193. Home-Made Ray Filters

Home-Made Ray Filters. If you desire to make your own orthochromatic screen, you will find the following experiment very interesting, as well as instructive. In gaslight take an ordinary lantern plate and fix it, in a solution of 4 ounces of hypo to one pint of water, for 10 minutes; then wash it for one hour and allow it to dry in a room free from dust. The plate must be dried in a vertical position or in a drying rack. This gives you a piece of glass which is colorless, and as it contains a transparent coating of gelatine you can stain it to any desired color by soaking it for the necessary time in a dye solution. The following solution we recommend: Napthol (yellow), 5 grains dissolved in 4 ounces of distilled water. The dye must be completely dissolved before the solution is used, and if you have a funnel and filter paper, filter it in the ordinary manner.

Illustration No. 27   See Paragraphs No. 186 190

Illustration No. 27 - See Paragraphs No. 186-190.

Illustration No. 28   See Paragraph No. 191 B. & L Bichromate of Potash Ray Filters

Illustration No. 28 - See Paragraph No. 191 "B. & L" Bichromate of Potash Ray Filters.

Illustration No. 29. Attaching Home Made Screen on Lens See Paragraph No. 195

Illustration No. 29. Attaching Home-Made Screen on Lens See Paragraph No. 195.

194. After the solution has been carefully filtered and all sediment removed, take a clean dish and lay in it the fixed-out lantern plate; then, with an even "sweep," pour over it the yellow solution, being very careful to avoid any air bubbles. In about ten minutes time the gelatine film will have become colored to a pale lemon yellow. You can now rinse it under the tap and set it up in a perpendicular position to dry. It is advisable to stain two or three glasses in this manner to varying depths of yellow. The longer the glass remains in the solution the deeper the color.

195. How To Attach Home-Made Screen

How To Attach Home-Made Screen. A piece of wire long enough to form a loop over the lens barrel should be secured and be bent in the manner shown in Illustration No. 29.

196. Disadvantages Of Color Corrected Materials

Disadvantages Of Color Corrected Materials. In landscape work the use of orthochromatic plates causes increased length of exposure. The color sensitive plate used without a filter is, in some instances, very little better than an ordinary plate. It, however, is of value (even used without a filter) when the light is yellow, or when there is an almost complete absence of blue in the subject and a predominating amount of yellow. With many subjects the greater length of exposure is impossible, and in most cases it is a disadvantage. Of course an exposure of a couple of seconds is not a long one for a landscape; but, you will find it much more advisable, in many cases, to use the ordinary plate and secure a quick exposure, rather than run the risk of a total loss of the subject through "blurring" caused by movement of trees, etc.

197. The increase of exposure is also a serious matter for the photographer using a hand camera, and in many cases it is almost an impossibility to use a ray filter of any depth when the camera is held in the hand, even under the most favorable conditions. For serious landscape work it is necessary, however, to employ a tripod, and this difficulty, therefore, will be overcome.

198. As color corrected plates are sensitive to orange, yellow and similar shades, there is considerable danger of fogging the plates during the process of loading the plate holders and development. Until you have learned how sensitive an ordinary quick plate really is, and have become accustomed to the precautions necessary in handling them, it is much better to leave the orthochromatic plate alone. (See Vol. II. - Paragraphs 605, 641, 713, 810.)