So what is Frequency Separation?
It’s basically a retouching technique that allows us to work on different parts of a picture and by that I mean, in simplistic terms, pictures are made up of two things, the colour and the detail. So if we are able to split our pictures into those 2 parts it means we would be able to work on one without affecting the other. Sounds kind of strange but all will become clear…trust me.
If you’re anything like me, at some point you’ve used something like the Healing Brush to remove a mark say on someone’s face that is on their skin right near to their hairline and as you have done the result looks like a smudgy mess. Well that’s because when you are trying to remove the mark (detail), Photoshop is bringing in nearby colour; Frequency Separation would prevent this from happening because we would be able to have the colour on one layer and the detail on the other…as an example of just one of the many things we can do with it.
To show you what I mean, here’s a written step-by-step tutorial showing the process and also at the very bottom I’ve included a video for those who like to watch rather than read.
So here’s a portrait where I have separated the colour and the detail. Figure 1.1.is the colour layer and yes you can see that it’s a portrait however there are no defined edges or sharpness; it’s basically an arrangement of colour right?
Now Figure 1.2 is the detail where you can see no colour but can clearly see the defined edges and sharpness within the portrait showing through.
I guess we now need to look at exactly how we separate the colour and the content in our pictures. Now there is a slightly different way to do this depending on whether you’re working on a 16Bit or 8Bit image. I’ll cover both during the session but for now let’s look at the method for a 16Bit image.
- With your image open in Photoshop, create 2 copies in the layer stack by holding down CMD (Mac) / CTRL (Windows) and pressing J two times. Rename the first copy colour and the second copy (top layer) detail. Change the Blend Mode of the detail layer to Linear Light (Figure 1.3)
- Turn off the detail layer by clicking on the layer eye icon and click on the colour layer (Figure 1.4). Now we’re working on a high resolution image, so to have a layer with just colour and no sharpness / detail we go to Filter > Blur > Gaussian Blur (Figure 1.5) and input a Radius of around 5 pixels (Figure 1.6) (If we were using a low resolution file then we would look at maybe 2 or 3). Click OK
- Now turn on, and click on the detail layer to make it active. Go to Image > Apply Image (Figure 1.7) We’ll discuss all the settings and options within the Apply Image dialog box during the session but in Figure 1.8 you can see what you need to input.
Note: Make sure that in the Layer drop down menu you choose your colour layer
Tip: If you’re working on an 8Bit image then in the Apply Image dialog, you would not tick the Invert checkbox, in Blending you would choose Subtract and for the Offset, you would input 128.
- When you click OK, in the Layers Panel you need to change the Blend Mode of the detail layer to Linear Light (Figure 1.9); this keeps the detail on the layer but makes the layer visible by hiding the grey.
- Now we’ve split our picture into it’s colour and detail, let’s put the technique to use. Let’s just say I want to remove some of the stray hair on Sophie’s forehead. Now this is exactly what I meant earlier about sometimes getting smudgy result. To remove the hair we’ll click on the detail layer. Then choose the Clone Stamp Tool from the Tool Bar and in the options at the top of the screen make sure that Sample is set to Current Layer (Figure 1.10)
- Now using the Clone Stamp Tool, choose an area on the forehead where you want to remove some stray hairs (Figure 1.11), hold down the Alt / Option key and click to sample an area of clean skin then trace over the stray hair. Notice how when we do this, we can remove the hair without smudging (Figure 1.12)
Note: On the detail layer we will always tend to use tools like the Clone Stamp Tool or Healing Brush; on the colour layer we’ll tend to use tools such as Brushes, Smudge Tool, Gradients…
See how quickly and effectively we can work using this technique to remove distracting elements.
Now let’s look at how we can use the colour layer to remove something like skin shine. Of course there are many other ways we can do this, but Frequency Separation works so well and so quickly.
- Click on the colour layer and add a new blank layer above it. Rename this layer skin shine (Figure 1.13). Choose the Gradient Tool from the Tool Bar and then in the options at the top of the screen choose the Foreground to Transparent Gradient from the Gradient Picker (Figure 1.14) and then choose the Radial Gradient option (2nd gradient from the left) (Figure 1.14)
- Now choose an area of shiny skin, hold down the Alt / Option key to click and sample an area of non-shiny skiny as close to the shine as possible (Doing this places the sampled colour as the Foreground Colour in the Tool Bar). Then click down and drag to cover over the shine (Figure 1.16). Make a few more samples around the shine if necessary and drag over to remove it completely.
- You can also use this technique to maybe reduce bags under eyes. Hold down the Alt / Option key to sample an area of skin underneath the eye (not the bag) and then drag over the area with the gradient (Figure 1.17)
Now you might notice that as you apply a gradient, it does tend to cover more area than maybe you want. This isn’t a problem as it allows us to work quicker and looser. When done we can simply use a layer mask to control where the gradient covers.
- Hold down the Alt / Option key and click on the Layer Mask icon at the bottom of the layers panel. This now adds a black layer mask to our skin shine layer (Figure 1.18) and hides what we have just done in the last couple of steps. Now simply choose a soft edged brush and with a white foreground colour brush over the shine areas you have just covered over and the eye bags to only reveal the covering that you want and for it to not appear / spill onto anywhere else (Figure 1.19)
I just love using Frequency Separation for sharpening eyes. It works so well adding impact to the eyes but without any halos, colour shift, artefacts etc…
- Click on the detail layer and then using the Marquee Tool, make a rough selection that includes the eyes (Figure 1.20)
- Hold down CMD / CTRL and then J to put this selected area up onto its own layer and rename this layer eye sharpen (Figure 1.21)
- Hold down the Alt / Option key and then click to add a Layer Mask. This adds a black layer mask which hides the eye sharpening so as before, choose a soft round brush with a white foreground colour and then paint over the eyes to reveal the sharpening (Figure 1.22)
Here we can see the Before (Figure 1.23) and After (Figure 1.24) sharpening. Of course if you want even more sharpening you could simply duplicate the eye sharpen layer and use opacity to control how much sharpening.
Here’s a recording of a LIVE Broadcast that I did over on my YouTube Channel that goes through the whole process too; just jump past the intro if you want to dive straight in…
Right that’s all from me for now so as always if you have any questions / comments, then feel free to make use of the comments section below and make sure to get back to you.
In the mean time though … I’ll catch you next time.