Here is my DIY Tilt-Shift lens. It is a 75mm f2.8 medium format lens I bought off ebay for $30 plus a $5 toilet plunger that I cut down.
I inserted the lens inside the plunger and wrapped black hockey tape around it. I then superglued a Canon EOS body cap on the back of it.
If you build this yourself be sure to cut small holes in the bellows to allow air to escape. The first time I used this lens I wrecked the shutter in my Mark-II because of the air pressure! I didn’t use it for two years because of that. I finally just cut two holes and now it works fine.
You have to use a medium format lens for this (35mm lenses won’t work) because MF lenses produce a larger imaging circle and are meant to be positioned farther away from the “film” (sensor) of the camera.
I learned how to build it on Keith Loh’s blog.
I used this lens for this and this picture. Notice how the face is in focus and the rest is out of focus. That is because I tilted the lens so that so that the plane of focus crosses the face. Since nothing else falls in the plane of focus it goes out of focus ( a.k.a. bokeh).
It’s an artsy effect and can come in handy but this isn’t a lens you can use all the time.