r AMATEUR PHOTOGRAPHY. 



409 



didn't know what was the matter. She 

 had habitually and prodigiously over ex- 

 posed. I* told her so, and advised her to 

 use a Wager Exposure Scale. She has 

 obtained some of the first good negatives 

 of her life within the last 3 weeks. 



Speaking of over exposure, I find noted 

 in my book the following, from Photo- 

 Beacon: "For great over exposure, soak 

 plate 5 minutes before development in 2 

 per cent, solution of tartar emetic and use 

 developer strong in the reducing agent 

 and bromide." You will get a good con- 

 trasting negative. I exposed a plate 2 

 minutes (normal exposure 2 seconds), and 

 succeeded as above. 



A word about intensification. Some of 

 us have never realized, until we have seen 

 or tried, how much many negatives may 

 be benefited by this simple process. Soak 

 until well bleached in bichloride of mer- 

 cury, 60 gr. ; bromide potassium, 60 gr. ; 

 water, 6 l / 2 oz. Wash thoroughly; then 

 blacken in a solution of sodium sulphite 

 for moderate intensifying, or in fairly 

 strong ammonia water for greater effect, 

 and wash. 



One more suggestion, for landscape 

 work. Get a dozen medium speed iso- 

 chromatic plates and a ray filter. Use 

 them carefully and see if you aren't glad 

 you have them. Develop with not too 

 strong light. Have ready a tuft of cotton 

 soaked with 10 per cent, solution of bro- 

 mide. When the sky and clouds are at all 

 clearly defined, go over them with the bro- 

 mide, and put back in the developer. Re- 

 peat if you find they are getting too dense 

 before the other portions are done, and 

 you will have a better landscape negative 

 than you ever had before. 



By all means use the fixing bath given 

 in the Wager book. Have the tempera- 

 ture of your solutions right. If you have 

 some new ideas or suggestions, let's have 

 them. We will all thank you. 



FOGS AND FRILLS. 



There is undoubtedly something about 

 fresh varnish that will fog plates. When 

 using a new plate holder just from the 

 factory, one not infrequently comes across 

 a most unexpected case of fog, and, while 

 certain it is due to the plate holder, can 

 not find a leak. It has been proved that 

 plate holders fresh from the factory will do 

 this. One has only to shut a plate in one 

 over night and then develop it alongside of 

 another plate out of the same box to sat- 

 isfy himself that this is a fact. Something 

 in the vapor of fresh varnish does the dam- 

 age, so it is well to draw the slides and 

 give all new holders a good airing before 

 use. A little thing like this, if not under- 

 stood, is likely to produce a strained feel- 

 ing between customer and dealer, and as 



the ^eaier has enough troubles of his own 

 without any more, I advise him to air all 

 new holders ere he sells them. It's easier 

 to do than to stand a lot of abuse from a 

 disappointed customer, have the holder re- 

 turned, and have to waste time looking for 

 a leak that does not exist. 



Thanks to formaldehyde I have not had 

 a frill or a softening of emulsion all the 

 past hot summer. I've worked, much 

 against my inclination, in a temperature of 

 100 to 106 with no ice in the solutions, and 

 my prints still came out safe. This is due 

 to a few drops of formaldehyde in the de- 

 veloper or toner. Gelatine can't melt after 

 it has been treated with this invaluable 

 chemical ; that is, it can't, under any cir- 

 cumstances likely to occur in photography, 

 and if for no other reason than that, every- 

 one should have a bottle of it on hand. 

 As a preservative of starch paste or other 

 vegetable compounds likely to spoil, a few 

 drops of a 40 per cent, solution of formal- 

 dehyde is most efficacious and yet harmless 

 to the prints. — E. W. Newcomb in the 

 Photo-American. 



DEFINITION OF SPEED. 



What is meant by the speed of a lens 

 being F. 6 or F. 12? Should a Zeiss Series 

 II and a Zeiss Series V have the same 

 speed when working with stops marked 

 F. 18? Why is a wide angle lens slower 

 than a narrow angle lens? Why is the 

 angle of a lens increased by diminishing 

 the size of the stop? 



S. R. Cates, M.D., Abilene, Tex. 



ANSWER. 



By the speed of a lens is meant the rela- 

 tive quantities of light which the different 

 diaphragm openings allow to pass in a 

 given time. A lens whose opening is 

 F -f- 6 would work 4 imes faster than a 

 lens whose opening is F ■—• 12, since the 

 quantity of light passing through the dia- 

 phragm varies as the square of the diame- 

 ter. If the U. S. numbers were 6 and 12, 

 respectively, the lens would work twice as 

 fast with U. S. 6 as with U. S. 12. 



The Zeiss Series II should have the same 

 speed as the Zeiss Series V when worked 

 with stops marked F. 18, if the focus were 

 the same in both; but I believe it is not. 



A wide angle lens is slower than a nar- 

 row angle lens because the aperture is 

 smaller. 



In "Modern Lenses" you will find full 

 information in regard to increasing the 

 angle of the lenses by diminishing the size 

 of the stop. — Editor. 



REMEDY FOR SPOTS. 

 What makes plates spot when set up 

 to dry? There will sometimes be spots 

 from the size of a pin point to 1-16 inch 



