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#41
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difficulty drum scanning negatives
Jytzel wrote:
Thanks for all who responded. I got the scans from the office and they look horrible. I donīt think itīs grain, ítīs noise, noise, noise! Colors look posterised with no gradation observed. The histogram shows no abnormalities however (?) That comment makes me think you are viewing it on a monitor, and judging it as noise. A smooth Histogram should indicate a smooth tonal transition. The reasoning behind drum scanning is to eventually print the image. I think at this point, you should do a test print, proof print, or match print, and then make a better judgement. I don't believe the problem is the film, it's the scan that it's bad. If anybody is interested I can send portion of the image for viewing. J All monitors are such poor resolution in comparison to printing, especially commercial offset printing. I have seen many image files that seemed noisy on a monitor, yet printed very smoothly. You could easily be running into a limitation of viewing on a monitor. If you can do a test print, then you would have a better item to judge scan quality. If it still looks bad, then the original scan is at fault. If you still find that after viewing printed results that things are not working, it is then down to operator error, or a weird technical problem. I remember working on one workstation that showed unusual results on most scans. What we finally traced that down to was an extra monitor interfering with the SCSI cable of the scanner, and causing strange noise issues. The reason that was so tough to track was that the monitor was a secondary monitor, and not always used at that workstation. Routing the SCSI cable further from that monitor solved the unusual noise problem. While I would be surprised if that is the problem you are having, if nothing else is working, then investigate that direction. Best of luck. Ciao! Gordon Moat A G Studio http://www.allgstudio.com |
#42
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difficulty drum scanning negatives
"Neil Gould" wrote in message ink.net...
Recently, Jytzel posted: Thanks for all who responded. I got the scans from the office and they look horrible. I donīt think itīs grain, ítīs noise, noise, noise! Colors look posterised with no gradation observed. The histogram shows no abnormalities however (?) I don't believe the problem is the film, it's the scan that it's bad. If anybody is interested I can send portion of the image for viewing. Out of curiosity... have you made an optical print of the film yet? And, how are you observing the scans? Regards, Neil No, not yet. Iīm observing the scan on the monitor! I donīt really understand what you mean. thanks, J |
#43
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difficulty drum scanning negatives
In article et, Neil
Gould writes However, for the purpose of establishing grain aliasing, one should only have to examine the edge of a high-contrast portion of the image under magnification and compare that to an equivalent zoom magnification of the digital file (obviously not to the pixel level). If the on-screen profile matches the optical profile... no aliasing... if they're overly blocky... aliasing. Why would this method not yield a "valid comparison"? Gaaaah!!! Not again! Go back to the start fo the thread and read all my posts again! Recorded image resolution is likely to be less than the granular resolution, so no, you can't just examine a high contrast edge and looks for jaggies - even if they aren't there, there could still be grain aliasing. Furthermore, jaggies are not an indication of aliasing, merely a consequence of a square pixel output filter representation! You've heard it all before, had the details spelled out in single syllables and complained that you undertand it all, yet you still cling to this untruth - so what's the point? -- Kennedy Yes, Socrates himself is particularly missed; A lovely little thinker, but a bugger when he's ****ed. Python Philosophers (replace 'nospam' with 'kennedym' when replying) |
#44
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difficulty drum scanning negatives
In article , Jytzel
writes Thanks for all who responded. I got the scans from the office and they look horrible. I donīt think itīs grain, ítīs noise, noise, noise! Colors look posterised with no gradation observed. The histogram shows no abnormalities however (?) I don't believe the problem is the film, it's the scan that it's bad. If anybody is interested I can send portion of the image for viewing. Yes, send me a section, but I am going off on business for a week, so won't be able to comment on it till I get back. -- Kennedy Yes, Socrates himself is particularly missed; A lovely little thinker, but a bugger when he's ****ed. Python Philosophers (replace 'nospam' with 'kennedym' when replying) |
#45
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difficulty drum scanning negatives
In article , Gordon Moat
