Visual (Spatial) Frequencies for Retouching

I've written a series of tutorials on the topic of spatial / visual frequencies as a part of retouching work which I thought the membership here might enjoy. They remind me a lot of old conversations we had on similar topics for skin work here when I had more time to post.

While I'm well aware that it's poor internet etiquette to just post a link to one's self, I hope that you'll read a segment or two before condemning me - these are long entries, and would be a bit much to have in a thread which I'd rather focus on discussion of the matter.

In any case, I hope they help!

Visual Frequencies - a Primer
VF - Tools of the Trade
VF - The Mechanics
VF - Why, Sean, Why?!?
VF - Dirty Secrets, Dirty Tricks

Happy Labor Day!

Sean, these are great. The big gripe I have about most PS and LR content is that it just hashes over the same things that are in the help files. It's nice to learn something new.

That will keep me in reading for tomorrow

Thanks, hopefully will get an understanding of this technique.

Thanks guys! FWIW, I'll be attempting a few video followups for this - I know that reading such lengthy material isn't the easiest way for everyone to learn.

It's like a lightbulb just went on ....

I have been using FFT and frequency-based filtering for a while to isolate and to correct certain regular pattern features in images, but separating an image into frequency components for retouching never crossed my mind. I just downloaded your actions, opened a casual snapshot portrait I happened to have on my computer and, after studying the image for a few minutes, could visualize which corrections fell into which frequency band. I ran a 2 layer separation and within a few minutes had cloned out high-frequency blemishes and stray hair on the high-freq layer and reduced redness in the chin and cheek areas on the low frequency layer. I don't really do retouching, but now I can see how, in a few minutes, those kind of corrections will become standard. This is similar to the revelation of separating luminance from color information in Lab.

Thanks for sharing, this is very cool. I appreciate the effort.

Kirk

Nice effort - I remember what it was like trudging through the Highpass sucks thread and how much time it took trying a method, then comparing it to previous results and trying to figure out if it was easier or harder or even did what it was supposed to do. Your "synopsis" is a nice breakdown of the information.

It's pretty cool seeing an image split up and come together via all the bands.

Also, I must have missed the -50 contrast correction to the HP filter - I didn't know you could 'fix' it - been using the Apply Image 'fix' since I'm used to that from Dan Margulis's image correction stuff.

Good work, I had dreams of doing the same, but am way less ambitious.

Kirk - Way to go, spoiling my FFT followup surprise! :P Glad to hear it helped!

cmchavis - The HP filter's 'brokenness' was just its naive (or brilliant, depending on how you want to look at it) design. we just had to overcome that naivete (as well our own as to WTH was going on).

Ahhhh physics applied to post processing. You've made my day...reading......

Sorry about that - I'll pretend I've never heard of it. Post away!

Kirk

Been reading for quite a while.
Useful stuff.

Obviously very nifty for retouching people.
Have to try the results for sharpening compared to other methods.

Trying to come up with uses of bandstop and bandpass. Might come in handy as well.

Edit: Ah. Another lightbulb: Separating a portrait shot into low-medium and high frequencies, then masking off the medium frequencies for a quick smoothing of the skin. Nice.


As for the differences between the "Apply Image" method and photoshops "HighPass" filter followed by a contrast -50: Not that big of a difference from what I see...
And the latter can be used on smart objects. (With the Brightness/contrast as a clipped adjustment layer). Nifty

Side note: Would be nice to have a link on the bottom of the articles to the next article for ease of browsing.

René Damkot wrote in post #10905790
Have to try the results for sharpening compared to other methods.

Be sure to try sharpening with 'medium-high' frequencies like 1.5px-0.5px. By removing the finest detail, some of the oversharpened aesthetic can be avoided. You can also use noise reduction in the same way that we discussed using Median / Surface Blur / etc. in order to minimize artifacting, yet not really changing the image (great if you want to sharpen an image which you want to retain its grittiness).

René Damkot wrote in post #10905790
As for the differences between the "Apply Image" method and photoshops "HighPass" filter followed by a contrast -50: Not that big of a difference from what I see...
And the latter can be used on smart objects. (With the Brightness/contrast as a clipped adjustment layer). Nifty

Be careful with this for anything but a bandstop filter (and even then sometimes) - the -50 contrast has to come before the HP filter is applied, otherwise its clipping will always come into play. You can, however, create a SO of the image, and then edit that SO to include a -50 Contrast adjustment layer so that you retain a nondestructive / adaptive workflow, but get the advantage of working entirely with SOs.

René Damkot wrote in post #10905790
Side note: Would be nice to have a link on the bottom of the articles to the next article for ease of browsing.

Good point - I'll add that in this evening. Thanks!

seanbaker wrote in post #10912485
Be careful with this for anything but a bandstop filter (and even then sometimes) - the -50 contrast has to come before the HP filter is applied, otherwise its clipping will always come into play. You can, however, create a SO of the image, and then edit that SO to include a -50 Contrast adjustment layer so that you retain a nondestructive / adaptive workflow, but get the advantage of working entirely with SOs.

Hadn't thought about including the -50 contrast into the SO. I now duplicate the SO, then add the -50 contrast as an adjustment layer. That means it's applied after the HP filter though.
Better to apply it as an adjustment inside the SO indeed.
Good point