Posted in News
06/10/2021

Breathing new life into an old vintage slide projector lens with 3D printing

Browsing thru an antiques store, I stumbled upon a Kodak slide projector with an overly unusual attachment: a big lens. This explicit lens stuck my eye because it used to be an absolute behemoth. It used to be heavy and had “ISCO GERMANY” engraved into it.

After seeing the cost of simplest $10, I had no selection however to carry it house with me. My intentions have been discovered however now not smartly idea out; take away the lens and convert it to suit on my DSLR. After poking and prodding the projector, I thought the lens used to be detachable and went at it with a screwdriver. Thankfully this assumption used to be proper, and it used to be got rid of simply.

The lens is just about a foot lengthy, the entrance glass has a diameter of 4 inches and it’s HEAVY. The aperture is fastened at f3.5 and the focal vary is an adjustable 300-400mm. After a handy guide a rough blank of the glass, I started to suppose “how the hell am I going to glue this factor to my camera?”.

With the lens now got rid of, wiped clean and nonetheless the similar gargantuan hunk of glass and steel it used to be previously, it used to be time to look if it might even paintings on a contemporary DSLR. The rear diameter of the lens and component regarded identical in dimension to that of my Helios 44/2, which makes use of an M42 mount. The Helios 44/2 is a vintage Soviet lens and M42 is a lens screw mount that used to be commonplace on older movie SLRs, and it’s simply tailored to most current DSLRs.

Measuring and evaluating the rear parts and lens diameters with calipers showed that they have been just about an identical to one another. Fueled through interest, I got rid of the M42 to EOS adapter from Helios lens and tried to glue it to the rear of the Isco lens with tape, which didn’t paintings (marvel, marvel). I don’t surrender very simply (sure, I do) so I made up our minds to stay going.

Screwing simply the M42 adapter into my DSLR allowed me to make use of reside mode with no lens connected. With the camera now in reside mode I held the Isco lens about an inch or so in entrance of the opening the place a lens will have to be connected. To my marvel, I may just see, and I may just range the focal point through converting the space between the lens and the camera. It used to be crude, unsafe, and dumb but it surely labored! Now I had to design an adapter that may be rather less crude than this setup.

My preliminary design used to be a easy barrel focusing device, so I started through modeling a couple of tubes in CAD; simple, proper? The first tube used to be 40mm lengthy, and the interior diameter used to be just a hair better than the rear outer diameter of the lens barrel. This allowed the tube to be pressed over the rear of the lens, a couple of 8mm down, and held in position by way of friction. With what I’ll name the male facet whole, I started paintings on its feminine counterpart. Fortunately, it used to be simply some other tube with an inside diameter moderately better than the male tubes outer diameter, permitting it to slide freely when inserted. I additionally added an base to the ground outer diameter, which might permit me to attach an M42 to EOS adapter to it, so it might be fixed to the camera.

I exported the fashions and 3D published them in black PLA. After a little of sanding and cleanup, I glued the M42 adapter to the outer feminine base, pressed the male facet of the adapter over the rear of the lens, after which slid over the feminine facet of the adapter. To my marvel the whole lot are compatible smartly and labored! Focus used to be received through sliding the lens additional or nearer to the camera, like the usage of a hand held telescope.

The focal vary used to be right kind for only a wager, and I used to be ready to take quite a lot of fascinating footage with it. However, it used to be tough to acquire correct focal point because it used to be tedious to make use of. Moving a heavy, awkward formed lens *simply* the correct amount to get an symbol in focal point used to be tough, as I discovered I’d pull the lens too a long way out of the barrel or push too a long way inward. This led me to depending on shifting myself fairly than the lens to get photographs in focal point. I additionally had an apprehension that the glue on the base and the M42 adapter would fail and sheer the lens from the camera.

To remedy those issues, I followed a helicoid design for the focusing barrel and built-in the EOS mount, so there used to be no want to glue one on. Helicoid focusing barrels employ a easy spiral or thread to lead the lens within the barrel. This threaded barrel permits you to screw or unscrew to carry the lens nearer or additional clear of the camera’s sensor to focal point the picture.

The up to date helicoid design used to be a easy one, sticking with the preliminary barrel adapter premise, I simply added some threads, and altered a couple of dimensions. The feminine finish of the adapter used to be prolonged, totaling 48mm, and I included a receiving thread to the interior diameter. The receiving thread is 1.5mm extensive and deep, necessarily a half-circle, with a pitch of 40mm. Since the pitch used to be so nice, I used to be ready so as to add some other thread of identical dimensions at once throughout, forming one thing very similar to a double helix, for extra strong threading. I then modeled an EOS adapter the place the outer base used to be within the earlier design, so there used to be no want to glue one on. The male finish of the adapter used to be additionally prolonged, and I added threads to the outer diameter of the barrel. The threads have been made 1mm extensive and deep for clearance, with the similar pitch of 40mm.

The general duration of the barrel is 50mm, alternatively, I simplest modeled threads at the first 10mm. This permits the adapter to be screwed totally in and ready to trip all of the focal vary with out the threaded male phase exiting the barrel. I used to be ready so as to add a “forestall” to the top of the feminine barrel, so the lens may just now not be unscrewed such a lot that it might fall out. This forestall used to be a easy ring with the similar inside and outer diameter of the feminine barrel that had no threads at the inside diameter. Once the male finish used to be threaded in, the forestall used to be glued in position.

Phew, that used to be so much. However, after exporting the information from CAD, printing in the similar black PLA and assembling the whole lot in combination, the effects have been in! It labored higher than the preliminary design. It’s a lot more uncomplicated to focal point and there’s no worry of the adapter breaking; plus, it’s a bit of extra “delicate” taking a look. All in all, this used to be a amusing venture to observe thru and I will be able to’t wait to take extra footage with this setup.

About the Author

Nick is a tinkerer, photographer, and at all times has too many tasks to complete. Creating, development and iterating make their means into just about each and every interest he has, and virtually each and every a part of his life. Currently, a pupil learning electric engineering, Nick has many passions out of doors of engineering and has at all times liked images, filming, writing and the humanities. You can to find out extra about Nick on his website and observe his paintings on Instagram. This article used to be additionally printed here and shared with permission.

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