions with a sharpening effect, even at the least compressed settings. I stand by what I stated: "a JPEG is a poor way to judge how a printed item will turn out". That has nothing to do with "fear", and I highly disagree in your assertion that my "concerns" are "unfounded". If you want to believe otherwise, you are entitled to your opinion. Hmm.. Your words we "I have been mostly opposed to these internet challenges mostly due to the degradation of images by posting and viewing JPEGs." That's the statement I was refering to. Also, you're dead wrong about sharpening being implicit in "the JPG algorithm." My contention is that, in a fair test, you would not be able to distinguish between the same image as TIF vs. high- quality (low-compression) JPG. Whether you view it on screen or print it -- makes no difference. rafe b www.terrapinphoto.com rafe is right and here are the images to back it up. These are down sampled to get a good clean image. http://www.sewcon.com/temp/DSC02676%20sized.tif http://www.sewcon.com/temp/DSC02676%20sized.jpg jpeg does no shapening. Scott |
#24
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In article .com,
"Scott W" wrote: rafe is right and here are the images to back it up. These are down sampled to get a good clean image. http://www.sewcon.com/temp/DSC02676%20sized.tif http://www.sewcon.com/temp/DSC02676%20sized.jpg jpeg does no shapening. Scott What you and perhaps Rafe are failing to see is that Gordon works with offset printers, and clients that send cheap low res jpegs they pull out of their yin yang to save actually hiring someone to re shoot and supply the printer with a respectable size file. The problem with jpegs are that you can't manipulate them to a great extent and so therefore once in the hands of a print shop where they may need to be adjusted for the requirements of the specific device, they become a problem, do to that nature. ....that is the more they are opened the quicker they degrade for printing purposes, yes they may look fine but in print they will suck. You can perhaps get away with giving people clients lower res jpegs or and its all well and good until they need a bigger file like a tif. So you can look at jpegs all you like on screen and state there's no issue but i believe your misinformed. -- "To announce that there must be no criticism of the President, or that we are to stand by the President, right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public."--Theodore Roosevelt, May 7, 1918 www.gregblankphoto(dot)com |
#25
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On Wed, 07 Dec 2005 22:39:56 -0500, Gregory Blank
wrote: What you and perhaps Rafe are failing to see is that Gordon works with offset printers, and clients that send cheap low res jpegs they pull out of their yin yang to save actually hiring someone to re shoot and supply the printer with a respectable size file. The problem with jpegs are that you can't manipulate them to a great extent and so therefore once in the hands of a print shop where they may need to be adjusted for the requirements of the specific device, they become a problem, do to that nature. ....that is the more they are opened the quicker they degrade for printing purposes, yes they may look fine but in print they will suck. You can perhaps get away with giving people clients lower res jpegs or and its all well and good until they need a bigger file like a tif. So you can look at jpegs all you like on screen and state there's no issue but i believe your misinformed. You are asking us to argue with a strawman. Gordon does not talk about multiple cycles of JPG encode/decode. Separate issue. Gordon's argument is that even *one* cycle of JPG encode/decode produces a result visibly inferior to TIF. And that is only the case when high levels of JPG compression are used. Furthermore, the context of our discussion is (to use Gordon's phrase) "these internet challenges" presumably, full-res film scan or digicam output, and the like (like the stuff on my scan snippets site, or Leigh Perry's site, which is the subject of the thread...) In all such cases, high-quality (low-compression) JPG settings are used. It's a silly thing to argue about, really, because it costs nothing but a bit of time to verify all this for one's self. rafe b www.terrapinphoto.com |
#26
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Gregory Blank wrote:
