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DIY V-Mount for Cheap

The V-Mount system is a popular battery mounting standard that is designed for large batteries in the 60-90+ Wh range. This means that with such a system you can run small cameras all day and even many of the more demanding ones for hours. However, since this is gear for serious enthusiast and professional filmmakers, it does cost a lot of money. After I got my hand on a second-hand Li-Ion battery pack, I decided to explore the options in making my own V-Mount for under $150.

Overview

The main components of a V-Mount system are listed below. For a great little overview of affordable batteries, check out this DSLR Video Shooter blog post by Caleb Pike. I will compare semi-professional solutions as found on Amazon or B&H with the parts that I used for my build:

  • The battery pack: should use good, branded Li-Ion cells for obvious safety and performance reasons. There can be pretty dramatic differences even between branded off-the-shelf V-Mount battery packs as seen in this (highly entertaining, like the whole channel) video (these guys deserve more views!) I don't expect to compete with high-end V-Mount batteries but the recycled pack I'm using still contains genuine Panasonic 18650 cells. We managed to find a pack for, I would say, 1/10th of the price of a good V-Mount battery but because it was quite a lucky find and specific to our local area I won't post details or exact costs. Individual 18650 cells go for around $11 a pair so you could still build your own 90 Wh pack for about $66. The configuration is 3 batteries in parallel and 4 in series. Make sure your pack has over-current and over-temperature protection! So let's say total cost so far: $70.
  • The battery pack mount: This keeps the battery securely attached to the mounting system. In V-Mount batteries it is part of the battery pack mould and there shouldn't be any way it could fall apart under normal usage. My recycled pack didn't have much in the way of strong attachment points and I didn't want to rely on glue but luckily some bolts through the plastic tabs on the side worked great. There is no way the battery is falling off and the mounting plate can hardly move despite my mediocre machining skills. Purchased from Aliexpress this was the most expensive part at $33. This brings the total cost to a nice round $100.
  • The camera rig mount: Most packs mount directly to the back of a camera or a 15 mm rails rig. Besides strong rail mounts, the mounting plate usually also provides outputs at varying voltages to power different devices such as camera, monitor, audio equipment, etc. Decent plates, e.g. from Lanparte or more professional brands, can easily cost $250 or more. Buying the parts separately, it really comes down to a cheap $9 plate, a $1 voltage converter, and a $18 rail rod clamp from SmallRig. This only bumps the total cost up slightly to about $130.
  • Now all that's left are some cables to connect the battery plate to your camera, your monitor, and other equipment. Since we're already building this ourselves, absolutely avoid regulator cables like the ones listed in the DSLR Video Shooter blog post above: they are horrendously over-priced for what they do. A standard low-power step-down voltage regulator (this means it's efficient and won't produce much heat) only costs $1. For my camera I got a D-Tap to BMPCC cable for $3.50 feeding the 14-15V from the battery directly into the DC input, and for the monitor a dummy LP-E6 for $4 which has to be regulated down to 7.2V to match the LP-E6 batteries.

Cost

So there you have it: a fairly sturdy DIY V-Mount system for just $150, maybe less if you can find some cheap recycled batteries. Obviously, cost is the main reason why an enthusiast would go through the trouble of building something like this from scratch, spending 1-2 days getting everything figured out and assembled, instead of dropping $300-$500 and just getting something off the shelf. Time will tell if it is sturdy enough to hold up to regular hobby usage (to be perfectly honest, I wouldn't recommend it for daily and professional use). Hopefully my instructions and photos are useful and will save others a lot of time.

Assembly

So here is how it was put together. First, I had to drill several holes in the metal bottom plate of the V-Mount adapter that will be screwed onto the battery. These holes are for the five wires that are connected to the battery pack. Two are positive and negative (make sure the insulation is sturdy since the plate is made of metal) and the three others get soldered onto the control pins of the battery pack to put it into discharge or charge mode.