writes Jytzel wrote: Thanks for all who responded. I got the scans from the office and they look horrible. I donīt think itīs grain, ítīs noise, noise, noise! Colors look posterised with no gradation observed. The histogram shows no abnormalities however (?) That comment makes me think you are viewing it on a monitor, and judging it as noise. A smooth Histogram should indicate a smooth tonal transition. ....or a noisy one - as Jytzel has described. Noise will only show up on a histogram as a distribution around what should be perfectly uniform areas - but few real world images have such areas so noise, to all intents and purposes, is not observable from histogram views. However, I agree with your concern that this is simply a case of viewing on a monitor. Essentially there are two extreme options: * viewing at 1:1 on the monitor pixel scale, which will result in the image appearing soft and grainy, just due to the magnification, * viewing at actual print scale, in which case the image will look grainy due to aliasing due to the simple downsampling algorithm for display. Jytzel, if you want to view the image effectively on the monitor for a fairly valid comparison with an actual print then resample the image to your monitor size, do not just zoom it. For example, a 35mm frame scanned at 4000ppi is around 5500x3700pixels. My monitor display is 1600x1200pixels, so I would resize the image to 25% of the original, to get 1375x925pixels. If you implement the resize in Photoshop or PSP then some filtering is implemented prior to the resize to reduce aliasing, however it can be worth additional filtering before the resize to be sure that no aliasing occurs. In Photoshop, the best way of achieving this is to use gaussian blur with a radius no more than 2pixels for a resize to 25% - ie. half the resize factor. After the resize, implement an unsharp mask at around 150% with a radius of 0.7 pixels to recover the loss in sharpness caused by downsampling without introducing aliasing. This will show you roughly what the image will look like when actually printed without exaggerating the granularity of the image. -- Kennedy Yes, Socrates himself is particularly missed; A lovely little thinker, but a bugger when he's ****ed. Python Philosophers (replace 'nospam' with 'kennedym' when replying) |
#46
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difficulty drum scanning negatives
Hi,
Recently, Jytzel posted: "Neil Gould" wrote in message Out of curiosity... have you made an optical print of the film yet? And, how are you observing the scans? No, not yet. Iīm observing the scan on the monitor! I donīt really understand what you mean. The best way to know the quality of your scan will be to get a photographic print made. If artifacts exist, they'll show up in the print, and you'll have a basis for correcting those problems. Viewing a scan on a monitor is only useful if you have a good quality monitor and video card capable of displaying tonal transitions well (I won't say "accurately", because the color model for transmissive and reflective viewing are different). These are not commonplace purchases, and as you've reported visible "posterization" of transitions, I suspect that this may be part of your problem. Regards, -- Neil Gould -------------------------------------- Terra Tu AV - www.terratu.com Technical Graphics & Media |
#47
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difficulty drum scanning negatives
Recently, Kennedy McEwen posted:
In article et, Neil Gould writes However, for the purpose of establishing grain aliasing, one should only have to examine the edge of a high-contrast portion of the image under magnification and compare that to an equivalent zoom magnification of the digital file (obviously not to the pixel level). If the on-screen profile matches the optical profile... no aliasing... if they're overly blocky... aliasing. Why would this method not yield a "valid comparison"? Gaaaah!!! Not again! Go back to the start fo the thread and read all my posts again! Recorded image resolution is likely to be less than the granular resolution, so no, you can't just examine a high contrast edge and looks for jaggies - even if they aren't there, there could still be grain aliasing. Furthermore, jaggies are not an indication of aliasing, merely a consequence of a square pixel output filter representation! I was *not* referring to "jaggies", though that may not make a difference to your campaign, Kennedy. In an attempt to avoid such misinterpretation -- an effort that apparently failed on you -- I stated "obviously not to the pixel level". A salient question might be, "Why look for artifacts at the edges of high-contrast portions of an image?", as grain aliasing can have representation in any part of the image. But, rather than ask such questions, you only jump to conclusions and rant on. You've heard it all before, had the details spelled out in single syllables and complained that you undertand it all, yet you still cling to this untruth - so what's the point? I'm wondering the same thing... though it's becoming clearer why we're the only two still hashing about with this. -- Neil Gould -------------------------------------- Terra Tu AV - www.terratu.com Technical Graphics & Media |
#48
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difficulty drum scanning negatives
Gordon Moat wrote in message ...