In article .com, "Scott W" wrote: rafe is right and here are the images to back it up. These are down sampled to get a good clean image. http://www.sewcon.com/temp/DSC02676%20sized.tif http://www.sewcon.com/temp/DSC02676%20sized.jpg jpeg does no shapening. Scott What you and perhaps Rafe are failing to see is that Gordon works with offset printers, and clients that send cheap low res jpegs they pull out of their yin yang to save actually hiring someone to re shoot and supply the printer with a respectable size file. The problem with jpegs are that you can't manipulate them to a great extent and so therefore once in the hands of a print shop where they may need to be adjusted for the requirements of the specific device, they become a problem, do to that nature. ....that is the more they are opened the quicker they degrade for printing purposes, yes they may look fine but in print they will suck. You can perhaps get away with giving people clients lower res jpegs or and its all well and good until they need a bigger file like a tif. So you can look at jpegs all you like on screen and state there's no issue but i believe your misinformed. -- So I have posted a tiff and jpeg, try to do any edit that you might do before printing that will show a difference between them. In fact they are are same to within one level, in other words in the noise. Scott |
#27
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Scott W wrote: Gregory Blank wrote: In article .com, "Scott W" wrote: rafe is right and here are the images to back it up. These are down sampled to get a good clean image. http://www.sewcon.com/temp/DSC02676%20sized.tif http://www.sewcon.com/temp/DSC02676%20sized.jpg jpeg does no shapening. Scott What you and perhaps Rafe are failing to see is that Gordon works with offset printers, and clients that send cheap low res jpegs they pull out of their yin yang to save actually hiring someone to re shoot and supply the printer with a respectable size file. The problem with jpegs are that you can't manipulate them to a great extent and so therefore once in the hands of a print shop where they may need to be adjusted for the requirements of the specific device, they become a problem, do to that nature. ....that is the more they are opened the quicker they degrade for printing purposes, yes they may look fine but in print they will suck. You can perhaps get away with giving people clients lower res jpegs or and its all well and good until they need a bigger file like a tif. So you can look at jpegs all you like on screen and state there's no issue but i believe your misinformed. -- So I have posted a tiff and jpeg, try to do any edit that you might do before printing that will show a difference between them. In fact they are are same to within one level, in other words in the noise. I've checked carefully and I do not see any difference in the detail. |
#28
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Scott W wrote:
rafe b wrote: On Wed, 07 Dec 2005 13:10:07 -0800, Gordon Moat wrote: Perhaps if you read a bit closer to what I stated; I don't print from JPEGs, and my concern with image files is their printing quality. Obviously, storing TIFF files would take up a huge amount of space, and is not practical for websites. The JPEG algorithm also functions with a sharpening effect, even at the least compressed settings. I stand by what I stated: "a JPEG is a poor way to judge how a printed item will turn out". That has nothing to do with "fear", and I highly disagree in your assertion that my "concerns" are "unfounded". If you want to believe otherwise, you are entitled to your opinion. Hmm.. Your words we "I have been mostly opposed to these internet challenges mostly due to the degradation of images by posting and viewing JPEGs." That's the statement I was refering to. Also, you're dead wrong about sharpening being implicit in "the JPG algorithm." My contention is that, in a fair test, you would not be able to distinguish between the same image as TIF vs. high- quality (low-compression) JPG. Whether you view it on screen or print it -- makes no difference. rafe b www.terrapinphoto.com rafe is right and here are the images to back it up. These are down sampled to get a good clean image. http://www.sewcon.com/temp/DSC02676%20sized.tif http://www.sewcon.com/temp/DSC02676%20sized.jpg jpeg does no shapening. Scott JPEG is a lossy compression algorithm. It functions by retaining more information in higher resolution areas, then compressing lower resolution areas. The effect is that contrast along high resolution edges can change. Very difficult to see this in smaller images, though it becomes more noticeable in larger images. This is different from sharpening as most consider it, though if you recall I stated it has the effect of sharpening. Follow this next paragraph for an example of this. Simple test for your two images. Take the JPEG, copy it, then paste it onto a layer above the JFax TIFF you provided. Then choose Difference as the layer blending. If they were exactly the same, the result would be completely black. If it looks that way, then zoom into the image to enlarge the view, and spots will be apparent. Next flatten the image to create one layer, which looks like the black spotted image. Then select ImageAdjustThreshold and type in "2" as the value. This will give you a field of white spots on a black background. If you view that at exactly 100% magnification, and