VFXhack

I’m always on the lookout for a new way to simultaneously do something productive and keep from getting bored while I’m on set waiting for a VFX shot to come up. My latest arts and crafts project involves creating the ultimate LED tracking marker. Now you may ask “Why LEDs? Why not a triangle inside a circle, or newspaper, or a tennis ball for god’s sake!” Well those methods are still valid but the in the right situation and LED tracking marker can really do the trick. Here are some reasons why you might want to go the LED route.

1. LED stands for Light Emitting Diode. As the name suggests you don’t need to light them because hey are a tiny light source onto themselves. This is perfect for areas of the frame that don’t have enough exposure for your common variety tracking marker.

2. LEDs hold up better when they are out of focus. When you shot a greenscreen with a long lens and an open F-stop, the background of your shot is gonna go way out of focus. Regular tracking markers turn to mush in this situation causing more a problem for clean-up than helping with the tracking process. The LED will bloom but tends to hold it’s intensity and not break-up as much.

3. The are small. LEDs are compact and light. A little bit of snot tape on the back and the can be affixed to anything from a patch of skin to a set wall. Ball up in some strong tape (sticky side out of course) and you can even throw them up on a wall that’s too high to reach. No more asking that grumpy grip if you can borrow his ladder.

4. Power is not an issue. A single battery can keep an LED running strong for days depending on the temperature. Battery life deteriorates rapidly in the cold so if you are shooting outside in the winter, make sure you grab a few packs of extra batteries for your kit bag.

There some things to watch out for with LEDs though. Their biggest strength (the fact that they emit light) is also their biggest weakness. LEDs can spill unwanted light all over the place if they are to close to (or on) the subject they are shooting. Fortunately, LEDs come in different flavors that include color variations and frosted plastic casings. The frosted casing cast a lot less spill but also need to be aligned to point at the lens for maximum effect. Try and find some samples and try out some color and casing combos before you head out. You never know how things could change on set, so it’s important to carry a bunch of LED options with you in your kit bag.

At this point you may be asking yourself “Wow, LEDs sound great. Where can I buy some?”. Well, the short answer is you can’t. You have to build LED tracking markers yourself. But never fear intrepid VFX explorer! Here’s a step by step on on how to create your very own set of LED tracking markers.

Step 1: Buy some LEDs

You can get these babies on-line or at your local electronics supply store. The come in different colors and you can also find them with frosted plastic. You can frost clear ones yourself with some dulling spray or spray mount. You can also file off the top of the plastic to expose the diode if you want them to be even brighter.

Step 2: Buy Some Heat Shrink Tubing

This is a great trick. Heat shrink tubing is a strip of vinyl that shrinks down to 1/2 it’s original size when exposed to heat. You can get it in all different kinds of colors including green which makes it almost invisible when affixed to green screen.

Step 3: Buy Some 3 Volt Batteries

These are the kinds of batteries that most cameras use. You can buy them from a store but it’s much cheeper to buy them in bulk on-lne.

Step 4: Cut the Tubing, Slide in the Battery Apply Heat

Cut the tubing so that is just a little bit larger than the battery, then just slip the battery inside the tubing. Apply heat with a heat gun and “Viola!”, the tubing makes a nice tight jacket around the battery. Make sure when you are applying heat that you hold the battery and tubing with a pair of pliers so you don’t burn yourself.

Step 5: Insert LED

All that’s left to do now is slip the wires of the LED between the battery and jacket and you’ve got yourself a tracking marker. You can stick these to surfaces using double sided tape, stick them to people with a Band-Aid or just rest them on flat surface. Happy shooting!

LINK to a del.icio.us tag with places to buy the stuff you need to make your own.

This entry was posted on Friday, February 29th, 2008 at 11:27 pm and is filed under 3d, howto, techniques, tips, vfx, visual effects. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.