Smoothing Skin in Gimp

October 9, 2009

Hey look! I’m not breaking a promise! I told you I’d write later this week about how to smooth skin using the High Pass Filter – and I AM!

In the last entry, I talked about using either the Unsharp Mask or High Pass Filter to sharpen a photo, which is incredibly useful. But if you’re taking photos of people, you often want to soften parts of that photo – specifically their skin. And the High Pass Filter can help with that, too!

Here’s the photo I’m going to work with today – it’s already been edited some, but while I’m happy my face does not show my age (I’ll be 32 in less than a month, and I know you never would have guessed from this photo), I’m still quite aware it’s not perfect. To top it off, I almost never wear makeup, so chances are my skin’s looking a little drab in all the photos I’m in.

Me in Vegas

Remember when we were sharpening the image, we wanted to get our High Pass filter to the point where you could see the edges in it but not much more. When we use the High Pass for smoothing, we want to take it further. I played around until I picked the level of 75 to give me this (don’t forget, your High Pass Filter, after installed, is under Filters –> Enhance –> High Pass Filter):

High Pass of 75

Now if we take that layer and set the blending mode to Overlay, it will look like we’ve over-sharpened the photo:

Too sharp!!!

Oooh, but here comes the exciting part! Go to Colors –> Invert and suddenly everything is really soft and smooth:

All Smooth

At this point you can play with the opacity of High Pass layer to adjust the intensity of the effect. I’m gonna stick to 100%, though. Of course, this is smoothing my entire image we don’t want the entire image smooth, we just want the skin smooth, so we’re going to add a layer mask now.

For those of you that haven’t used layer masks before, they’re pretty helpful. What it does is allow you to paint on your layer with shades of black and white. If you paint pure black on an layer, it will turn the layer transparent there, and painting white will undo that. It’s similar to just erasing a layer, but it gives you more control because if you realize later that you erased something you didn’t want to, you don’t have to undo to get it back, just paint it white again. You can also paint in shades of gray, too, to make some spots semi-transparent.

We’re going to right click on the layer and select “Add Layer Mask”:

Add Layer Mask

(please ignore the fact that I have 15 million layers of my face in that screen capture. You don’t need that many, I had been playing around with some other things first before doing this tutorial, so I had a bunch of excess layers hanging around)

In the dialog box that pops up, select “White (full opacity)”. Now our layer has a white box next to it in the Layers dock:

Blank Layer Mask

Now, we start painting black to make things that we don’t want smoothed go away. This will make our original layer below show through… I’m going to zoom in and start with the eyes – making sure I get those eyelashes back – no one wants fuzzy eyelashes!

Unsmoothing my eyes

As you paint, you’ll notice that you can see the black showing up on the mask in the Layers dock. Here’s my mask after I’m done – I’ve painted back in the eyes, hair and mouth:

Finished Layer Mask

Now, I did this all by hand with the paint brush, but that’s because I didn’t have to worry about the detail in the background, since it was pretty much all black. If you need to paint in a lot more, though, what I suggest you do is that you use the paint brush by hand to get around the skin, but then once you have enough of a “buffer”, use the Free Select Tool (the one that looks like a lasso) to select the rest of the image and use the fill tool (the paint bucket) to fill it in with black.

Anyway, here’s my final image:

Final Image with Smooth Skin

As a reminder, here’s the original:

Me in Vegas

I’m sure there are other methods for smoothing skin, but this is all I’ve tried so far, and I’m pretty happy with it – please chime in using a comment if you know of another way!

Also, as a warning, I’m hoping to take some time tomorrow (Saturday) to work on fixing a few layout issues that I’ve noticed around here recently. And I’m not exactly perfect at this – so if you notice some quirky things going on, I apologize, it will be back to working order ASAP, I promise!)

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  • I love this - so cool to find another Gimp fanatic :) Must follow your blog right now !

  • Thanks so much for this tutorial - I've used it a few times now! So easy to follow, and very useful :)

    Keep up the great work!

  • James

    This is a brilliant blog

  • Nyal Cammack

    Finally! An easy to understand site for those of us in the real world of photography! I've been shooting for a long time and love it, but don't have time or energy to waste on the pretentious gits and "photography experts" that seem to be everywhere on the WWW. You've got an easy to read writing style, very informative posts, and you shoot some very nice photos! I'll check back again to see what other tidbits I can pick up and maybe come up with a tip or two I can leave.

  • evelyninoregon don't look almost-32! As for all these 'methods,' I am totally illiterate in such things, so I skim-read. ;-) I follow your blog, anyway.

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