The Abc Of Photography PDF Download

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1882 edition. Excerpt: ....Pyro... 1 to 2 grains according to subject Ammonia 2 minims Bromide H minims To each ounce of developer. This is a very slow developer, and even if the plate be much over-exposed, the image will not appear for some time. A little experiment will enable the photographer to know whether the plate has been over-exposed, correctly exposed, or under-exposed by the length of time which elapses between the time of pouring on the deveioper and the appearance of the image. If the exposure appear to be correct, let one minim of ammonia be added to bring the strength up to that recommended. If it appear to be over-exposed, let development proceed, or even add more bromide. If the image be very long of appearing, showing that there has been under-exposure, ammonia may be added to any amount short of that which will produce fog. Good plates should stand ten minims of ammonia with one and a-half grains of bromide. The greater the quantity of bromide, the larger the amount of ammonia that may be used; but the quantity of ammonia permissible is not proportionate to the bromide used. Doubling the quantity of bromide will not permit double the quantity of ammonia to be added. With the ferrous oxalate developer, under-exposure and over-exposure may be corrected to a certain extent, but not so greatly as with the alkaline developer. The developer may be accelerated by the addition of any quantity up to ten minims of a 1 per eent. solution of hyposulphite of soda to each ounce of developer, or retarded by the increase of bromide. It is commonly said that there is difficulty with gelatine plates in getting a sufficiently dense image. Such a difficulty results from ignorance of the principles of development. The secret of getting "plucky" negatives...