American cinematographer (July 1922)

July 1, 1922 THE AMERICAN CINEMATOGRAPHER 5 focused at 13 feet shows practical sharpness from 10 feet to 18 feet, and this proportion of front and back depth holds fairly true under all conditions. Of the several lenses adapted to cinematography, only three are in general use, these being the Zeiss Tessar, by Carl Zeiss, E. Krauss, and Bausch and Lornb, the Goerz Kino Hypar, and the Cooke Cinematograph. In the early days of the motion picture, the Goerz Celor was used, but this lens is no longer in use, and its manufacture has been discontinued. The Celor does not compare with the more recent lenses, in anastigmatic Qualities, but is occasionally used for close-up work, because of its soft working qualities. The Heliar, F.4.5., a really excellent lens, is out of favor on account of its comparative slowness, although at one time it was very popular. A little known, very new lens is the Wollensak Cinema Velostigmat, of which more will be said latter. There is no “best” motion picture lens. Tastes vary, and a lens quality that is suitable to one type of work is not suitable to another. Image quality in lenses designed for the same purpose is found to vary, and that variance seems to be based on the number of glasses, cemented or not, the softer the image quality. The Carl Zeiss Tessar is one of the oldest standard lenses on the market, and one of the best. The Tessar formula is of four glasses, two of which are cemented. Theoretically, the lens might be classed with the three glass systems, but in practice, it is less brilliant than these. This lack of high brilliancy is by no means a detriment; it simply means that a Tessar image shows a full line of graduation, a ready appreciation of low shadow detail, and full registration of overexposed highlight detail. The fact that the Tessar has actually four glasses, and these comparatively thick ones, has a great deal to do with this image quality. A cemented pair of glasses, such as the first two of the Tessar, is stoutly claimed to be equal in all ways to a single glass — that the cemented surfaces cannot reflect light to be lost or shown as flare. This theory has been the subject of considerable controversy, some opticians claiming that cemented surface nearly, but not quite, fulfills this condition. The thickness of the glasses has this application: no glass is absolutely transparent, and thus, all glass transmitting light is made slightly luminous in itself by this light. This luminosity is extremely slight, and does absolutely no damage. Indeed, quite the reverse is true, because of a little discussed characteristic of a negative emulsion called inertia. The inertia of an emulsion is the amount of light absorbed without photographic reaction, this amount being a small percentage of the exposure which varies with the speed of the emulsion. An emulsion already exposed this amount is in condition to record the slightest additional light. Astronomers often take advantage of this fact by exposing plates to a weak light long enough to overcome the inertia, in order to reduce exposures. The amount of extraneous light transmitted by the Tessar, and the still softer five-glass Heliar, seems to be of great value in overcoming this inertia, and possibly accounts for the particularly pleasing richness of lowlight graduation so characteristic of the Tessar negative. The extraneous light is below the inertia point so there is no suggestion of fog; the blacks are clean. The Tessar is a deservedly popular lens. No greater tribute could be paid a lens than the willingness of cameramen to pay fancy prices for the Tessar when importations were impossible during the war. The Goerz Kino Hypar is a three-glass system lens especially designed for motion picture work. It is particularly notable for its crispness of definition, and clean working qualities. The three thin glasses transmit less extraneous light than the Tessar, and its glasses are smaller. The result is a crisper image quality. Since there is no criticism without comparison, it may be well to compare these two absolutely standard lenses. The Tessar is soft and rich; the Hypar is brilliant and very clean. The Hypar will give a more brilliant image under poor light conditions than the Tessar, and has a greater latitude of exposure, due to this clean working. The Hypar may be summed up as a clean, clear, optically fine lens. There are probably more Hypars in use than all other lenses put together, and there is a very good reason for this. It is easy to use, will handle difficult exterior locations, with poor light, and is not at all “tricky.” The Cooke Cinematograph is also of the simple, three-glass construction, with the resultant brilliancy. The additional aperture of F.3.I., is really valuable, as the lens is quite efficient at that speed. The one outstanding thing about the Cooke is its fine workmanship, optically and otherwise. It is absolutely sharp, and very clean working, and seems to be about as fine an optical instrument as one could desire. In comparing work, there is little to choose between a Cooke negative and a Hypar negative, both being of the same quality class. The Cooke does have, however, the undeniable advantage of greater speed, and it is a little better made, especially in the matter of diaphragms. One peculiar thing about the Cooke is that the diaphragm control turns just opposite to other lenses in fading out — a valuable thing to remember when working with one of them. It must be remembered that the differences in image quality given here is not the result of observations of single individual lenses. That would be hardly fair. These differences, which by ordinary standards are very slight, still are great enough to be well worth considering. It would be a task to distinguish between the work of these three lenses when used under ideal conditions, and by men who know how to get the best out of them. It is in difficult places the lenses show their characterstics. These three lenses practically dominate the field of general utility lenses, and they represent the best of their type. The war, however, has brought about new possibilities of lens constructions in America, due to the development of American made optical glass. This will be a big factor in future motion picture lenses. Lens makers are trying hard to improve their product, and are making every effort to supply every known want, all of which is very fine for the cameraman. One point of special interest is the effort to produce a really useful soft image lens for motion picture work. These lenses, as well as the special purpose lenses, will be material for future discussion in this article. .j SPEED! Harry Thompson, chief electrician for the Elmer Clifton Productions, claims he has to his credit one of the speediest little pieces of “hooking up” on record. The Charles W. Morgan, oldest whaling vessel afloat, was brought across the river from Fairhaven to New Bedford Saturday where she is being used for deck and cabin scenes in Mr. Clifton’s “Down to the Sea in Ships.” Mr. Thompson had two transformers brought up, ran leads to the masthead, connected plugging boxes to a switch in the forecastle, hooked up ten Wohl lamps and two 85-ampere spotlights, and had the entire forecastle ready to shoot in an hour and a half from the time the ship touched the pier. If there are any other electricians running around who think they can beat that, Mr. Thompson would like to hear from them. It will cost you less than ONE CENT A DAY to subscribe for The American Cinematographer for one year If you are a technical man it will be worth a hundred times that much to you. $3.00 A YEAR