Jytzel wrote: Thanks for all who responded. I got the scans from the office and they look horrible. I donīt think itīs grain, ítīs noise, noise, noise! Colors look posterised with no gradation observed. The histogram shows no abnormalities however (?) That comment makes me think you are viewing it on a monitor, and judging it as noise. A smooth Histogram should indicate a smooth tonal transition. The reasoning behind drum scanning is to eventually print the image. I think at this point, you should do a test print, proof print, or match print, and then make a better judgement. I don't believe the problem is the film, it's the scan that it's bad. If anybody is interested I can send portion of the image for viewing. J All monitors are such poor resolution in comparison to printing, especially commercial offset printing. I have seen many image files that seemed noisy on a monitor, yet printed very smoothly. You could easily be running into a limitation of viewing on a monitor. If you can do a test print, then you would have a better item to judge scan quality. If it still looks bad, then the original scan is at fault. If you still find that after viewing printed results that things are not working, it is then down to operator error, or a weird technical problem. I remember working on one workstation that showed unusual results on most scans. What we finally traced that down to was an extra monitor interfering with the SCSI cable of the scanner, and causing strange noise issues. The reason that was so tough to track was that the monitor was a secondary monitor, and not always used at that workstation. Routing the SCSI cable further from that monitor solved the unusual noise problem. While I would be surprised if that is the problem you are having, if nothing else is working, then investigate that direction. Best of luck. Ciao! Gordon Moat A G Studio http://www.allgstudio.com Thanks Godon, But why donīt all photos show noise then? The ones scanned from positives are perfect. If it was just a monitor limitation then it would affect all scanned images, right? J |
#49
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difficulty drum scanning negatives
Kennedy McEwen wrote in message ...
In article , Gordon Moat writes Jytzel wrote: Thanks for all who responded. I got the scans from the office and they look horrible. I donīt think itīs grain, ítīs noise, noise, noise! Colors look posterised with no gradation observed. The histogram shows no abnormalities however (?) That comment makes me think you are viewing it on a monitor, and judging it as noise. A smooth Histogram should indicate a smooth tonal transition. ...or a noisy one - as Jytzel has described. Noise will only show up on a histogram as a distribution around what should be perfectly uniform areas - but few real world images have such areas so noise, to all intents and purposes, is not observable from histogram views. However, I agree with your concern that this is simply a case of viewing on a monitor. Essentially there are two extreme options: * viewing at 1:1 on the monitor pixel scale, which will result in the image appearing soft and grainy, just due to the magnification, * viewing at actual print scale, in which case the image will look grainy due to aliasing due to the simple downsampling algorithm for display. Jytzel, if you want to view the image effectively on the monitor for a fairly valid comparison with an actual print then resample the image to your monitor size, do not just zoom it. For example, a 35mm frame scanned at 4000ppi is around 5500x3700pixels. My monitor display is 1600x1200pixels, so I would resize the image to 25% of the original, to get 1375x925pixels. If you implement the resize in Photoshop or PSP then some filtering is implemented prior to the resize to reduce aliasing, however it can be worth additional filtering before the resize to be sure that no aliasing occurs. In Photoshop, the best way of achieving this is to use gaussian blur with a radius no more than 2pixels for a resize to 25% - ie. half the resize factor. After the resize, implement an unsharp mask at around 150% with a radius of 0.7 pixels to recover the loss in sharpness caused by downsampling without introducing aliasing. This will show you roughly what the image will look like when actually printed without exaggerating the granularity of the image. thanks for the tip |
#50
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difficulty drum scanning negatives
Kennedy McEwen wrote in message ...
In article , Jytzel writes Thanks for all who responded. I got the scans from the office and they look horrible. I donīt think itīs grain, ítīs noise, noise, noise! Colors look posterised with no gradation observed. The histogram shows no abnormalities however (?) I don't believe the problem is the film, it's the scan that it's bad. If anybody is interested I can send portion of the image for viewing. Yes, send me a section, but I am going off on business for a week, so won't be able to comment on it till I get back. thanks, send me your email address |
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