The production of a photograph is governed by natural laws, and a definite effect must result from a definite cause. The same cause, under the same conditions, always produces the same effect. The law which governs the action of light upon the sensitive plate teaches us that only a limited range of such action is available in photography if truthful representation be demanded, and hence the necessity of accuracy in exposure...
I earnestly hope that this little work may be the means of inducing some amateur photographers to take up the scientific method, and I feel very confident in assuring any who may do so that they will discover a new field of unexpected pleasure in the pursuit of photography.