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A Spring-Loaded Digital Movie Camera

Digitize a vintage 8mm camera. Not for the sake of convenience, but for the enjoyment of video recording.

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Shooting video is very fun and convenient. Today, it has become a very familiar tool, as smartphones and action cams make it easy to shoot high quality video.
On the other hand, the ability to easily take videos is very valuable, but I feel that the fun has been lost a bit.

For this project, we plan to remodel an 8mm video camera manufactured 70 years ago and shoot digitally.
I plan to keep modern modifications to a minimum and revive it as a slightly inconvenient, but fun, piece of equipment for cinematography.

Unlike past 8mm film movie camera digitization projects, the camera to be converted is a spring-driven ancient relic. The unstable shutter timing made development difficult, but I succeeded after much hard work using a photo sensor.

I was going to submit this project to "Challenge 3: hack it back" of the Hackaday Prize 2022, but on second thought, this camera is not an "old electrical device".
Perhaps it does not meet the regulations?

The camera modified for this project is a Bell & Howell Model 172 magazine-loading 8mm camera manufactured in the 1950s. The film standard is double 8, but it is set in a special magazine.

As a magazine-loading 8mm film, super8 was widely used.
I have found several projects to modding Super 8 film magazines into Digital, but this camera is even older than those.

The film feed and shutter are powered by a mainspring, and when the spring is wound up, the camera can shoot for about 35 seconds at 16 fps. It can also shoot back and forth on a single roll of film, recording approximately 100 seconds per side.
There is no single item that can be automatically controlled; aperture and focus are controlled by the lens, and exposure time is fixed in conjunction with the frame rate.
The preview is not visible and the viewfinder is very small, so it takes some technique to get the image you want.

Of course, I have never shot with 8mm film, but my goal was to recreate the fun of the surprise box-like experience of not knowing the result until the film is developed.

Why not revive this delightful heritage buried in the depths of our garage drawers?

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Wow!!

I was able to capture very atmospheric images.

IMX219recoder.py

Cinematography Controller

py - 10.01 kB - 05/19/2022 at 23:48

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  • Making the main board

    AIRPOCKET@rastaman vibration5 天前 0 comments

    Now that we are able to detect the shutter movement, which had been a pending project, we have started fabrication of the main board.

    It has a DC-DC converter, a photo sensor for shutter detection, DIP switches for inputting shooting conditions, and pins for connecting to the Raspberry Pi.
    When we checked the operation, we found that the Raspberry Pi was reset due to lack of power when continuous shooting was performed. As a countermeasure, we changed the DC-DC converter from the LM1117 3V3 version board (top photo) to the MP1584 version board (bottom photo).


  • Detection of shutter movement

    AIRPOCKET@rastaman vibration05/07/2022 at 14:32 0 comments

    Now that the circuit for detecting shutter movement using a photo reflector has been established, we will test whether it is possible to detect the actual shutter opening and closing movement.

    After examining the areas inside the camera where shutter operation could be detected, it appears that the movement of the film feed claw can be detected. However, the claw itself moves right next to the lens, so it would collide with the image sensor.
    Although we wanted to avoid touching the camera body as much as possible, we decided that we had to touch this part, so we cut off the claws.
    The following video shows the claws on the film feed component cut off and the reflector attached where the claws used to be.

    As a reflective material, aluminum tape was used, which reflects the IR light of the photo reflector well. In this video, the camera is running at the FPS 16 setting.

    When the photo reflector was temporarily mounted in front of the reflective material to check its operation, the LED for the indicator flickered quickly. Although it is currently impossible to determine if there is any capture, it appears that shutter movement can be detected in this way.

  • IDLE TALK

    AIRPOCKET@rastaman vibration04/28/2022 at 09:06 0 comments

    This is the first time I have touched an 8mm film camera, but when I touched it, I was pleasantly surprised by its presence and texture, such as its weight and fast-moving shutter, more than I expected. It is an anachronistic spring-driven mechanism, but because of that, it is also robust enough to work even now, more than 70 years after its manufacture.

    When I was doing some research, I found an advertisement of the watch on sale, so I ended up buying it.

     "When you choose a Filmo, you choose a movie camera made with the high skill of Bell & Howell craftsmen who have built Hollywood"s preferred professional equipment for 41 years. Only Filmos can offer you this priceless heitage."

  • Change image sensor to IMX219

    AIRPOCKET@rastaman vibration04/27/2022 at 08:32 0 comments

    Until now we have been using the OV5647 image sensor, the biggest advantage of which was that it could handle up to 90FPS, but we were not satisfied with the image quality. 

