Amateur Photographer & Cinematographer (1933)

December 6th, 1933 The AMATEUR PHOTOGRAPHER I o 6 CINEMATOGRAPHER o 1 ‘Deader s' Questions A ANSWERED General. — All communications for the Editor should be addressed : “ The Editor, The Amateur Photographer and Cinematographer , Dorset House, Stamford Street, London, S.E.i ” and in every case, without exception, must give the name and address of the writer. Contributions. — The Editor is glad to consider original, up-to-date manuscripts on photographic subjects. All contributions must be typewritten, or in very legible handwriting on one side of the paper only. Letters or communications arising out of matters already appearing in the paper are net paid for. The Editor disclaims legal responsibility for the safety of matter submitted to him, but he will endeavour to return rejected manuscripts, etc., when a stamped addressed envelope is enclosed. MSS. or prints that are not actually accompanied by a stamped wrapper or envelope can in no case be returned. Reproduction fees for prints are only paid by arrange¬ ment beforehand. The sending of a print, without any condition stated, will be taken as permission to reproduce it without fee. Enquiries and Criticism. — Advice, Criticism and Information are freely given, but the following conditions should be read carefully before applying, as any communication which does not comply with the rules must be ignored. (1) See “ General ” above. (2) Every question and every print for criticism must be sent separately through the post, and must be accompanied by a separate stamped addressed envelope. No exception can be made in any case to this rule, except so far as enquiries or prints from Overseas are concerned. (3) Neither enquiries nor prints for criticism must be enclosed with competition prints. (4) On the back of each print sent for criticism, in addition to the name and address of the sender, must be the title (if any), and the criticism coupon from the current issue. (5) Enquiries should be clearly written, on one side of the paper only, and should be specific and not general. Such enquiries as “ How can I take interiors ? ” or “ Can you give me some hints on outdoor portraiture ? ” are too general to be dealt with in this section. (6) All envelopes should be distinctly marked “ Query ” or “ Criticism,” as the case may be. (7) Prints are sent for advice or criticism on the distinct understanding that by so doing per¬ mission is given for their reproduction without fee. We endeavour to deal promptly with enquiries, but cannot undertake to answer by return cf post, nor can we give precedence to any enquiry. A selection of those replies is printed each week, but all questions are answered by post. Enquiries from abroad must contain a coupon also, but it need not be from the current number, and should be cut from the latest issue to reach the enquirer. Full Aperture. Please excuse my ignorance, but what is meant by using a lens at full aperture ? K. R. (Southampton.) Practically all lenses used for photo¬ graphy have a number of circular openings of different sizes through which the light passes. These are known as stops, diaphragms or apertures. A lens is being used at full aperture when the light is passing through the largest of the openings available. Desensitising Film. As I am thinking of using fast panchromatic roll film this winter will you tell me the best method of putting it through the desensitising solution ? T. M. (London.) With tank development no desensi¬ tising is necessary, so we presume that you will develop the films by hand. Seesaw the film as usual through plain water till limp, then pass it backwards and forwards through the desensitising solution for at least two minutes, fol¬ lowed by one or two runs through water again. All this must be managed in absolute darkness. You can then develop by a yellow light suitable for bromide work. Wide-angle Lens. I have a 4$-in. lens, f/4.5, which is fitted to a quarter-plate camera. If X use it on a whole-plate mil it act as a wide-angle lens ? F. P. (Plymouth.) A lens of such focus would certainly include a wide angle on a whole-plate, but it would not cover it properly, even if stopped down. The chances are that the circle of illumination would be much too small. Proper wide-angle lenses are specially constructed so as to give a large