This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Distortion Of Wide-Angle Lenses. The focal-length of the lens is also of vital importance, for a wide-angle lens invariably gives a violent perspective and apparent distortion and does not produce a true rendering of the subject. A clear demonstration of this principle is shown in Figures A and B of Illustration No. 51. Figure A was made with a lens of good focal-length, it being equal to twice the longest side of the plate, and thus its angle is about 40 degrees. Figure B was made with a wide-angle lens, which had an angle of about 90 degrees.
207. On studying Figure B it will be noticed that the table of this machine appears tipped, and although a very-small stop was used, the drill head and the portion of the table nearest the camera are out of focus. With the exception of blocking out the backgrounds no hand-work has been done on either of these illustrations, and they, therefore, show exactly the advantages of a lens of normal angle over one of wide angle, the former giving a perfect rendering of the subject, while with the latter a very misleading impression is produced.
Preparing The Subject. All classes of machinery will not require special preparation for photographing; generally this is necessary only when it is desired to show the article in its new state to best advantage. Even then it is sometimes advisable to have some parts specially prepared so that they will photograph to the best advantage.
Parts To Be Specially Prepared. Usually the frame-work of all classes of machinery is painted a deep green, which photographs very black. Where deep green is not used a jet black is substituted, either of which reproduces very dull and without detail. Metal, even though painted, will reflect light and cause halation, which will be very difficult to avoid even though non-halation plates are employed. It is, therefore, advisable to paint the machinery or tools with some paint which will give a good matte surface with detail in the photographic print. This paint should be such that it may be easily removed after the exposure has been made. These surfaces are usually gone over and prepared in advance by the manufacturer, with a coat of dull lead color prepared with turpentine (not oil) that is readily removed after the picture is made. The nickel or bright parts may be dulled with putty, by rolling a ball of the putty over the surface within the angle of view of the camera. Other portions in shadow which require more detail may also be treated with the putty.
211. Usually, manufacturers in preparing machinery for photographing, which photographs are to be used for catalog and advertising purposes, paint and prepare it especially for this purpose, using neutral colors throughout, thus supplying detail. Where this method is unknown to the manufacturer, and such work is being prepared for photographing, the photographer should acquaint the former with the methods employed, thus enabling him to produce much superior results.
212. Machinery is usually photographed in the workshop, with the working machinery, belting, etc., surrounding it, requiring the blocking out on the negative of the entire surroundings, and a point of view should be chosen which will give a good, clear outline to the ends of the object. If this is impossible, a piece of white muslin or ordinary light-colored wrapping paper placed back of the ends of the object to be photographed will supply sufficient detail to enable you to trace the outline and block out the background.