‘Creative’ Sharpening Edge Undershoot/Overshoot Control

Moderator: jsachs

den
Posts: 612
Joined: April 25th, 2009, 6:33 pm
What is the make/model of your primary camera?: Canon EOS-350D/Fuji X100T
Location: Birch Bay near Blaine, WA USA

‘Creative’ Sharpening Edge Undershoot/Overshoot Control

Postby den » April 5th, 2014, 10:41 am

The following suggested technique will allow precise control for the amounts and ratio of edge Undershoot to edge Overshoot for multiple sharpening methods used to increase an image’s edge contrasts… …inter-actively separate smooth/minor edges from major edges for further 'creative' sharpening… …and most importantly, preserve the integrity of the selected sharpening algorithm(s)

Reference: “Guide to Image Sharpening” http://www.cambridgeincolour.com/tutori ... pening.htm

Definitions:
Img0 = the starting image with little or no sharpening…

Img1 = Img0 Amount 100 sharpened by any one of the following methods and settings: Sharpen; Heavy Sharpen; Unsharp Mask; Bilateral Sharpen; or Advanced Sharpen…

Img3 = Special Effects/Difference – Offset Difference where Img1 is subtracted from Img3 at Amount 100…

EUOCM = Edge Undershoot/Overshoot Control Mask where black maps the sharpening edge undershoot and white maps the sharpening edge overshoot of Img3

MEM = Major Edge Mask where black maps the smooth/minor edges image areas of Img0 and white maps major edges starting at a threshold with a diminishing gradient to lesser major edges in the selected range…

Workflow:
1) Sharpen Img0 to an Amount 100, creating Img1
2) Offset Difference Img1 minus Img0 at Amount 100, creating Img3
3) Mask Img3, creating EUOCM using Mask Tool – Brightness Curve…
Edge_UndershootOvershoot_Control_Mask.jpg
Edge_UndershootOvershoot_Control_Mask.jpg (47.25 KiB) Viewed 6100 times

4) Mask Img1, creating MEM using Mask Tool - Texture… …leave ‘active’ on Img1… …Neighborhood Size should be as close to the Sharpening radius used to create Img1 as the setting allows…
Major_Edge_Mask.jpg
Major_Edge_Mask.jpg (48.27 KiB) Viewed 6101 times

5) Composite-Blend where: Input = Img0; Input Amount Mask = MEM; Overlay = Img1; Overlay Amount Mask = EUOCM… …adjust mask amount black/white sliders to preference while monitoring 1:1 Zoom factor Preview image areas to avoid viewing anti-aliasing artifacts…
Composite-Blend_Edges_Undershoot_Overshoot_Amounts_50+KB.jpg
Composite-Blend_Edges_Undershoot_Overshoot_Amounts_50+KB.jpg (69.79 KiB) Viewed 6105 times

In the illustration above, Img0’s smooth/minor edge image areas are sharpened [blended] to a 90% amount while the major edges are sharpen to a 45% amount [ratio of smooth/minor edges to major edges is 2:1] with edge Overshoots 2/3’s [67] of edge Undershoots [100] of Img1… …as MEM is ‘active’, Img0’s masked smooth/minor edges and major edges image areas can be adjusted with a Mask Tool None or Undo; re-adjustment of the threshold setting [black slider]; and a lower-left Apply Add and the Preview will auto update if checked…

For “High Pass – Hard or Soft Light” ‘creative’ sharpening methods, Img3 = the High Pass blur image of Img0 and is the Overlay for Composite – Hard or Soft Light… …mask creation is the same as previously described…

If smooth/minor edges and major edges separation is not preferred, omit step 4) and use ‘No Mask’ for the Composite – Blend or Composite – Hard or Soft Light Input Amount Mask.

…den…
P.S... ...Thank you Maciej for the on/off message board discussions that crystalized my thoughts regarding the above possibilities...

jsachs
Posts: 776
Joined: January 22nd, 2009, 11:03 pm

Re: ‘Creative’ Sharpening Edge Undershoot/Overshoot Control

Postby jsachs » April 13th, 2014, 10:21 pm

Interesting ideas -- FYI, Something similar to this will be built into PWP for a future release.
Jonathan Sachs
Digital Light & Color

den
Posts: 612
Joined: April 25th, 2009, 6:33 pm
What is the make/model of your primary camera?: Canon EOS-350D/Fuji X100T
Location: Birch Bay near Blaine, WA USA

Re: ‘Creative’ Sharpening Edge Undershoot/Overshoot Control

Postby den » April 14th, 2014, 1:03 pm

Looking forward to the added features for sharpening controls... ...thank you Jonathan!!!

My apologies... ...noticed an error in Definitions in the Original Post...
Img3 = Special Effects/Difference – Offset Difference where Img1 is subtracted from Img3 at Amount 100…

…should read...
Img3 = Special Effects/Difference – Offset Difference where Img0 is subtracted from Img1 at Amount 100

The suggested Workflow is correct.

