Fog In The Studio.

           IN many localities, notably in the London district, the state of the atmosphere has left much to be desired from the photographer's point of view. Not only has there been an actual deficiency of light through the presence of more or less yellow fogs, but there has been great difficulty in securing brilliant negatives on days when the light was fairly good, because of the general haziness of the atmosphere. Many photographers suffer from this fogginess without quite being aware of the actual cause of it. A simple experiment which will show in a rough way how much fog is present in any room at various distances can be made with the aid of two ordinary black velvet focusing cloths, velvet being chosen because it has leas reflecting power than any other material in ordinary use. One piece of velvet is crumpled up so that some parts produce deep shadow and put on a table in the position usually occupied by the sitter. The operator then stands by the camera at the distance at which a full-length portrait would be taken, and holds up the other about a foot from his eyes so that it half covers the piece on the table. If there is any appreciable amount of haze present he will find that the deep shadows on the distant piece appear quite grey in comparison with those on the piece which he is holding, and at once finds an explanation of the flat negatives which he has been obtaining.
           Having established the existence of the fog, our aim is now to minimise its effects, and there are many methods by which this end may be partially attained which, when put together, result in a substantial improvement in the quality of the negatives. In the first place, the studio windows should be kept clean, so that as small an area of glass as will give the desired lighting will be needed to obtain short exposures. By thus closing out all unnecessary light we reduce the general illumination of the fog and get a much brighter image. This can perhaps better be seen when working with artificial light. If we build the lamps in with screens or backgrounds so that the light falls upon the sitter only and none reaches any other part of the studio, there are only three or four feet of fog to work through, while if the whole of the studio is illuminated the amount is greatly increased.
           In foggy weather the lighting of the sitter may be more concentrated than is usually necessary, as a more vigorous negative will then be obtained, and printing can be carried on until the shadows are of sufficient depth. Windows become coated with smoke in a day or two in the winter and act as undesirable diffusers, so that it is advisable to clean at least the panes which it is intended to leave unscreened.
           A fairly warm temperature and good ventilation tend to reduce fog and to clear it away quickly. We have often noticed that a room or studio has remained foggy long after it has become fairly clear outside. When the necessary power is available, an electric fan will do much to establish a current of air, which should be directed towards an open window or door. A proper exhaust fan fitted near the roof is the best form, but the portable ones are of considerable value.
           We have already pointed out how the effect of fog may be reduced by cutting out all unnecessary illumination. A further improvement may be made by using a lens of as short a focal length as possible, though not so short as to introduce distortion. Where sufficient length of studio is available, it is now common to use sixteen or eighteen-inch lenses for all-round cabinet work, and it is quite good practice in clear weather. But at other times a tea or twelve-inch lens will be found to give much brighter pictures. As a matter of fact, many photographers have found this out without knowing the reason, and attributed the improvement in brilliancy to some other property in the lens than its focal length. Whatever lens is being used, it should be kept clean. Lenses will get as dirty as windows do in a smoky atmosphere, and will then yield flat images in the clearest light. If a lens has not been kept clean it is interesting to take a negative with it before cleaning and one directly afterwards. In most cases the contrast will be striking. Lenses should be cleaned carefully, a vigorous rob with the corner of the focussing cloth is not to be recommended, as such treatment soon "greys" the surface. An old worn handker-chief, kept in a box free from dost and grit, should be used. If there is a greasy deposit from town smoke, a single drop of pure alcohol may be applied on a tuft of cotton wool, and then the surface quickly polished with the handkerchief.
           Although we are opposed to all “tinkering” methods of development, the judicious use of bromide upon exposures which have been made under adverse conditions is quite permissible. To describe the action of bromide in popular language, we may say that, when used upon an over-exposed or foggily lighted plate, it allows the high-lights to get a start before the shadows begin to develop. If the plate be developed right out this advantage is lost, but as most portrait negatives do not reach this stage there is a decided benefit to be obtained by the use of bromide in the cases we have mentioned. It is necessary to add the bromide to the developer before immersing the plate. Once development has started it is of little, if any, effect. The character of the plates used should also be taken into consideration. Some brands tend to give brighter results than others. These should be chosen for foggy weather, as, although the scale of tones may not be so long, the resulting print is more satisfactory.

