To provide more information about our Digital Super-8 Cartridge solution we publish the ‘bill of materials’. This is for the version with external module. Development is underway for a new prototype with no external module, it will have all electronics inside the cartridge.
Bill of materials:
The Cartridge: 3D printed Super8 cartridge, Ximea MU9-MBRD subminiature camera (with Aptina MT9P031 sensor), our own designed shutter sync circuit PCB with photodetector for film claw detection, microUSB breakout board with image capture indication LED, IR Filter, connector cable from PCB to microUSB board, high quality USB cable to connect cart to external module.
External module: Raspberry Pi3, 32GB SanDisk microSD card, Raspberry Pi touch screen with plastic casing, 6600 mAh power bank with microUSB cable to power the module.
Code: C++ application designed built on Qt Creator to control the capturing, settings, and to develop raw images into video, colorgrading.
We shot some new footage to test the quality of the Digital Super8 Cartridge. Our software app takes the RAW Bayer images of the cartridge and performs S-Log encoding before we do any further processing. Using the Digital Super8 application we added contrast with S-curve and then applied individual S-Curves on the RGB channels to add warmth. Because Digital Super8 consists of individually captured 12 bit RAW images (global shutter) there’s a lot of flexibility in how to process afterwards. One could do B&W, natural color, warm, cool or whatever else. Also the software provided allows for export of TIFF image format.
The Nizo 801 Macro we used has some motor instability, leading to a bit of flicker.
Over the last couple of weeks a lot of spare time went into improving the code that controls the image capturing. The main bug to address was that the image capturing would ‘hang’ after a certain amount of time when capturing say round 10 seconds or more of 720p 12 bit images.
We revisited the code and the multi-threaded buffering algorithm. Putting the buffer and the code that empties the buffer on a separate thread, away from the main user interfacing window thread dramatically improved the performance. The ‘hanging’ capturing was solved except for the fact that at some times the output of Ximea API messages can still interfere with the code, which is at the capturing stage pushing all boundaries of the raspberry pi 3. When run with an open terminal window the problem is solved but we will ‘silence’ the API output further in order to completely solve the issue.
The only other point to note is that when capturing 720p resolution (the highest option) and at 12 bit, the image capture buffer fills up quite rapidly as the large RAW images take time to be written to microSD card. When ~300 images are in the buffer the raspberry pi sort of gives up and starts ‘sputtering’. Waiting long enough for the buffer to empty solves the situation but you will lose images.
Best options in this ‘best mode’ are to capture shorter shots. Also scaling back to 8 bit RAW dramatically slows down filling up of the buffer. Another option is to move to 540p at 12 bit.
A final ‘disturbing’ issue is that the Ximea camera every now and then ‘disconnects’ and throws an error. The ConnectCam button needs to be pressed to reset the connection and filming can resume. Whether this is a bad USB cable issue or something else will be investigated.