circle of illumination compared with their focal length. As a rule they can even then be used only at a small aperture, often f/16 as the maximum. Concentrated Developer. Hojv can I prepare a highly concentrated M.Qdeveloper that only requires dilution for use ? L. E. L. (Conway.) This is rather a " tricky ” operation. In 8 oz. of very hot water dissolve 50 grs. of metol and 200 grs. of hydroquinone. Then stir in i£ oz. of anhydrous sodium sulphite. The result is a -white, pasty mass. This is put into a bottle and well shaken up with 130 grs. of sodium hydrate (caustic soda). The solution becomes clear as the hydrate dissolves. For use take 1 part to 15 or 20 parts of water for negatives, and to 25 or 30 parts of water for bromide prints. Stock Pyro. How can I prepare a stock solution of pyro that will keep reasonably well ? W. H. (Leyton.) In, say, 6 oz. of water dissolve 100 grs. of potassium metabisulphite, and then anounce of pyro. Make up the solution to 8 oz., and keep in a well-stoppered bottle. A suitable No. 1 solution consists of 2 oz. stock pyro and 18 oz. water. Spotting Carbro Prints. I find it difficult to spot Carbro prints. Can you advise me ? E. D. (Margate.) Possibly your difficulty is matching the colour. Keep a small strip of the carbon tissue used, and work up a little of the pigmented gelatine with a small brush and hot water. The colour is necessarily a perfect match. Cleaning off Negatives. What is the best way of removing the gelatine from old negatives so as to get clean glass ? B. J. (Hitchin.) Soak the negatives for some hours in cold water. Lay one in a dish and pour boiling water over it. Clean off the soft gelatine with a nail-brush, and rinse the glass in cold water. Megilp. I find megilp often mentioned for rubbing into the surface of bromide prints, but never see it advertised. Can you tell me where I can obtain some ? W. Q. (Preston.) Another photographic use for megilp is for thinning down ink or colour for oil pigment work. It is mainly used, however, in oil painting, and is obtain¬ able in collapsible tubes from any artists’ colourman. Removing Image. Can you recommend an effective method of removing entirely a photographic image which has been drawn over with fixed indian ink ? W. T. N. (Rugby.) A simple formula for the purpose is : Copper sulphate . . . . 100 grs. Common salt . . . . 100 grs. Water . . . . . . 10 oz. After bleaching, rinse the print, fix for ten minutes in plain hypo, and wash. If you are doing much of this work it would pay you to yse instead a solution of 1 oz. potassium iodide in 20 oz. water, with enough metallic iodine added to make the solution a deep port wine colour. The procedure is the same as above. The paper turns indigo blue, and the image brown, but both stain and image vanish at once in the hypo bath. Comparative Exposures. If I know the exposure for f/8 how can I find it for f/6.3 ? G. R. (Derby.) Your question gives us yet another opportunity of stating the fact that all such problems can be solved by squaring the f/ numbers of the stops. The square of 8 is 64 ; the square of 6.3 is 39.69 (say 40). The relation is therefore 64 to 40, which is the same as 8 to 5. That is to say that with f/6.3 the ex¬ posure should be rather more than half the exposure with f/8. Paper Negatives. What is a good method for making paper nega¬ tives more transparent ? S. P. (London.) Lay the negative face down on glass, and apply vaseline oil with a brush. After an hour, give a second coat. Let this stand for two hours. Use fluffless blotting-paper to remove surplus oil, and hang up till the oil has set and dried. Boiled Water. Is there any practical advantage in boiling water before using it for making up solutions ? F. W. (Ealing.) Yes. The water should be kept boiling for about ten minutes, and allowed to stand till cool. If the water is “ hard ” a good deal of the contained lime, etc., will be precipitated, as is shown by the “ fur ” on the inside of the kettle. In addition, the air in the water is expelled ; hence the “ flat ” taste of boiled water. Book on Colour Photography. I have an idea that Mr. Newens wrote a textbook on colour photography recently ; if so, can you put me on the track of it ? L. A. L. (Truro.) The book is “ Colour Photography,” by Frank R. Newens. It was published at 4s. 6d. by Blackie & Sons, in 1931. 42 532