Retouching and low pass/ high pass blends

Moderator: jsachs

Post Reply
tomczak
Posts: 1367
Joined: April 25th, 2009, 12:56 am
What is the make/model of your primary camera?: Fuji X-E2
Contact:

Retouching and low pass/ high pass blends

Post by tomczak »

I was trying to resurrect this retouching technique, but just realized that Composite (or Blend) doesn't have Low-pass/High-pass blend mode anymore... The technique is similar somewhat to the speck removal tool discussed recently, but I find it more subtle and realistic...

Can anybody think of some similarly realistic retouching technique that could be done with new (or old) transformation and tools in PWP8?
Last edited by tomczak on January 6th, 2020, 9:15 am, edited 1 time in total.
Maciej Tomczak
Phototramp.com
tomczak
Posts: 1367
Joined: April 25th, 2009, 12:56 am
What is the make/model of your primary camera?: Fuji X-E2
Contact:

Re: Retouching and low pass/ high pass blends

Post by tomczak »

Something somewhat similar can be done with Bilateral Sharpen. Here is my recipe:

- Set Halo Limits and Blur Threshold to 100% and all the other sliders to 0.
- Adjust Blur Radius in such a way that the blemishes you want to remove are blurred, but just enough (smaller and larger textures will get blurred as well at this point.
- Lower the Blur Threshold so that the larger-scale textures and edges are un-blurred but the blemishes are still smeared
- Increase the Sharpen Threshold just a little to un-blur the high-frequency noise/grain, adding some realism to the corrections

You can make that into a tool by adding an interactive Mask into the Amount control, but it becomes a bit of juggling act as you need to paint mask on the Display Input and observe the change on the BS small preview (or hit the 'Running Man' button and then see the effect on the Display Output, but that's not exactly interactive).

With the Sharpening set to zero (or less than 1 anyway), the Halo Limits seem to have the same effect on small-frequency details blurring as Sharpen Threshold, but there is more control on the subtlety of the effect. With Halo Limits set to 0%, nothing gets blurred.

It may sound a little complicated, but perhaps there is enough general usability in such a technique to petition Jonathan to consider combining Bilateral Sharpen and Masks into Blemish Reduction/Sharpening Tool in a fashion similar to recent Levels and Colour Tool? Or allowing for something similar to high, mid, low pass image splitting that both of these retouching techniques use in effect.
Last edited by tomczak on January 6th, 2020, 10:39 am, edited 2 times in total.
Maciej Tomczak
Phototramp.com
jsachs
Posts: 4203
Joined: January 22nd, 2009, 11:03 pm

Re: Retouching and low pass/ high pass blends

Post by jsachs »

The original feature in PWP 7 was an initial stab at emulating the Photoshop healing brush. The way I was doing it was not working out so I abandoned it a long time ago. The idea was to let you clone high pass detail from another part of the image over the low-pass image data, or vice versa, with an adjustable amount of blurring/sharpening.
Jonathan Sachs
Digital Light & Color
tomczak
Posts: 1367
Joined: April 25th, 2009, 12:56 am
What is the make/model of your primary camera?: Fuji X-E2
Contact:

Re: Retouching and low pass/ high pass blends

Post by tomczak »

This example may work because there are 3 frequency bands in effect and only the second highest gets blurred. But it's done in-place, so it's easier than cloning.

BS may have potential too because Blur Threshold can exclude low frequencies and Sharpen Threshold the highest, but may be a little awkward to apply with paint masks.

I did like experimenting with Composite low/high pass modes - the only place that I can think of that I can find them now is Brightness Curve advanced mode (which I started using lately and I find it quite effective with similar potential of increasing global contrast yet preserving details in shadows and highlights to 2-Zone Transformation)
Maciej Tomczak
Phototramp.com
tomczak
Posts: 1367
Joined: April 25th, 2009, 12:56 am
What is the make/model of your primary camera?: Fuji X-E2
Contact:

Re: Retouching and low pass/ high pass blends

Post by tomczak »

While only marginally related to high/low pass cloning, with the new Replace Channel it is now easily possible to clone or use other tools on one channel only (using one split branch to extract channel and do editing on it, then insert the output back to the other branch with Replace Channel). Great!

The only problem is that doing the corrections on one channel, I can not interactively see what it does to the image reconstructed by Replace Channel... That's related to this idea: https://www.jonathansachs.me/phpbbBB3/v ... f=4&t=2341
Maciej Tomczak
Phototramp.com
tomczak
Posts: 1367
Joined: April 25th, 2009, 12:56 am
What is the make/model of your primary camera?: Fuji X-E2
Contact:

Re: Retouching and low pass/ high pass blends

Post by tomczak »

Sorry for resurrecting old threads: I've been recently thinking of some technique that would work similarly to the Healing brush and played with the Specs Removal tool. The number of techniques available in the Speck Removal as well as several movable control points paradigm is a great thing, but there are still some retouching tasks that I'm struggling with. There are also a few observations (perhaps it works as it should as I'm not too familiar with it).