The receiving plate already has a D-Tap socket built in so I only had to add the 7.2V output for the dummy battery for my monitor. The regulator has a little screw that needs to be calibrated using a multimeter to output exactly 7.2V (input voltage can vary as long as it's over ~10 and below the regulator's maximum of 23V). It is so small that it easily fits inside the housing.

I then bolted the SmallRig rail clamp into the bottom (two would be better but I don't see a need at the moment) to mount the whole system onto my camera. With the cables I've linked to earlier, I can then connect my camera and monitor to whooping 90 Wh, compared to the next-to-nothing mAh of the BMPCC batteries and the 1800mAh of genuine LP-E6s.

To charge the pack you'll need a dedicated Li-Ion charger or a good programmable power supply. However, this is the case for any battery system and there are of course proper V-Mount chargers out there. Because the receiving plate was so cheap, it would be easy to use one as a dedicated charger port.

Please use the comment section below or head over to Google+ or Twitter @tobiaswulff to discuss this article or any of my photography and videography work. My Flickr, 500px and Vimeo pages also provide some space to leave comments and keep up to date with my portfolio. Lastly, if you want to get updates on future blog posts, please subscribe to my RSS feed. I plan to publish a new article every Wednesday.

Home-built LED Panel for Video

Over the last weekend plus a few days I put together an inexpensive DIY LED panel that is so bright it will blind your interview subjects but doesn't break the bank - at all.

I won't explain all the steps and parts for this build because someone else has already done a much better job than me: DIY Perks on Youtube (you'll want to watch most of his builds once you discover the channel!). Watch the video from start to finish, then check your electronics and tools box for the few parts that are needed. I had to get a roll of 300 LED lights, a voltage regulator (or PWM controller if you're not worried about flickering lights but for video work a voltage dimmer is recommended), some MDF and some woodworking and power tools I didn't have (but they will serve me for many years to come). The rest is really simple and if you decide to skip painting it can probably be all done in one afternoon.

The colours here look a bit funny because I had the whitebalance on my camera set to my working light which is a tungsten light bulb whereas the LEDs are clearly much cooler. However, even though it was a cheap roll of LEDs (about $15), it doesn't have that nasty green shift that cheap LEDs are kind of known for. Its colour probably isn't perfect but I'm pretty happy with it. DIY Perks linked to some equally cheap LEDs that he measured at something like 95 CRI (which is really good) but I had already ordered some from another seller on Aliexpress.

The brightness is amazing and while I haven't tested its limits in daylight yet it's definitely too bright to point at your talent (say at an interview) at full power. Note that you need some fairly thick wires to hook everything up until it gets fanned out to the individual LED strips - I chose AWG16 but 18 is probably alright as well as long as you don't power more than 300-400 LEDs. With bigger panels your wire thickness requirements (and the ones for your power source) will obviously go up. I power the panel with 18V from a universal laptop power supply (I would prefer around 14V but the power supply chooses 18V with the 2.1 mm DC connector at the end) but a good LiIon or LiPo battery does work as well.

The box that houses the regulator as well as a switch and a potentiometer is actually a clear Raspberry Pi case that I had lying around. Due to the thick wire it was a bit of a squeeze and a solder joint popped off at one point due to the strain on a cable so better give yourself plenty of room for the electronics. This will also help with dissipating heat but with only 300 LEDs the heat sinks on my regulator don't get too hot.

One section where I deviated from the instructions in the video above is the dimmer circuit. While DIY Perks uses a multi-K Ohm resistor and a 22K pot, I used a 10K pot and no fixed resistor. I get the perfect voltage range out of it (I think my trim pot on the regulator is actually turned fully clockwise), meaning 7V (when all the LEDs just turn on) to about 11V which is as high as I want to go without compromising the lifetime of the LEDs.

