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February 8th, 2009, 04:13 PM | #11 |
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Why do I see this & how to fix it? (slightly OT)
I hope you have an answer to this "problem" ...
Why are more and more scans not vibrant? Essentially they are about 5% "white pixels" so they do not look anything like photographs at all-- they just look bleached and bleah like a poor newspaper photographs. Is there a way for people who scan to avoid this happening to their pictures? Is there a way for an end-user to fix a picture like this? I miss pictures of people that look ... real! e.d. |
February 8th, 2009, 08:38 PM | #12 |
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I don't know if I understand you right. If the histogram shows a vertical bar at the white end, then there was something wrong with brightness/contrast.
With print, there's one important thing to remember: It can't get any "whiter" than the paper. However, if the dots of the AM screen are too small for the scanner to detect them, they might get read as "paper white". While this is related to contrast and dynamic range, another topic is color calibration. I'm still working on these... |
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February 8th, 2009, 09:20 PM | #13 | |
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February 8th, 2009, 09:48 PM | #14 | |||
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Yes, exactly. Amplitude means that the point size is modified, frequency means that the amount of dots per area is modified. Quote:
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Laser printers usually print AM with diamond-shaped "dots", while ink jet printers (more exactly the driver software) are supposed to print FM. I think some ink jets have a certain control over the drop size, but not that much, so maybe it's FM with slightly modified dot size. In the meantime I did nore experiments on the amount of gaussian blur needed. Using 0.707x the screen resolution might kill too much detail, while using 0.5x the screen resolution might leave some moiré. It looks like this depends on the ratio of screen and scan resolution. The best setting for Gaussian Blur seems to be somewhere between 0.5x and 0.707x the ratio of scan resolution to print screen. Please note that in case of less gaussian blur, less sharpening is needed: Amount 200% and Radius 0.6 seems to be enough when using the 0.5x ratio. Last edited by cccmagfan; February 10th, 2009 at 04:38 PM.. |
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November 20th, 2009, 03:33 PM | #15 |
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I hope no-one minds me butting in here, I just want to add my bit to the information: I think scans are better if you can't see the print on the back of a photo so I used to put a piece of dark paper between the photo and the white 'plate' that holds the photo flat when you close the lid, but now I've just painted the white 'plate' black and Hey presto, no more show-through of what's on the back of the photo.
I was also a little surprised about the recommendation to not use 'de-screening' when scanning. I always 'de-screen' with 'sharpen' but I always scan so the image is much bigger than I want and then, using micrografx piture publisher 8, shrink the image to the size I want then I I use any blurring/sharpening/cloning to smooth out skin tones and get rid of any distractions. I realise this is my own peculiar way of doing things, but it suits me. Here's a scan I did yonks ago using this method: It was a rather tatty image as I'd had for yonks, but seems to have scrubbed up quite well.
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July 19th, 2011, 08:19 AM | #16 |
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Adding my little bit of knowledge to this thread:
One of the most important things is that the scan reolution is at least double the original print DPI. cccmagfan mentions it in the first post, if you don't sample the "data" at least double it's original resolution you can easily end up with errors. There's a lot that's been written about this, its called the Nyquist sampling criterea the wikipedia article's pretty good. |
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