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Thread: (USM) Unsharp mask... how?

  1. #1

    Default (USM) Unsharp mask... how?

    Aware that a lot of you guys do apply this filtering in Photoshop, care to share what's the recommended setting if I want to give it a try?

    ie. Amount: xx%
    Radius xx pixels
    threshold: xx levels

    Thanks in advance.
    Canon 40D|17-55 f/2.8 IS|100 f/2.8 Macro|135 f/2L|300 f/4L IS|430ex|BG-E2

  2. #2
    Senior Member
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    Quote Originally Posted by ST_sg
    Aware that a lot of you guys do apply this filtering in Photoshop, care to share what's the recommended setting if I want to give it a try?

    ie. Amount: xx%
    Radius xx pixels
    threshold: xx levels

    Thanks in advance.
    Try playing around with it till u get the desired result you want ?
    -Express yourself not in words-
    http://www.majere2sg.com

  3. #3

    Lightbulb

    try:

    190%
    1.5 pixel
    3 threashold

  4. #4
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    It really depends on the size and the "blur factor" of the original pic.
    Usually I use minimum 100%, 1 pixel, 2 threshold level to max 200%, 2 pixel, 2 threshold level. There is something called local contrast usm which is used to improve contrast (kinda), settings at about 400%- 500%, 0.1-0.2 pixel, 0 threshold.

  5. #5

    Lightbulb

    i just collected my 8"x12" test print and realised that it looked too "artificial". the USM setting used was:

    190%
    1.7pixel
    3 threshold.

    which means for 8"x12", the above mentioned setting still needs further refinement...

    i was wondering: is there any URL that mentions something like:

    4"x6": use so n so setting,
    8"x12": use so n so setting...

    ie u get the idea lah . if such a URL exists...it wld be great

  6. #6

    Default

    Try it for yourself and you will realize that there cannot be any recommended setting.

  7. #7
    Senior Member Virgo's Avatar
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    There are no hard and fast rules and recommended settings. You have to try out and convince yourself that the image is sharp by testing on the different settings. Take extra care not to over USM, cos the image may look 'artificial'.
    Kind Regards
    My Picture Website

  8. #8

    Lightbulb

    right now im researching on the "optimal" USM settings for the following sizes:

    4"x6"
    8"x12" (which is almost same size as A4)
    12"x18" (which is almost same size as A3)


    will post my findings once i am able to get soem concrete conclusions .

  9. #9

    Default

    Quote Originally Posted by clive
    i just collected my 8"x12" test print and realised that it looked too "artificial". the USM setting used was:

    190%
    1.7pixel
    3 threshold.

    which means for 8"x12", the above mentioned setting still needs further refinement...

    i was wondering: is there any URL that mentions something like:

    4"x6": use so n so setting,
    8"x12": use so n so setting...

    ie u get the idea lah . if such a URL exists...it wld be great
    If you are going to develop the photos in a shop, do not perform USM as i was told that the machine are programed to sharpen up the photos before printing. If you have done the USM yourself, tell the shop to bypass/inactivate that step, else you will USM it twice, and hence the artifacts.

  10. #10

    Default Sharpening

    Your sharpening is too aggressive. For printing use 300/0.5/1 These settings assume that sharpening is set to 'normal' in the Canon 300D or 10D.

    It is best to sharpen only the luminosity to prevent color haloing. Two ways to do this in PS.

    1) Go: Image -> Mode -> Lab Color. Then click on the lightness channel (on the layers pallete). Apply USM with the settings above. Then go: Image -> Mode -> RGB.

    2) Apply USM to your photo with the settings above. Then go: Edit -> Fade Unsharped Mask -> Mode Luminosity. This way you can also adjust the slider if you want to back off the sharpening a bit.

    If you are resizing at all, remember that sharpening must come after resizing.

    You might need to adjust the percentage of sharpening based upon the lens. The L-series Canons and the new 'DO' Canon lenses need less sharpening.

