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OKTO35 – Blaž Semprimožnik

OKTO35 – Blaž Semprimožnik

2023-05-01 22:28:48

An affordable and straightforward approach to shoot and scan 35mm movie films


OKTO35 movie film digicam

A few years in the past I’ve been often capturing 35mm movies with level&shoot nonetheless cameras whereas additionally having the need to shoot movement image movies. Upon reviewing my choices, the easiest way can be to do it with Super8 movie, however after monetary concerns, I concluded that it could be very expensive in the long term since capturing only one normal 50 ft cartridge wouldn’t be sufficient for me. Buying, growing, and digitalizing prices for only one can be over €100! And to not point out the lengthy turnaround time of some weeks! There needed to be a greater answer to the issue.

After researching, since I had some expertise with 3D designing and printing, digital design, and coding, I got here up with the thought to construct my very own analog movement image movie digicam. I’ve determined that my digicam would make the most of the usual 35mm movie cartridges since these are cheaper and are broadly accessible in a lot bigger portions and kind varieties (B&W, Coloration, Reversal, UV, IR, particular sorts …) and might be bulk loaded.

The principle objective was to search out an optimum stability between the variety of frames, fitted on the cartridge and the dimensions of the body itself. Right here I concluded, that the body dimension needs to be the identical because the Super8 format or bigger. Different targets have been an ergonomic and sensible digicam design, person interface with show, many helpful features, a totally computerized movie feed/rewind mechanism, and a few form of developed movie scanning capability. This might end in rather more reasonably priced and sensible movie capturing versus the Super8 format. And it’s method simpler to home-develop 35mm movie than Super8.


The essential inner digicam design and its inner workings have been firstly roughly sketched on paper. There I made a decision that the very first thing to create can be some form of intermittent mechanism for advancing the movie in the course of the blanking interval by one perforation gap. Right here I’ve chosen the geneva mechanism, which is able to reworking a steady rotational motion from a DC motor into an intermittent rotary movement on sprocket gears. A easy 8-position geneva drive with sprocket gear on a primary platform was modeled on a pc and 3D printed. Utilizing one full motor axis rotation, it strikes the 35mm movie by precisely one sprocket gap.

First concepts placed on paper
The primary 3D-printed geneva intermittent mechanism with a DC motor
Geneva mechanism in motion
Movie advances by one sprocket gap

After profitable testing, different parts quickly adopted reminiscent of a information airplane for transporting movie from a motorized 35mm cartridge holder to a take-up drum, a motorized C-mount shifter for choosing movie observe publicity with built-in solenoid mild shutter, and room for a printed circuit board, a battery, and a show. Most of those parts have been held in place by the primary platform, spacers, and screws. The intent was additionally for the digicam to have a easy film-loading process, that doesn’t require any pre-slicing/combining or exterior reel movie loading, simply drop/load a normal 35mm cartridge and you’re able to go. For the lens I wished help for interchangeable lenses, right here was chosen the C-mount system attributable to its very vast possibility choice (from vast to telephoto), reasonably priced costs and nonetheless being in manufacturing. Nearly all parts have been 3D printed from black PLA plastic so as to block any exterior mild supply.

Superior building with movie information airplane and lens help
Exterior tough design with higher cartridge holder
Excessive-speed recording of lively solenoid shutter gate
Excessive-speed recording of lively movie information airplane
Assembling and wiring varied parts
Assembling the ultimate model type

Relating to electronics, the plan was to make a single printed circuit board design containing all parts with extra element enlargement functionality. An STM32F1 sequence microcontroller was chosen attributable to its massive variety of GPIO pins, an unlimited collection of totally different features, and high-speed operation. The board was fitted with an influence administration system, motor driver chips for movie transport and shutter management, a stepper driver chip for C-mount lens shift for observe publicity choice, and a connection array for exterior sensors reminiscent of a light-weight meter. All parts are powered by an inner LiPo battery with charging functionality.

Overview of inner parts

The following process was coding. Its challenges have been the creation of a user-friendly GUI with easy menu system navigation utilizing a joystick button, 4 totally different modes of operation: Film, Picture, TimeLapse, Scanner, and a system, that gathers and processes all knowledge and shows it to the person reminiscent of measured publicity values, remaining recording time, present/saved settings, and many others. Nearing the tip of coding, many different helpful options have been added like a timer, recording button modes, and a visible/audible warning system. Programming was carried out in C language within the STM32 IDE setting.

The final process was selecting a reputation for the digicam. Amongst vast preselection, the identify OKTO35 was chosen. ‘OKTO‘ is equal to the quantity 8 within the Greek language and refers back to the Super8 format. ‘35‘ refers back to the 35mm movie format.


