1851 Great Exhibition: Official Catalogue: Class X.: R. Beauford
406. BEAUFORD, R., Hastings — Inventor.
Registered daguerreotype accelerator. This consists of a properly-constructed lens, applied in a particular manner to the ordinary daguerreotype instrument. Its advantages are assumed to be as follow:—
The actinic rays (which have their primitive source in the solar beam, and which produce the photographic effect) diverge from the object of which an image is to be produced on the photographic plate. These rays are made, by the action of the ordinary daguerreotype instrument, to converge to a point at a certain distance within the camera. By applying the accelerator, these rays are made to converge more rapidly; and, by putting the prepared plate more forward, a smaller image is procured by means of the accelerator than could be obtained without it. Hence, by means of the accelerator, the actinic rays are condensed into a smaller area, and the intensity of the effect is heightened.
This latter fact is considered to include three others, namely—photographic effects can be obtained by the application of the accelerator, when, without its aid, the desired effect could not be obtained; as, for instance, on a dark and cloudy day. Again, all other things being the same, the image of the object is much more intense and well-defined with the accelerator than without it— the flatness and deadness generally observable in photographic portraits being exchanged for a roundness of surface, and a natural projection or "bringing out" of the parts, which constitute an effect highly pleasing. A third benefit secured by the accelerator is observable in the diminished time required for producing a photographic effect, owing to the actinic rays being intensified by the introduction of the accelerator. The time required for producing a photographic picture with the aid of the accelerator, is only one-half or two-thirds of that required with the ordinary apparatus alone.
A further advantage obtained is the economy of space. When the daguerreotype instrument is used without the accelerator, the artist, if he wish to obtain actinic rays of less divergence (which is often the case), must remove from the object. In removing further, ho must use (in most cases) a large instrument. Such inconvenience is avoided by means of the accelerator; for, when this is stated to be applied, the rays can be at once refracted into the right course, whereby the increase of distance and the change of instrument are avoided; the accelerator therefore favours not only the economy of space, but also the economy of means, the use of the larger instrument being in this case obviated. This will appear to be still further the case, when we consider that by applying accelerators of different foci, we can produce portraits or views of proportional magnitudes; so that from one daguerreotype instrument both large and small plates can be produced.
Another advantage of the accelerator is, that it prevents that distortion of the image often observable in photographic portraits. Without the application of the accelerator, the image produced is of such a size that any exaggeration of relative magnitude, due to the superior forwardness of any part of the object, is magnified to an inconvenient extent. The image produced by the accelerator is reduced in size, and this exaggeration is reduced in an equal degree, so that it appears free from all distortion; by this means, the ingenious but troublesome contrivances hitherto adopted to avoid this source of annoyance are superseded.