Matthew Perks, creator of the DIY Perks YouTube channel has shared how he built a ‘35mm F0.4’ equivalent lens built around an episcope lens taken from some of the earliest projection technology.
As Perks explains in the video’s introduction, the episcope lens was the optical element used in epidioscopes to project well-lit objects onto a wall or screen in a dark room. One of the unique characteristics of these lenses is their extremely large image circle when used to capture light instead of projecting it. Due to needing to capture scenes behind the lens, the image circle these lenses project is absolutely massive. In the case of this particular lens, Perks says the image circle is an insane 500mm in diameter.
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So, how do you make use of this half-meter image circle when even medium format cameras would struggle to capture a small percentage of the scene? Well, in Perks’ case, you create a custom light screen using a large piece of diffuser film sandwiched between two pieces of plexiglass. Even in its primitive form, it’s possible to see the image projected from the lens. But Perks takes it a step further buy building an entirely custom framed light screen.
Since the screen would lack contrast without being enclosed, Perks uses flocked pieces of aluminum to build out the frame of what is effectively the lens’ body. He then makes another frame and effectively mirrors it so he can then mount the lens on one side, have a camera on the other side, and capture the projected image onto the image projected onto the diffuser film. Focus is done by moving one side of the rig forward and backwards on a set of steel rods via linear bearings. With this in place, the rig was completed and ready to roll. Or, at least, it looked like it was.
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| An illustration shared by Perks showing the fresnel lenses (green) sandwiching the diffusion panel to better focus the light from the lens to the camera. |
When looking at the projected image, Perks noticed heavy vignetting that rendered the image almost unusable. To combat this vignetting Perks took lessons from his DIY projector project and placed fresnel lenses on both sides of the diffusion screen to better redirect the incoming light into the camera opposite of the episcope lens.
To cap it all off, Perks added bellows made from folded black paper and a motorized focusing system with 3D printed parts and gears, as well as some bearings and other components.
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| If you thought nailing focus on an F1.2 lens was challenging, this lens will make that look easy by comparison. |
With all of that complete, it was time to take a look at the results. As visible from the comparison images below, the DIY lens has an ultra shallow depth of field, giving a look similar to what you’d expect from large format cameras or using something like the Brenizer Method. In some scenes, it almost has a tilt-shift-like effect, making the subjects appear as though they’re miniature models instead of real life.
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| Screenshot from video captured with the Canon R5 with a 35mm F1.8 lens attached. | Screenshot from video captured with the Canon R5 with a 35mm F1.8 lens attached, but through the DIY lens Perks built. |
It’s a distinctive look that you won’t get with even the fastest primes on a full-frame camera. In fact, this lens has a crop factor of 0.08, meaning the 432mm F5 episcope lens is roughly equivalent in field of view and depth-of-field as a 35mm F0.4 lens.
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| A comparison image showing what the DIY lens looks like compared to a 35mm F1.8 lens on a full-frame camera as well as a smartphone camera. |
So, how much did all of this cost? The entire rig, including the 3D printed part and lens, cost only $190 in materials: approximately $200K less than the Carl Zeiss 50mm F0.7 (the fastest lens ever produced) went for in the last auction it sold in. Sure, you’ll need the know-how and time to create this monstrous lens, but when it’s all said and done, you’ll be able to say you have one of the most unusual camera lenses out there, and have the photos and video to prove it.
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This article comes from DP Review and can be read on the original site.
