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Out of Bounds
Smooth Skin Action
Sky Replacement
Window Arrange

EASY SKY REPLACEMENT FOR WHITE SKY

Foreword:
This method is an easy and quick way to replace a white sky with one from another image. No complicated masking involved and you can have as many gaps in your foreground as you like. Reading this might take longer than actually doing it, so don't worry and try it.

[1] Open your image and if possible, work on a copy of the original. It will look better if you use the largest possible image and then at the end resize. In my example, I'm going to use a photo with trees against a white sky (left), to show you plenty of gaps and how to fill them (right). I've worked on a large version too, so using my copy here on the website to try, will not give you the same results as seen here.

[2] Select the lasso tool with Feather set to 0. Make a rough selection of the white sky. The point in this, is to include all the sky with the bits and pieces between the trees but without any white seen in the rest of the image. Go to Selection/Feather and enter a Radius of 5-10 pixels.

[3] Having done that, go to the bottom of the layers palette and click on the adjustment layer icon . Choose the Selective Color. In the following window, under Colors, choose the Whites.

What we want to achieve here, is to make the white sky turn into a blue one, similar to the blue of the new sky. The general rule is Cyan more than Magenta, Yellow even less and Black is used to define the brightness of the sky. The method used for this is Absolute.

If you prefer, you can also work by numbers for an exact match of the new colour. Use the eyedropper and sample (3 by 3 or 5 by 5 Average) the colour of your new sky, somewhere near the border where it will be pasted into your image. Take that RGB value, go to this site and convert the RGB value. Use the resulting CMY values as shown in percentage and dial in those numbers for your Selective Color adjustment. Black is set to 0, the other numbers as converted and you should have an exact match. If you work in CMYK, rather than RGB, simply take the CMYK values, no need to convert.

[4] It's looking much better already but now you have to find a good sky replacement. My advice, take plenty of pictures, whenever you see a nice sky and keep them for later. When you choose a replacement, select one with the sun in a similar position and try not to overpower the image with your new sky, except if that is what you want.

The advantage of having your own archive, is that you have photos from the same camera. This will give you a very similar look and grain, compared to a photo taken with a professional camera and another one with a mobile phone. It doesn't cost you anything either, the sky is always there, you just have to shoot it. I think you get my point.

Here is my replacement for this example:

[5] As you can see, this doesn't really fit yet but should look alright in the end. After opening your replacement, drag it over to your other image. This will create a new layer on top of the selective color adjustment layer.

Bring up the Free Transform (Ctrl+T) under Edit/Free Transform. When you right click inside the selection, you can choose from different options. In my case, I rotated the image and used perspective to make it fit a little better.

[6] Turn off the two layers on top, by clicking on the eye icon . Click on the background layer to make it active and select the Magic Wand Tool (W). Turn off the Contiguous option and dial in a suitable Tolerance. In my example, I've used something around 15-25.

Click on the white sky, which should give you a selection of the sky and most of the gaps in between the trees. Shift click on any white area in the sky you didn't get completely, to add to the selection but don't worry too much about the gaps.

If necessary, select the lasso tool, Alt click and drag around any area inside the picture to deselect the white areas. In my case, parts of the river were selected too, because it has some white in it. My sky doesn't reach down there but still, deselecting is quick and easy.

Click on the eye symbol of the two other layers to turn them back on and select the top layer with your new sky replacement. Now, with the selection still active, click on the layer mask icon on the bottom of your layers palette and you should see the magic.

[7] So...what's the fuss about that selective color thing you might ask. The point in that, is to fill all the gaps you might have in the foreground, without making a complicated mask. Placing your new sky on top of it is then much easier and will look like it blends in just perfect, even though you "only" used the Magic Wand Tool.

Let me show you. Look closer at the edges of a 100% crop showing the trees. On the left side is the selection without selective color and on the right side is the one with the adjustment layer turned on. This may vary between different images but you should be able to clearly see the white edges on the left side and the nice blue/green edges on the right side.

Note: The blue fringing on the leafs was there in the original image already, caused by the overload of the CCD, this is not due to the sky replacement technique used here.

[8] Fine tuning to blend the sky even better is optional but should be done on obvious parts. The advantage of the adjustment layer and the new sky on it's own layer, is that we can go back and tweak the settings any time we like.

Here is what you might want to do, depending on your image and selection:

• Double click the selective color adjustment layer, select the Whites and adjust the settings to match the blue with your new sky.
• Paint with black using a small brush on the layer mask of the adjustment layer or the sky layer to hide the blue and reveal some of the foreground (in this case the trees).
• On an active layer mask, go to Filter/Other/Minimum or Maximum to change the size of the mask.
• Use Gaussian Blur on the layer mask to soften the edges.
• Lower the opacity of one or the other layer.

[9] Finishing up, I decided to lower the opacity of the new sky replacement layer to 85% and added a touch of saturation and sharpening to it. This is definitely not a keeper, even after the sky replacement but I hope this will help you to make the most out of YOUR images in no time.

As with all things in Photoshop, there are many ways to do the same thing. In this case, if you are serious about any kind of selections, I strongly suggest you to look at the channels and use those to make your mask. The time spent on creating a good mask is well worth the time but if you need a quick and simple sky replacement, this tutorial might just be it ;)

Thanks to 'Kent Christiansen' for the tip with the selective color adjustment layer
Posted: Updated November 4, 2005 (tested with PS CS2)