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Thread: "smart" sharpening software

  1. #11

    "smart" sharpening software

    High-end drum scans made for the purpose of going to off-set press (atleast at the Lithographers here in Germany) ARE done during the scan. High-end scan software such as LinoColor establish the necessary criterian (contrast, brightness, sharpness and color balance) using a detailed "pre-scan". The changes are then caluculated and applied during the fine scan.

  2. #12

    Join Date
    Nov 2000
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    56

    "smart" sharpening software

    The Epson TWAIN driver does unsharp masking at scan time. This *is* the best spot in the chain to do it. Because the scanner driver has all of the physical pixels available to it, it is possible to actually increase sharpness as long as you aren't scanning at max optical resolution. (like increasing DMax with a higher bit count ADC) The problem is finding out whether any particular driver actually does this. I'm still not sure about the Epson driver.

  3. #13

    Join Date
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    "smart" sharpening software

    hey guys-- there have been a couple of misstatements here about sharpening that i wanted to help correct so you don't end up with bad results.

    --first, NEVER use the sharpening algorithms that come with scanners. they don't have the flexibility that Photoshop's USM has, and once you've done it, you're stuck with it. make your scans with no sharpening, and save them with no sharpening. sharpening is the VERY LAST step to do before printing.

    --don't sharpen the image until you make a final print. do all of your photoshop tweaks and save the file. then resize the image to the print size, do your sharpening, and print it out. if you want to save that file, save it as a different file, so the original non-sharpened image will be available in the future so that if you ever want to make a different sized print, you can resize it again and sharpen it for that size.

    next, someone's suggestion here of using a high radius (i.e., 6 pixels) and low amount (i.e., 50) is a terrible way to sharpen. there are lots of reasons why it degrades the quality of your image, but for now i'll just say that top-notch printers who really know what they're doing, never sharpen that way. among the fine-art photographic printers there is some consensus on how to sharpen, which is to follow these concepts:

    --do your sharpening ONLY while looking at the image in 100% mode (actual pixels). if you look at it in "View print size" or anything less than 100%, you will end up with an oversharpened image.

    --use a threshold of zero.

    --use a very low radius-- never more than 1 pixel, and usually in the 0.3 to 0.4 range.

    --because you're using a low radius, you will need a large "amount". try starting with the amount at 300, and go from there based on how it makes your image look. stay in 100% view mode!

    --after applying the unsharp mask, go to FADE, and fade it at 100% (i.e., it doesn't fade at all), but put the fade in LUMINOSITY mode instead of normal mode. what that does is turns the sharpening effect into a black-and-white-only effect, so it doesn't increase the saturation of the color of your image. this is a super important step!! it accomplishes the same thing as converting to LAB and sharpening only the L channel (but without doing the conversion, which can degrade your image depending on what RGB colorspace you're in).

    --sharpen selectively in different areas of the image by making a copy of the background layer and sharpening that, then painting the sharpened areas selectively. that way you can sharpen some areas more, other areas less, and for areas that are supposed to be blurry, you can leave then unsharpened. you can even make several copies of the background layer and sharpen each one differently, and paint different areas from each one. this technique makes for a more 3-dimensional look and eliminates the creation of grain in smooth areas where you don't want it.

    --another way to sharpen is to use the "sharpen" tool, which actually is a fairly sophisticated tool. but it almost always oversharpens the image, so after applying it, go to "FADE" and fade it back. stay in 100% view mode when doing this, and also put it in "LUMINOSITY" mode instead of normal.

    okay, those are my nuggets for the day. happy printing.

    ~chris jordan, Seattle

  4. #14

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    "smart" sharpening software

    p.s.: there are other sharpening engines out there other than Photoshop's USM, but having done lots of testing with them the consensus among the fine-art studios around the country is that Photoshop's USM is still the best if properly applied using the principles set out in my previous mesage. ~cj

  5. #15

    "smart" sharpening software

    Josh:

    Agree with you 100% about Fuji Frontier prints and their unnatural appearance. What keeps me going back for more is the superior masking and exposure/color control, though.

    The sharpening can be really awful-to the point of obliterating differences in sharpness between very different classes of lens.

  6. #16

    Join Date
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    "smart" sharpening software

    Great discussion! Thanks for all the intelligent ( meaning: relevant) advice and input and a great question too!

  7. #17

    "smart" sharpening software

    I use the same methods and levels as exposed by Chris Jordan and find it working well. I tried however the UltraSharpen 2 script and find it really worthy of interest. Could not find any information on Sharpen Only Edges, but I think UltraSharpen must be pretty similar in the way it works, with the ex ception that SharpenOnlyEdges works on the red channel only, have I read. As Chris reminded me, I have made good experiences resizing images with bilinear mode (instead of bicubic). Fine detail s are preserved and the images especially if they are small (web images) are much more detailed.

  8. #18

    "smart" sharpening software

    Some points about USM,

    a) Any digital image, both from scanners and digital cameras, will need some amount of USM in order to be sharply viewed at final step (screen, inkjet, photogrphic paper, etc.). There are a lot of particular characteristics of digital imaging process that induces lost of sharpness.

    b) The amount of USM necessary for a given picture depends on, essentially, three questions: The first is the scanner or digital camera own performance. The second arises from the amount of present detail (image frequency) in a given picture. The third, finally, is related with the final step of visualization (screen, inkjet, photogrphic paper, etc.).

    c) All the stated above concludes to the impossibility of the existence of any rule of thumb about wich is "the best" amount of USM or "the best" smart software to apply it.

    d) There are at least two questions to have into account: It seems obvious that we need some test of our equipement (scanner and/or camera) to try the best amount of USM to apply to our pictures. In second place we need to analyze EACH picture in particular and the amount of texture and detail to decide the appropriate amount of USM to be applied. It is too important to realize if it is necessary or advisable to apply the USM or the same USM to the whole picture area.

    e) Using the USM tool a gaussian blur is applied to a copy of the original image to produce a new image with no fine detail; the blurred image is then substracted (mathematicaly) from the original image to extract the fine detail. This fine detail is added to the original to highlight the detailed areas.

    f) The RADIUS determines the amount of gaussian blur first applied (Probably large files need more radius than small files to be the same effect). The AMOUNT defines de quantity of detailed version added to the original. The THRESHOLD indicates how different in brightness (from 0 to 255) must be two adjacent pixels to enables the USM be applied.

    g) The threshold permits to avoid some areas to be contrast enhanced by the USM, like the face skin in a portrait or the sky in a landscape. May be interesting to analyze previously the neighbor pixel differences in those areas with the INFO Palette in order to decide the thershold to be applied.

    Disagreement or discussion will be welcome,

    Carles Mitja

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