To mount it on tripods etc I sandwiched a coldshoe with 1/4" thread between two pieces of MDF glued together, than screwed (and glued) that onto the back of the panel. Because the panel isn't very heavy, this is an extremely sturdy connection. Just watch the video to see exactly how it's done. I've since applied the same technique to make some adjustable mounting "bricks" for my motorised timelapse slider.

Please use the comment section below or head over to Google+ or Twitter @tobiaswulff to discuss this article or any of my photography and videography work. My Flickr, 500px and Vimeo pages also provide some space to leave comments and keep up to date with my portfolio. Lastly, if you want to get updates on future blog posts, please subscribe to my RSS feed. I plan to publish a new article every Wednesday.

Weather-proofing the GH4 with Speedbooster

When I upgraded from an Olympus OM-D E-M1 (de) to a higher-quality kit, it was pretty clear that the weather-sealing of the camera body, lens and accessories won't be as good - it doesn't get much better than the Olympus OM-D E-M1 (de) plus Olympus 12-40mm F2.8 PRO lens (de) (rain, dust and freeze proof) so it could only decrease. However, watching most professional documentary and expedition shoots, apart from when using GoPros, video cameras are simply not made for rough conditions. Usually you work around the weather-related issues, often with a crew, using umbrellas and camera bags/sleeves.

The Panasonic LUMIX GH4 (de) is a great video camera and it is weather-sealed. For a full weather-proof package you would have to get the Panasonic lens which isn't really the best option for video shooters for multiple reasons:

  • MFT lenses deliver amazing images and they certainly make sense in a lot of situations (my landscape photography camera uses one and I wouldn't dream of putting Canon L glass on it when going hiking) but they are not a good long-term investment for film;
  • going wide with a GH4 in 4K mode (2.3x crop) or with a Blackmagic Pocket Cinema Camera (2.88x crop) is quite difficult so a focal reducer is a must for wider than normal angles;
  • smaller sensors such as MFT and Super16 still have quite a disadvantage over full-frame or cinema cameras such as the C100/C300 when it comes to low light so a speedbooster can greatly help to get those f1.0 or better apertures.

All of this combined means that vintage or modern Canon EF or Nikon mount lenses, both APS-C and full-frame, are the best choice for film. Good glass greatly improves the image and will work on many other, higher end cameras as well, for instance Blackmagic Ursa Mini or RED. Canon L lenses are great because not only do they deliver the goods optically, they are also weather-sealed, one example being the very versatile Canon EF 24-105mm f/4 L IS (de) .

This, of course, leaves only the Metabones Canon EF to BMPCC Speed Booster (de) in between the camera and the lens vulnerable to the elements. It's a shame that Metabones hasn't implement better sealing because the front and back end of the speedbooster is a pretty standard EF and MFT mount, respectively, and it is made of solid metal. I think the lens side of the speedbooster might actually be slightly sealed because of the rubber gasket from the Canon L lens, however, the camera side of things is just metal on metal and therefore not sealed at all.

Taping over the speedbooster with Gaffers tape works pretty well since it is easy to work with, and it comes off without leaving and residue behind (unlike Duct tape and other, stronger tapes). Unfortunately, it is kind of hard to get the camera to speedbooster interface taped off perfectly because of the awkward protrusion that is the GH4 EVF/flash housing. I added a layer of cling film as a first layer of protection, then taped everything in place. So even if the sides of the tape let some water in (which they shouldn't), hopefully the plastic will still keep the openings in the speedbooster dry.

My test consisted of a roughly 40 minute walk in moderate to heavy rain, keeping the camera level or pointing down (mostly to keep rain off the front of the lens) and always horizontal. I also decided to throw my SmallHD 501 On-Camera Monitor into the mix which also meant exposing the HDMI interface of the GH4. A plastic bag and more tape covered it nicely and I could still operate the buttons and joystick on the monitor. Swapping batteries on the monitor also still worked but it'd probably try to cover it more completely in the future and just cut a little opening for the HDMI cable (it was easier if it attached to the bottom of the monitor instead of the back at a 90 degrees angle).

