AND TREES 



43 



hole" appearance of the background; and if there is 

 wind going, we have trouble on our hands and probably 

 spoiled plates in our holders ! Now, with a 7-inch lens, 

 the background will be soft without painful sharpness, 

 and also subdued in size, at an opening of /122, taking 

 not over one-third the exposure of the other lens. 



For field work, isochromatic plates are almost an abso' 

 lute necessity, because there is so much yellow to be 

 considered. It will also tend to better results, and render 

 one more independent of the directigripf, the light, if the 

 plates are "backed," to prevent halation, unless a double- 

 coated orthochromatic plate, such as the Orthonon, be 

 used for the same purpose. 



I have so much 'enjoyed a formula for 

 Plate Backing, backing (picked up in one of the annuals) 

 which works most perfectly, and is free 

 from the messiness and pinhole certainties of the caramel 

 and other smear compositions, that I append it in full. 

 Shake ^ oz. powdered ':astile soap in 10 oz. 95° alcohol, 

 repeatedly, until partly or fully dissolved. (It is better to 

 keep this on hand a week or more ahead, shaking the 

 bottle when you see it. The solution is ready or use 

 when half the soap is taken up. ) Filter off 2 oz. of the 

 soap solution, and add to it 10 grains of erythrosin and 

 ro grains of aurin, which will dissolve promptly. Paint 

 the backs of the plates with this, and allow to dry. Use 

 a very faint red light arid much care in applying the 

 coating, which is colorless in red light, but will be very 

 apparent on development if it gets on the face ! My plan 

 is to coat the pair of plates just as it is taken from the 

 ■package, without exposing the face at all. 



Wipe off the backing with a wad of wet cotton before 



development, and rinse the whole plate carefully in a 



'ray of clean water — all in very faint red light, of course. 



. A bichromate cell ray-filter, with the 



pMj I per cent, solution as recommended, 



Ray-Filter, ^jjj prepare .he operator for the shades 

 of blue and lavender he may find, and will also enable 

 him to get enchanting white clouds in a blue sky 

 for his background occasionally. There are also now 

 available good ray-filters of stained gelatine. One should 

 be chosen of light or medium tone. 



For this outdoor work, weather condi- 

 Weattier ^^^^^ ^^^^ ^^ considered. It is very hard 



Conditions. ^^ gg^ ^^y satisfactory pictures in bright 

 sunlight, and it is best not to start for a photographic 

 jaunt on a day promising an unclouded sky. If, however, 

 the work must be done on such a day— and very many of 



