Fixing Highlights and Shadows - Part 2: Multiply and Screen

In the first part of this tutorial we used the dynamic range correction, which will help us most of the time. But for situations like in this photo, we need more horse power:


Obviously this photo needs some improvements, but we will fix here only the luminosity. First of all I try levels and dynamic range approach:


Definitely, not so lucky like in the first part. I have a highlight gap, I will fix it of course, but the effect is not so impressive, I need something more:


I will duplicate the background layer twice and I rename the layers: shadows, respectively highlights. To duplicate a layer, first select it in the layers dialog and than click on the duplicate layer button or just press Ctrl+Shift+D. To rename a layer just double click over its name, than edit and press enter to validate.

Next I will change the mode of the Shadows layer to Multiply and the highlights layer to Screen mode. The multiply mode always darkens the image, the screen mode always make the image lighter. More details on render modes can be found into the Gimp manual.


You may wonder why do I need a layer like multiply, which darkens the image, since I already have a too dark one. Basically I have two reasons: I want to reduce the light of the sky a little bit and also because it will help me to give a more natural feel to the final result. The good thing is that you will do not need both multiply and screen layers all the time. It depends on your photo.

Here I have the result when only the background and the shadows layers are visible, next only background and highlights and all of them visible in the third one.





The screen mode increases the highlight of an image, multiply the shadow. The biggest problem we have now is that the highlights layer (screen mode) makes the sky too much brighter, unreal, loosing almost all the details.

In order to fix the sky I am going to use a layer mask on the highlights layer. Layer masks are very useful in lots of photo retouching scenarios, so please consult the Gimp manual for more details on this subject. Basically, you may consider a mask as a fully transparent foil placed over all the surface of a layer. After that placing the foil, you start to paint over it in order to hide some parts of that layer. You only have white pint to use with your brush. To be transparent, this foil is composed only of pixels with no value (0, which is equivalent to black). Pixels with maximum value (255, which is white) will obstruct completely the visibility to that layer. Anything between 0 and 255 will me partially transparent, the lower the value, the higher the transparency. Finally when you are happy with the painting you have made to that foil (mask) you will stick it to the layer, using a fully transparent glue (which means apply layer mask).

If you got the point with this masks I suppose you already know what I am going to do in order to this the sky: use a layer mask on the highlights layer, fully transparent (black) over the sky and fully white over the rest of the picture. In order to improve the transition between black and white I will use a gradient.


In order to create the gradient I will use the blend tool. This tool fills the selected area with a gradient blend of the foreground and background colors by default, but there are many options. To make a blend, drag the cursor in the direction you want the gradient to go, and release the mouse button when you feel you have the right position and size of your blend. The softness of the blend depends on how far you drag the cursor. The shorter the drag distance, the sharper it will be.For more details please consult the Gimp manual.

For this photo I want a sharper gradient, just above the line where the sea begins. To do this, I fist create a layer mask (no meter what option you select when creating this mask because the gradient will replace it anyway). To create a layer mask, select the layer you want to affect, than either right click and select Add Layer Mask, or go to Layers -> Mask -> Add Layer Mask. Click Add in the dialog which opens.

Notices that white rectangle next to the highlights layer? This means we have a fully opaque layer mask on this layer. Now, select this mask by clicking inside the white rectangle (in the picture above is already selected). In the layers dialog you can see where the current selection is by the color of the border surrounding each thumbnail. All, except the selected one are surrounded by a black border. The selected is surrounded by white, but since our mask is white we cannot observe that white border around it (the absence of a white border on other thumbnail should be the clue). While the layer mask is selected, pick the blend tool, leave all options to default and make sure your foreground color is black and the background color is white.

If you look carefully at the photo you will notice that I already have a gradient at the sea level (lighter close to the beach, darker at the horizon line). This is where I will place my gradient also. Usually you will do it just above the horizon line, but since I have also the sea I will do it below the horizon and above the beach (a no sand beach actually). Draw a vertical line starting from the line where the sky meets the sea and stop just above the beach line. Make sure the line is perfectly vertical and release the mouse.

Now watch the result below, the sky is not so over burned anymore (to sharp gradient, indeed but it will be fixed later as a side effect). The highlight layer is not applied anymore above the sky part of the picture:

We are almost finished. This gradient trick seems to work, but now we have a big problem. The guy with a yellow t-shirt has the head on the gradient area and now, part of his face is lighter than the upper part. He is too pretty to deserve this (unfortunately for you girls is married also). We should adjust that mask in order to be fully opaque over his head.

If you didn't noticed so far the problem with my dear fiend's head, I will turn off the visibility of all the layers except the highlights one (as you remember, this is done by clicking those eyes) and I zoom in. Do you see how his head is becoming almost transparent at the top of the face? In the not fully opaque zone, the highlights layer will not be fully applied, unlike it happens with all the other people in this photo and this is simply unfair:


We have to fix this because I do not what him to be upset on me. Select the layer mask (like we did before gradient) by clicking on it in the layers dialog. Select the intelligent scissors selection tool by clicking on the scissors icon in the tools dialog. This tool will let us select the head with enough detail. Click around the head an see the result, finally click on the starting point in order to close the curve. If you are not happy with the selection on different zones you can click on any point of the curve in order to move it or click on the curve in order to add more points. When happy with the curve, press enter to transform it to selection (since we are interested to fix only the semitransparent part, I didn't contoured all the face, just the part we need to be fixed):


After hitting enter and we got the selection, we will use the bucket fill tool in order to paint on the selected zone in white. Make sure the mask is selected, not the layer. Make sure you use white color. In my case, since the white is the background color I selected BG color fill. If you have it as foreground, select FG color fill. If you don't have it at all, select the white color by clicking on the foreground color (the black square). Also make sure that for the affected area you've selected Fill whole selection (this is not the default).

With the bucket fill tool picked, just click inside the selection we've just made around the head. Is there any non fully opaque part remaining on his head? If yes, you did something wrong, undo and start over again. Here is the result after this painting and pressing Ctrl+Shift+A for clearing the selection:


In order to clearly see what we actually did, right click on the layer mask in the layers dialog and check Show layer mask. You should see the below image. Notice the white head we've made with the bucket fill.


Now uncheck Show layer mask in order to return to out photo. We finished with the mask, we have to stick it with some glue. Right click on the highlight layer and select Apply Layer Mask. Also make visible all layers again by clicking the eyes on layers dialog. We are in this stage now:


Now we really are one step behind our great job finish. We now have a better photo but it is not really natural. We still have to make some adjustments. First of all it is not lighted enough because of that multiply (shadows layer). Also that gradient is to sharp. The good news is that we can fix these easily, using the opacity slider for shadows and highlights layers. If you do not like the effect of the shadows layer you can skip it since the beginning. But remember that it has its advantages, mostly on sky and the beach rocks. I let you experiment with the opacity sliders. My decision was to keep 25% for the shadows layer and 90% for highlights, but since I am really tired now it may not be the best decision. Can you find a better one?


Anyway here is the result:


The original was:

Do you consider this difficult? Not really, but sometimes you can achieve a good result using a third party filter, which of course is also free. We will discuss about this in the third part of this tutorial, which I promise it will be shorter than this.

Part 3: Shadows & Highlights Filter

Part 1: Dynamic Range