Retouching - Part 2 How it's done.

August 24, 2015  •  Leave a Comment

Yesterday I published a quick blog to show how I had used a technique called Frequency Separation to retouch an image. Just as a quick recap this is what I started out with and where I ended up.

So, how do we get to the final image? Let's start by looking at the retouching technique known as frequency separation. 

A bit like with audio sounds, images can be broken down into high and low frequencies. The low frequencies contain information about large areas of colour and tone whilst the high frequencies contain information about fine details, skin pores, hair, blemishes and fine lines. Frequency separation splits the two frequencies into separate layers so that we an work on each individually. 

We work on a colour layer to balance skin tone and even up any harsh light or dark areas and we work on a texture layer to remove skin blemishes. 

To understand why it is important to work on the layers separately we can compare it to an older method I have used to retouching skin. 

A simple way is to create a duplicate layer of the image, apply some gaussian blur on the second layer and using a layer mask paint detail back into the image.

First duplicate the layer by right clicking on the background layer and selecting Duplicate Layer (or CTRL+J/Command+J)

Now apply a gaussian blur to the new layer

Select a value that removes a lot of the skin detail (blemishes) and click o OK. Here I have gone for 7.8 but it will vary depending on your image.

Now we are going to add a layer mask to paint out where we do not want the skin softened. Making sure the blur layer is selected (I have renamed it from Background copy) click on the Mask icon highlighted in red below.

Now making sure the layer mask is highlighted in white in the layers palette select the brush tool, make sure you are using the default black and white colours (hit the D key) we can paint back in the detail. Adjust the brush size and opacity to paint the mask. Here I used a large brush with opacity set to 100 to paint in the background and dress, then reduced the brush size to paint details back into the hair before reducing the opacity of the brush down to about 20% to paint details back into the lips and eyebrows. Finally a small brush with the opacity set to 100 was used to pull detail back into the eyes.

This gave me this as a final (quick) product.

The problem with this technique is that the gaussian blur layer can remove all of the skin detail leaving a rather plastic effect. What we need is a way to retain the skin detail we want but at the same time blend the skin tones in the same way the gaussian blur technique does.

This is where frequency separation comes in. We start in a similar manner as before but this time we create two layer copies of the original image. 

After duplicating the original layer twice (using CTRL+J/Command+J), rename the first copy to Colour and the second copy to Texture. Turn off the visibility of Texture. Select the Colour layer and apply a gaussian blur to it. Apply just enough to remove any skin detail.

Now turn on the visibility of the Texture layer and go to Image -> Apply Image

In the dialogue box that comes up set the following values

What this essentially does is subtract the colour information from the Texture layer and will just leave us with the texture information.

Finally set the blend mode of the texture layer to be Linear Light

Our image now looks essentially the same as the original background layer.

What we have now done is split out the two frequencies onto separate layers and we can use each one to retouch our image. 

Make sure the Texture layer is selected and select the Clone Stamp tool from the toolbox. Make sure in the options at the top of the screen Sample is set to Current Layer.

Zoom in on your image and select an source for the clone stamp (ALT+Click) near to an area you want to remove a blemish (keep it close to where the blemish is to retain similar detail). Now paint over the blemish. Because we are working on the texture layer only the texture will be cloned out and colours will remain unaffected.

Now the long bit, go around your image removing skin blemishes and fine lines. Don't worry you can always come back later and finish it if you miss some be reselecting the layer, and clone tool.

Once we have completed the texture later we want to look at smoothing out skin tones. To do this we need to select the Colour layer. Then select the Lasso tool and make sure you set a reasonably large feather (around 30-50 pixels for a hi-res image). 

Select an area of skin you want to even out (I have selected under the chin) by drawing a rough outline around it. Then from the Filter menu select Gaussian Blur and apply just enough blur to even the tones out nicely.

Repeat this for all areas of the skin you want to even out. Be careful around the eyes and cheeks not to remove too much shadow as this can make the portrait look unrealistic.

Because we are only working on the colour we do not loose the texture detail. You can see this by zooming in.

There are no short cuts. You need to take your time over both the texture layer cloning and the colour layer blurring to get a nice effect. I'm reasonably pleased with my first attempt at using this technique and I am sure if I spent more time on it I could get better results but I'm learning as well!

To get the final 'fashion' look I created four additional layers. The first layer is just a colour layer and I chose a slightly yellow warm tone for the whole image and reduced the opacity down to about 30%

Then I added two graduated filters. A radial one positioned top right to act a little like a sun flare and a linear filter from the bottom up just to tone the base of the image again both with slightly yellow warm tone and opacity set between 50-60%

The final layer was a Selective Colour layer which allows you to pick a base colour (mainly green in this image to reduce the contrast of the leaves in the background) and adjust the CMYK values to alter the overall hue of the selected colour. I also selected the red colour and boosted the redness of the hair.

This gave me my final image.

These are some very basic layer adjustment to give an effect and I am playing around with other colour tones, and adjustment layers (e.g. Vibrance, Curves) to see what effect they have.

Frequency separation is quite a hard technique to put into words but I hope this tutorial can point you in the right direction. There are plenty of online video tutorials if you search for photo shop frequency separation which might help enlighten you some more ...... if you are remotely interested!
















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