The objective of the exterior design was to be made easy and ergonomic. The partitions have been to be constituted of no less than 2 mm thickness to make sure mild tightness and structural stability. The entrance face incorporates a scorching shoe mount for a removable optical viewfinder, a built-in scene lightmeter for lense F-stop adjustment, a C-mount lens thread, and a tactile recording button. With the again facet, the person makes use of the viewfinder for scene preview, operates with OLED show GUI through the thumb joystick button, and has the entry to movie cowl for movie cartridge loading. The main target port is used for focus test and the DSLR connector is for sync scanning connection cable. On the backside, we discover a buzzer gap for audible timer/warning sounds, a normal 1/4” tripod mounting screw, and a micro USB port for charging.

Back and front view of the digicam
Backside view of the digicam


The movie loading consists of a easy drop&load process. No pre-slicing, movie combining, or any exterior reel loading is required. The movie cartridge is positioned between the motorized rewind shaft and the holding block. The movie is extracted from the cartridge, positioned down the movie information airplane, previous the publicity gate and the primary drive, and hooked up to a motorized take-up drum. The movie cowl acts as a movie stress plate and sledge information. It’s held down by robust neodymium magnets and the double wall seal design offers good mild tightness. After loading, the movie ISO and dimension settings are entered through GUI and movie recording can start.

Opened again view with a movie cowl
Loaded again view with a movie cowl


The chosen show GUI construction concept was a easy 3-page system: Dashboard Settings Common. Switching between major pages is finished by the left/proper joystick button motion and web page possibility choice with up/down motion. OLED show expertise was chosen attributable to its good distinction and sun-readable functionality.

Switching between a 3-page GUI system

The content material of each the Dashboard and Settings pages modifications relying on the set Digicam Mode possibility, which is the primary function of the digicam. It permits a change of 4 totally different modes of operation: Film, Picture, TimeLapse, and Scanner.

Content material of the dashboard web page modifications relying on which of 4 totally different digicam modes is ready

Film mode permits the digicam to be a standard recording digicam with a major frames-per-second setting. Picture mode makes a nonetheless digicam with a shutter velocity setting, additionally helpful for cease animation. TimeLapse mode is used for lengthy interval exposures with the primary interval setting. These three modes can be utilized interchangeably on the identical movie cartridge. The final mode is Scanner mode which modifications the digicam right into a film-scanning system. Movie cartridge, that was beforehand uncovered and developed can now be reloaded again and scanned within the frame-by-frame technique by entrance lens swap and utilizing a DSLR or a mirrorless digital digicam linked to a DSLR connector port.

All person settings and present movie standing are saved on built-in inner reminiscence, which retains it saved even in a battery under-voltage incidence (flat battery).

The battery share standing, calculated F-stop, and remaining movie recording time or body data are at all times current on the dashboard web page. The digicam additionally has different built-in features reminiscent of a timer, recording button kind, and many others. GUI additionally options a sophisticated message system. It responds visually and audibly with warning or recommendation messages reminiscent of the tip of the movie, invalid setting, low battery, and many others.


The present digicam design makes use of a normal 8 mm lens with guide F-stop and focus. The 8 mm approximates a 50 mm lens on a full-frame 35mm digicam (near human imaginative and prescient). The digicam utilization was made to be as user-friendly as attainable. The intent was additionally to behave like a degree&shoot digicam with extra person settings. This was achieved in addition to the 2 guide settings: F-stop and focus, that are often wanted.

The guide focus is ready as soon as and doesn’t should be set once more except a extra close-up scene recording is required. Below regular operation present 8mm lens presents a centered vary from about 1.2 m to infinity. If re-focusing is required, the person goes to the Common web page and permits the choice “Verify focus”. The lens shift motor units the lens to the center of the movie and opens the shutter. The person then opens the viewport on the movie cowl and screws in a 25 mm lens. Because of the movie’s partial transparency, the main focus is checked on the movie itself (because the focusing airplane). When completed, the person closes the viewport and disables the choice, ensuing within the lens shift motor returning the lens to the earlier observe place.

Right F-stop worth is calculated by making an allowance for measuring present scene illuminance through a built-in scene mild meter and set movie settings reminiscent of movie ISO, fps, shutter velocity, and many others. The person factors the digicam to the specified scene through the optical viewfinder and presses the enter button, calculated lens F-stop is then refreshed immediately on the dashboard. The person then units the lens F-stop in response to the displayed worth. If the scene illuminance doesn’t change a lot, the identical lens F-stop setting can be utilized a number of instances because of the movie’s vast dynamic vary.