Some Notes On Print-Meters

           Of the many forms of print-meters, or actinometers, the type dependent upon miniature negatives of graduated density is preferred by some, as no matching of tint is required, and for occasional work with only a few frames exposed it certainly is convenient. On the other hand, the most accurate of all probably is the "single-tint" tint-matching type, almost essential when many frames have to be kept going and taken in and out during the day's work, but it requires constant inspection, and if one tint is over-done accidentally only a rough estimate is possible to compensate for the over-printing. Single-tint meters, such as Johnson's, supplied by the Autotype Company, are provided with a roll of P.O.P., which under varying atmospheric conditions does not always make a good match: with the surrounding tint, the yellow glass above necessarily being of insufficient depth to remove colour contrast. Greater accuracy in reading is secured by not attempting to effect a colour match, but to work in the following way: If the nearest edge of the rectangular aperture is viewed obliquely from a fair distance with the eyes partially closed, it will initially stand out lighter than the darkening silver paper beyond it, and at a certain stage will merge into the tint and be lost, which point is taken as "one tint." Tests have shown that this method largely eliminates the personal equation, one printer, practically speaking, registering the same number of tints as another, whereas in the case of colour matching by gazing directly downwards on the meter wide differences in the estimation of what constitutes a tint have been found. A variant of "Johnson's" is the circular meter with disc refills: it is cheaper, but for professional use the former is the better. In some cases celluloid is used to protect the tint, but it is an indifferent substitute.
           To insure accuracy with thin or medium negatives, the meter should register three or four tints during the printing, accuracy being of more importance when printing platinotype or palladiotype by meter than with the carbon process, which has greater latitude in exposure, or, rather, errors in exposure are more readily corrected in development. But a quick-printing single-tint meter is a decided nuisance when dense negatives are being dealt with, and in such a case a fixed-out lantern plate dyed yellow with bound-on cover-glass can be placed over the meter and will be found very useful to slow down its indications. As a matter of curiosity, it may be mentioned that the extreme variation in the rate of contact printing met with in one trade printing concern ranged from three minutes to twenty hours, the negatives - being exposed to the same

mercury light, and each negative affording good prints. The perpetrator of the twenty-hour gem had "faithfully promised his customer a dozen prints at the end of the week," as is usual in such cases.
           Other forms of print-meters based on tint-matching are illustrated by "Sawyer's" and the "Akuret," the sensitive paper being exposed under translucent tints of different densities. They possess an advantage over the single-tint type, as no movement of the paper is required whilst the negatives are being printed, but their scope is not so wide. The familiar Wynne's meter, dependent upon numbers successively printing out, is a favourite with many, though others experience a difficulty in deciding whether any particular number hat, or has not, appeared Finally, the type first alluded to is the device of Mr. H .J Burton, on the lines of which the making of an efficient home-made article is to be described.
           Not a few have attempted to make print-meters of the graduated miniature negative order, by copying a photograph in the camera, or by exposing by contact a dry-plate behind a positive, in either case successively on different parts of the plate, with an increased time of exposure for each small negative, but this method is very uncertain, and the results are usually far from satisfactory for fairly obvious reasons. It is also obvious, when mentioned, that to attempt to design a meter capable of indicating exposures from thin negatives up to those of extreme density, either means an undesirable multiplication of the tin; guide negatives, or an equally undesirable abruptness in the translation from one to another. For unnaturally dense negatives, one or more pieces of ground-glass placed over the meter will meet the case.
           Fig. 1 represents a quarter-plate negative of nine prints stuck on white cardboard, which are reduced by copying in the camera to a little less than 2*(1/2) inches high over all, in position shown on the plate. The prints should be of the same subject, preferably a portrait rather large on the plate, and whilst it is an advantage that the set be uniformly lit, even illumination is not essential. Over-exposure is to be avoided as bright, but fast printing negatives with almost clear glass shadows are the moat suitable. If the ground prints through it is blocked out.
           Assuming the figure to represent the glass side of the plate, and the negatives to read from left to right in the usual way, the graduation in printing rate is effected by covering No. 2 with one layer of celluloid, about the thickness of that used for cut films, No. 3 with two layers, and so on. Fig. 2 shows the first sheet of celluloid applied with extremities extending beyond the miniature negatives,

but clear of the edges of the glass; on the right about 1*(1/3)th inch, on the other three sides more space is available. The next sheet has space 2 cut away, and is stuck down at each end with a touch of celluloid varnish, the procedure being continued mutatis mutandis until No. 9 is covered with eight thicknesses.
           When the first test of the meter is made everything may appear right, the lower numbers being nicely graded, and on printing further the faint images of the highest numbers apparently the same. But here exists an unsuspected trap, for on printing, say, No. 5, to the "pretty" stage, No. 6 may now be found to be almost indistinguishable in depth, and therefore require further ho. ding back, together with the numbers following it.
           Accordingly, the only safe plan is to test each number right through the series at its "pretty" stage against the next less printed one. Some pieces of stripped thin roll- film may be found of service when only a very slight holding back is demanded. The celluloid covering is then edged all round with cardboard slips stuck down with seccotine, and a thin cover-glass bound on. If the lower numbers print too quickly for the negatives in use, the cover-glass may be of ground-glass. A three-quarter-view quarter-plate printing-frame holds the finished article; white wood frames are sold sufficiently deep to take it. A packet of 3*(1/2) x 2*(1/2) ordinary gelatine P.O. P. provides the meter paper, and will keep for years if stored in an airtight tin with some dry calcium chloride. Self-toning papers are not so good for the purpose. When the number indicating the correct exposure is found by trial, naturally only a narrow strip of paper need be utilized afterwards.
           In the model constructed, which has worked well, for identical depths of printing the last number requires about six times the exposures of the first, a range sufficient to satisfy most requirements. This ratio, of course, only holds good for the particular thickness of celluloid employed. Comparative values might be given each negative if a single-tint meter is at hand, or improvised, by registering the number of tints necessary to bring each negative in turn to the pretty stage.

