At Genus we often get asked about the various rod sizes and standards used to support camera accessories in film and video production.
To aid in explaining we have done a camera rod diagram. Rods which are also known as rails and bars commonly come in two sizes, 15mm and 19mm.
When both designing and buying camera accessories which mount on rods like matte box and follow focus units it is important to understand these standards
The critical measures in all rod standards are rod height and rod spacing. Rod height is defined as the distance of the optical centre of the lens also known as the optical axis and the centre of the rods. Rod spacing is defined as the distance between the centres of the rods.
The diagram below illustrates the the rod height and spacing of the different standards. Affer the rod diagram we will discuss the standards individually.
15mm Light Weight LWS
This is the smallest of the rod standards and also the most recent. .It has became popular with the rise of video cameras in production.
Light weight cameras and lenses didn’t require the heavier 15mm and 19mm studio rod systems popular in traditional motion picture production.
15m LWS is also prefered by many for steadicam , gimbal and hand held work when it is vital to minimise camera rig weight.
15mm Light weight system rods are aligned with the optical centre of lens. The rod height is 85mm and the rod spacing is 60mm.
In a lot of ways 15mm studio rods is a legacy system. It is most commom in motion picture production on the West Coast of the USA.
The unsual feture of 15mm studio ros is that they are offset 17.25mm from the the optical cente of lens. Evidently it reason why they are offset is historical.
In the past there was issues with weight distribution on cameras rigs and offsetting helped.
15mm rod system conforming to the studio standard have a rod height of 118mm and spacing of 100mm offset 17.25mm from optical centre of lens.
As camera , rigs and lenses have got bigger and heavier 19mm has become the standad for large high end production away from Hollwood , where 15m studuo remains popular.
Many lens too large and heavy for 15mm LWS so they need the added height and spacing of the 19mm studio standard. Also because of weight 19mm rods are usually stainless steel for adder strength .
19mm studio rods are 120mm below the optical centre or axis and are spaced at 104mm.
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