When a brand new contemporary movie is loaded and the movie specs (ISO, dimension) are entered, the person has the choice of three totally different modes of operation: Film, Picture, and Timelapse. All three can be utilized interchangeably on the identical movie cartridge.

If the person selects Film mode, an fps setting is taken into consideration and movement recording can start. A time counter is displayed on the backside exhibiting the remaining observe and whole recording time in minutes and seconds.

Picture mode transforms the digicam right into a nonetheless digicam, capturing frame-by-frame through presses of the recording button and with the shutter velocity setting taken into consideration. This mode is beneficial for cease animation or simply nonetheless pictures. A body counter is displayed on the backside exhibiting the remaining whole variety of frames.

Timelapse is used for lengthy interval exposures with interval setting taken into consideration. Consumer can choose the timelapse length and interval time and begins the recording course of. A timer is displayed on the backside exhibiting the remaining time till the method is completed.


After some body dimension and place math consideration I got here up with the thought of shifting movie vertically by way of the digicam and putting 1 body per sprocket gap and 4 frames per helpful width of the movie edge to edge, successfully yielding 4 very lengthy tracks in whole of 1152 frames, which was later optimized to 1200 frames per one 36-exposure dimension 35mm cartridge. This technique resulted in virtually an identical body dimension in comparison with the Super8 format aside from elevated body dimension. In comparison with Super8 at 5.8×4.01 [mm], the brand new body dimension is 6.3×4.73 [mm], successfully making the floor space elevated by roughly +30% and diagonal dimension by +12%, which delivers smaller movie grain and larger/extra detailed frames in conventional 1.33:1 side ratio.

Closeup of developed black&white 35mm unfavourable movie (Fomapan 100)
Black&white film body (Fomapan 100)
One other black&white film body (Fomapan 100)
Color film body (Kodak Gold 200)
One other shade film body (Kodak Gold 200)


Utilizing one normal 36-exposure dimension cartridge and capturing @18fps, we are able to get hold of the recording time of 1 minute and seven seconds. Evaluating that to the Super8 normal 50ft cartridge’s recording time of three minutes and 20 seconds @18fps, three 36-exposure dimension cartridges are equal to one Super8 50ft cartridge in recording time.

See Also

One normal Super8 50ft cartridge has the identical recording size as three 36-exposure cartridges (@18fps)

That brings us to the entire value estimation evaluation spreadsheets. Relating to improvement, I personally develop uncovered movies at dwelling, this fashion I’ve full management over desired pushing/pulling, high quality, and the sheer velocity of movie improvement. Consequently, the spreadsheets include totally different improvement and scanning prices for 35mm movie as to Super8 movie.

Black&White Buy value Growing value Scanning value Turnaround time Complete value
1 pcs Super8 50ft cartridge ~ 40€ ~ 25€ (business lab) ~ 45€ (business lab) 1-3 weeks ~ 110€
3 psc 35mm 36-exp cartridge ~ 15€ ~ 2€ (at dwelling) 0€ (at dwelling) few hours ~ 17€
Black&White Complete value per 10-minute recording @18fps
Super8 ~ 330€
35mm ~ 51€

Utilizing Black&White 35mm as a substitute of Super8, the entire value has, consequently, been lowered by about 85%.

Coloration Buy value Growing value Scanning value Turnaround time Complete value
1 pcs Super8 50ft cartridge ~ 40€ ~ 25€ (business lab) ~ 45€ (business lab) 1-3 weeks ~ 110€
3 psc 35mm 36-exp cartridge ~ 27€ ~ 4,5€ (at dwelling) 0€ (at dwelling) few hours ~ 32€
Coloration Complete value per 10-minute recording @18fps
Super8 ~ 330€
35mm ~ 96€

Utilizing Color 35mm as a substitute of Super8, the entire value has, consequently, been lowered by about 70%.

The bulk loading possibility makes these cartridges, much more, cheaper: with a Black&White worth of about 2,60€ per 35mm cartridge the entire value is about 30€ for a capturing time of 10 minutes @18fps. This brings the worth down by about 91%.

Frames per second Recording time for one 35mm 36-exp cartridge
10 2 minutes 0 seconds
12 1 minute 40 seconds
16 1minute 15 seconds
18 1 minute 7 seconds
24 0 minutes 50 seconds
Various capturing fps and its recording instances


Most, if not all movement image cameras solely have a recording perform. After publicity and improvement, a unique and specialised machine is required or a lab service for scanning functions.

