Halation.—When dealing with interiors, the best method of preventing halation must be considered, more especially if brightly lit windows be included in the view. The use of backing on plates has been widely advocated as a preventive of halation, and no doubt it serves the purpose very well up to a certain point ; but there are plates on the market, such, for instance, as Messrs. Lumiere's anti-halo plate, and the Agfa Isolar anti-halation plate, which are decidedly preferable to any backed plate, if we wish to prevent halation or reduce it to a minimum. These plates are prepared with a sub stratum of gelatine, coloured a deep red, between the film and the glass, which effectually prevents any light, sufficiently actinic to affect the sensitive emulsion, from reaching the glass, and being reflected back again on to the film. The red colouring is removed from the negative, either during development, fixing, and washing, or in a subsequent clearing bath. Nothing is gained by backing these anti-halation plates, a fact which clearly proves the efficiency of the red substratum. In practice, as well as in principle, they are undoubtedly superior to backed plates, and, although rather more expensive than the latter, the better results obtainable with them make them well worth the slightly higher price.
Attempts have been made from time to time to justify halation, and to claim that, so far from being a fault, it is often beneficial in pictorial work. It is said to give " mystery " to such subjects as church interiors. But while the effect thus gained may possibly be helpful in rare instances, there can be no doubt that in the great majority of " pictures," as well as in all records, halation does far more harm than good, obscuring detail and destroying all fine gradation of light and shade.
For most exterior photography backed plates are suffi ciently halation-proof, although, of course, there is no objection, except the extra cost, to using the substratum plate for outdoor subjects also. Orthochromatic rather than ordinary plates should be chosen, their greater colour sensi tiveness being useful for interiors where there is much stained glass, and for exteriors where the stone-work is more or less yellow or at all warm in tone.
With regard to orthochromatic screens, these will very seldom be found necessary or desirable, except when, for instance, a photograph of a stained-glass window showing correct colour-values is required, or occasionally out-of doors, when the sky may form a considerable part of the picture.
the matter of developers, no less than in that of plates, each photographer has his personal fancy ; and, while there is probably not much to choose between the various re-agents when outdoor work alone is concerned, the question as to which is the most suitable developer for interiors is worthy of a certain amount of consideration. In many interiors there are strong contrasts of light and shade, and in such cases, in order to obtain a negative with a full and pleasing scale of gradation, more care must be exercised in the developing of the plate than is usually necessary with exterior subjects.
Developers may be roughly divided into two classes— those which bring up the whole of the detail quickly and then gradually add density, such as rodinal, amidol, and metol, and those which give considerable density in the high lights, before filling in detail in the dark parts of the subject, such as pyro (used with various forms of alkali) and hydroquinone. Pyro-soda is an old favourite, and is still very popular among architectural workers, but for interior work it has a tendency to clog the high lights before the shadows have reached suffi cient strength ; and the contrast may be further augmented by the slight yellowish stain sometimes present in the pyro developed negative. But if rodinal be employed, there is no fear of the high lights clogging before the shadow detail is through ; and, such developers being non-staining and the deposit given a pure black, the printing quality of the nega tive is more uniformly reliable than is often the case with pyro Permits.—With regard to the necessary permission to photograph interiors of cathedrals and churches in England, this can, as a rule, be obtained from the local dean or rector, full particulars being given in the Photographic Red Book. In France the cathedrals are State-controlled, and application should be made to M. le Ministre des Cultes at Paris. We may mention that the French authorisation has sometimes to be countersigned by the diocesan architect, and does not always apply to crypt photography, for which a separate permit may be necessary. Similar rules are in force in most other countries.
In conclusion we would point out that to get an idea of the charm of architectural work one has only to give it a trial. The more closely we study our subjects, the more will their intensely human interest and associations appeal to us, and the more shall we be in sympathy with the artistic ideals of the mediatval craftsmen. The mere setting about to record a building carefully is bound to lead to a more thorough appreciation of it. One is inclined to think some times, say, on arrival at an unfamiliar town, " There is not much worth taking here " ; but a closer inspection, with a view to doing a single church or castle something like justice with the camera, will most likely bring about a change of opinion. In our own experience a slight feeling of disap pointment has often been changed to one of appreciation and enjoyment, by allowing ourselves time to examine a place from a photographer's view-point, and waiting, perhaps till next day or longer, for a particular lighting, when the average tourist would have been content to "do" the town in a few hours. Especially is this the case with a church interior. The effect of the building " grows " on one, new aspects pre sent themselves, and what might have been but a superficial and easily effaced impression becomes a lasting memory.