The science and practice of photography : an elementary textbook on the scientific theory and a laboratory manual (1920)
Roebuck, John R. (John Ransom), 1876-1965 · New York ; London : D. Appleton and company · leaf 196
i66 PHOTOGRAPHY as it occurs but where there is any choice in the matter it will always improve the definition to have the objects as near together as possible. The actual amount of blurring which the eye will not detect will be fairly constant, that is, the image of a point … Fig. 42. can be widened out into a circle of a definite size before we object to it as being blurred. It will be evident that with a short focus lens the difference in the object distances which will produce this al- lowable blurring will be much greater than with a longer focus lens. For this…
Photography
Internet Archive · Getty Research Institute · Public domain (published before 1931). Free to use for anything.
![An illustration from Colour vision [electronic resource] : being the Tyndall lectures delivered in 1894 at the Royal Institution (1895)](https://img.insideoutlibrary.com/img/200/ia-b21285913-117-0.webp)
