WHAT IS A NEGATIVE? 



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What is a negative ? The picture is taken upon a glass 

 plate or celluloid film covered with a coating of gelatine 

 and silver bromide, or some other silver salt. Light falling 

 on this silver compound causes a change in its composition, 



Which of these two pictures is the negative ? Which the positive ? 



so that when it is put into a developer containing certain 

 chemicals which complete the change and make it perma- 

 nent, we have a negative as a result. This negative gives 

 the light values in black and white, but just the opposite of 

 what they were in the objects photographed and just the op- 

 posite of what we have in a positive, or completed print. A 

 study of the accompanying figure will show this very clearly. 



