The Quark2 has a manual focus lens ring, which may seem very difficult to turn at first. Quark2 lenses are rotated from the outside, similar to SLR lenses on traditional cameras. Quark2 lenses are typically factory-focused at infinity.
The length, or `Z` dimension of the camera will depend on the focus point of the lens. Therefore, the camera should be focused per the application requirement before measuring the length. For example, for a close focus application, the length of the Quark2 camera will increase because the lens will need to be turned counterclockwise, moving it in an outward direction from the lens holder.
We recommend using a silver Sharpie™ to mark the location of the lens to the holder, as both are black and it can otherwise be difficult to remember where the rotation started or finished.