The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

Home | About | Photography | Contact






Enlarging
full power at once, and place it close up to the condenser, and then be surprised if your condenser cracks. Warm everything gradually by having your light low and some distance from the condenser, and gradually reduce the distance and increase the light. It will be obvious to the merest tyro in enlarging that the farther the lens is from the sensitive paper the larger the image, and vice versa; and also that there are certain distances which bear a certain relation one to the other, so that when enlarging, the distance between the negative and lens and lens and sensitive surface bear a strict relation to one another. The approximate distance between the negative and lens and lens and paper may be found from the following formula : -
Or to the non-mathematic mind we will put it in another way. To find the distance between the lens and sensitive surface, add one to the number of times (linear measurement) the negative is to be enlarged, and multiply by the focus of the lens. To find the distance between the lens and negative, divide the product of the above calculation, or the distance between the lens and sensitive surface, by the number of times of enlargement, and the quotient will be the distance between negative and lens. For example, it is required to enlarge a quarter-plate negative to 16x12 with a 6-inch lens, enlarged to 16 x 12 =4. times (linear). The distance will be then approximately (4+1) x 6 = 30 inches, between lens and sensitive surface. To find the distance between lens and negative To save trouble, however, there are well-known tables which have been calculated for enlargements with lenses of varying foci, and the Table of Enlargement or Reduction, given on the next page, is based on the principles already explained, and is convenient for ready reference. The dis-tances given in the tables will be found to be approximately correct ; but in all cases accurate focussing should be obtained
266