Sharpening with High Pass filter

In this tutorial I will explain how to sharpen an image using the High Pass Filter in Photoshop CS4. Let's open up the image that we worked with in the previous article (skin color correction)


In order to use this filter, we must duplicate the layer. Then, with the new layer still selected, go to Filter - Other - High Pass (if under the Filter menu you can't find Other, click Show all menu items). Choose a lower value (start from 0, and move the slider to the right until the edge of the objects are visible). For this picture I chose 2.4


Go to layer blending modes, and chose a mode that's favorable for your picture. For this one, Soft Light did the trick. Now the image is sharper.


Ctrl+Shift+E to Merge Layers, than save your work. That's it!

Skin Color Correction

As i talked in my post regarding white balance, almost any digital camera (even DSLRs) are not able to reproduce exactly the real life colors, and tend to give a reddish/blueish tint to the whole image, especially to the skin.


Let's open this image in Photoshop. Before beginning, you should duplicate the layer. White Balance was manually set, and the image is taken straight out of the camera.

First step - put some colour samplers on a white point, a black point and somewhere on the skin. Select the Eyedropper Tool (press I and make sure Sample Size is at least 3 by 3 average) and Shift+Click on the points mentioned earlier. Use thresholding to find the whitest/darkest points. I picked these 3:


For the second point, corresponding to the skin color, I am working in CMYK format (click on the eyedropper icon in the Info Tab to select it) because these numbers are more helpful.

But first, the black point. Notice that the RGB values for the darkest point are 4,4,4 which is ok (5,5,5 ideally). The RGB values for the white point (point #3) are: 255,232,234. Ideally, these should be: 245,245,245. We got to work on correcting this. Open up Curves, go to the Red Channel, pick the right end of the line and drag it downwards until the R value is 245.
Now, go to the Green Channel, and drag that point to the left, until G is 245. Repeat this for Blue Channel.


Now, for the skin: it's better to work in CMYK color mode, because there is a simple rule regarding natural skin color:
-C (Cyan) should have a lower value, usually between 7-12
-M (Magenta) should have a value equal to 3*Cyan: 30-35
-Y (Yellow) should be a little higher than M

In our case, C is a little high and Y is very low. Go to Red Channel, click on the button with the hand and 2 arrows (with the help of this, you can click and drag in the image to modify the curve)
place the cursor over colour sampler #3, and click&drag upwards. Notice the curve is changing shape, and keep dragging it until the C value is about 11.


Repeat this step for M (go to Green Channel and click&drag upwards until M is about 33-34) and then for Y (go to Blue Channel and click&drag downwards until Y is about 36-37). The skin looks much better, doesn't it?


While modifying the curves, the RGB values for the white/black point changed. This can be easily fixed by modifying the end of the curves. So this is a simple way of correcting skin color in Photoshop. Shift+Drag your eyedropper samplers away from the image and save your work.