Pulling Focus Like a Pro with a Palm-size Camera?
A Guide to Distance-accurate Focus Pulling with Blackmagic Micro Cinema Camera via SBUS
Let’s say your director comes up with an idea to shoot a helmet cam shot. He won’t accept GoPro because the image quality is far too low. He also needs to shift focus during the shot. You need to come up with a solution. What would you suggest?
The most common solution today would be a DSLR/mirrorless camera like the Sony A7Sii or a Panasonic GH5. Once you have the remote follow focus system and the required power supply added, the setup will end up looking like this:
image by courtesy of mantasjockus.de
Do you know there is a far better solution that has existed for more than two years? The Blackmagic Micro Cinema Camera supports wireless focus pulling via its SBUS input. You can use a common RC model plane controller to directing control the internal autofocus motor of the lens. You can pull focus repeatably and reliably with accuracy down to feet and inches - the same way a Hollywood focus puller like to work.
What’s more? You can remotely control its aperture, shutter angle, ISO, start/stop, white balance, and even the sound recording level.
Sounds like it will require a complicated rig to setup? Actually, no.
Some Background Info
Several years ago, I used to own a full-size setup of the original Blackmagic Cinema Camera 2.5K as my main camera. At that time, it was a decent camera for what it was, with its own list of limitations. Mediocre color, bad ergonomics, noisy low light, no slow motion. Dynamic range was closer to 10.5 stops than the advertised 13 stops. But with a kit of carefully chosen accessories, it served me fine in a number of short film projects. It actually helped me captured some of my favorite images that made it into my reel. The camera was later retired and replaced by the Sony FS7 when it came out.
When the Blackmagic Micro Cinema Camera was announced back in 2015, it first appeared to me as an uninteresting product. It shared the same sensor as the BMCC 2.5K (slightly cropped down to super-16mm size), so these two cameras should have similar limitations in image quality. But my opinion changed when I learned about its support for SBUS control. I became highly intrigued by the possibilities presented by this camera.
While its image quality is lacking as the main camera, it is still highly usable as a specialized palm-sized camera. Just think about all the special user cases that can benefit from such a camera: helmet cam, bicycle-mounted cam, extreme sports, crash cam, hidden camera, shooting small animal in miniature space… The possibilities are endless.
At that time, I couldn't find much information online about this camera beyond the usual camera reviews. There was even less info about its SBUS capability. Blackmagic Design clearly meant to treat SBUS capability as an experimental feature for DIY users or advanced custom rig builder.
It took me two months of full-time research and tinkering to arrived at this setup that I am very happy about. Now, I am going to share all my findings with you here.
This is everything you need to perform accurate distance-based focus pulling.
It is currently the smallest, simplest camera setup that produces cinematic images.
This guide is about the Blackmagic Micro Cinema Camera, not the Blackmagic Micro Studio Camera 4K. The former records to an internal SD card at 1920x1080 resolution and 23.98/24/25/29.92/30/50/59.94/60 frame rates. The latter does not accept SD card and does not record internally.
The Expansion Port
The camera accepts Futaba SBUS signal via its expansion port. It is a 15-pin DE-15 female connector, which happens to be identical to a VGA connector found on a computer monitor. A cable is required to connect a SBUS receiver to the camera.
The expansion port also has many other functions. It takes 12v power input, accepts LANC control signal, allows four channels of analog servo remote control, and it outputs SD composite video. But I only need SBUS for my purpose.
RC Controller & Receiver
I have no experience with Futaba RC controllers. I find the Frsky Taranis X9D Plus to be working beautifully, at a lower price. Its menu is highly customizable, but it is also quite complex.
How Does It Work in Practice?
I created this video to show you how this setup performs distance-accurate fous pulling, as well as other remote functions:
Marketing photos are usually quite lame because they never show you the accessories needed to make the camera work.
But this picture does show you what a Blackmagic Micro Cinema Camera actually looks like when it is set up as helmet cam, ready to pull focus accurately. (Well, you do need to add a SBUS receiver, but it is tiny.)
Photo by courtesy of http://blackmagicdesign.com/
You need the Frksy X8R receiver. The receiver has a 3-pin SBUS output that connects with the camera.
I like to stick the receiver on the camera body with some industrial-grade velcro to keep everything in one piece.
The SBUS Cable
The original expansion cable that comes with the camera isn’t suited to work with this receiver. The 3-pin SBUS connector does not provide the 5V power required by the receiver. You need to make a custom SBUS cable. It is actually quite easy to do if you know how to solder two cables together.
This is a DIY cable I made by joining a VGA monitor cable with a 3-pin SBUS cable.
The original SBUS cable doesn't provide +5V power at pin2.
Follow this wiring diagram to make your own cable.
(You may also try adding a 12v input jack to make this into a Y-cable. I wasn't sure which ground pin to use for 12v power and didn't want to fry anything, so I skipped it.)
