Читать книгу A Practical Manual of the Collodion Process. Giving in Detail a Method For Producing Positive and Negative Pictures on Glass and Paper онлайн

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Babtista Porta, when he saw for the first time, on the walls of his dark chamber, the images of external nature, pictured by a sunbeam which found its way through only a small hole, little thought of the importance which would be attached to the instrument he was, from this cause, led to invent. The camera obscura of this Italian philosopher remained as a mere scientific toy for years, and it was not until Daguerre's discovery that its true value was estimated. It now plays a very important part in giving employment to at least ten thousand persons in this country alone.

It is of the utmost importance, in selecting a set of apparatus, to secure a good camera; for without such no one can obtain fine pictures. In testing it, see that it gives the pupil of the eye and lineaments of the features sharp and distinct; and that the whole image on the ground glass has a fine pearly hue. Look also to the field, and observe that the focus is good at the centre and extreme edges of the ground glass, at the same time. A poor camera generally gives a misty image, with the lights and shades apparently running together. The best American cameras are fully equal to those imported, while they cost much less; but there are great numbers sold which are not worth using.