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Frequency Things

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  #1  
Old 06-10-2012, 02:51 AM
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Stroker Stroker is offline
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Frequency Things

I have seen freq things come and go. Maybe some dialog. Not sure as I am retired from such things.

I was originally introduced to the idea of frequency seperation by an awesome tutorial called The Power of High Pass. This tut is what originally set me thinking of such things.

http://www.gamasutra.com/view/featur...ass_filter.php

Then I briefly met a product photographer that used the same basic technique, but used Median for sharpening. All of that coalesced into the one of the greatest branches in my personal journey. I expounded in a myriad of directions.

One thing that I did was use other filters to divy up photographs. I also divied up into more than two. Used Lens Blur to divy up into perfectly blended multiple gradiated freq layers. Used Mosaic to divy up into 16, 8, and 4 squares. So much fun.

But I guess the big thing for me right now is 3 layers of seperation. This is what I wish to impart, even if in an imperfect way. I am retired from such things and I don't care for writing such tutorials anymore.

I am including two actions in a zip file that I used to use for exploratory purposes.

Because our eyes work mostly on luminosity information and because of how PS works, I devised these around those two dynamics/ideas/limitations.

Open a new document and extract lum right on the background layer.

Edit > Fill
black/white/50% grey
saturation

Then run the first action. That will give you high, medium, and low frequencies. It shouldn't be too hard to view and deconstruct the action to see how I did it.

Then run the second action. This will take the various R channels of the first action and dump them into RGB for a completely different view of HML.

Deconstruct, understand, and run with it.

If you folks decide to pursue and discuss various aspects, I will be watching. However, it is hard to say if/how/when I, personally, will respond. But don't let that little foible of my retired mind discourage more open discussion of such things.

Now learn and run!
Attached Files
File Type: zip FreqJunkx2.zip (972 Bytes, 43 views)

Last edited by Stroker; 06-10-2012 at 02:57 AM.
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Old 06-10-2012, 05:33 AM
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Der_W Der_W is offline
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Re: Frequency Things

Stroker, that's some really neat ideas !
I used a similar idea a while ago to create a more flexible frequency separation that'll work with smart objects and let the user decide for the separation radius later on the fly with the use of channel mixers (the high pass will be automatically generated).
I've attached a copy for you and others to play around with if you like. It too works only with luminosity information (though you don't need to worry about that, the action sets up everything like it needs).
There's so much fun you can have with this technique, it's unbelievable !

Edit: Forgot to say that, there should be two blank layers, one called "High Pass", the other one called "Low Pass" working on them will change the according frequencies. E.g. set the clone stamp tool to "Current and below", go to the blank "High Pass" layer, set your clone source and clone the high frequency detail wherever you like it. Same for the "Low Pass" layer.
I updated the action to give a better reflection of this behavior.
Also you have to set the group's blending mode to "Normal" for it to work, "Luminosity" mode will wreck the mix.
Attached Files
File Type: zip Frequency Separation Channel Mixer.zip (1.3 KB, 59 views)

Last edited by Der_W; 06-10-2012 at 07:48 AM.
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Old 06-10-2012, 07:16 AM
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Re: Frequency Things

Hi Der_W..
Just tried ur Action in cs5... Highpass and Low pass layer is empty....
not sure how it works...
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Old 06-10-2012, 07:20 AM
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Re: Frequency Things

Stroker.... still I'm using Low and high pass.... two layer for working with the texture.... if I needed I'm putting duplicate the low pass as a middle layer.... and work on it..... idea using 3 pass is new to me... can u explore how we can take advantage of this method.....
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Old 06-10-2012, 07:45 AM
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Re: Frequency Things

Hi ashphotoart,

you're right, sorry I forgot to add the proper instructions!

The empty "High Pass" and "Low Pass" layers are for your actual high pass and low pass work, so they should be empty at the beginning.
If you want to work with them, use your clone stamp with "Current and below" as sample point and just clone your high/low frequencies around.
However to work with the mix, it's important to first set the group's blend mode to "Normal"! When you're finished, set it back to "Luminosity". Unfortunately "Luminosity" mode will mess up the mix when you're applying it the whole time.
I updated the action to make the process a little more clear (better naming).
You should also notice, that the original idea was to set up the high pass layer so that it automatically adds the proper difference to the low pass layer, so changing the low pass' blur shouldn't affect the composite layer (it should only make a difference when you've already worked on the work-layers).
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Old 06-10-2012, 11:20 PM
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Re: Frequency Things

Hi Stroke,

Was trying out your action and was seeing a significant loss in detail when comparing the separation from the original, as well as some color shift and posterization particular in the shadow detail. I've attached a copy of what I am seeing, its hard to see in the before and after because of the compression so i've included a comparison using difference and a cures to highlight the loss, but the loss is visible at 100% view.

