A Stop Motion Studio Recipe
How we came to doing stop motion is another story, suffice to say that, during the March 2020 lockdown (European timezone here), my partner and I decided to setup a stop motion studio … in the room formally-known as the living-room!
This was a labour of love that took several months to reach this point. A lot of learnings and optimisations were made along the way. Neither of us had any experience with stop motion nor film before starting out. All of this was completely new for us.
We will only address the technical side, the other side of the medallion is developing storyboards, building the sets and props, setting up camera angles, getting the lighting right and post production.
The Recipe
Prep time: about 8 Months, give or take.
Difficulty: Painful and Frustrating :) Stop motion, as everyone says, is an art-form requiring a good serving of patience; equal amounts of eye-for-detail and dedication!
Serves: Lots!
End results (and here comes the self-promo): our films can be viewed at the-oswalds.de.
Ingredients
- 6x Raspberry Pis (a mix of Pi4 and Pi3s)
- 5x DMX-based Strobe lights
- 2x Nikon DSLR cameras and lenses (one will suffice!)
- 2x NETGEAR Gigabit Hubs (at least a one gigabit)
- 2x SanDisk Extreme SSD (two since a Raspberry only has two USB3 slots)
- 1x DMX Interface for Raspberry (an additional Raspberry mini is required for this)
- 1x Monitor for displaying the last frame captured
- 1x Big Red Button for deleting the last image taken (We actually had one lying around, so we didn’t purchase this for 95 Euros!)
- 1x Sewing Machine Pedal for triggering frame capture
- Various LEGO motors for turning things
- Cables in various lengths and forms: DMX cable, Ethernet cable, USB3 extension cables and power cables
- And sugar and spice (mostly software) for making all things nice (and tasty)!
Nutritional Facts
What are the main overarching goals of the recipe?
- Speed — take as many frames as quickly as possible,
- Easy of use — technological should not get in the way, it should facilitate the way, and
- Automation — make the technological take care of itself and be scriptable.
We want technological to do everything that we do not want to think about, and that reliably and reproducibly.
Steps
As with the film business, it’s all about lights, cameras and action! And so it is with stop motion, so let’s get started.
Step 1: Lights
Stop motion requires constant and even light sources, natural light is not desirable. Also lighting that flickers is a no-go, even if you don’t notice the flickering. Since each frame is taken with slightly difference in lighting, the overall effect for a film is noticeable and annoying.
We now use dimmable LED colour strobe lights, the type used by theatres and nightclubs. We initially purchased cheap LED strobe lights, that wasn’t a good idea. The Ibiza lights we bought flicker noticeably when dimmed. Our second purchase were two Cameos Flat PAR Lights which can be dimmed without flickering.
To have full control over our lights, we use the DMX protocol. The advantage of using DMX is configurability and therefore reproducibility. So that we can store the light settings for one scene, film a second scene, then going back to the exact same light settings to continue filming on the first scene.
In addition to all of that, DMX is designed to be flexible: adding another strobe light or remove one is absolutely no issue. This makes it perfect for our needs.
We combined a DMX Interface with an OLA Daemon and to make usability a little simpler, we use the PyDMXControl package to bundle individual strobes into “fixtures”. Each strobe has it is own fixture description. Each fixture is defined by the number of channels it uses and a DMX address. From there we have lights that we can configure in colour and intensity.
Step 2: Cameras
We began with Webcams but soon realised that the image quality was not consistent, both resolution and flickering caused headaches. Not surprisingly we moved to DSLR cameras which provide more consistent quality and better resolution.
We purchased a Nikon D7100 and long-term loaned a Nikon D50. Each camera is controlled by its own Raspberry. This ensures that frames are captured simultaneously and makes frame capturing faster than having both cameras hooked up to the same Raspberry.
When interacting with DSLR Cameras, there is only one open-source go-to package: Gphoto2. It provides a unified interface for various digital cameras. Gphoto2 supports a long list of cameras, check that before purchasing a DSLR.
Gphoto2 allows configuration of all main features of a DSLR: shutter-speed, white-balance, iso-speed, resolution and f-number. In addition, Gphoto2 also triggers the camera and retrieves the images from the camera.
So our camera remote control became a USB cable connected to a Raspberry, triggered via web requests. It is important to remotely trigger cameras since any movement of the camera will become a shake in the final film. We explicitly do not use infrared camera remotes since this would mean the animator would need to use their hands to trigger frame capturing, and support for multiple cameras means multiple remotes.
We are using batteries for our cameras, ideally you really want to use an external power source for each camera. Our compromise is to have second battery packs for both cameras. The downside to this is that replacing the battery causes minimal movement of the camera, which can affect the final film.
Of course, there is no obligation to use two cameras all the time. For specific scenes, though, it great to have two perspectives that are edited together in post production.
Step 3: Storage
We work with DSLR cameras at their highest resolution. Using the highest resolution gives more flexibility in post production: cropping and zooming are possible without quality loss. In addition, the final product looks far more captivating.
The drawback is that individual frames can be up to 13 MB in size. That sums up to large storage requirements. Thankfully storage is cheap, so per-se this is not an issue. However, we want to immediately view images taken, so it becomes a matter of: taking the image, transferring the image from the camera to a central storage, retrieving the image and display it on screens; as fast as possible.
