PHOTOGRAPHIC NOTES

Evening Star, Issue 21518, 16 September 1933, Page 8

PHOTOGRAPHIC NOTES

[By Panchro.] In this column will appear week by week nows and notes of interest to amateur photographers. It is intended to be of use to both sections of that large fraternity, those who are on speaking terms with facts, formulas, and darkroom lamps, and also to those who frankly confess themselves as mere “ button pushers.’ FLAT NEGATIVES. Let ns consider tho case of -a negative which is not sufficiently contrasty. In a print from such a negative the parts that should be black are merely greyish, and the whites are flat. We may get a better print by using a very contrasty paper or we may improve the negative. So we examine the film carefully in order to diagnose the case. It will almost assuredly be under-development that has caused the flatness. But its appearance will be totally different in the cases of a cor-rectly-exposed negative and one that is over-exposed. In the first place, the film will be clean looking, very .thin, and lacking in contrast. As its only fault is that the deyeloper was not allowed to act upon it for sufficient time, tho remedy is to make up for that deficiency; and that we do by intensifying it. But if the negative has been overexposed, and having flashed up quickly in the developer, has been put rather too hurriedly in the fixer, as it appeared to be going black all over, then the cure may be more complex. Wo may have both to reduce and to intensify. For that blackening all over means that we have too much deposit in places whore we do not want it. And the fact that we did not give the developer full time to act means that- in other places we have not enough density. So ,wo must use a reducing chemical that will quickly remove the unwanted deposit, while attacking the already too thin denser portions as little as possible. Obviously we cannot use persulphate of ammonia, since that has tho contrary effect to what we want. But there is a chemical that fills the role, and that is potassium ferricyanido, that is the same chemical that we used in making up the bleaching bath. It is sometimes called red prussiate of potash, because it has a brother whose colour is yellow. Take a crystal of the ferricyanide about the size of a pea, put it into a measuring glass, pour a little water into the glass, and swirl it round. Then pour it away This was to wash the crystal, which should now appear bright red. Pour about an ounce of water into the glass and let the ferricyanide dissolve. Into another glass put an ounce or so of ordinary hypo fixing bath. And by the word ordinary we mean a nonacid hypo. If you are using exclusively acid-fixing baths, as many people do, you must buy half a pound of pure hypo and use it for purposes of reduction. In this case, take a large pinch and dissolve it in water which has been slightly warmed. It is well to remember that ferricyanido is somewhat poisonous. Into a developing dish put the offending negative that has previously been wen soaked in water. _ Add enough of the ferricyanide solution to the nypo solution to give it a pale lemon colour, and pour it over the negative. As you rock, you will notice that the negative is losing density in the thinner portions, and that the general fogginess is disappearing. Hold it up to tho light from time to time, and when you judge the reduction to be nearly sufficient put it under the tap to wash, and wash it very thoroughly unless you want to have subsequent trouble with it. _ When the ferricyanide . and hypo solutions are mixed they will not keep. Nor is it advisable to try and keep the ferricyanide solution in a bottle by itself, unless some ordinary kitchen salt is mixed with it. On the whole, it is better to mix it up fresh each time. ~ If, on examination, you considei the negative has been insufficiently reduced, the process can be repeated. At the end of half an hour’s washing the negative is ready for »ts second treatment. This, and intensification generally, must be the subject of our next article.

IMPROVING A DARK ROOM LAMP. Dark room lamps as sold by most dealers are generally fitted with oil burners. These, at least in my case, have proved an intolerable nuisance, for, if the oil supply in the lamp manages to last out an important bit of developing work the thing smokes abominably. This state of things is not conducive to the best of work, and, indeed, I have sighed many times and wished for electric light or gas in my “ den ” However, these not being available, and absolutely losing patience with my present light, it behoved me to find something vastly different, and after casting about in various directions I solved tho difficulty by means of a Uashlamp bulb and a battery. My lamp is of the reflected ngnt variety, fitted with the usual safe light. After removing the oil burner a quarterinch hole was drilled about two inches from the top. This was gently enlarged by means of a round file till _ a flashlamp bulb screwed in fairly tight. A piece of square cardboard was now fatted on, glued to the wall of the lamp house. V. non this was dry the bulb was found to bo quite firm, and ready wiring up. For this some wire (electric light twin flex will suit), a switch of the plain board type, and a battery such as is used for cycle lamps were obtained. Tho wires being divided, one was attached to the end of tho bulb by means of a spot of solder, the other wire going to the screw portion. The wires were then taken to tho battery terminals, via the switch. . ■ I have fitted a bulb which is rated at a .2 amp., and using a battery of the type described, I have had a good trouble-free light to work by for tho past five weeks, using the lamp pretty often at that. Tho battery shows no sign of diminished power, and continues to give a constant light. As these batteries are inexpensive, the upkeep cost is not much greater than oil. Of course, the light obtained is much whiter than with the oil lamp, and, before using it, after converting, I thought it wise to test for safety. This was done by means of the dark slide and plate test, as described in the text books, and after being developed in darkness the plate showed no signs of fog. During development of negatives I find it a groat asset to bo able to switch off the light as soon as the plate is covered by developer. Incidentally I suppose this will lengthen the life of the battery, as it is never on duty many seconds at a time. EXPOSURES ON TOUR. The old hand will not need the advice to take an exposure meter when travelling amongst subjects which are unfamiliar to him. This is a safe course, and will result in a higher percentage of successful negatives. It is also a good plan to have a spool of film developed by a competent dealer with a

view to ensuring that exposures are approximately correct, and that the apparatus is working properly.

ITEMS OF INTEREST. Potassium permanganate, if rendered acid, will remove developer stains from dishes. Any stains left by the permanganate can be dissolved out with a solution of ordinary strength Pot Metabisulphite. Panchromatic material demands absolute darkness or desensitising during development. Other materials can be handled in a deep red light, if precautions are taken to screen the light or cover over the developing dish most of the time. Desensitisers are easily used, and greatly simplify the development of Sims for those whose dark room lacks the necessary conveniences. Every beginner at photography should aim at undertaking a little of his own developing and printing. It is surprising how quickly faults in handling tho camera can be detected and remedied by so doing.