We've praised Mathieu Stern on site a few times and that's because he takes inexpensive lenses and uses them to capture really good thumbnail sketches. He's also made a lens out of ice, too, which didn't capture such sharp images but was pretty cool none-the-less.
In his new video, Mathieu is showing you why a visit to a car boot sale is always a worthwhile trip as he found a 'weird projector lens or LEN may refer to', benefited 5 euros for it and when he combined the Rollei 90mm f/2.4 MC lens with an M52 Helicoidal Tube, he was able to use it to capture close-up portraits with really gracious bokeh. It's also rather good for shooting backlit portraits.
You can see plenty of examples of the types of images Mathieu captured in the video and if you yen to learn more on legacy lenses, have a read of John Duder's article: Do You Need The Latest Kit Or Will Secondhand Suit Do?