The Optical Magic Lantern Journal (February 1897)

The Optical Magic Lantern Journal and Photographic Enlarger. bo = CamrRA Opscura.—An optical instrument so constructed that real images of external objects may be thrown upon a screen by the aid of a convex lens. There are several forms of camera obscura, both for single and double reflection, one of these being the ordinary photographic camera. A simple form of instrument can be made from a common cigar box, by cutting a hole at one end to receive the lens mount, which for focusing purposes is made to slido in and out. Atthe other end of the box, but inside, is placed a mirror at an angle of 45°, and immediately above this is fixed a pane of ground glass cut same size as mirror, and when in position lays in tho rabbet that receives the lid; part of the lid is cut away, that the whole is flush. The light may be shiclded from the focusing glass by any devisable means. To ensure regular reflection the box is blackened inside. Camera CLuB.—A term given to a society by its members, whose object is to come into touch with one another, and cxchange, or debate, any subject matter appertaining to photography. Camera Stanp.—The table upon which a camera is held or fixed. Canava Barsam.—Largely used for cementing glass, lenses, microscopic objects, and many other articles. It is one of tho turpentine species, and obtained from the Canadian coniferous tree, from whence it takes its name. By gentle heat it becomes very thin, but when set or cold, is both hard and transparent. (To be continued.) feoeiy, yids Architecture as a Subject for Lantern Slides.—No. IV. By T. PERKINS. Practican Hints on Procepure. INTERIOR. PRINCIPALLY Wes (i: AVING provided ourselves with all the necessary apparatus as described in the last chapter, we will choose a suitable day for commencing actual work. And here let me say that we need ‘not fancy that archi tectural work, interior or exterior, is only possible in the summer months. Summer and winter have their advantages and disadvantages. In summer the light is stronger and exposures will consequently be less, and for very dark interiors this will be a great advantage ; and again in the early summer morning and late summer evening the sun shines on the north side of churches that are built east and west, and allows well-lighted views of certain parts of the exterior to be obtained, which cannot be as well taken in the winter. On the other hand, the lower elevation of the winter mid-day sun is often an advantage, as it makes the shadows under projecting parapets or canopies less, and lights up the interiors of south porches and doorways, ani the absence of foliage on the trees that grow in churchyards or cathedral closes, often makes it easier to get uninterrupted views of the building, or views unspoilt by the heavy shadows of unseen trees falling upon the walls. Again, at no time of the year are inner roofs or ceilings so well lighted as when the ground outside is covered with snow on which the sun is shining, for the sunlight reflected, or scattered, to use the more accurate term, from the surface of the snow-covered ground passing upwards through the windows lights up the dark rafters which support the roof. That it is possible to obtain good interiors late in the year is shown by the fact that towards the end of November, 1896, I had occasion to go to Christchurch Priory, Hants, for interior work. TI arrived at my destination about halfpast ten in the morning, and left a little before three o'clock in the afternoon, and during that time had exposed ten plates, all half-plate size, using one camera only. The shortest exposure was one of five seconds with stop 4, and the longest twenty minutes with stop 4; on my return I found that all of the plates had received sufficient exposures, two of them, in fact, would have been all the better if they had had shorter exposures. I may add that I was using Imperial ordinary plates marked with a speed number of 110. The building was what would probably be called a fairly lighted interior. A friend, who accompanied me, was under the impression that all my pictures would be ruined by under-exposure, because it was towards the end of November, and he gave his plates much longer exposures, with the result that more than half were of no use. I have often had it said to me, “You know you cannot over-expose an interior ;”’ but from my experience, which has been tolerably extensive, I have found that one cau as easily overexpose inside a building as outside. Of course, both for exteriors and interiors, it is better to over than under-expose, as though the result may be a flat negative, yet by a judicious selection of printing paper, a bright print, and one full of detail, may be obtained, whereas, if the negative is so much under-exposed that the light proceeding from the darker parts of the subject has made no impression on the film, no amount of accelerator in the developer will bring out detail, and in the print the shadows will be a mass of black or brown. Still, great care must be exercised to get a correctly exposed picture. (To be continued.)