"Redscale" is a technique which was accidentally discovered by users of color sheet film, when film was loaded improperly with the substrate (acetate) side facing the lens.
(As an aside, for some reason, at least on the monitor I'm testing on, most of these images look REALLY bad on the previews, but normal when opened with a mouse click. I'm going to go ahead and publish this, but to get a good view of most of the photos, you may have to open them.)
The result is that the red-sensitive layer of the film, the layer usually closest to the substrate, is well-exposed, the green-sensitive layer, normally in the middle, is underexposed, and the blue-sensitive layer gets very little exposure.
As expected, the images have a strong red cast, with oranges and yellows in the highlights, very few blues and greens except for an occasional bright green peeking through.
Redscale has become trendy in some circles, being seen as somewhat artsy, and is embraced as part of the lo-fi (low fidelity) genre of photography. Lo-fi can best be described as a shift away from technical perfection in a photograph.
Special "redscale film" is available commercially for several dollars per roll, but in actuality, all this happens to be is regular 35mm color film wound backwards into a 35mm cartridge.
Total slop shot from the breakfast table in the restaurant, looking out:
All red except for the yellow light bulbs ...
The more pleasing results seem to occur when there's enough exposure to tickle the green-sensitive layer of the film, resulting in more yellow. Fans of this technique say to overexpose by one stop to compensate for the lack of exposure of the blue-sensitive layer.
If I try this again (BIG if!) I'll overexpose a bit more.
Green stoplights are sometimes bright enough to shine through and appear as green in the redscale image:
Just for fun, I tried creating a B&W image from one of the redscale shots, using only the red channel.
The result was not unlike the look and feel of many of the urban scenes I took back in my late teens, when I was first getting into photography, using Kodak Tri-X, such as this example, shot in the late 1960s, not to admit to my real age. :)
Redscale is one of those things I'm glad I tried once, but I really don't see much of a practical use for it.
Technical information: Canon QL17 GIII, Kroger (Ferrania) el-cheapo house-brand 200 color film. (All except last B&W.)