The present invention relates in general to photographic enlarger apparatus. In particular, it relates to an alignable negative stage for a photographic enlarger.
In making high quality photographic prints or enlargements using a photographic enlarger, highest quality for the prints or enlargements is best achieved when a negative being printed is accurately aligned, i.e., parallel with, the plane of an enlarging lens in the enlarger, and parallel with the plane of paper receiving a projected image of the negative.
Commercially produced photographic enlargers are generally not supplied with alignment devices. It is frequently assumed by an enlarger user that necessary planes in the enlarger are aligned by the enlarger's manufacturer. A user generally adjusts only the enlarger's focus during use. This is generally accomplished by closely scrutinizing the projected image from the negative being enlarged, and adjusting a focus control until the sharpest overall image is obtained.
It is now possible to obtain, commercially, optical apparatus for precisely aligning principal planes of a photographic enlarger, such as the negative plane and the lens plane. One such apparatus is discussed in U.S. Pat. No. 5,075,862, which discloses a optical device which may be attached to one principal plane, and is cooperative with a mirror attached to another principal plane. A user looks through the optical device and adjusts the appropriate planes until a series of concentric circles is observed, indicating that the planes are parallel. This allows the planes to be fine aligned with a high degree of accuracy.
While this alignment operation may appear from the description to be relatively easy, it is in fact complicated severely by the fact that most commercial enlargers are constructed such that their principal planes are not readily adjustable. Generally, alignment of the planes may only be accomplished, at best, by loosening and re-tightening screws that are used to assemble and coarse-align the enlarger at the manufacturer's plant, or, at worst, by forcefully twisting or bending structural components of the enlarger.
It is not uncommon during enlarger operations to hold photographic paper, for receiving the projected image from the enlarger, on a platform or easel which is placed in position on an enlarger base. This easel may be aligned easily by means of shims or the like, or by adjustable feet attached thereto. An easel is generally heavy and rigid and, once aligned by any of the suggested methods, will remain firmly in position on the enlarger base under its own weight.
A particularly useful addition to an enlarger, either as an accessory or an integral component, would be a fine alignable negative stage. Given the availability of such a stage, at least two principle planes, i.e. the negative plane and the paper plane would be easily fine alignable and these two planes would be readily fine alignable with the lens plane whether or not the lens plane was alignable. Generally it is not.