Understanding Iris Rods: ARRI Breaks it Down in This Simple Infographic
In the flooded market of new camera accessories, one can easily become confused as to which support gear is best for which camera setups. Iris rods should be found on almost every camera setup in the world, but which sizes and spacings should you use? Read on to clear up any confusion you might have between ARRI's three rod standards: 15mm LWS, 15mm and 19mm Studio.
Matthew Duclos writes on his blog about pertinent information for each setup:
15mm LWS (Light Weight Support):
The smallest and newest system to be utilized for motion picture work and as of recent, possibly the most common. // The 15mm LWS is aligned to the center of the lens mount, with a relatively narrow spacing (60mm) and a fairly shallow axis to rod height (85mm).
If there was an “old school” rod setup, 15mm Studio would be it. 15mm Studio rods are the same rods as 15mm LWS but spaced farther apart (100mm), farther from the lens axis (118mm), and slightly offset from the optical center (17.25mm).
If you’re anywhere other than Hollywood, you’ll likely find 19mm rods used as the standard. 19mm Studio is the updated version of 15mm Studio. // The 19mm Studio setup is spaced even farther apart than 15mm Studio (104mm), and slightly more distant from the optical axis (120mm) but is centered on the lens.
For most of us independent filmmakers (especially starting out) we'll be using some variation of symmetrical 15mm LWS rods, which are standard for most entry-level DSLR and lightweight rigs out there. As you work your way up and build upon your rigs though, you'll quickly see how heavy things can get. In terms of build material, Matthew recommends stainless steel for 19mm and 15mm Studio setups. Carbon fiber and aluminum rods are most acceptable for a 15mm LWS system.
Of course it all depends on what you're putting on your rig, but I hope this post elucidates the issue for some of you. Check out Matthew's blog post for more information, and share your thoughts in the comments below.