International photographer (Jan-Dec 1934)

May, 1934 T 1 1 INTERNATIONAL PHOTOGRAPHER Eleven such a case the difference in the effects produced by both filters may be negligible. The idea was then hit upon to substitute green glass filters for the usual yellow glass filter. Green glass is made from a so-called true solution glass, which unlike yellow cadmium glass is homogeneous in evenness of color. The glass can be given perfect optical treatment as in the case of yellow filters, and we also have the decided additional advantage of the even distribution of the coloring matter. The density of the filter can also be varied by the difference in thickness of the finished filter. Thus with a given melt of glass different filters may be simply prepared by varying the thickness of the glass. Now to return to the discussion of filters in general. If the photographer is to have but one or two filters he can obtain them in slip on mounts. Such filters are ordered in sizes according to the diameter of the lens mount. They are supplied in fixed mounts which slip over the front of the lens. Some of us more interested in the art of filtering may be contemplating the acquisition of a set of filters. Such a set may be purchased complete at one time, or the filters can be acquired singly over a period of time until the desired set is complete. In this case it is advisable to choose a definite size in which all the filters purchased will be such as the 31-32 mm. round glass filters, or two inch square filters, etc. A filter holder, or one of the newly introduced combined sunshades and filter holders accommodating the size of filter chosen, is obtained. The various filters can now be acquired in one definite size to accommodate a single holder, making for greater compactness and portability. Photographers choosing a size such as the two inch square filter, can avail themselves of the varied filters employed by the motion picture industry. I am including below a partial list of such filters and the general purpose for which they are used to enlighten the photographer in making his choice: K-l (Yellow) — For moderate correction. K-2 (Yellow) — For medium correction. Aero No. 1 and No. 2 — For aerial work and landscapes. G. (Orange) — For full correction. 23-A (Red) — For over-correction and night effects. 25-A (Red) — For greater over-correction and night effects. 29-F (Red) — For extreme over-correction and night effects on regular panchromatic film. 72 ("Gamma") — For night effects on supersensitive film. 56 (Green) — To reduce contrast. Fog Filters — For producing artificial fog effects. Besides these there are also a large number of graduated filters such as the Scheibe graduated filters, available in the two inch square size. The graduated filter enables the sky and foreground to be rendered in a different manner. The simplest one of this type is that in which the upper half of the filter is yellow, and the lower half composed of colorless optical .glass, the yellow half blending into the colorless portion at the center of the filter. In using these filters they are adjusted so that the sky is photographed through the yellow portion whereas the foreground is recorded through the clear half. Normally, when exposing for the foreground the sky will be found to have been over-exposed, due to the vast amount of actinic light it contains, in comparison to that reflected from the objects in the foreground. When using the graduated filter the upper yellow half will correct the unevenness in exposure and improve the tonal reproduction of the sky. There are also more advanced graduated filters available such as those in which the upper half is either red or orange, thereby producing darker skies. Some have the lower half yellow instead of being clear, and the upper half red or orange, enabling one to obtain correction for the foreground, and at the same time overcorrect the sky. Question will arise as to the XI and X2 green filters. This set is designed primarily for use with Eastman Supersensitive Panchromatic film in both daylight and artificial light. Too Much Contrast: Many photographers get too contrasty results with the film and developing formula they are using. Such films as the DuPont Micropan and Perutz Persenso are prone to produce excessive contrast when employed for the making of ordinary run of photographs. In copy work or photomicography strong contrast would be desirable, but this is not the case in pictorial, or similar photographs. The simplest means of controlling contrast is to shorten the developing time. If the instructions of your chosen developing formula prescribe 20 minutes at a definite temperature, reduce the developing time to about 15 minutes, and you will find the resulting negative to be less contrasty. The modification in the developing time will naturally be dictated by the amount of contrast desired. Contrast increases as the development of the film is prolonged. Incidentally, the decrease in the development time will also favor a finer grain. As development proceeds density increases, and it has been proven that if a print of constant density is made from negatives of increasing density, the graininess in the print increases as the density of the negative increases. The shorter development will produce a negative of lower density. The New Weston Leicameter New Weston Leicameter: This Leicameter now appears in a new form similar to the regular Weston Electric Meter. When pointed at the scene the meter indicates the proper shutter setting for Superpan film at f:6.3 or Plenachrome fil mat f:4.5. A guide is attached with which the meter shutter speed rating can be quickly converted to the proper exposure necessary for films whose speed differs from those mentioned. The meter incorporates the well known Weston Photo-electric cell, which converts the light reflected from the object into electrical energy, obviating the use of batteries. It is a very compact and handsome instrument and will no doubt be very well reecived. Use Lens Hoods: Despite the fact that many new lens hoods of accurate design have appeared lately, such as the Hollywood combined sunshade and filter holder, the Solite, the Counter Light Cap distributed by Hugo Meyer, etc., many miniature camera users still persist in photographing without the use of a lens hood. The lens hood deserves to be classed as a necessity rather than an accessory to be employed occasionally, especially when consideration is taken of the greater use today of speed lenses. When used without a hood the lens will pick up a large quantity of extraneous light, resulting in a negative which appears flat, and is lacking in brilliance. The faster the lens the larger is its aperture, and it will be more apt to pick up stray light. (Turn to Page 26) Please mention The International Photographer when corresponding with advertisers.