Tilt-shift simulation in Gimp

There are a lot of tutorials out there that tell you how to simulate tilt-shift photography (actually the technique is just tilt simulation, but I’ll call it tilt-shift since everyone else does) in Gimp. And those tutorials are okay, but all the ones I’ve seen take a rather simple approach that leaves some elements of the image blurry when they shouldn’t be. So here’s my way of making the best tilt-shift simulation in Gimp.

1. Image selection

A good candidate for tilt-shift simulation is a photo that is taken from high up and far away from the subject. While it’s not completely necessary, the end result will be better if you choose an image with this perspective. For our tutorial, I have chosen this photo I took of Arkansas Nuclear One from the top of Mt. Nebo.

This is a completely unedited photo straight out of the camera. It was a hazy morning, so the photo lacks contrast and sharpness. We’ll take care of it in the next step.

2. Pre-editing the photo

Now you’ll want to do your typical photo editing, like adjusting colors and whatnot. One important step is to make sure your image is as sharp as possible. A particularly good method for sharpening is the high pass filter, but if you don’t want to install that plugin, you can use the less-effective Filters → Enhance → Unsharp Mask. If you use the high-pass filter, be sure to flatten the image afterward. Here is my photo after adjusting curves and sharpening:

3. Duplicate the background layer

On your layers palette, click the background layer and then click the duplicate layer button below the list of layers.

4. Apply a gaussian blur

Make sure you have the duplicated layer selected, then click Filters → Blur → Gaussian Blur. The photo I’m working with is 10 megapixels, so I’m going to set the blur radius to 50. Your mileage may vary. Just be sure to look at the preview window and choose a blur radius that you’re satisfied with. Here is what my photo looks like after adding the blur:

5. Add a layer mask

In the layers palette, right-click the blurry layer and choose Add Layer Mask. In the dialogue box that pops up, choose to initialize the mask to White (full opacity). For more explanation of layer masks, check out my tutorial: Everything you need to know about Gimp layer masks.

6. Apply a bi-linear gradient to the mask

From the toolbox, choose the Blend tool (I think it should be called the Gradient tool, but I digress). Set your foreground and background colors to black and white, respectively, by clicking the reset button right below it. In the tool settings, change the shape to Bi-linear.

Now place the cursor at the point in the center of the area you want to be in focus. Draw a vertical line to the edge of the area you want to remain blurred. To keep the line vertical, you can hold down the Ctrl key while you draw it.

This will create a gradient across the layer mask, with its darkest part in the center (where you started to draw) and fading to the lightest parts at both the top and bottom (where you finished drawing). It masks the blurred layer in those areas, making the sharper image on the layer beneath it visible.

For my photo, I have made just a very thin strip for my gradient. In this screenshot, you can see the black gradient on the layer mask thumbnail on the right.

A lot of tutorials skip the next step and go on to manipulating the colors, but that’s where they fail and this tutorial succeeds. To make a more realistic miniaturization of this image, the tower of the power plant needs to be in our depth of field, along with the steam coming out of the top. So we’ll take care of it in the next step.

7. Clear up elements that should be in focus

Look at your photo and determine if there are any items in it that are the same distance from the camera as the area you’ve got the focus set on. Perhaps a tree or some other vertical object which has its base in the area of focus. In my photo, I’ll get the tower and steam in focus by manipulating the layer mask to let the sharper image show through in those areas. Choose the Paintbrush tool and a soft round brush. Paint over the areas you want to get in focus. The layer mask changes as you paint. If you make a mistake, you can either press Ctrl-Z or you can change the foreground color to white and paint over the area you didn’t mean to paint over before. Here’s what the process looks like:

And here is what it looks like after painting is complete (I also painted a little bit on the top of the buildings to the right):

8. Flatten the image and push the colors

Once you have the layer mask manipulated the way you want it, click on Image → Flatten image. Now you can make some adjustments to the colors. A plugin that I like for this step is Lasm’s LAB Ultra Vivid from FX Foundry, and turning down the opacity on the layer it creates to about 25 percent. But if you don’t want to download that, you can just turn up the saturation from the Colors menu. Here is my finished image with the colors tweaked:

So there you have it. I hope you find this tutorial helpful. Drop a comment below and show me your tilt-shift images.

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