Tilt shifting in photography is when you deliberately put your lens out of line with the sensor in such a way that it changes the focus on the sensor/film rather than just based on distance of objects and depth of field. The resulting photos and videos trick the eye into thinking it is seeing a tiny scale model rather than something miles away. A similar effect can be created through video/image editing. In the above pictures, artcyclopedia has added an effect similar to tilt shift via software to several of Van Gogh’s works (click the picture to see their full gallery and the originals). I love the effect.
I think the kind of visual cues we take from tilt shifted photography are to some extent a product of the photographic age. We are used to seeing two dimensional representations of three dimensional space as seen through the single eye of a camera. When you look at a real scene through two eyes, whatever you are looking at is in focus, while anything out of focus is blurry and doubled (and by definition, not what you are currently looking at). One of the flaws with the current round of 3D movies is that while things have depth cues based on sending a different signal to each eye, there is no adjustable depth of field based on what you are looking at. The focus of any given object is chosen by the camera, rather than the viewer, and the whole image is the same distance away, even if each eye sees a different angle.
I did a little experimenting on my own to get a better understanding of things. I think the choice of impressionism is a good one. Impressionists have a tendency to capture the soul of a thing crisply, but without much detail. This means that when you blur a background, it looks believable rather than smeared. Creating this effect in Photoshop can be pretty simple.
Part of what makes tilt shift photography make things look miniature is the difference distance makes to depth of field. In tilt shift, focus is much more independent of distance. In a large scale photo, once you are focused a ways out, it tends to focus to infinity. Painters tend to make their paintings fully focused at all distances, which improves clarity, but degrades the feeling of depth. With a tilt shift effect I wanted to choose a subject in the composition, bring the eye to them, and then create the illusion of depth in the rest of the image by virtue of knowing where the eye is already looking. This is counter to one of the usual goals of composition: To keep the eye moving. Below is a Monet I found with a quick image search that served my needs nicely for a very simplified test.
The alterations I made can be seen below. I don’t think it made the image nicer, but I think it accomplished my compositional goal of directing the eye and holding it on the subject.
I chose it because it covers a vast distance, contains a subject to draw the eye, and has a tree that exists within the plane of focus, but in front of an area that I planned to blur. The  clarity of the tree is what makes the end result different from what you would see with a tilt shift lens. This only took a few minutes. Below are the steps I took. If you have a copy of Photoshop, give it a shot. It’s a good skill to have in your repertoire.
- After opening the image, duplicate your background layer and work in the duplicate.
- Select anything outside your intended focus area that needs to remain sharp. In this case, the tree and the canopy on the right.
- Click on Select/Inverse.
- Click the add layer mask button in your layers pallet.
- Click select/Reselect.
- Click on the gradient tool and make sure you have it set to a black to white reflected gradient.
- Click on the part of your image that should remain focused and drag toward the edge of the picture perpendicular to the intended strip of focus and release.
- Right Click on the layer mask and click on Apply Layer Mask.
- Click on Filter/Blur/Gaussian blur, and drag the slider to create the blur.
I’m sure you can find a more long winded tutorial somewhere, but if you have a moderate knowledge of Photoshop, this should suffice as a bare bones process to get you started.