Johnson, George Lindsay, 1854- · New York, E. P. Dutton and Co. · leaf 185
en in colour and have no bubbles or flaws, as shadows of these would be reproduced in the image. It is always advisable to focus the image through one of the filters, owing to the shift in the position of the image produced by the filter, considered as a plate of glass and quite apart from its… … there is no shift of the image Fig. 23. or alteration of focus unless the object is near. The second effect of a plate of glass placed behind the lens is to produce a slight alteration
Color photography
Internet Archive · Getty Research Institute · Public domain (published before 1931). Free to use for anything.
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