- Alt-scrolling on either input or the output image zooms fine and the zoomed before and after images can be compared easily by switching between Display Input or Output buttons, but hitting the Preview Side-by-side reduces the zoom to fit, which needs to be zoomed in again. Going the other way (from the zoomed side by side to Input or Output) does the same thing.

- When the image is zoomed in, holding and dragging the mouse (hand icon) seems to work in side-by-side preview, but only on the output image. With Display Input or Display Output, I'm having trouble moving the image around with the mouse (although after zooming in the hand icon appears briefly). Addendum: holding-Alt when dragging the mouse seems to solve the problem for all views.

- When I semi-accidentally made the speck radius too large, and admittedly my computer is not the fastest, the background calculations took a long time (understandably), but there was no indication that something was happening and the PWP appeared stuck, with no way of stopping it.

- Turning off the Auto Preview and hitting the Running man may allow for setting several points and adjusting their radii unmolested, but once hit, I'm never sure if PWP got stuck or doing something and I don't know how to cancel it if it takes too long. I'm not sure if in the Speck Removal context it makes sense, but the convention of the Running man turning red when changes are made but the Preview is not updated yet doesn't work with Speck Removal.

- I'm a little confused with the cross vs. circle in the middle of the speck control points. If I keep adding several control points, all of them show crosses (as in the current control point?). Clicking near an existing control point changes (but not always) several crosses to circles, but it doesn't keep the cross on the active/current control point whose parameters are currently being adjusted. Sometimes I managed to create an orphan cross that was not associated with any control point and disappeared after creating new control points.

And lastly, unrelated to the Speck Removal, if you look at previous posts in the thread there are links such as: http://www.jonathansachs.me/phpbbBB3/vi ... ?f=5&t=894, but they don't seem to work anymore.
Maciej Tomczak
Phototramp.com
tomczak
Posts: 1367
Joined: April 25th, 2009, 12:56 am
What is the make/model of your primary camera?: Fuji X-E2
Contact:

Re: Retouching and low pass/ high pass blends

Post by tomczak »

There is one more comment, probably of low importance. As I was playing with multiple control points/specks, small and all over the image, I noticed that I had a hard time finding previous specks in a bussy image to readjust them. Maybe some way of centering/zooming on control points in turn could be helpful?
Maciej Tomczak
Phototramp.com
pierrelabreche
Posts: 414
Joined: January 29th, 2019, 11:47 pm
What is the make/model of your primary camera?: Nikon Z8

Re: Retouching and low pass/ high pass blends

Post by pierrelabreche »

Would you consider Advanced Sharpening using spatial frequency controls while interactively painting a mask ?
tomczak
Posts: 1367
Joined: April 25th, 2009, 12:56 am
What is the make/model of your primary camera?: Fuji X-E2
Contact:

Re: Retouching and low pass/ high pass blends

Post by tomczak »

Interesting idea. Do you mean with the AS Noise Reduction tab? I'm not sure how Jonathan feels about it but unlike the Sharpen tab, there is only one set of double threshold sliders in NR (blurring), which I think means that you can only restrict blurring of the 'rougher' (more spacially contrasty) parts of the image, not the 'smoother' parts - I don't know how to set the blurring band restricted from both sides

In the Sharpen tab you have two sets of double threshold sliders that can be used to select a band of 'roughness' that is sharpened, and limited from both ends.

viewtopic.php?f=4&t=3354

I guess Multipass sharpen could be used in a similar fashion. With Sharpen Factor set to zero, Blur Threshold limits blurring at the rougher end and Sharpen Threshold from the finer one. Halo Limit slider also interacts with blurring in the fashion, I think limiting blurring of the rougher parts, but I'm not entirely sure. Guided Filter seems to produce smoother results than Bilateral Filter.

One way to get one's bearings as to what the sliders and thresholds are doing is by using Test Patterns/Shapen Test image and playing around with that.
Maciej Tomczak
Phototramp.com
pierrelabreche
Posts: 414
Joined: January 29th, 2019, 11:47 pm
What is the make/model of your primary camera?: Nikon Z8

Re: Retouching and low pass/ high pass blends

Post by pierrelabreche »

Have you tried the speck removal tool in Advanced sharpening ? It is pretty neat : the user does not need to identify specks one at a time. Specks are detected.
Post Reply