This node describes a method of creating photographs which look a little bit like impressionist paintings.
It's really very simple. All you do is take a double exposure, with one of the exposures in sharp focus and one exposure slightly out of focus. Of course it works best if your subject is the sort of subject that normally appears in impressionist paintings to begin with.
There are a few minor points to watch out for. First, since you'll be doing a double exposure, the camera and subject must remain mostly motionless for the duration of both exposures. Use a tripod, and be careful not to move the camera between exposures while adjusting the focus and zoom.
Second, each exposure should be for half the duration of a normal exposure. The easiest way to accomplish this is to simply set the film speed (ISO) setting on the camera to be twice that of the film in use. That is, lie to the camera. If you're using ISO 200 film, tell the camera it's ISO 400. That will automatically cut the exposure time in half for each exposure. Just remember to reset the ISO setting when you're finished doing double exposures.
Third, most modern autofocus lenses have a tendency to zoom in or out a little bit when defocused. So, when making the unfocused exposure, you usually have to compensate for this zooming effect by actually zooming the lens manually. The best way is to note something in the frame that's right next to the frame edge during the focused exposure, then, when making the unfocused exposure, make sure whatever it was is still right against the edge of the frame. Otherwise you'll get a weird zooming effect which is usually not all that cool looking. If you're using a fixed lens, you won't be able to compensate. An older manual focus fixed lens (without "internal focusing") may not exhibit this zooming effect when defocusing.
Fourth, to accurately control the amount of defocusing, use the widest aperture setting. When you look through the view finder to see the amount of defocusing, the aperture is wide open, so you want it to be wide open when the exposure is made as well. This is especially important at wide angle settings. At wider angles, it can be impossible to get the image unfocused enough. I've found focal lengths of 50mm and above work nicely. Below 50mm, you may have too much depth of field, depending on the maximum aperture of your lens.
Doing all of the above correctly should yield some interesting shots.
But, with one more step, the "painting" effect can
often be greatly enhanced by scanning the image and using something like the gimp or photoshop and twiddling the colors, etc. I have found that trying to simulate the double exposure by combining a blurred image with a focused image entirely within the computer is not as satisfactory as the results achieved in-camera. (I'm not sure why not, but that's how it worked out for me.)