guide to the frequency separation technique

8/10/2019 Guide to the Frequency Separation Technique

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5ike in music any audio can be represented in sine waves, we can also break up an ima"e into

low and hi"h frequency sine waves. Hi"h frequencies in an ima"e will contain information about

8ne details, such as skin pores, hair, 8ne lines, skin imperfections (acne, scars, 8ne lines, etc.).

5ow frequencies are the ima"e data that contains information about volume, tone and color

transitions. n other words shadows and li"ht areas, colors and tones. f you look at only the low

frequency information of an ima"e, you mi"ht be able to reco"ni6e the ima"e, but it will not hold

any precise detail.

9ou may have seen this optic illusion that e4ploits the frequency separation principle. f you look

at this ima"e from a normal distance from your computer while readin" this article you will see

&lbert instein!s photo. :ow, "et up and walk away from your screen. 5ook a"ain. 3ho do you

see now;


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ssentially, this ima"e is a combination of photos of arilyn onroe in the low frequency layer

and instein!s in the hi"h frequency layer. 3hen you look at the ima"e from a close distance you

see the hi"h spatial frequency ima"e (instein), the 8ne details, the outlines of his facial

features. low pass 8lter> of your vision will kick

in 2 and you will see the low spatial frequency ima"e (arilyn onroe).

3ithin the di"ital photo"raphy editin" craft, the separation of spatial frequency data in ima"escan be utili6ed for skin (and not only) retouchin". 3hile there are a number of ways to implement

the Frequency Separation technique, the steps you take to "et to the 8nal result will de8ne the

amount of time spent and the quality of the outcome.

1efore we be"in, want to make a quick note re"ardin" the use of the Hi"h $ass 8lter in the FS

technique. 3hen it is used to separate the ima"e into hi"h and low spatial frequencies, the

results are inaccurate. n other words, after the separation your ima"e data is sli"htly skewed, so

you compromise the quality of the outcome before you even be"in retouchin".

1ut? 'hat inaccuracy is mainly a7ectin" the pi4els with e4treme bri"htness, and when used

smartly, it can actually be bene8cial to the outcome in some situations. will talk about this later.

5et!s 8rst talk about this more accurate al"orithm.

&$$59 &/ S'#$

a. %uplicate your 1ack"round layer twice the top layer is the base for the hi"h frequency ima"e

data and the bottom duplicate is for the low frequency ima"e data.

b. 'urn o7 the visibility of the Hi"h Frequency layer and select the 5ow Frequency layer.


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*. 3ith the 5ow Frequency layer selected, run the /aussian 1lur 8lter and choose $i4el @adius

with which all the 8ne details will be blurred. 3e turn o7 the visibility of the Hi"h Frequency

layer, so that we can better see how our choice of $i4el @adius a7ects the entire ima"e. &fter

you!ve applied the /aussian 1lur 8lter, turn the Hi"h Frequency layer!s visibility back on.

A. :ow select the Hi"h Frequency layer and "o ma"e B &pply ma"e and dependin" on what

color depth you!re workin" in your settin"s will be as follows (click to enlar"e)

:ote that in the 5ayer dialo" you will need to select the layer that contains your 5ow Frequency

(blurred) ima"e. n my e4ample it is called =ust that >5ow Frequency layer>.

-. :ow chan"e the 1lendin" ode of the Hi"h Frequency layer to 5inear 5i"ht and your overall

ima"e will look e4actly as before you started the separation.


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9ou!re set up. usually also "roup these two layers, so my 5ayer stack is more or"ani6ed.

From this point on, every retoucher and photo"rapher chooses his or her preferred tools to work

their ma"ic. 1asically, we aim to soften and even out color and tone transitions on the 5ow

Frequency layer, without a7ectin" skin te4ture, which was captured and preserved on the Hi"h

Frequency layer.

9ou will normally hear that the Clone Stamp tool or the Healin" 1rush tool with Current 5ayer

Samplin" settin" and very low Hardness are the tools to work on the 5ow Frequency layer thesame tools only with very hi"h Hardness settin"s are your Hi"h Frequency layer tools.

Check out my old video where only used the Healin" 1rush tool. !ve chan"ed my ways

drastically since then, but we!ll talk about that later. 'he "oal of this video was to show how fast

this technique can be, so you will see a countdown clock at the top of my screen 2 *D minutes,

boom?

httpEEyoutu.beE6fG"%3#a@w

:ote named the Hi"h Frequency layer >Hi"h $ass 2 te4ture> in the video, which is incorrect,

because was actually usin" the &pply ma"e setup. 3ell, live and learn?

f that!s all you!ve been doin" so far, let me share a few more strate"ies that !ve learned from

my own e4perience and from my talented friends. 3e all love e4perimentin" and comin" up with

new ways to use ordinary tools and techniques, so here!s what we!ve come up with so far.

H/H $&SS F5'@ S'#$

Hi"h $ass 8lter setup for the Frequency Separation technique isn!t all that bad, and shouldn!t be

completely written o7 as an inaccurate way to separate spatial frequencies.

