# Slide cube projector

The Slide Cube Projector is a slide projector and system, manufactured and marketed by Bell & Howell, which was introduced in 1970 and marketed through the 1980s. The projector derived its name from its transparent cubical plastic slide storage magazine, approximately 5.5 cm (2.2 in) in each dimension (a bit larger than a standard 135 film slide mount), that held 36 to 44 slides, depending on the mount thickness. The magazine used a sliding lid to hold the slides in place. Unlike competing systems which used straight tray or carousel magazines, the slides in a Slide Cube are stacked on top of each other rather than stored in separate slots.
The system consisted of Slide Cubes and a projector designed to use them. Bell & Howell subsequently introduced a Slide Cube Projector II, with revised features, before discontinuing the system in the 1980s. Although Slide Cube Projectors are no longer manufactured, as of 2024 cubes, bulbs, a few replacement parts, and complete used projectors are available on the second-hand market.

## Design and operation

When a cube is placed on the slide projector in the PRE-LOAD position, then slid into the LOAD position, its lid opens. As the advance trigger is activated, a sequence is initiated which starts by dropping a single slide into the slide advance mechanism, which uses a circular turntable with slide-size holes. The turntable has four distinct positions; in sequence, these are:
* LOAD
* PREVIEW
* PROJECTION
* RETURN
The turntable is thinner than a single slide, which allows just one slide at a time to drop from the cube into the LOAD position. The PREVIEW position allows the operator to check if the slide is loaded correctly before advancing into the PROJECTION position, where the image is projected onto the screen for viewing by the audience. The next position, RETURN, is available so the turntable can be reversed, allowing a slide in RETURN position to move back to PROJECTION, which gives the projector the capability to manually reverse the show by a single slide. After the RETURN position, the turntable finally rotates to the (RE)LOAD position, where the slide drops out of the turntable into a stack and another slide is taken from the cube. After the slides have been viewed, the operator presses a lever which lifts the slides back into the cube.
Most of the projectors use a 300 watt 120 V multifaceted reflector halogen lamp (ANSI code ELH) as a light source; early models use a 500 W lamp without reflector (code CBA) instead. In addition to the on-projector controls, it could optionally be operated by a wired remote control, or the "Time Cube" automatic advancement accessory. The projector had an integrated handle, plastic lid or optional lid which incorporated additional cube storage. A sliding front foot or tilting lens adjustment were used to change the elevation of the projected image. Several alternative projection lenses were offered.
Bell & Howell Slide Cubes were less expensive than trays and provided denser and cheaper storage capacity, with a book or drawer of 16 forty-slide cubes (640 slides) occupying the same space as a single round tray holding at most 140 slides. Stack storage and preview facilitated editing of slideshows; slides could be added to or removed from the show without having to move all of the remaining slides to fill the gap. Some tray-based projectors (e.g. some Kodak round-tray and Hähnel straight-tray slide projectors) also could use stack loaders to view a stack of slides, but did not allow addition or removal of slides, and did not have an associated storage system.
Drawbacks of the slide cube included the inability to go back by more than one slide, the fragility of the cubes, and the advancing turntable's tendency to jam if a slide mount was not perfect, interrupting slide shows and making the projectors challenging to operate.

### Models

Bell & Howell Slide Cube Projector models :
| FeatureModel | Series | Lens | Lens | Lens | Focus | Lamp |
| FeatureModel | Series | Focal length | Aperture | Tilt | Focus | Lamp |
| 965Q | Slide Cube | | | Yes | Automatic | CBA |
| 975Q | Slide Cube | | | Yes | | CBA |
| 977Q | Slide Cube | | | Yes | | CBA |
| 978Q | Slide Cube | | | Yes | | CBA |
| 981Q | Slide Cube | | | Yes | Automatic | CBA |
| 982Q | Slide Cube | | | Yes | | CBA |
| 991 (early) | Slide Cube | | | Yes | Automatic | CBA |
| 452 | Slide Cube (transitional) | | | Yes | | ELH |
| 986 | Slide Cube (transitional) | 100 mm | f/2.8 | Yes | | ELH |
| 987 | Slide Cube (transitional) | | | Yes | | ELH |
| 991 (late) | Slide Cube (transitional) | | | Yes | Automatic | ELH |
| 992 | Slide Cube (transitional) | | | Yes | Automatic | ELH |
| RC55 (857BH) | Slide Cube (transitional), Slide Cube II | 100 mm | f/3.5 | No | Manual | ELH |
| RF60 (859B) | Slide Cube (transitional), Slide Cube II | 100 mm | f/3.5 | No | Remote | ELH |
| AF70 (861BH) | Slide Cube (transitional), Slide Cube II | 100 mm | f/3.5 | No | Automatic | ELH |
| AF70Z (861Z, 861BHZ) | Slide Cube (transitional), Slide Cube II | 85–115 mm | f/3.5 | No | Automatic | ELH |
| AF80 (863BZ) | Slide Cube (transitional), Slide Cube II | 85–115 mm | f/3.5 | No | Automatic | ELH |
| CP40 | Slide Cube II | 100 mm | f/3.5 | No | Manual | ELH |
| RC50 | Slide Cube II | 100 mm | f/3.5 | No | Manual | ELH |
| RF50 | Slide Cube II | 100 mm | f/3.5 | No | Remote | ELH |
| AF66 | Slide Cube II | | | No | Automatic | ELH |
| AF72 (861H) | Slide Cube II | 100 mm | f/3.5 | No | Automatic | ELH |
A version of the AF70 was sold by Sears as the Opticube (model 802).

### Lenses

All Slide Cube projectors are compatible with any of the four available lenses. Lens appearance depends on age, with the earliest lenses featuring silver-colored finishes on the focusing (and zoom) ring, coordinating with the earliest Slide Cube projectors; lenses originally sold with the Slide Cube System II may be marked as Lumina II.
* Lumina 64 mm (21⁄2") f/3.5 for 110 film slides
* Filmovara Lumina 85–115 mm (31⁄2–41⁄2") f/3.5
* Lumina 100 mm (4") f/2.8
* Lumina 100 mm (4") f/3.5