We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
250 THE ADVANCE OF PHOTOGRAPHY
the lens if the focussing screen is arranged as described. It need hardly be added that the lens itself should contain no trace of coloration.
The exposure required by these plates is long compared with that for ordinary plates ; thus under the best conditions, with a lens working at //8, they require about onesecond. On this account the camera must have a firm support.
Full particulars as to the speed of the plates, and also full working directions, are supplied with the plates.
The new method of development as recommended by Lumiere is as follows : —
Make up the stock solution used for developing, by dissolving 15 gms. of Quinomet in 1000 c.c. of warm water, add to this 100 gms. of anhydrous sodium sulphite, then 32 c.c. of ammonium hydrate of specific gravity 0*920 ; lastly, add 6 gms. of potassium bromide. This developer can be bought ready mixed in a concentrated form, when all that is necessary is to use one ounce of developer to 4 ounces of water.
This quantity of developer can be used for one J-plate. If the exposure is correct, develop for just two and a half minutes, the temperature of the bath being about 60° F. For reversing the image the stock solution is composed of 1000 c.c. of water, 2 gms. of permanganate of potash, and 10 c.c. of sulphuric acid.
When the negative is removed from the developer it should first of all be rinsed in running water and then placed in about 3 ounces of the reversing solution. After it has been placed in this it should be taken into daylight. The plate gradually becomes transparent and the colours will be visible. The plate should be quite transparent at the end of three or four minutes, when it should be removed from the bath and washed in running water for about half a minute. After this it is necessary to redevelop the plate. This may be done in full daylight, making use for this