CONCLUDING REMARKS ON REDUCTION.
There is rather more risk in the process of reduction than in that of intensification, and greater care is therefore necessary on the part of thd operator. If a negative is over-intensified, it can, as a rule, he brought back to its former condition ; but a negative which has been reduced too much is practically. spoilt. It may still be intensified, it is true, but the original beauty of gradation cannot be restored. It is for this reason, probably, that many workers will have nothing to do with re duction ; and would rather put up with negatives which take a week to print, or which are decidedly chalky and hard, than run the gauntlet of possible dangers. This, however, is going to the other extreme. With ordinary care, and a proper consider ation of the effect desired and the correct method of obtaining it, almost any difficulty may be successfully overcome. Finally it must be understood that the choice of a reducer must be governed by the character of the existing negative, and the contrast and gradation desired in the resultant print. There are four distinct types of negative which may require re clueing : (a) Those correctly exposed and, developed but with shadows fogged. (b) Those correctly exposed but developed too far, giving too brilliant contrast. (c) Those correctly developed but under-ex posed, resulting in a hard effect ; the nega tive having dense high lights and want ing in detail. (d) Those over-exposed and over-developed. Obviously a method which would be suitable for one of these would be unsuitable for another, for whereas in a and d the contrasts need increasing, in b and c the contrasts need decreasing.
In a and d the shadows need reducing most ; in c the lights need reducing most ; whilst in b the contrasts will be sufficiently reduced by a reduction all over the nega tive in the same proportion to the deposits in each part. For suppose the densities of lights, shadows and half tones of a nega tive to be represented by figures 2-4-6, and a density equal to 1 be subtracted, then they become 1-3-5 ; so that, al though an equal amount has been taken from each, the shadows have really suffered most as they had least to spare ; and consequently, the half tones are now three times as dense and high lights five times, instead of twice and three times as before. It is probably due to a misun derstanding on this point which has led to such contradictory statements as to the effect of various reducers. Photomicro graphs of deposits before and after reduc tion seem to indicate that the lower par ticles are first attacked by the ammonium persulphate and consequently most re duced, whilst a comparison of results of the action of various reducers upon a graduated set of deposits of known den sity is exceedingly interesting and an easy experiment to perform. A thorough soak ing of the negative before the reducer is poured over tends to a more even reduc tion in the case of ammonium persulphate. Negatives answering to the description of a should be reduced by the ferricyanide and hypo. bath ; those like b and c in ammonium persulphate and those like d • in ferric chloride or either of the other reducers described.