AMATEUR PHOTOGRAPHY. 



Si 



necessary to add enough ealt to the solu- 

 tion to bring the hydrometer reading to 

 the standard made with the fresh chemi- 

 cals. In that way solutions will always 

 be of uniform strength, an important 

 point. 



By a per cent solution is meant the 

 number of parts, by weight, of a solid 

 contained in ioo parts, by volume, of a 

 solution. Consequently, to make, say, a 

 10 per cent, solution of potassium bro- 

 mide, dissolve 1 ounce of the salt in q 

 ounces of water and when completely dis- 

 solved add sufficient water to make the 10 

 ounces. 



Always use distilled water when obtain- 

 able. It may be had of wholesale drug 

 houses for 15 cents a gallon. If you can 

 not obtain it, boil the water an hour and 

 when cool filter through paper. 



Be exact in weighing and measuring. 

 Never allow yourself to fall into careless 

 habits in those respects, as the best re- 

 sults in photography are never obtained 

 without the most Careful attention to de- 

 tails. Most of the cheap blown glass 

 graduates sold by stock houses are inac- 

 curate. Get a tested one from a dealer 

 in chemical supplies. 



Get a good pair of scales and take good 

 care of them. They will repay the outlay 

 in results if carefully used. 



DEPTH OF LENSES. 



I have a Zeiss lens, number 15, series 

 VII a. When both combinations are used, 

 the focus is 11 inches. When the com- 

 binations are used separately, the back one 

 has a focus of 16^ inches and the front 

 one 23^ inches. In photographing a 

 bird's nest^ the lens did not give much 

 depth of focus. When the near side of the 

 nest was in focus, the far side was out of 

 focus. I also have a small rectilinear lens. 

 I could get the nest in better focus with 

 the $10 lens than I could with the $165 

 lens. This seems strange. Has a large 

 lens less depth of focus than a small one? 

 Has an anastigmat lens less depth than a 

 rectilinear? The high priced lens does not 

 seem much more rapid than the small 

 rectilinear. Does a large lens work 

 slower than a small one? 



I should like to know what to clean a 

 lens with. 



I am greatly interested in photography. 

 Your magazine affords me great pleasure, 

 especially the photo department. 



I would much rather get a good picture 

 of a bird than shoot it, although I am fond 

 of shooting. 



J. B. Pardoe, D. D. S., 



Bound Brook, N. J. 



ANSWER 



Lenses of longer focal length have 

 per se less depth of focus than shorter 



lenses, when both are used at the same 

 relative opening. When making pictures 

 of birds' nests, and in general when mak- 

 ing pictures which are nearly or equally as 

 large as the object, the depth of focus of 

 every lens is limited. Only by using small 

 stops can satisfactory results be obtained. 



A large lens is not necessarily slower 

 than a small one, but for equal depth of 

 focus the larger lens must be stopped 

 down more, and thereby it will, of course, 

 become slower. 



Depth of focus depends on the focal 

 length and relative aperture of a lens, and 

 is entirely independent of astigmatic or 

 aplanatic qualities. 



Clean a lens with any soft material con- 

 taining no grit; but never polish a lens be- 

 fore first removing all specks of dust by 

 means of a soft brush, preferably camel's 

 hair. 



There is not the slightest doubt that 

 from a purely optical point of view the 

 $165 lens is in every respect far superior 

 to the $10 lens. The failure of the more 

 expensive lens to produce as satisfactory 

 work as the $10 lens is not be- 

 cause the former is not better in 

 itself, but only because it was not 

 so suitable a lens for the work in 

 hand. By selecting the proper lens from 

 the series in which *he $165 lens belongs 

 results should be obtained which would 

 completely eclipse the pictures of the $10 

 lens. — Editor. 



ILLUMINATED LABELS. 

 I greatly admire Recreation and the 

 good work you are doing to exterminate 

 the game hog. I look forward with anx- 

 iety for each issue. I am especially in- 

 terested in the amateur photography de- 

 partment. In the February number Mr. 

 Harry Knowles says an invention by 

 which labels on bottles could be read 

 easily in the dark room would be a boon 

 to photographers. The following prepara- 

 tion for labeling bottles has served me 

 well: 



Phosphorus y 2 dram. 



Oil of cinnamon y 2 ounce. 



Put in vial, cork tightly and apply heat 

 slowly until mixed. Writing or lettering 

 done with this mixture will have the ap- 

 pearance of fire and can be easily read in 

 the dark room. 



Can someone tell me through Recrea- 

 tion a formula for a transparent paste for 

 mounting photos with the face against the; 

 glass? 



C. Hebbard, Detroit, Mich. 



ANSWER 



There are 2 methods of mounting prints, 

 facing the glass. One is to mix thorough- 

 ly the white of an egg in a pint of water, 

 filter, and coat as many glasses as neces- 