    As an alternative, we obtained a small sensor unit with an IMX219 sensor. It is possible to divert the Raspberry Pi camera V2 board and replace only the sensor unit.
    There is one problem, the MIPI connector on the Raspberry Pi camera V2 is 1mm pitch x 15PIN, but the Raspberry Pi zero is 0.5mm pitch x 22PIN, so a conversion cable is required.
    The conversion cable we obtained was too long to fit into the case, so we modified it to cut the cable at the same time.
    The Raspberry Pi camera V2 board is also in the way, but if the placement of the main board is improved, it will fit in.


  • Consideration of a sensor for shutter movement detection

    AIRPOCKET@rastaman vibration04/25/2022 at 03:22 0 comments

    This 8mm film camera has a variable FPS. In order for the image sensor to capture moving images, the shutter timing of the camera must be synchronized with the sensor operation.

    It is very difficult to detect the shutter timing operation, and if a mechanical mechanism is added, it may become a burden and change the shutter timing itself.
    In this case, we will attempt to detect the movement by attaching a reflector to the shutter rotation mechanism and using a photo reflector.
    First, I used a breadboard to check the sensor sensitivity and circuitry.
    When the part with aluminum tape in front of the sensor comes to the front of the sensor, the LED shines.

    Although the sensitivity needs to be adjusted, we will test the actual device using this method.

  • Case Design

    AIRPOCKET@rastaman vibration04/22/2022 at 06:17 0 comments

    The case is designed to house the image sensor and other components.

    The following items are stored in the case.

    • Image sensor
    • Raspberry Pi 2
    • Main board
    • Sensor for acquiring shutter movement
    • Battery
    • Power switch
    • 2 LEDs
    • Dip switch

    The specifications of the device itself, which will be placed inside, have not yet been clearly decided, but I will make a mock-up and check it as we finalize the design.

    After three prototypes, I will proceed with development based on the shape shown in the photo.

    キャプションを入力できます

  • Started software development

    AIRPOCKET@rastaman vibration04/14/2022 at 23:49 0 comments

    In 8mm film cameras, the shutter timing is linked to the frame feed of the film. When controlling the image sensor, the shutter timing must be detected in some way to capture an image. The captured image data is later connected and converted to video.
    First, we created a time-lapse tool that uses test opencv to take a picture at a specified timing, convert it to a movie, and then output it.

    Looks good. 

  • Shell splitting the image sensor

    AIRPOCKET@rastaman vibration04/14/2022 at 06:33 0 comments

    The lens attached to the OV5647 was removed as it was not needed. The image sensor housing was still in the way and could not be installed in the focal position, so the shell was split.

    Since the image sensor shell is welded (probably vibration-welded) to the bottom section, it is necessary to split the welds. The four corners of the shell joint were cut with a nipper blade to break the weld.
    There was no damage to the sensor that we were worried about.

    キャプションを入力できます

    Since I had a chance to observe the sensor, I took pictures of it under a microscope.

    Unfortunately, the magnification was not enough to see the pattern of the sensor.

    キャプションを入力できます

  • Select image sensor

    AIRPOCKET@rastaman vibration04/13/2022 at 01:36 0 comments

    Select the image sensor to be used in the project. The image sensor must be placed just behind the shutter, but must be a small sensor board due to the limited size of the film chamber.
    The maximum width of the space for the sensor should be 20 mm, and less than 15 mm is desirable for optical axis placement.
    We originally planned to use a Raspberry Pi Camera V2, but the width of the board is 25 mm and it would not fit.

    Therefore, we decided to use Arducam's OV5647 camera board with image sensor.

    The width of the sensor part is as small as 8.5 mm, which seems to allow free placement in the film chamber.

    The sensor size is 3.68 mm x 2.76 mm; the image size recorded on double-8 film is 4.37 mm x 3.28 mm, so the angle of view drops to about 84%, but this is within acceptable limits.

    In actual testing, the Raspberry Pi Camera was able to transfer data at 90 fps at 800 x 600 size, although the image quality was not as good as the IMX219 Raspberry Pi Camera. In this project, we plan to synchronize the shutter timing and shoot at a maximum of 64 fps, so we believe we have confirmed that the performance is sufficient to handle this.

  • Maintenance

    AIRPOCKET@rastaman vibration04/11/2022 at 02:56 0 comments

    Immediately after purchase, it was in good shape, but suddenly the shutter stopped working. Since it is an old machine, we enjoy this kind of trouble as well.

    Remove the flat-head screws on the four corners of the body to remove the case cover.
    The mechanism is held in place by six more screws.
    Since the viewfinder lens is also attached to the mechanism, both objective and ocular lenses were removed to take out the mechanism.

    Since there were no cracks or chips on the parts, I moved the gears by hand and they started to move little by little. Perhaps some deteriorated grease or dust got caught in the gears.
    Many failures of old cameras and watches are said to be caused by deteriorating grease.

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