    Robert

  11. #11

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    A *generic* USM setting for web photos (640x480 or less) is:
    85/1/4

    If not sharp enough, apply another time.

    Experiment more, everyone has their own preferred settings for each set of lens+body combination (if using dSLR)... there is no one "cure-all" setting.

  12. #12
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    Quote Originally Posted by clive
    i just collected my 8"x12" test print and realised that it looked too "artificial". the USM setting used was:

    190%
    1.7pixel
    3 threshold.
    Clive, your setting are too aggressive for A4.
    Typically I set the amount to 80%-150%, you slide the % from 80% onwards, until you see the grainy/pixel effect on monitor then you stop there.
    For raduis typically I set to 0.5-1.0, normally I am just lazy and fix at 1.0.
    For threashold I set to 1.

  13. #13

    Lightbulb

    Quote Originally Posted by Astin
    Typically I set the amount to 80%-150%...
    For raduis typically I set to 0.5-1.0...
    For threashold I set to 1.
    ah..this setting is closer to what i originally guessed that would work for a print of size between A5 and A4 . [my test print verified that 190/1.7/3 is indeed somewhere crossing the "upper limit" already ie too sharp ;-) ]


    Quote Originally Posted by nutek
    A *generic* USM setting for web photos (640x480 or less) is:
    85/1/4
    mmm..i will take this as an arbitrary "starting point" to work on, and will use your "family love @zoo" as an arbitrary on-screen visual reference point ;-)


    Quote Originally Posted by r52lanc
    For printing use 300/0.5/1 These settings assume that sharpening is set to 'normal' in the Canon 300D or 10D.

    If you are resizing at all, remember that sharpening must come after resizing.
    the 300/0.5/1 for the case of without in-camera sharpening...sounds logical..looks like the main difference is the first variable (ie the %)

    "sharpen after resize"...that means the effects of sharpening is non-linear w.r.t. to the change in image size. this sort of ties in with my suspision: while brushing my teeth, i roughly did soem mental maths...i dunno exactly how the sharpening algorithm works i terms of the actual maths involved; but i hazarded a quick guess--suppose the effect of sharpening, denoted by S (higher value of S =>sharper), is dependent on 3 basic veriables: percentage (%), radius (r) and threshold(t). ie we can define S = f(%,r,t). now the main experiment is to find out how S varies with image size I. ie there exists a relationship between S and I such that S=F(I). or in other words, we can say f(%,r,t)=F(I). rearranging, we get:

    I = g(%, r, t). where g is a nolinear function. in more detailed terms,

    L1.L2 = h. (%)*c1.(r)*c2.[k*(-c3.t)]

    where L1,L2, cz, z=1,2,3; %, r, t are all positive with t being the only variable that can be zero (introduction of base k is to remove the singularity of the function g in the case where t=0)

    now...the aim is to unravel the values of c1 ,c2 and c3, and most importantly, what the mystery parameter h is. it can either be a positive real number or a function. once we know all these 4 values, then given any image size of L1 by L2, we can input into the function g and derive a solution set of desired values for %, r, and t. that is , assumign that the assumption of the existence of function g is valid i nthe first place, which i believe to be so

  14. #14
    Phildate
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    I have recently done some research on USM (after I asked Sarah Silver and she didn't know!) - it appears that you should not use a pixel size greater than 0.5 else it introduces too much noise into your picture.

    Clive is correct in that you should resize before sharpening so save a copy of your file unsharpened incase you need to resize and then you will want to sharpen again.

    The one point I read conflicting views on is whether or not you can apply USM more than once? I have been experimenting with applying first USM at 200/0.5/0 and then a second at 100/0.3/0 to give the sharpness I require. However, I know others who will say that you should not apply USM twice.

    JMTCW

  15. #15

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    There is the fade command right after you sharpen. Hence if u oversharpen, u can use the fade command to 'reduce' the effect to your desired one.

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