Frankenstein's Monster: GoPro with a Nikon Mount

March 01, 2014  •  1 Comment

Hey everyone! Welcome to my first blog post. I figured I'd start off my blogging career by making a post about a pretty cool project I've been working on. As some of you know, at the end of 2012 I released a short timelapse showcase called A Walk on the Dark Side. I had a blast going to all the National Parks, Forests, and other amazing locations and spending all night watching the stars while my camera clicked away. Now that it's 2014, I've decided to try and one-up that film by making a new film that includes video as well as timelapse. Specifically, I wanted the epic slow motion wildlife shots you see on Planet Earth and other nature documentaries.

There was only one problem. To get those slow motion shots, you need a camera that can shoot very high numbers of frames per second. For some reason, camera manufacturers decided to make all of the "professional" video cameras that shoot high frame rates at useable resolutions very expensive. However, one day as I was browsing the internet, I came across the tech specs for the newest GoPro, the Hero 3+ Black. It shoots 60 frames per second (fps) at full HD resolution (1920x1080), which is enough to slow down fast moving birds a little bit, but still not what I was hoping for. Scrolling farther down the stats page showed that it can also shoot 100 fps at a slightly reduced 960p resolution, 120fps at standard HD 720p resolution, and 240 fps at WVGA (800x480) resolution. Those numbers had me thinking that if I could figure out a way to attach my Nikon lenses to the GoPro, I would have a pretty capable little action camera (albeit with some limitations such as lack of manual exposure controls and no viewfinder.)

After weeks of searching the web, I had decided that if I could get the lens off the GoPro and mount the Nikon lens the exact right distance away from the GoPro's sensor, I would have a functional video camera. In fact, I'd found 2 examples of companies that had done just that. One made a completely new aluminum body with the GoPro electronics inside and rented it to professional film studios for crazy high prices, while the other was a reasonably priced modification kit available for sale that basically replaced the front of the GoPro with an aluminum plate and a lens mount. I opted to take the second route, and after a lot of sketching, decided on a plan. 

The GoPro with its lens removed inside the aluminum cage from Amazon, with the attached IR cut filter

View of the extension tubes, aluminum plate, and IR cut filter

Side view of the extension tubes and aluminum plate

After all my sketching and brainstorming, I had decided that completely fabricating a new body was more than I could handle with my lack of metalworking tools and lack of a budget to buy aforementioned tools. I had come across an aluminum cage on Amazon that is designed to fit the GoPro snugly inside, but still be easily removeable, and decided to use that as the base for my mount. It also has a 37mm diameter thread on the front that I can attach an infrared blocking filter to, which is necessary since the sensor is sensitive to infrared wavelengths and won't display a proper picture without it. However, if I want to shoot at night, all I have to do is take that filter off and get an infrared spotlight and I can shoot without disturbing wildlife. The next challenge I had was to figure out how to get attach a Nikon lens mount to the aluminum cage. I ended up taking a set of inexpensive extension tubes, sawed the male lens mount off, and screwed it into an aluminum plate, which in turn was screwed into the cage. Drilling the holes through all three layers could have gone smoother, but fortunately for me, the holes I drilled in the wrong spots aren't visible from the outside. 

At this point, I had a prototype that functioned fairly well, although I could never get my zoom lenses in focus when they were zoomed all the way out. Nikon lenses are designed to be 46.50mm from the image sensor, and when they're too close, you lose your ability to focus on close objects, and when they're too far, you lose the ability to focus on faraway objects. My first aluminum plate was made out of 1/8" bar stock, which was not thick enough to give me the entire focus range. My second plate was made of out 1/4" bar stock, which ended up making the setup 0.2mm too thick, but it's easier to remove 0.2mm of material than to add it. I ended sanding off just a little too much, but since a vast majority of my filming is going to be focused on farther away objects, I'm not too worried about losing a little bit of close focusing.

The GoPro looking ridiculously small with a Nikon 17-35mm lens and the 10" monitor

Like I said previously, one of the shortcomings of the GoPro is its lack of any kind of viewfinder. I had a 10" HDMI screen that I had bought a while ago but hadn't built an enclosure for, so after a trip to Lowe's and $10 worth of toolbox type thing and Lexan later, I had an enclosure with room for the screen and a large battery. The picture above is where the project is as of this date. In the near future I will be adding some sort of aperture control ring so I can use lenses without an aperture ring. In the meantime, I'll be testing out the Franken-GoPro and undoubtably finding more improvements to make. Thanks for reading this blog, and stay tuned for more updates as I tweak the design and get more footage.



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Fernando(non-registered)
How i can buy? from Chile
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