...den...

den
Posts: 612
Joined: April 25th, 2009, 6:33 pm
What is the make/model of your primary camera?: Canon EOS-350D/Fuji X100T
Location: Birch Bay near Blaine, WA USA

Re: ‘Creative’ Sharpening Edge Undershoot/Overshoot Control

Postby den » April 15th, 2014, 2:44 pm

.... A Major Edge Overshoot Amount Mask…

I was not going to post this as the underlying reasoning is a bit esoteric but the reality if accepted is too good to pass up. It WORKs and is easy to do!!!

In the Original Post, an image’s over-sharpened image version was “Composite-Blend”-ed as its Overlay where Input and Overlay Amount Masks were used to preferentially control the amount of blending of undershoot and overshoot to smooth/minor edges and major edges…i.e., four way control over edge contrasts which may be over kill except for extreme gallery quality ‘creative’ sharpening…

The following mask suggestion inter-actively maps a sharpening transform’s Input image’s major edges overshoot allowing the transform’s sharpening algorithms to apply differing amounts of sharpening to the smooth/minor edges and the selected major edges undershoots then to the selected major edges overshoot… …thus preventing objectionable ‘white’ overshoot sharpening at major edges while allowing a higher amount of non-objectionable sharpening to occur in the smooth/minor edges and major edge undershoot image areas.

Creating a Major Edge Overshoot Amount Mask workflow…

...1) Img0 = any PWP sharpening transform’s [Method/Operation] Input Image to be transformed…
...2) Lower-left Apply Add a Mask Tool – Texture where: Method = Maximum Difference; Neighborhood = 5x5; black slider set to a preference threshold; and white slider set to the right most histogram end… …to Img0, then…
step 2_major_edges_Texture_mask.jpg
step 2_major_edges_Texture_mask.jpg (43.17 KiB) Viewed 5907 times

...3) Lower-left Apply Overlay a Mask Tool – Brightness Curve Step curve [0,0], [50,0], [50,100], [100,100] to Img0… …[OPTions Load the curve from a previously Saved curve]…
step 3_major_edges_Overshoot_mask.jpg
step 3_major_edges_Overshoot_mask.jpg (46.89 KiB) Viewed 5887 times


Leave the Mask Tool ‘active’ on Img0 allowing if preference re-selection of a major edges threshold/range with a None and repeat of steps 2) and 3)… …if a transform’s Preview Auto is checked, Preview will update…

Open any one of PWP’s sharpening transforms/methods using Img0 as the Input Image and the suggested mask as the Input Amount Mask… …mask black controls the amount of sharpening to occur in Img0’s smooth/minor edges and major edges undershoots… …mask white controls the amount of sharpening to occur in Img0’s major edges overshoots… …suggested white slider amount to be approximately 10% of the preference black slider amount while monitoring 1:1 Zoom factor Preview image areas to avoid anti-aliasing artifacts… …for example, if the black slider preference setting is 70%, then most likely the preference white setting will be near 7% or 0% to avoid objectionable white edge halos…

Explanation attempt…

...1) The suggested mask’s white/grays map the Overshoot of the selected Major Edges range and the black maps the smooth/minor edges and major edges undershoot image areas of a sharpen transform's Input Image, Img0. Setting the black amount allows the transform's algorithms to blend its normal undershoot/overshoot to the smooth/minor edges and major edge undershoots to the amount selected. Setting the white amount allows specific overshoot blend control of the major edges.

...2) The mask seems to work better if during the Texture phase [step 2)] for major edges if Method=Max Difference and Neighborhood=5x5 rather than Method=Ave Difference.

...3) Specific minor/major edge undershoot/overshoot do not need to be identified. The transform in effect Composite-Blends the virtual over-sharpened version of the Input image, Img0, depending upon the Input Amount Mask’s black and white slider settings and the transform’s settings for radius, threshold, etc.

...4) Perhaps this will also help... ...when performing steps 2) and 3), switch the Mask Tool to show Mask Only on the applied Img0 image. Notice the subtraction of the potential undershoot image areas from the major edges when step 3) is performed where the 50% tone step curve acts as a threshold separating major edge range undershoots and overshoots.

For High Pass - Hard or Soft Light sharpening, perform steps 2) and 3) on the High Pass blur image of Img0 and use the resulting 'active' mask as the Composite - Hard or Soft Light blend Input Amount Mask... ...the suggested black/white setting ranges apply...

Does it work?... Will it improve your ‘creative’ sharpening post-processing game?...
The following example is a side by side 1:1 Zoom factor image area crop. On the Left is a Heavy Sharpen No Mask Amount=70 Preview and to its Right is the suggested steps 2) and 3) Input Amount Mask where mask black=70 and mask white=7…
HeavyShrpn_Left-NoMsk70_Right-MskBlk70-MskWht7_Qual90.jpg
HeavyShrpn_Left-NoMsk70_Right-MskBlk70-MskWht7_Qual90.jpg (84.13 KiB) Viewed 5892 times

Have fun experimenting!!!...

…den…


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