T-Scann 8 - project page
Super 8 / Regular 8 film scanner
T-Scann 8 is a frame by frame scanner. Unlike the original Flying-spot scanner principle
which works like a reverse old Tv / CRT this principle was used until the year 2000, and is one
very complicated construction. The advantage of current technology is higher image resolution and better quality.
Luckily this technology came, otherwise we hobbyists would not have been able to build our own scanners.
The fine and expensive commercial film scanners use global shutter cameras, acting as a super 8 camera each frame is exposed in its entirety directly, then the film does not need to be stopped, each frame is exposed with a short exposure time type 1/1000 partly second
then the image is frozen. Now global shutter cameras are expensive, so we have to make do with rolling shutter cameras which is the principle for most cameras. If you try to freeze the image with rolling film, only half the image will be good, the other part blurry will not be good at all.
Now there is probably someone who says you can film off the screen or put a video camera in front of a film projector, of course you can but then you get worse image for several reasons, one is that video compression is worse than still image compression as image by image
The principle of my scanner is thus to stop the film for each frame, take a picture, drag the next one, etc., 3600 frames on a film roll 15 meters super 8.
Uses Raspberry PI camera V2, Microscope lens with C-mount and specially made adapter to connect the lens with the camera in addition, I have removed the tiny lens that sits on the camera original. It is not good to have several lenses in a row, color errors easily become red edges around the subject and similar errors.
To pull out the film, 2 stepper motors are used, a capstan that is the one that pulls out the film according to approximately the same principle as one tape recorder for audio. Furthermore, the film should be wound on a wheel. When the film is finished, it should be rewinded so then there is a 3rd stepper motor for this.
It is possible to save at least 1 stepper motor, but then it becomes mechanically much more complicated.
The reason for using stepper motors that they are easy to control can go very slowly or very quickly without using any gear of some sort. The capstan pulls out the film with friction rubber roller, then it does not matter if it is Super 8 or Regular 8.
Here's how to scan:
- capstan pulls out the film
- wheel B - unwinds the film, so that the stepper motor does not hack, it stops - Traction stop - the stepper motor to wheel B when the pull arm becomes so tightly tensioned that the power switch is turned on. This happens many times per second.
LED shines through the perforation of the film and hits the light detector / phototransistor
when the perforation reaches the trailing edge of the hole, the capstan and coil B operation are stopped.
It is an Arduino Nano that reads the light detector / phototransistor and the stepper motors. A signal sent to the Raspberry PI computer "TAKE PICTURE"
Arduino waits for the Raspberry PI to send the command that the image is exposed and
that the image should be saved on a hard disk..
Then repeat the above procedure until the entire film is scanned. Then you have 3600 still images in Jpg format which are included in Video editing the program black magic resolve and is turned into a video movie.
Now you have to know or try it out until is this film recorded at 16, 18 or 24 frames per second? before exporting to an mp4 video file.
Reading the perforation of the film with white LED light is not always so easy, around the perforation of the film it should be black then it will be quite easy, but now it will not always be as this example shows for that reason I use very weak white light, the light is stopped more easily if the film is not completely black and lets through some light.
If the film is completely blank, it immediately becomes much more difficult, you can drive with "Dead man's account" you know that for example between previous windows there has been, for example, 160 steps on the stepper motor, so if you drive with this value, there will be poorer precision
so should not run so many frames with this method, it is usually not completely blank between the perforation so probably the frame is blank nothing to scan in other words !.
Although this way of detecting the perforation goes quite well, I have not got it perfect, it requires stabilization of the image in editing programs.
Traction stop switch
Light source LED RGB 3Watt
light detector / phototransistor