Purpose of This Guide
This guide aims to help you set up a Blackmagic Micro Cinema Camera as a palm-sized kit capable of repeatable, distatnce-accurate wireless focus pulling. This is a general concept guide, which means I can’t walk you through every step of setting up the rather complex RC control menu system. This setup also requires a basic level of DIY. Be prepared to invest some time to tinker and to troubleshoot. The good thing is there ain’t too many components in this setup, and not much can go wrong. It is loads of fun, and the resulting kit will be super useful in real productions.
Obviously, I have not tested every micro 4/3 lens in the market. I can only speak from my own experience and share my opinion on what does and doesn't work for me. You may have other lens preferences if your goal isn't to set up a palm-sized kit. Please feel free to enrich this guide here by sharing your findings in the comment section.
The Lens Kit
All native micro 4/3 AF lenses from Panasonic and Olympus can be controlled by SBUS. But only a handful of them have focus motors that are smooth enough for focus pulling.
I tried the Panasonic first-gen 20mm/1.7, 14mm/2.5, and the Pana-Leica 25mm/1.4. The stepping action of the motors is way too jumpy and too distracting. I don't recommend them for focus pulling.
Olympus prime lenses are more useful for our purpose. The focus motor is acceptably smooth (although I wish they are smoother…) They are perfect match with this camera.
I recommend these three Olympus micro 4/3 prime lenses as a starter kit:
Olympus M. Zuiko Digital ED 12mm f/2.0
Olympus M.Zuiko 17mm f/1.8
Olympus M.Zuiko 25mm f/1.8
KOWA 6mm f/1.8 C-mount ultra wide angle lens works great with this camera
This filter thread adapter made by D Focus is specially designed to add 77mm filter thread for this KOWA lens. (Lists as discontinued on B&H)
You will need a set of ND filters for outdoor. I haven't done extensive testing with this camera for IR sensitivity. But I try to be on the safe side and opt for ND filters with IR cut.
I try to keep this setup compact and don't want to use square filters and mattebox.
Hoya makes very good IRND filters and I don't see a lot of talk about it online. I haven't done scientific tests with them, but I don't notice any objectionable color casts. I have owned IRND filters from Tiffen, Formatt Firecrest Series, and NiSi, so I have some reference points to compare to. (By the way, the Tiffen has really bad color cast. So much so that I don't want to see them ever again. But that's for another article.)
The Hoya makes them in many sizes. The 46mm is a perfect match for the three Olympus prime lenses.
Hoya IRND filters is a great choice for this camera.
Other Useful Accessories
DIY Battery Adapter Plate
This excellent idea from Cheesycam is truly a gerat help. A Canon LP-E6 battery is very small and sometimes the run time is too short to work with. I made this DIY battery adapter plate to mount a Sony NP-F battery on this camera when I need the runtime and don't mind the bulk.
I took apart a Canon LP-E6 battery and glued the casing on to a Sony battery plate with some 2-part epoxy glue. I also had to solder the contacts together. A pretty basic DIY job.
This DIY battery adapter plate allows Sony NP-F batteries to be mounted on the camera
Sony NP-F Compatible Battery by SWIT
This SWIT battery features a 7.4V output, and it has a power level indicator. A single battery can now power the camera and the monitor. Makes things simple.
P-tap to Canon LP-E6 Dummy Battery Cable
I made this cable by joinning a voltage regulator with a Canon LP-E6 dummy battery. Companies like SmallHD also make such cable. It allows me to use a V-mount battery to power the camera remotely for a long time. It helps keep the camera small and makes car-mounted or hidden camera setups much easier.
I didn't further pursue other lens options because the above lens kit is good enough for me and I want to keep the kit small. For those who want faster, longer lenses, or don't mind the larger size, I think the Olympus 45mm f/1.8, 17mm/1.2, 25mm/1.2, and 45mm/1.2 could be good candidates to try. I don't have personal experience with these lenses. Please share your experience here if you do.
All the equipment you need for precision focus pulling is shown in this picture:
So far I really like this kit because they are small and sharp. They are relatively inexpensive so I don’t need to worry too much when I use them as crash cam. They also share the same 46mm filter thread.
Zooms are more tricky. The focus motor in my Panasonic 7-14mm/4.0 and 35-100mm/2.8 seem to be quite smooth. But these zoom are not parfocal. The focus shifts slightly when I zoom. i.e. If you mark your lens at 35mm, your marks will be off at 100mm.
So I didn’t bother with my 35-100mm/2.8. (Who needs telephoto for such a tiny specialty camera anyways?) I did create a lens profile for the 7-14mm/4.0 at 10mm. It serves as a middle-ground reference, and it is still holds focus reasonably well at 7mm and 14mm. The huge DOF of this wide angle lens also helps too.
For the ultra wide angle at lowlight, I found the KOWA 6mm f/1.8 C-mount to work excellently. It is equivalent to a 12mm in super-35mm terms. It has similar ultra wide field of view as a GoPro, without the nasty distortion. It is not distortion-free, but nothing too distracting for a lens this wide. It is a mechanical manual focus lens, so no remote focus pulling via SBUS. But it is wide enough that its DOF can cover most situations. This lens doesn't show dark corners on this camera.
The Olympus 12/2.0 17/1.8 25/1.8
They are roughly equivalent to 24/35/50mm in field of view and f/4.0 in depth of field super-35mm terms.