There exist dual format projectors with a swapable film gate you can take out. This helps in enlarging the film gate in case you want to scan the area usually not seen in a normal projection. This is however a challenging operation - you want to be careful not to introduce any scratches in your film gate while enlarging it. You might stick with the projection window as it is, much easier.
There are lots of examples here in the forum about projector-based Super-8 scanners. Also, youtube is certainly your friend. Try “telecine DIY” for example. And yes, a lot of people do use NEMA-17 motors. Be aware that this is only the mounting specs - it has nothing to do with the power a motor can deliver. Be sure to source a sufficiently strong motor. Also, do not drive this motor with a stepper driver connected to 12 V. Use at least 24 V.
Be sure to throughly clean and re-lubricate at the appropriate place the projector you obtain. These things usually have been sitting tens of years unused in some storage. This eases the amount of work your stepper has to perform.
Again, browse the forum. Both machines have been used for driving the stepper motor and triggering a frame capture. Normally, the Arduino or a similar microprocessor is better suited for time-critical task (like driving a stepper), as the Raspberry Pi’s Linux-based operating system is no real-time operating system. However, there is software available on the internets for both machines. From a system design point of view it might be a good approach to drive the projector/stepper via an Arduino and to take the scans with a Raspberry Pi 4 and a HQ camera connected to that Raspberry Pi. Again, search the forum - I know of at least three people (@dgalland, @PM490 and @Manuel_Angel) who published their approach to a film scanner in detail here on the forum and on github.
If you want to go high res, choose a digital camera. But be aware the storage requirements and processing time increase exponentially with the pixel count. Note that even the best Super-8 footage I have seen never exceeds HD resolution. Because you might want to opt for doing overscan (include part of the sprocket hole for example for frame stabilization) and you might want to have some head room for post processing, you should opt at a scan resolution for Super-8 of at least 2k.
Note that picture taking with a normal digital camera is a quite slow process.
Which brings the Raspberry Pi 4 equipped with a HQ camera into play. A lot of people here in the forum are using that combination, as it is able to capture 2k-like scans with quite some speed. Again, there are ready-made software solutions available on the internet (see links above).
depends on your overall system design. If you do not want to spend a sizeable amount of time for your film scanner, simply use existing software. That will most probably be written in C++ for the Arduino and in Python for the Raspberry Pi.
A lot of people obtain quite good results with the Schneider Componon-S 50 mm. It is a lens actually calculated for the 35mm format. So if you are using that lens with Super-8 film stock and a Raspberry Pi HQ camera, you will be using only the sharpest part in the center of the lens. Best performance is achieved with f-stops between 4 and 5.6.
There is no question that the best software for post processing is daVinci Resolve. There’s a free edition which is very powerful; daVinci Resolve is especially reowned for excelent color grading - which you will have to do a lot of when scanning Super-8 material. Only if you already familiar with another video editor stick with what you already have mastered - daVinci Resolve comes with a steep learning curve. But again, the internet and youtube are your friends (lots of tutorials there).
Your video editing program should be able to read single frames and output these into a movie. daVinci Resolve certainly is able to do that. You might want to get the fastest PC you can affford, equipped with the best graphics card you can get (as daVinci Resolve and most other video editors nowadays use the graphics card for computing). Your other bottleneck will be the hard disks. Be sure to use SSDs if possible, large ones. Things can speed up if you have the input frames on one fast disk and output the movie onto another one. Also, put the chache of the video editor on yet another drive.
well, the Rasperry Pi-combo is about the cheapest option you can use for digitizing Super-8 material. I think the Raspberry Pi 4/HQ camera option should set you back at most 150€, all in all. A used projector (if it is in good shape, and for the sake of your movies, you probably want it to be in good shape) will run between 50€ to 400€ on ebay. A new PC with which it is fun to postprocess/edit videos will take you back at least 1000€. But daVinci Resolve is free 