Nikon Special Effects (introduced in the D5100) can be applied to about-to-be-taken images and previewed on the LCD monitor. Effects include such items as Selective Color (records one to three colors you select, with the rest of the image in black-and-white), Miniature, Color Sketch, Night Vision, Silhouette, High Key and Low Key. You can apply some effects to movies as well as still images. Effects images are saved as JPEGs whether you're shooting JPEG or NEF (RAW) images. You also can apply a selection of effects to already-shot images via the retouch menu in a number of Nikon DSLRs.
Olympus introduced Art Filters in its E-30 DSLR, and has included them in its DSLRs and mirrorless E-P series cameras ever since. The filter selection varies a bit from camera model to camera model; the E-P2's Art Filters include Pop Art, Soft Focus, Grainy Film, Pin Hole, Diorama and Dramatic Tone. With some cameras, such as the E-P2, you can apply effects to movies as well as still images.
Recent Pentax DSLRs offer Digital Filters, whose effects you can apply to already-taken images in-camera. These include Toy Camera, Retro, High Contrast, Sketch, Extract Color, Warm Color, Pastel, Miniature, Monochrome, Color Filter, Soft, Starburst, Posterization, Fisheye, Slim, Custom Filters and more.
Multiple ExposuresPhotographers have been combining two or more images to create new montage images for a long while. Digital cameras make the process easier and more effective. With some, you can display the first image on the camera's LCD monitor and use that as a guide to compose the second image you're about to shoot—much easier than trying to remember where everything was in the first shot as you shoot the second image. Of course, you can combine images in your computer, too, with more control. But doing it in-camera is quick and convenient.
Grid Lines and Virtual HorizonsViewfinder grid lines make it easy to align the horizon and other horizontal or vertical lines in an image. In film days, you could purchase and install an optional focusing screen with grid lines (with higher-end SLRs).
Today, a number of DSLRs offer on-demand viewfinder grid lines and electronic virtual horizons that serve the same purpose. The virtual horizons are especially useful in that they show when the camera is level even when the horizon doesn't appear in the image. Generally, grid lines and virtual horizons can be displayed in the eye-level optical or electronic viewfinder and on the LCD monitor, whichever you prefer using.