The Bausch & Lomb amateur photomicrographic outfit is built around a Kodak No. 0 Brownie 127 film box camera. Before getting into the process of actually using it, it might do to look at just what is different between the photomicrographic No. 0 and the standard No. 0. Apart from the addition of a focusing telescope and a stand-clamp the only difference is purely optical. While in the off-the-shelf No. 0 the camera is equipped with a simple meniscus lens, the photomicrographic No. 0 is completely free of optics in the image forming path.
With a modern professional photomicrographic apparatus there’s certainly going to be some optics in the photomicrographic light path—more about why in a moment. This most often consists of a focusing relay lens system, usually in the form of a reducing series .7x or .5x being the usual magnification factor. This reducing series may additionally include lenses for the correction of spherical aberration (as in the BalPlan or flat-field DynaZoom/Dynoptic). In standard achromatic systems the system is free of such correction optics and may well consists solely of a beam splitter, or reducing lens only.
The reducing factor of such systems is, somewhat confusingly, sometimes found coupled with a body tube labeled anywhere from 1x to 10 or even 15x. The two portions work together and serve to provide a cropped frame that is then enlarged to fill entirely the film frame. In third party “eye-piece” cameras this crop factor was accomplished by quite inferior optics (if any at all). The reason such a reduction is necessary is owing entirely to the small size of what’s become the standard imaging surface. Currently, that’s a CCD or CMOS sensor somewhat smaller than a 35mm film frame. Where film photomicrography is still pursued, or was prior to the great digital migration, that nearly always meant a 35mm film frame. It bears remembering that 35mm film is a “miniature” film format—no matter how many folks tout their “full frame sensor” camera—it’s still miniature, which means reducing the image forming cone of light to get something near to the optical field of view in the frame. Early photomicrography used large format film and handled cropping with long bellows extensions.
With no optics in the camera, and a box ‘bellows’ of three inches, the No. 0 can be expected to offer almost no crop factor at all. This is functionally a good thing. By greatly restricting the ‘bellows’ enlargement chromatic and spherical aberration present in the simple optics of the Model R are prevented from revealing themselves (as they surely would be at greater enlargements).
The other significant upshot of an lensless camera is the practical impact on focusing. With no optics to worry about the system that is employed to focus the camera is made more simple. To duplicate the focus of the camera one need only use a device of identical length with a ground glass at the imaging surface. In the Photomicrographic No. 0 that is a tube one inch in diameter with a circular ground glass at the far end. Although the ground glass is much smaller than what one must expect the film to capture it certainly enables accurate focusing. One must ensure the primary feature of which a photomicrograph is desired is centered, and hope for the best.
In a complete system there is a further component, a circular bushing (also void of any optical components) which fits one end over the Model R’s ocular while the other end inserts into either the focusing telescope, or No. 0 as required. It should be a simple matter to drill out a hardwood dowel as a fabricated replacement. With that knowledge, the reason for the unique aspect of the shutter opening on the photomicrographic No. 0 becomes apparent. It is constricted as it nears the shutter mechanism (while the standard No. 0 is wide open) because the bushing must be prevented from pushing too far in and obstructing the shutter mechanism.
In use then, one would attach the photomicrographic No. 0 to a ring stand with the Model R held steady underneath. The camera may then be rotated such that the focusing telescope is over the ocular while the a slide is positioned and brought to a clear focus. The camera may then be swung into place and the shutter tripped for either an instantaneous (snapshot) exposure of the time bar may be pulled out if a longer exposure is required.