Initially we used USB2 and WiFi but this became painfully slow. Especially since we used multiple cameras to capture each frame simultaneous from different angles. To improve performance, we started using a Raspberry 4 with USB3 SanDisk SSDs, cabled to a NETGEAR hub.
Raspberry Pi 4s are the first generation of raspberries that have gigabit ethernet slots: RPi3+ have 330Mbit and RPi3 have 100Mbit slots. Plus the RPi4s are the first raspberries with USB3 slots.
Beware that a lot of USB3 storage devices claim to be USB3 but do not deliver. A good place to look for storage benchmarks for Raspberries is James Chambers site. It is a community-driven collection of storage benchmarks for various drives connected to various raspberries.
Ensure that your ethernet cable supports gigabit hubs. There are different categories of cable and at a minimum Category 5e is required for gigabit networks.
Another learning was that USB-Sticks do not perform as well, always use SSD hard drives. Perhaps I was naïve here but USB sticks are not good for constant reading and writing, as required by a stop motion studio.
So, what is the end result all of this? Write speeds directly to the disks are in the order of 160MB/s and via ethernet cable they easily reach the one gigabit maximum of 125MB/s.
Step 4: Motors
In our first three films we always had something that turned. Be it a traffic cone or disco ball or ceiling fan. All of them where powered by LEGO motors acting as step motors.
To make this happen, a Raspberry controls two relays that toggle the power to the LEGO motor. By controlling the time interval, we control how far the motors rotate between frames.
Since the Raspberry controls the motors, this becomes programmable. So before each frame is taken, the motors are triggered and rotate just a little, to make a constant rotation in the final film.
This went so far that we purchased a LEGO Crane that could raise and lower things into scenes!
Step 5: Action
The process of animating is very repetitive, requiring good focus (and not only of the camera) and concentration. It comes down to focusing on what will happen in the scene, concentrating on what needs to be animated and stepping back to capture a frame, then rinse and repeat for a substantial period of time.
Being a very hands-on process, we want to keep the hands free for animating. So that is where the sewing machine pedal comes in: frame capturing is feet triggered. Notification of frame capture completion is an audible bong. We can then continue with the animation.
The last frame captured is shown on a preview monitor. If the image needs to be deleted and retaken, the big red button is hit and the last frame is deleted.
All of this happens automagically and that is where the six raspberries come into play. One for each camera, one for the strobes, one for the preview monitor and big red button, one for the motors and the final one for the pedal and speakers.
Having six Raspberries is very similar to having six servers to administrate. All the same issues arise: updating, deploying, monitoring, downtime, etc. There is Python code that glues all this together. Not only for triggering and configuring the various components, but also for image preview and creating the final films from individual frames.
The code base is the same on all raspberries. This is done for a number of reasons: deployment is simpler, we can interchange devices (e.g. cameras) amongst the raspberries and adding a new Raspberry is trivial.
Post production is done with DaVinci Resolve using individual films for each scene. DaVinci is amazing for creating films, it provides so much functionality yet it remains intuitive and easy to learn — a great product.
So there we have it, our setup for making stop motion films starts with a sewing machine pedal and ends with a bong, frame by frame. We have a making-of film to give a taste what it looks like in the trenches.
Variations
There are lots of other things that go into the recipe and we could go on for hours, instead, here are the top four in alphabetical order:
- We have two separate electrical circuits (i.e. power): one for the lights and one for the raspberries. This allows us to switch off all the lights with one switch! It’s a minor thing but also symbolic to kill all the lights with one click when done ;)
- Thick black curtains to block out natural light. Stop motion is definitely for people who can go without sunlight …
- Nice neighbours that do not complain listening to 60’s garage music at four in the morning. We always underestimate how long set preparation takes and nearly always end up working late into the night!
- Why not take off-the-shelf software for doing this? Partly because we didn’t really find anything that combines everything that we needed into a complete package and secondly: if you walk along trodden paths, you will only end up there, where everyone else is. But maybe, we both just like tinkering ;)
Outlook
We are currently experimenting with 2D animation, specification collage and cut-outs. Here we’re working with a pocket beamer for projecting outlines onto paper between frames. To make sure that the beamer image is only shown between frames, a servo motor (with a tiny flag) blocks the beamer before the cameras capture frames.
Sourcing
We source all our gear from local shops, large-online-consumer-goods-selling sites were not directly involved. Even if the shop from whom we purchased our gear sources from large-online-consumer-goods-selling sites, we’re still paying extra to support that shop.
An incomplete list (for anyone living in Berlin):
- Segor is a good provider of everything electronic, i.e. relays, raspberries, cables and power supplies.
- Reichelt if Segor doesn’t have it, then Reichelt will!
- Onkel Philipp is a good source of LEGO and set props.
- Conrad although not as good quality as Segor or Reichelt, they still have good selection of “stuff”!
- Foto Braune is a good source of secondhand camera gear.
- Just Music is great for music and lights.
- Modulor is the source for building sets and characters. Although rather pricey, they are also a good source of inspiration.
- Hobby Rüther the go-to store for quick fixes for sets and props!
- Boesner which is similar to Modulor but more focused on basic art materials.
- eBay Kleinanzeigen is also good source of peer-to-peer used products.
- Solid Earth for digital prints for our backgrounds.
- CSV for stickers and large prints.
Admittedly, none of these places will not — hopefully — close any time soon, with or without our support but without their support, we couldn’t do what we love!