This digicam is designed in such a method, that additionally serves as a developed movie scanner with a couple of extra components. The scanning process begins with loading the developed movie cartridge again into the digicam, changing the entrance C-mount 8 mm lens with a 25 mm lens so as to appropriate the field-of-view, and opening the Viewport. A change of digicam mode is carried out through GUI into the Scanner mode. Right here the person can set the scanning interval size. This places the digicam into scanner prepared state.

The person then makes use of a DSLR or mirrorless digicam for lense-to-lense picture switch (utilization of a smartphone digicam with a wi-fi connection technique can be attainable within the subsequent digicam model MK III). For movie backlight sources by way of Viewport, a standard LED desk lamp will suffice. The lens focus, zoom, and F-stop changes are made so as to get hold of the very best picture high quality. The final process is to attach the DSLR or mirrorless to the digicam utilizing a standard DSLR 2.5mm connector cable. Utilization of cease movement animation mode within the DSLR or mirrorless digicam produces video, made up from all scanned frames.

Scanning is began and carried out routinely one observe at a time utilizing the frame-by-frame technique so as to get hold of the very best flicker-free picture high quality. In the meantime, the show Dashboard web page offers helpful data relating to observe quantity, remaining frames, and scanning time (it takes about 25 minutes per one 35mm 36-exp cartridge). When the scanning is accomplished, the person is notified and a brand new movie might be scanned.


  • C-mount lens help
  • 4 perform modes: Film, Picture, Timelapse, and Scanning
  • totally motorized and automatic movie wind/rewind and movie publicity observe shift
  • built-in scene mild meter for F-stop publicity calculation
  • brilliant and solar readable 128×64 1-inch OLED show with user-friendly GUI
  • easy and ergonomic thumb joystick button GUI management
  • built-in massive capability LiPo battery with charging functionality
  • built-in buzzer for audible timer and warning sounds
  • removable and adaptable optical viewfinder
  • the film body charge might be set from 10 to 24 frames/second with a standard 180° shutter velocity
  • photograph shutter velocity ranges from bulb mode to 1/100s with a settable timer
  • timelapse interval ranges from 1 to six seconds with a standard 180° shutter velocity
  • helps vast movie ISO vary from 50 to 3200
  • the digicam can use a number of normal 35mm cartridge sizes of 12, 24, and 36 exposures
  • helps unfavourable and reversal black&white, shade, UV, and IR movies
  • ergonomic and intuitive exterior design
  • responsive system because of the quick STM32F1 sequence processor
  • magnetically sealed movie cowl for straightforward cartridge loading and good light-tightness
  • self-cleaning movie cartridge design for mud discount throughout recording and scanning
  • movie cowl sledge information design for scratch discount throughout movie transport


Thankfully, this isn’t the tip of the mission. I’ve the need to construct a brand new and improved MK III model, however additional mission improvement depends upon your suggestions and curiosity. Constructing the OKTO35 MK II model took lots of vitality, time, and talent however it additionally introduced me lots of old-school analog recording enjoyable, newly acquired information, and a really distinctive working digicam. The brand new model must be subsequently value doing.

If you’re within the mission continuation, wish to give me suggestions or solutions, or have another questions, please let me know. You should utilize my contact data on the ContactMe web page or another social media platform (YouTube, Instagram …) and I’ll fortunately assessment and reply them.

In case of sufficient curiosity in mission continuation, the event of OKTO35 MK III would begin. I’d launch common video updates relating to the constructed progress on my YouTube channel. These subsequent enhancements can be included within the subsequent MK III model:

  • attainable scanning process utilizing a smartphone through a wi-fi connection
  • digicam distant operation through smartphone
  • crystal-sync true fps velocity, enabling excellent sound recording synchronization
  • lowered working noise attributable to a quieter stepper motor
  • elevated film fps choice from 1 to 30 frames per second
  • elevated timelapse interval vary from 1 to twenty seconds
  • discount in movie shake and higher mid-exposure body stabilization
  • simplified and extra sturdy inner design for an extended lifetime
  • improved exterior unibody design for higher light-leak discount
  • digicam energy on/off through the GUI menu
  • improved multilanguage GUI with added options
  • charging and firmware replace through USB-C connection
  • extra outlined body edges with lowered neighboring observe bleed-out
  • lowered distance between cartridge and take-up drum for much less wasted movie
  • improved take-up drum movie connection through built-in magnet

In case of general big curiosity, a small-scale digicam manufacturing may be attainable within the close to future.

I see, that you just made it to the tip ???? Thanks for trying out the mission. Once more, any suggestions is massively appreciated!

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