gBeam Prime is the first release of guerillaBeam.
it’s a modular projector, designed to be compatible with every 35mm lens ever made.
35mm is a film format (35mm wide), and was arguably the most popular image format of the 20th century.
Until the advent of digital imaging, photos would usually be exposed and stored as negatives on lengths of 35mm wide transparency film.
To view them, one would have to copy them onto photo paper or reversal film.
Today, the most prominent uses for 35mm are SLR (Single Lens Reflex) cameras, movie cameras and cinema projectors.
Most interchangeable photo and projection lenses ever created are 35mm, just because 35mm has been most popular standard in professional as well as consumer photography for more than 100 years now.
35mm and guerillaBeam
guerillaBeam uses 35mm lenses for projection.
that is, because 35mm lenses are available plenty, and
Projection is reversible
Physics teach us, the path of light in a lens system is reversible.
All 35mm lenses are formulated to project an image to or from 35mm film or a (roughly) 24x36mm image area.
This means that a projection lens can be used for photography, and a photo lens can be used for projection.
gBeam Prime is a projector that (re-)uses 35 mm lenses for projection.
with its 3d printed adapters, guerillaBeam can connect virtually every lens type. it already has adapters for Canon EF, Pentax, M42, Nikon (currently pre-AI only), slide projector lenses and others.
3d printable connectors
instead of remodeling camera bayonets or screw mounts, guerillaBeam employs much more robust and 3d printing-oriented connectors. gBeam printed lens adapters can hold lenses that weigh several kilograms.
the obvious choice for projecting with 35mm optics, are 35mm slides.
Reversal film or inkjet transparencies
Technically, the best option would be to get your slides developed on 35mm reversal film. I’ve never done that, because it’s expensive and slow.
A much easier process is to print the slides on transparencies. The limiting factor is the printer, however most photo printers will do sufficiently.
Slide frames measure 50mm x 50mm, and usually feature an image area of somewhat less than 24 x 36 mm (like 23 x 35mm).
Slide frames are made to hold 39mm strips from 35mm (wide) reversal film. They have a thickness between 1.5 and 3.5mm.
the gBeam slide holder is currently built for slides with a thickness up to 1.8mm. Using older slides will require reframing the slides, or a modified gBeam slide holder
Still available today, with a thickness of 1.8mm, are Agfa Compact and Secure slide frames under the Reflecta CS brand name.