A British man has built his own lens with a super fast 35mm f/0. 4 equivalent bokeh that is constructed around an old episcope projector lens and a mechanical system for controlling focus.
Matt Perks, aka DIYPerks, is a tinkerer who doesn’t buy anything he can’t build. On his YouTube channel, Perks has built everything from a DIY 4K home cinema projector to a DIY microphone for recording audio in his home-built studio with home-built video lights.
In this case, Perks turned his attention to a vintage episcope lens harvested from an old art projector. An episcope projector was very popular in the 1960s and 1970s and would fit over a piece of art or any object that a user would want to project onto a wall or screen. Because they were inexpensive and projected bright images, they are very popular among schools. The light is reflected from the housing of the projector, shining down on the subject. The light would then reflect off a mirror and through the episcope lens onto the wall.
As Perks admits, episcopes have largely been left behind by the steady march of technology into the digital realm which he clearly sees as a real shame because the episcope lens offers a remarkable bokeh thanks to its incredibly large image field — on the order of 500mm. This is roughly equivalent to 0. 016 the size.
To achieve the goal of using the episcopic lens with his camera, Perks would have to create a huge housing and focusing mechanism from scratch. Even then, there’s no digital camera sensor large enough to capture all the image potential of the episcope lens.
One option is to take the image while it’s being projected onto a wall. However, this comes with its own image quality problems from noise to distortion. It would also prevent mobile usage.
The other option would be to project the image onto an opaque surface and then capture the image from that. If the design is portable, this allows the array to be taken almost anywhere.
Perks used a diffuser sandwiched between two pieces of acrylic and then built around a pyramid-shaped aluminum housing as a custom light screen. Two, actually: one to hold the episcope lens, and one for his Canon R5 full-frame mirrorless camera. He then added a Fresnel lens in between to eliminate unwanted vignetting.
With an origami folded black bellows to block out as much adjacent light as possible, and a 3D printed joystick focusing mechanism to control the entire system, Perks was ready to test out his cumbersome, yet interesting array. It is more like an image captured from a mirror on an opaque surface than it does from a sensor.
The episcope lens optically produces a dreamlike image with incredible background separation. Perks worked out that his custom lens array has a crop factor of 0. 08 and an aperture of f/0. 4, which Perks claims makes his rig twice as fast as a $200,000 Zeiss 50mm f/0.7. The array even works with a smartphone, creating an optical bokeh far more natural than the simulated replication today’s handsets produce through computational photography.
The total cost to build his DIY “Perkiscope” episcope lens array is only $200. Perks promised to provide a link for the entire plans needed to make your own episcope camera system, however, this was not available at the time that the video description was being published. Even armed with those instructions, the lens itself may be the hardest thing to source for the project due to its vintage nature.
Image credits: All photos by Matt Perks