We have thus arrived to the answer to the question, Can negatives be produced such as defined to be theoretically perfect ? And the answer is, They can be produced, but only by so carefully adjusting the time to the intensity of the light that the exposures may fall within that period of correct representation. No variations whatever in development will correct an under or over-exposure.
A rapid method of measuring the density of negatives is a desideratum not only for the scientific investigator but also for the practical photographer. In a paper published in the Journal of the Society of Chemical Industry we have shown that the speed of photographic plates can be ascertained by a very simple method, provided an instrument be at hand which rapidly, and with a sufficient degree of accuracy, measures the relative amounts of silver deposited on a plate by a series of different exposures.