Amateur Cine World (April 1934)

Reversal OR Neg-Pos —WHICH? By “High Light” Ox of the first problems that confront the owner of a 16mm. camera is the purchase of film. What film should be used ? What will give the best results, and still more important to the majority of users, what will be the least expensive ? The great thing to be borne in mind is that, having bought the film for use in your camera (raw stock, it is called before use) you are only at the beginning of your expenses. There is an additional charge for processing, i.e., developing and printing your film, and it is at this stage that your film becomes either cheap, reasonably priced or expensive. No Separate Negative. 16mm. film is divided into two types— reversal and non-reversal. The latter, nonreversal, possesses a separate negative and positive just as your ordinary still ‘‘ snap’”’ has a negative from which is made a positive print. The former, reversal, has no separate negative as, by a process of development, the negative, when taken from your camera after exposure, is treated so as to become in itself a positive. Because of the simplicity of this operation, in addition to the fact that less material is used, one length of film only being necessary as against two lengths in the non-reversal process, it would appear to be cheaper to obtain and process reversal stock. If you purchase 1ooft. each of reversal and non-reversal stock, expose them and _ have them processed, the costs are identical. If Film is Spoilt. Suppose that, owing to an error in exposure (quite a common fault) a considerable portion of the film is spoilt. With reversal film you do not know of this until you have paid your processing charge and received back the completed positive. With non-reversal, however, the negative can be developed only, and on examining it the wasted portion can be cut away before a print is made for projection, thus showing a material saving on the total cost. Another great point in favour of nonreversal stock is the ease with which further copies may be obtained. When your first positive copy is scratched and worn out through use, any further number of perfect prints may be obtained from the original negative. If, however, reversal film has been used there is only one positive print and no separate negative. Unless you are prepared to go to the expense of having a St. Paul’s as it is and as seen in a city window—an original treatment of a rather hackneyed type of scene. separative negative made from the positive BEFORE USE, it will be impossible to obtain further really serviceable copies of what may be a valuable film. The reason for stressing the point that a negative should be made from the positive BEFORE USE is that, after projection, even though the film has gone through the projector only once or twice, scratches, dust marks and abrasions are bound to appear, and if the preparation of a negative is left until the positive has been used, all these markings are printed through, and are perpetuated on any further positives that may be made. Too many people realise this important fact when it is much too late to have it remedied, when a film which they prize is worn out and no further copies are obtainable. Accumulated Grain. Photographic emulsions are composed of various Bromide and Silver Salts held in suspension in gelatine and coated on a film of celluloid. If a portion of sensitised film is examined under a microscope it will be seen that these salts combine together so as to form a definite grain. This grain is easily perceived if a stop is made in projection and one frame of the film is shown on the screen. It will, therefore, be seen that when a positive print is made from a negative the resultant picture will show the accumulated grain of two emulsions. WHAT DO YOU THINK? We should be glad to receive your opinions | on the relative merits of reversal and non| reversal stock. While this would at first appear to be an argument in favour of reversal stock, it is not in fact the case, for while the first positive shows the grain of one emulsion only, any 29 further copies will show the grain of three —the original positive, the negative and the printed positive—as against two only for non-reversal film—the original negative and the positive print. A Great Saving. It should be remembered that this method of preparing a separate negative and positive is employed in the use of standard 35mm. film, where there is considerably greater enlargement in projection and any grain would be more readily noticed. A really great saving is effected by the facility for having the negative. developed only. Remember that even the best cameraman cannot always expose a spool so that there is no wastage after editing. How much more waste will there be when the exposures are made by one who is less experienced. With non-reversal film the negative may be edited so that a positive copy of the wanted portion alone may be obtained, thus avoiding paying for the printing of waste film. Getting a Good View-Point. It may be found better to have two cameras. working when the film is being taken so that a good view-point is obtained for all movements. This will necessitate a considerable wastage unless non-reversal film is used, as there will be a great amount of cutting to be done. There is this great additional advantage, titles may be spliced into the negative so that the positive print for projection comes out as one complete and unjoined whole, effecting considerable saving in wear and tear and lessening the possibilities of “jamming ’’ in the projector. It would, therefore, appear to be an established fact that the use of non-reversal substandard film lessens the cost of amateur cinematography. It remains for the user to demonstrate this for himself.