Overall, it worked beautifully and I feel like I could venture out into a few hours of rain if I had to shoot something without the help of an assistant holding an umbrella. Swapping batteries or lenses or fiddling with any of the accessories is almost impossible without additional cover, though. Also, using a microphone would require a broader rain cover as well.

Please use the comment section below or head over to Google+ or Twitter @tobiaswulff to discuss this article or any of my photography and videography work. My Flickr, 500px and Vimeo pages also provide some space to leave comments and keep up to date with my portfolio. Lastly, if you want to get updates on future blog posts, please subscribe to my RSS feed. I plan to publish a new article every Wednesday.

Use a MIDI Controller as a Video Editing and Color Grading Surface

Control surfaces can greatly speed up editing and color grading work and also avoid issues like CTS because your hand can move around more freely instead of clutching a mouse all day. However, like most things in the video/film world, they can be very expensive. At the top end there are full suites like Blackmagic's Davinci (multiple $10,000s), the Avid Artist line (many $1,000s) and smaller devices like the Shuttle Pro V.2 (de) ($129). While they are often very well made and can be worth it if your profession is to produce multimedia every day as efficiently as possible, the actual cost of the functional parts is actually much lower. So I decided to build something similar to the Shuttle Pro but with a few key differences:
  • Sends MIDI messages instead of registering as a keyboard
  • Fewer buttons but a shift function that doubles the number of functions, including the jog/shuttle wheels
  • Different placement so that the hand can rest on the left and easily access buttons on the top and the right

MIDI

The MIDI protocol has been around for decades and is primarily used in the audio and lighting world for input devices and synthesizers. As opposed to using an input device that emulates a keyboard, MIDI has got the advantage that the incoming messages can be easily translated to keyboard shortcuts, whereas an Arduino emulating a keyboard will always send the same shortcuts. This gives much more flexibility, e.g. when changing programs or modes within a program (think media, edit, and colour pages in Davinci Resolve).

Within Resolve, shortcuts can be configured (or are configured by default) for pretty much all functionality apart from curves and colour/lieft/gamma/gain wheels - without a dedicated control surface one still has to use the mouse to modify these parameters. In order to process incoming MIDI messages on Linux I use mididings. I actually gave a talk at KiwiPyCon 2014 about using mididings to control photography (or any) software on Linux. On Windows I wrote my processing code in C++ and used the rtmidi library which is easy to compile (I use MinGW gcc) and comes with many excellent examples.

Assembly

The physical parts come down to a few buttons (cents to a few $), LED(s) (cents) and the jog/shuttle made by ALPS ($15-20). Figuring out the pins on the jog/shuttle was pretty straight-forward but this article goes through the process in more detail and might be useful to anyone trying to get a similar part working. I already had the plastic case and an Arduino to power the project lying around. In order to turn the Arduino into a MIDI device you'll have to replace the firmware on the ATmega used to communicate with the computer via USB (which is different from the main ATmega on an Arduino Uno!). The firmware and detailed instructions can be found on the HIDUINO Github page.

The shuttle controls forward and backward play at different speeds (J, K and L in Resolve) and the jog dial advances or rewinds the playhead one frame at a time (left and right arrow keys).

I still need to figure out a way to make an outer wheel for the shuttle and a knob or inner wheel for the jog rotary encoder. 3D printing might be the best way but first I'll have to learn how to create the virtual parts for it. At least the shuttle and jog wheels have sturdy grooves that should make it fairly easy to attach knobs or wheels to it.

At the moment, the Arduino will be connected to each button, LED and ALPS shuttle/jog through cables that go into the female headers on the little green board. Eventually, the Arduino will have to move into the enclosure and more sturdy, soldered connections between its pins and the components will be made.

