Amateur Photographer & Cinematographer (1933)

December 20th, 1933 Thi amateur photographer Q 6 CINEMATOGRAPHER a ‘Deader s' Questions Ay 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 not 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 of 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. Safelight. Does a green safelight afford as much safety with panchromatic materials as a red one with nonpanchromatic ? Can a green safelight be used for orthochromatic material ? F. A. L. (Portishead.) If the green safelight is properly adjusted to the panchromatic emulsion it is just as safe in its way as a red safelight with other material. There is no reason why a green safelight should not be used with orthochromatic material, ex¬ cept that it is much less brilliant than an equally safe red light. Developing. I wish to start developing my own films. What light, if any, should be used in the dark-room ? What chemical should 1 use for developing ? How long do the negatives remain in it ? Is there any other process after this ? R. T. H. (Cowes.) Before you attempt to develop your own negatives we should strongly advise you to study a textbook, as you are evidently quite unfamiliar with the processes of development, and these cannot be adequately explained in the form of replies to questions. A suitable textbook for the purpose is “ Photo¬ graphy made Easy,” by R. Child Bayley, obtainable post free from our publishers, price 2S. 3d. Club Facilities. Can you tell me of any photographic societies having good dark-room and enlarging facilities either near Croydon or in London ? A. E. L. C. (Croydon.) The old Croydon Camera Club is the only one we know of in or near that town, and you already know that it has no such facilities now. There are several London clubs with the facilities you require, but for those we must refer you to the list to be found in ” Photograms of the Year,” or “ The British Journal Almanac.” The Royal Photographic Society has such conveniences, but only for the use of members, and the sub¬ scription is two guineas per annum. Photo-mechanical Work. Can you recommend any books dealing with photo-mechanical printing processes, particularly the half-tone method ? H. L. G. (Deptford.) We should advise you to consult Messrs. Hunter-Penrose, Ltd., of 109, Farringdon Road, London, E.C.i, so as to ascertain which of the books they supply will be most likely to suit you. Amidol Spots. Some carbon prints have been stained, while wet, with particles of dry amidol. Can I bleach out the spots ? A. E. F. (Southampton.) We know of no method whatever of removing the spots caused by particles of amidol. Lens for Enlarger. Will any ordinary lens used in cameras be satis¬ factory for an enlarger, or is a different type of lens used ? K. J. F. (Caine.) In a general way any lens that will take the negative will also enlarge from it. The best type of lens for enlarging, however, is an anastigmat, which will cover the whole field sharply at full aperture. Next to this comes a good rectilinear lens, which may have to be stopped down to get even definition all over the field. Keeping Amidol. I am told that it is possible to make an amidol developer that will keep longer than the usual day or so. If this is right, can you tell me how it is done ? P. N. (Cambridge.) We do not know of a purely amidol solution of the kind, but the following modification has been suggested : Amidol . . . . 45 grs. Hydroquinone . . . . 18 grs. Sodium sulphite (crys.) . . 1 oz. Potassium bromide . . 18 grs. Water . . . . 20 oz. The presence of hydroquinone has the effect of keeping the solution in good working order for over a month. Roberson’s Medium. For pigmenting prints I notice that Roberson’s medium is recommended. How can I prepare this ? R. B. (Battersea.) The medium is a well-known pro¬ prietary article, and we cannot explain how it is prepared. It is an alternative to megilp, which it closely resembles, and can be obtained in collapsible tubes from any artists’ colourman. Pinhole Exposures. What is the formula for calculating exposures for a pinhole used at different distances from the plate ? S. S. (Leyton.) It is necessary to know the diameter of the pinhole as a fraction of an inch. Call the denominator of this fraction the f/ number. Suppose the hole was made with a needle of such a size that twentytwo such needles laid side by side measure one inch across ; the stop is taken as f/22. Find the exposure for this stop, and multiply it by the square of the distance from pinhole to plate ; e.g., if this is 8 inches, multiply by 64. Vigorous Bromide. Will you explain the meaning of the word “ vigor ous " as applied to bromide paper ? L. B. (Northampton.) It is a grade of paper designed to give a more contrasty print than a normal paper would give with the same negative. Before the latter paper yielded deep blacks in the shadows the high-lights would have become grey. The vigorous paper gives strong blacks while keeping the high-lights bright and clear. Thus, instead of dark grey and light grey we get black and white. This description is a little exaggerated to convey the broad idea. Stained-glass Windows. Is it possible to photograph stained-glass windows, using ordinary roll film ? L. H. (Basingstoke.) It is certainly possible, and in some cases the results would be satisfactory ; in other cases the tones representing the different colours would be incorrect. When strong reds are present, as they often are, a panchromatic plate or film is necessary, and a filter may also be required to prevent certain blues from coming out too light in the print. Steaming Prints. What is the real reason for recommending steam¬ ing bromide prints to fix pencil and crayon work ? What exactly happens ? W. D. (Watford.) The steam softens the gelatine almost to melting-point, and the lead becomes embedded, so that it is held when the gelatine hardens again, and is far less liable to rub off. Thiocarbamide. Can you give me a formula for the thiocarbamide solution used for clearing up slightly foggy enlarge¬ ments ? Is this method reliable ? F. S. E. (Cardiff.) A suitable formula is : Thiocarbamide . . . . 20 grs. Citric acid . . . . . . 10 grs. Water . . . . . . 10 oz. The risk with all “ clearing ” solutions is that some of the lightest tones may disappear as well as the fog.