&s mentioned before, when Hi"h $ass 8lter is applied to the Hi"h Frequency layer in place of the&pply ma"e function, it "ives you an imprecise 8nal ima"e where the bri"htest pi4els are usually

"rayed out. &ccordin" to my friend &leksey, it actually plays out well when you are retouchin"

skin with a bit of overe4posed hi"hli"hts on it. 'hey "et toned down and the skin looks more

matte as a result.


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'o separate spatial frequencies with the Hi"h $ass 8lter, we need to create two duplicate layers,

=ust like in the &pply ma"e approach. 'he top layer will contain our Hi"h Frequency ima"e data

and the bottom layer will be our 5ow Frequency layer.

3e select the Hi"h Frequency layer, apply the Hi"h $ass 8lter to it (Filter B


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*p4 @adius isn!t enou"h because it barely picks up any te4ture, and we!re riskin" to leave

important 8ne details out.


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&t .p4 @adius we!re startin" to see what we don!t want to "o onto the Hi"h Frequency layer 2

e4cessive tonal transitions and volumes 2 so we have to "o back down.


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&nd at A.Dp4 @adius we "et the ri"ht amount of 8ne details, so this will be the number we select.Click


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hi"hly recommend tryin" all of the mentioned above tools and 8"urin" out in what situations

what tools work best for you.

&nd here!s the result of the quick skin retouch on &leksey!s photo throu"h the Hi"h $ass setup

&ccordin" to my crafty friend, this skin retouch took him only a few minutes because the

frequency spatial data of the ima"e was properly separated. &ll the te4ture remained intact on

the top layer 2 Hi"h Frequency layer 2 and the colors and tones were quickly evened out

underneath it.


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>'he &pply ma"e and Hi"h $ass approaches of separatin" frequency spatial data of an ima"e

are the two main ways of how use the FS technique,> says &leksey, >&pply ma"e setup is more

accurate, but the Hi"h $ass setup is quick and helps me to not only customi6e the separation of

skin te4ture from underlyin" colors, but also tone down >hot> hi"hli"hts on the skin. always "o

for the Hi"h $ass setup when need to do a quick retouch, especially when evenin" out skin. t is

really helpful to be familiar with and practice both approaches.>


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*. @emovin" skin blotchiness with the Surface 1lur 8lter.

9ou can add an additional duplicate layer of the ori"inal ima"e between the Hi"h and 5ow

Frequency layers (in either setup). 'hen apply Surface 1lur to it 2 @adius and 'hreshold numbers

will always be di7erent for di7erent ima"es. Kve never had to use Surface 1lur for anythin" in my

work before, so &leksey e4plained to me the correct way of selectin" @adius and 'hreshold

settin"s

3hile the 'hreshold slider is at its minimum position, move the @adius slider to where you want

it to be (dependin" on the amount of blurrin" that you need).

:ow push the 'hreshold to its ma4 position and start slowly movin" it back to the left until you

8nd the number at which colors donKt smear into each other. 3atch such areas as face and body

outlines, or the line where the hair meets the face, etc.)


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'hen cover this layer with a black 5ayer ask and paint with a white soft brush (low


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A. %on!t try to retouch the entire face with =ust one round of Frequency Separation.

Set up Hi"h and 5ow Frequency layers as many times as you need to solve problems in your

current retouch. personally do at least *2A rounds of Frequency Separation, and also %od"e 01urn the problems that remain.

&leksey su""ests that the best results can be achieved when you create custom Hi"h and 5ow

Frequency layers (=ust like he showed us earlier) for each part of the face that needs doctorin".

9our @adius settin"s for the Hi"h $ass and /aussian 1lur 8lters most likely will be di7erent for

each part of the face. t is a little more elaborate approach, but custom settin"s will help you

achieve the best results for each part of the ima"e.

-. ake sure to practice usin" di7erent tools for di7erent retouchin" problems.

@emember, than you can use the Clone Stamp, Healin" 1rush tools and a simple brush to 84 skin

problems on the 5ow Frequency layer, as well as on the Hi"h Frequency layer. 3atch the

Hardness and


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D. Create or download an &ction.

personally use custom settin"s for the Hi"h $ass setup, so don!t need an &ction for that. 1ut in

many situations, when the sub=ect!s face is not very close to the camera (the skin te4ture doesn!t

require a lot of doctorin") use a Frequency Separation &ction that recorded for myself. mainly

work in 2bit color depth, so my action is for 2bit ima"es. 9ou can break it down and re2create

one for L2bit photos usin" the settin"s !ve mentioned above.

9ou can download my Frequency Separation &ction alon" with a handful of useful beauty

retouchin" &ctions from my blo" (in the sidebar).

L. Sharpenin" skin te4ture with the Hi"h Frequency Separation

&nother trick that came up with in my e4periments is enhancin" skin te4ture by duplicatin" the

Hi"h Frequency layer. usually 8rst 84 all the most visible blemishes on the ori"inal Hi"h

Frequency layer, then duplicate it and cover with a black 5ayer ask. then paint with a soft

white brush (low says ichael 3olos6ynowic6.


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'hat!s all for today. am sure there are many more additional tricks that can be used with the

Frequency Separation technique, so if you know any 2 please share with us in the comments?

Some sources have come across in my research

& odel ayhem post by Sean 1aker.

& odel ayhem post by "rahams6.

guide to the frequency separation technique

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