I don't doubt the color shift is coming from the highpass layer, with such a high setting its going to bring over color into the HS layer without desaturating.

_ Update

Totally forgot to check if the image i was trying it on was 8 or 16 bit.
It was 8bit so the difference was noticeable, In 16 bit the difference is far less (though still mostly in the shadow details)and the color shifting is gone.
------

I think the same result could be achieved using apply image.
Attached Images
File Type: jpg before_after.jpg (99.5 KB, 49 views)
File Type: jpg Detail-Loss.jpg (82.2 KB, 29 views)

Last edited by ratpat13; 06-10-2012 at 11:57 PM.
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Old 06-11-2012, 01:06 AM
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Stroker Stroker is offline
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Re: Frequency Things

Okay, as far as practical application goes, I've only used high/medium/low in a real situation once. This guy wanted some shading fixed on a photograph of some abdominal muscles. Very exact and particular about what he wanted, and fixing shading (lighting information) can be damn tricky. Turns out what he wanted fixed was exactly in the medium frequencies. It took about 5 minutes to fix. Anyother way would have taken *far* longer.

Holy smokes, Rat! I have never seen anything like that in my fiddlings.

I do see spikes and artifacts in areas of clipping, but never a big deal to fix after everything else has been done.

I also get posterization and banding from rounding, but negligable and acceptable. When using Difference mode against the original, nearly all of my values are 6 and below (perfectly acceptable considering range is 0-255 and the acrobatics involved). I do get a few values above 6, but very sparse and no big deal.

I have never seen the kind of loss that you are showing. I currently have no idea what is going on. The only thing that I can think of is colour space or management, and even that is a stab in the dark.
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Old 06-11-2012, 04:27 AM
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Re: Frequency Things

I think it had to do with accidentally testing it out on an 8bit image, even with apply image an 8bit loses some HF information since it can generate a true 50% gray.

I'm just wondering if you have found any benefit from using high pass over apply image. Since you should be able to do the same in either though the only time I've found multiple separations usefully is if i want to correct two separate degrees of HF information in one pass (usually shadows (clothing or buildings) or large blowout areas).
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Old 06-11-2012, 05:42 AM
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Re: Frequency Things

Quote:
Originally Posted by Der_W View Post
Hi ashphotoart,

you're right, sorry I forgot to add the proper instructions!

The empty "High Pass" and "Low Pass" layers are for your actual high pass and low pass work, so they should be empty at the beginning.
If you want to work with them, use your clone stamp with "Current and below" as sample point and just clone your high/low frequencies around.
However to work with the mix, it's important to first set the group's blend mode to "Normal"! When you're finished, set it back to "Luminosity". Unfortunately "Luminosity" mode will mess up the mix when you're applying it the whole time.
I updated the action to make the process a little more clear (better naming).
You should also notice, that the original idea was to set up the high pass layer so that it automatically adds the proper difference to the low pass layer, so changing the low pass' blur shouldn't affect the composite layer (it should only make a difference when you've already worked on the work-layers).
Der_w > Awesome....... I see this is more advance method than regular frequency seperation.... in regular FS we manuplate actual pixels.... but by your method we are manupting the pixels in the fly for High and Low frequencies....

Stroker trying to explore the 3 layers for frequency speration
1.HIGH
2.Medium and
3.Low
can we do same thing with your channel mix method ? what is the advantage using 3 seperation ? I think here we got an interesting topic to discuss....

Der_w > I would like to make open disucssion for the channel mix method u use for frequecny seperation... give us theorical explanation if u can....you are such a talented guy.

p.s. I saved this new action in to collection I already have a lot of actions from you. Thank you very much.
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Old 06-11-2012, 06:38 AM
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Der_W Der_W is offline
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Re: Frequency Things

Thanks and you're welcome !

I just made a "short" tutorial about the frequency separation via channel mixer action: http://www.retouchpro.com/forums/sof...tml#post308724
I'm thinking though about using the more accurate version, which will unfortunately increase the complexity of the tutorial even more.

Edit: Yes, incorporated it. But for the sake of not adding too much complexity, I added a small explanation of this at the end of the tutorial, so I won't throw numbers after numbers at you .

Last edited by Der_W; 06-11-2012 at 06:47 AM.
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