Hello.
I recently got a high quality projector which I plan to base my scanner off of.
I plan to use the Raspberry Pi HQ camera and I want to trigger it similar to this persons method
Is it possible to do this and get frame accurate transfers at a lowest of 18 fps?
If it is would it be possible to go even further and do 2 exposure HDR at 18 fps?
Thanks in advance.
Hi @VideoMilk78,
First of all, welcome to the forum. It is certainly a good place to get useful information and share our experiences with other users in this interesting work of digitizing old films.
I don’t know if I understood your question correctly.
In the forum we find several members, including myself, who usually use the Raspberry Pi HQ camera for their capture devices.
In a frame-by-frame scanner, a capture speed of 18 fps with the HQ camera is impossible, and even less so if it involves HDR captures that require taking several images of the same frame and then merging them using an HDR algorithm.
With my current device, in the best conditions, I can get capture rates of up to 2 fps.
Normally, when using an old projector, for a frame-by-frame scanner, the original motor is replaced by a stepper motor that allows the controlled movement of the film and the triggering of the camera using software. You can see several examples in the forum.
Regards
I don’t think anyone in these forums has managed more than 1-2fps with the Pi HQ camera at (single image) full raw/dng resolution. Something around 10fps video is the best it can do at 4k, but then you’ll get compressed movie files.
If you want to go with live-recording, maybe have a look at https://en.film-digital.com/. They also have a bunch of videos explaining how they determine the correct exposure time for recording flicker-free. I’ve had decent success imitating their setup with a Canon DSLR and Magic Lantern firmware, but the camera only managed 18-24fps and the only projector I have available doesn’t run too steadily, so there were a lot of double-exposures and wobbly exposures mixed into the recorded footage that ultimately bothered me enough to go with a slow frame-by-frame scan.
Film-Digital seems to record at higher fps, then eliminates “bad” frames with an AviSynth script that they unfortunately haven’t made public. You can probably create a similar setup with the Pi HQ camera (and just start recording video manually), but single raw/dng at 18 fps is impossible.
I used this Avisynth/Getdub script for a long time on projectors that I was modifying.
If the image is sharp and the projector speed well stabilised, it works perfectly and removes all blurred images. On the other hand, using Avisynth filters is a pain, you have to find the right DLLs and the right version of Avisynth. It’s an old system.
The principle is to run the projector at 16.66 fps and the camera or camcorder at 50 fps. After passing the file through Avisynth, you get a film with no dubbed image.
We talk about it here: https://forum.doom9.net/showthread.php?p=567237
HDR aside for now it doesn’t need to be max resolution as that is way overkill (in my opinion)
as long as it’s HD 1080 that’s ok
Avisynth isn’t a pain at all. Once you get the hang of it you can match the results of extremely expensive software!
That’s where the problem lies. But if you already know what you’re doing, all the better.
The principle is to run the projector at 16.66 fps and the camera or camcorder at 50 fps.
They have a video calculating the required shutter speed for flicker free recording, depending on the number of aperture blades the projector has. Mine (Bauer T520) has 3. So 1/(blades*fps) is the required shutter speed. I had the projector and the camera running at 18fps with 1/54 shutter speed (which, in Magic Lantern) was represented as 120° shutter speed: 360°/number-of-blades.
But I don’t know if their AviSynth script has any requirements, I never had it (and also couldn’t get into AviSynth in general…).