Carbon Printing By Artificial Light

           Although many photographers, both professional and amateur will be familiar with the fact that the printing of carbon tissue can be done conveniently with the stronger sources of artificial light, such as the electric arc and mercury vapour lamp, as well as by daylight, it does not appear to be so well known that by choosing a suitable source of light prints without the usual lateral inversion can be obtained from ordinary glass-plate negatives by the process of single transfer only. A few remarks on the method of obtaining such prints may therefore be of interest to those who have the necessary facilities in their studios or homes.
           To obtain the unreversed print the tissue most be placed in contact with the plain glass side of the negative, the latter being placed in the printing frame with the film towards the light. The negative moat then be illuminated by a very small but sufficiently actinic sources, and care must be taken that as little light as possible, other than the direct rays from the direct rays from the source, falls on the plate during the exposure.
           The most convenient and satisfactory illuminant is undoubtedly the comparatively new Ediswan "Pointolite" lamp. The actual source in this lamp is a small metal ball, the diameter of which is about two millimeters, supported in the centre of a glass bulb, some 10 centimeters in diameter. The ball is rendered incandescent by a small electric arc, which obtained by placing a second electrode immediately over the ball. The usual rating is 100 candle-power, and the current required about 1,5 amperes. This intense and practically “point” source of light is highly actinic, and forms an ideal illuminant for many optical purposes. In using the lamp for the purpose under consideration it is well to place the negative end of box coated inside with a dead black, and to the lamp outside the box at the other end. A small rectangular hole is to be provided in thia end, so that when the lamp u placed as close as possible to the hole the beam of light which enters the box will just cover the film of the negative. The distance between the centre of the bulb and the negative may be 20 centimeters, or even less. It is clear that a number of negatives may be printed at the same time, the bulb of the lamp being placed for this purpose in the middle of a circular or, say, octagonal box with suitable radial partitions; light reflected from the film of one negative must not be allowed to fall on the others. When six negatives are printed at once the cost of printing may be less than that of the final rapport used in the double transfer process, and there is, of course, also a considerable saving of time. With negatives of average density the time of exposure required is 40 to 50 minutes. The time may be shortened, if fine definition is not required, by reducing the distance between the negative and the lamp. It may be added that the "Pointolite" takes so little current that is may be connected to any lamp-holder, special wiring not being required.
           A second illuminant which will be found to give satisfactory results is the iron arc, but this can only be used where ordinary arc lights are installed or where the electrical fittings allow the use of a current of 5 or 6 amperes. The advantage of an arc with iron pole, instead of the usual carbon poles is that the iron burns away very slowly, so that no “feed” is required. In fact, the lamp in this case may consist simply of two iron rods, 1 or 1*(1/2) cm. in thickness supported in the same vertical line with a space of about 4 mm. between their nearer ends. The poles must be, of course, insulated and connected to the mains in the same manner as the ordinary arc lamp. The arc is most conveniently “struck” by drawing a third iron rod across the ends of the pole piece. Once the pole, become hot the lamp will run for long periods, sometimes hours, without requiring attention. If the power is supplied by direct current the upper pole should be made the negative one. It is well to place a tray containing .water below the lamp, as occasionally small pieces of molten iron may fall. As the light is very rich in ultraviolet rays it should not be used except when the eyes are protected by plain glass or ordinary spectacles. With this more powerful source a larger number of prints may be exposed at once, the frames being arranged in a circle, say 50 cm. from the light. At this distance no special screens are necessary and reflection from surrounding objects is of no account unless they are light-coloured. The exposure required at 50 cm. is about 20 minutes, with a current of amperes.
           With the distances quoted above the diameter of the circle of confusion representing the points of the image is about .005 mm, but there is a slight loss of definition which appears to be due to reflection between the front and back surfaces of the negative. The want of sharpness, however, is remarkably slight, and in most cases amounts to no more than a softening of the otherwise hard lines of the picture, an effect which in many subjects is quite pleasing.

S. S. RICHARDSON.