EX CATHEDRA: Cheaper Plates; Supplementary Flashlight; Packing Negatives; Field-Camera and Cycle.

Cheaper Plates.

        It is announced that the prices of dry plates have been reduced as from March 11th last. The reduction brings quarter-plates to 3/- per dozen, half-plates to 6/6, and whole-plates to 12 3. Taking the quarter-plate as the basis of comparison it will thus be seen that the reduction to 3/- - from 3/8, which was the figure reached at the last rise on August 1st, 1918, amounts to a fraction over 19 per cent. The present price of the quarter-plate, in comparison with the pro- war figure of 1/3 per dozen, is still 140 per cent, higher. The schedules issued by the
Plate-makers give the complete figures of prices for extra rapid and ordinary plates, panchromatic and X-ray plates in both the English and metric sizes.

Supplementary Flashlight.

        Photographers as a whole are not fully aware of the advantages that flashlight has to offer as a supplementary illuminant when making exposures under difficult conditions. It sometimes happens that a certain amount of day or artificial light is available by which the exposure has to be made that is, in. sufficient of itself to light certain portions of the subject sufficiently for them to be fully exposed before the more brilliantly illuminated parts were hopelessly over-exposed. It is under conditions like these that the flash-lamp, which need only be of a simple form, or which may even be dispensed with if the prepared powder, such as Johnson, is employed, becomes of real assistance in solving the difficulty. We may, in explanation, cite an instance of this which occurred in our own work some years ago. The subject was an interior of an ancient abbey, the building badly lit through stained glass windows, two of which were directly facing the camera. The details of these windows, which were, of course, fairly well illuminated, were required in the negative together with a good rendering of some dark oak choir stalls in the foreground which were very badly illuminated indeed. A plate was exposed by meter for the windows, and just before this period was complete a strong flash was fired, sufficient to illuminate the whole of the interior. Careful development produced a negative that was "just right" for its purpose. The flash should be fired almost at the end of the exposure; if this is done before, there is a tendency for the smoke from the flash to cause a belt over the picture. The above indicates some simple means of overcoming difficulties due to bed illumination, and may be noted by commercial photographers who often are expected to produce first-class results under very unfavorable conditions of lighting. Some may be inclined to adopt the usual reflector and diffuser in connection with the flash, but though this may at times be desirable when dealing with very irregular lightings, we prefer to increase the flash in strength and keep further away from the subject if the building will admit.

Packing Negatives.

        Even in such simple matters as sending a negative through the post there are pitfalls for the unwary of which anyone to whom negatives come is being constantly reminded by the receipt of parcels of glass shattered to atoms by the thump of the post office stamp. Enlarging firms who would caution their customers ought to arrange for them to visit the sorting floors of a big postal depot. It would provide salutary warning against packing negatives between pieces of card or with no greater protection than the cardboard plate box in which they travel at the risk of their lives. Now that so many pursue the photographic process no further than the making of the negative the safe transit of the developed plates to the enlarger is as important an item of after-treatment as intensification, yet many people seem not to know that to make perfectly sure of its safe arrival the negative should travel in a wooden box so that the walls keep the shock of the defacing stamp off it. If it be prevented from shaking about in the box by cotton wool, wood shavings, or even crumpled paper above and below, the sender may challenge the Nasmyths of St. Martin's-le-Grand to do their worst. One other little precaution should be noted. If several negatives of different sizes are being sent together they should be placed so as to prevent the smaller bearing unevenly on the larger. For example, a quarter-plate should not be sandwiched between two half-plates, but be laid upon them with a piece of card between.

Field-Camera and Cycle.

        Those photographers who reside in country districts and have occasionally to carry a heavy field camera and tripod upon a cycle realize that if care is not taken such means of transit are likely to have a very detrimental effect upon their apparatus. The best place for the camera case is without doubt upon a strong back carrier firmly secured to the machine, though some workers have a preference for the front carrier. In the latter position there is a greater tendency for the camera to be shaken about, while if a proper carrier is not used there is a certain strain upon the aides in guiding the machine, especially if the instrument is a heavy one. Even on a back carrier there is a tendency for the case to get badly rubbed, and even the instrument itself may be scratched if a little care is not taken as a preventive. Some time ago, after a cycle journey of some miles across badly made roads, we had the experience of a camera case rubbed right through by the vibration between it and the cycle carrier, together with a broken plate in the dark slide, which necessitated a further journey for the purpose of making another exposure. Since then we have prevented such trouble ever recurring, very simply, in the following manner. A couple of strips of felt about two inches m width and about an inch in thickness, such as may be bought for a few pence at any saddler's, is placed the bottom of the camera case for the instrument itself slides to rest upon, and another strip of felt is I upon the carrier before the case is put on. The felt will absorb some vibration, and the troubles detailed above will not be encountered. We have also adopted this idea when traveling on a motor cycle, when is equally successful. The best place for the tripod is across the handle bars or along the top tube of the cycle. Such a plan is far better than slinging the case upon the operator s back when, if the instrument is a heavy one, its weight is soon felt.

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.