compare to the originals, you will see the ghost image of the ship and rigging. Those spots represent the changed edge contrast near the high resolution parts. Okay, so lots of people here probably go "so what" or "who cares". If you only print inkjet or some of the newer LightJet, Chromira or similar digital/chemical processes, you should rarely see a problem, or much difference; the dot gain will usually mask any small aberrations. This also assumes you would only work with RGB files, letting the printing software convert to CMYK (or CcMmYk, or other) instead of doing your own CMYK files. Gregory Blank got it exactly right. The difference becomes more noticeable when handling files for offset printing. This is even more true as the printed sizes grow larger. Do you have to look really close to find it . . . sure, and therein might be the trouble . . . probably many just won't look that close, or will accept any printed difference. All of us have stated it many times, the technology, technique and resolution will become less important when the image is of a compelling enough nature. Ciao! Gordon Moat A G Studio http://www.allgstudio.com |
#29
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Gordon Moat wrote:
JPEG is a lossy compression algorithm. It functions by retaining more information in higher resolution areas, then compressing lower resolution areas. The effect is that contrast along high resolution edges can change. Very difficult to see this in smaller images, though it becomes more noticeable in larger images. First off this is not how jpeg does it compression, and second my samples are 920 x 720, you trying to tell me that if these were larger I could see a differance? Simple test for your two images. Take the JPEG, copy it, then paste it onto a layer above the JFax TIFF you provided. Then choose Difference as the layer blending. If they were exactly the same, the result would be completely black. If it looks that way, then zoom into the image to enlarge the view, and spots will be apparent. Next flatten the image to create one layer, which looks like the black spotted image. Then select ImageAdjustThreshold and type in "2" as the value. This will give you a field of white spots on a black background. If you view that at exactly 100% magnification, and compare to the originals, you will see the ghost image of the ship and rigging. Those spots represent the changed edge contrast near the high resolution parts. You are talking about a change of 2 levels, and if you look at the differance you will see that what you are looking at is noise, no edge detail. Okay, so lots of people here probably go "so what" or "who cares". If you only print inkjet or some of the newer LightJet, Chromira or similar digital/chemical processes, you should rarely see a problem, or much difference; the dot gain will usually mask any small aberrations. This also assumes you would only work with RGB files, letting the printing software convert to CMYK (or CcMmYk, or other) instead of doing your own CMYK files. Gregory Blank got it exactly right. The difference becomes more noticeable when handling files for offset printing. This is even more true as the printed sizes grow larger. Do you have to look really close to find it . . . sure, and therein might be the trouble . . . probably many just won't look that close, or will accept any printed difference. All of us have stated it many times, the technology, technique and resolution will become less important when the image is of a compelling enough nature. I would be willing to give heavy odds that if printed these two photos would produce the same print to anybody's eye. But then your point was that jpeg was so bad that you did not feel you could judge differences in scanners if all you had to look at was the jpeg, this is just not true. In fact put each into its own layer and blink between them at 400% zoom, you can't tell one from the other. Jpeg can be bad, very bad, if the compression is set too high. But for a low compression jpeg images there is no visable change in the image, even if it is a large image. Scott |
#30
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In article ,
rafe b rafebATspeakeasy.net wrote: and the like (like the stuff on my scan snippets site, or Leigh Perry's site, which is the subject of the thread...) Since I started this thread I am well aware of the subject. & to correct you its not Leigh Perry's site its - largeformatphotography.info is operated on a volunteer basis by Q.-Tuan Luong and Tom Westbrook, using server space generously donated by Brian Reid, refered to us by Tim Atherton. -- "To announce that there must be no criticism of the President, or that we are to stand by the President, right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public."--Theodore Roosevelt, May 7, 1918 www.gregblankphoto(dot)com |
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