Please use the comment section below or head over to Google+ or Twitter @tobiaswulff to discuss this article or any of my photography and videography work. My Flickr, 500px and Vimeo pages also provide some space to leave comments and keep up to date with my portfolio. Lastly, if you want to get updates on future blog posts, please subscribe to my RSS feed. I plan to publish a new article every Wednesday.

DIY Motorised Dolly Slider

Motorised sliders (or dollies) bring motion and a nice parallax effect to timelapse shots. Commercial sliders have the advantage of being well built (hopefully roughly proportional the amount of money spent) and easy to set up. On the other hand, costs for rails and card alone can be several hundred dollars and adding motors and a control unit quickly pushes it $1000.

A home-made DIY slider can be made with $150-200 for materials and the Arduino board or other micro-controller, depending on what you already have lying around. I'd like to take mine hiking more often but it wasn't built with minimal weight in mind so this is definitely a point where a good commercial carbon-fiber slider and a cart with less metal could come into play one day.

There are many different designs out there but the biggest distinctions between them are:

  • continuous motion vs stepper motion
  • two rails vs monorail
  • motor mounted on end truss vs motor mounted on the cart

Continuous motion is cheaper because a very simple motor can be used and the expensive timing belt can be replaced with a wire to pull the cart. However, this does not work for longer exposures since the camera has to be absolutely still while the shutter is open so I opted for a stepper motor right from the start. Keeping a cart stable on a monorail requires more engineering than with two rails but it can cut down on weight and makes it easier to mount to a single tripod with a screw hole in the centre of the rail. I didn't know how to build this so I went with two rails and wheels on either side to keep it stable.

At first I thought I can keep the cart lighter by mounting the stepper motor to the end of the rails. While this is true, once you add up the weight of the metal cart itself, a camera body and lens, and ball head, a single stepper motor wouldn't make much of a difference any more. Having the motor on the cart has several advantages: everything, from the camera to the motor to the control unit is in one place and you won't need to run cables all over the place; only half the length of timing belt is required since it won't loop around the ends. Here is a link to a good example of a DIY monorail motor-on-cart slider.

    Here is a quick test video I shot using the slider. Unfortunately, I bumped it a bit at towards the end but you get the idea. There will be more exciting timelapses in the future that actually use the motion/parallex effect in a meaningful way.

    Material List

    • Arduino: $5-20 depending on original vs clone and capabilities - it's easier if it fits a shield
    • Motor driver shield for Arduino: $20
    • Battery pack and switching regulator: $10
    • 12V NEMA-size stepper motor and mount $23 - alternatively a smaller stepper motor
    • Timing belt and pulleys $40 - one could probably find much cheaper spare parts somewhere else
    • Aluminium rails $10-20 - I can't remember exactly
    • Steel or aluminium cart and ball bearings - can't remember how much it was, maybe $20; I had the ball bearings already
    • Cheap, small to medium-sized ball head - don't use the really small ones like the Giottos Mini Ball Head if you have anything bigger than a compact point&shoot because it will wobble a lot and adjusting it will be very hard: $20-$30

    In the photo above - once you look past the rat nest of wires - you can see the motor driver shield sitting on the Arduino. All connections come out of the shield (they are fed through from the Arduino), so the rainbow ribbon cable is for the rotary encoder, there are some wires for the LED, ground and 5V, and also the stepper motor itself which is hooked up to the left-hand side 4-pin screw terminal. The two "things" encased in plastic in-line with the wires are a fuse and a switching regulator to bring the input voltage (9-12V) down to 5V for the Arduino. A linear regulator like the one that is on the Arduino would work too but might generate too much heat for a closed up enclosure.

    Photo above: a cheap but decent-sized ball head that unfortunately wobbles a little bit but does the job. Since all ball heads (and all decent tripods) use the same screw sizes, you can mount whatever you want, small and cheap or big and fancy. I like that the ball head has got a two-way water bubble level built-in.

