Inspired by Charles Chevalier’s convertible lens system from the 19th century.
The the Lomography Society International’s Neptune Convertible Art Lens System is composed of multiple elements. There’s a rear lens element that attaches to the camera itself, and a selection of three front elements.
These are the Thalasa 3.5/35 Art Lens, the Despina 2.8/50 Art Lens, and the Proteus 4/80 Art lens. Together, they offer three of the most commonly used focal lengths for a variety of photography subjects. Shift from landscape photography to still life capture to portraits simply by changing the front element.
Because the Neptune system uses a dual aperture system with the rear lens element maintaining a typical aperture system, the aperture numbers only indicate the optimal maximum aperture for each lens. You can experiment with the entire range of aperture values no matter what front lens is installed.
Other things to play with are the drop-in aperture plates that go in between the front and rear lens elements. These come in a variety of shapes that affect the way the system renders bokeh, giving your images a unique look.
Unlike today’s lenses, the Neptune system relies on manual focus so you’ll be fully responsible for the sharpness of the images captured. But that’s a good thing, as it takes you back to the craft of photography itself, so you’ll learn to slow down and create your images.