    Programming

    On the Arduino platform I use the Adafruit_Motorshield library. To move the stepper motor the minimal distance and as smoothly as possible I run:

    Adafruit_MotorShield *motor_shield = new Adafruit_MotorShield();
    motor_shield->begin();
    Adafruit_StepperMotor *motor = motor_shield->getStepper(200, 250); // steps and speed
    motor->step(distance, FORWARD, MICROSTEP);

    I also set up an LCD and a rotary button using the SoftwareSerial and ClickEncoder libraries, respectively. Text can be written to the 16x2 LCD directly over the serial line, plus there are some special characters that move the cursor, clear the screen, and so on. The ClickEncoder uses up one of the timers of the Arduino and unfortunately it is the same used by the MotorShield library so I can't use both at the same time. This is ok because I only use the rotary encoder to set up all the timelapse parameters, and once the slider is moving and the camera is taking pictures I don't want to touch it again anyway. It's basically two separate programs: first the menu/settings, then the timelapse.

    Issues

    I found that the 200 steps per revolution that the stepper motor provides aren't quite enough for super smooth and slow motion, so after about 15-20 minutes with one frame every second the cart will already reach the end of the rails. It is possible that I haven't configured the motor correctly yet but it is set to micro-steps in the code and as far as I know this is the smallest possible rotation. I use micro-steps instead of normal steps because the provide smoother movement: a normal step would yank the cart and make the heavy camera wobble too much. It also makes sure that the motor is always enganged in case the rails are on an angle. This way the cart can't slide back down. To solve the problem of step sizes being too big I might incorporate some model kit plastic gears but for now I have avoided it since it isn't that easy to get everything lined up correctly without making the whole construction incredibly flimsy. There are also other stepper motors out there that provide twice or more the amount of steps per full revolution, usually through internal gears (see the alternative smaller motor I've listed above).

    Currently I'm running the whole setup off of 8 AA batteries, specifically Panasonic Eneloop AA Ni-MH Rechargeable Batteries(de). However, since the stepper motor requires 12V and 8 rechargeable AAs only provide a maximum of 9.6V, it does have issues climbing an incline stepper than about 20 degrees. On the flat it works great, though, and it lasts for many hours as well. In the future I might upgrade to a 12V battery or boost it up with a converter, maybe using a LiPo battery for their amazing energy density.

    Future Developments

    I've got a little micro-switch that I want to mount at the end of the rails so that it detects the cart hitting the end. This will eventually stop the timelapse. I also want to refine the menu system and hopefully improve the software side of driving the motors, i.e. better speed and step control.

    In case I've already exhausted all possibilities regarding the motors, I might actually have to add two differently-sized gears to the system to bring the speed down so that I can take hour-long timelapses with many hundreds of frames.

    And finally, panning while moving sideways would make my timelapses look much more impressive so adding a second motor is high up on the agenda. However, I'm not sure yet how to fit it between the camera and the top of the ball head (glue it to the quick-release plate?), or alternatively if it could or should live under the ball head in which case I'm worried about stability. The latter would see the motor mounted under the cart, however, which would be a very clean looking solution. Either mounting point will give very a different result when the rig is on an incline and depending on the subject it can work well or look really out of place.

    The most important improvement, however, to be made is getting it off the ground. At the moment grass or plants can easily get caught in the wheels and there are no points to screw in a tripod quick-release plate (the end trusses hook quite nicely into the top of my Manfrotto BeFree Travel Tripod(de) , though). Often something can look good at eye-level but having to put it all the way down on the ground limits my possibilities so a good 1/4" screw hole at either end would make it immensely more useful and stable in vegetation.

    Please head over to Google+ or Twitter @tobiaswulff (see links on top of the page) to discuss this article or any of my photography and videography work. My Flickr and Vimeo pages also provide some space to leave comments and keep up to date with my portfolio. Lastly, if you want to get updates on future blog posts, please subscribe to my RSS feed. I plan to publish a new article every Wednesday.