Q--I have inadvertently taken some pictures in artificial light using daylight film. What will happen and can I do anything about it?
A--The result will be a strong orange cast, and the only thing you can do is to make prints or duplicate transparencies from them and use heavy blue filtration to offset some of the effects of the cast. You will have to use a filtration equivalent to the 80B Tungsten-to-daylight conversion filter.
Q--Is there a correct way to hold a camera? I have been told there is.
A--Yes, the camera should be firmly supported, is comfortable, and its controls can be reached easily without disrupting the grip. This will obviously depend to a larger degree on individual cameras and individual people.
Q--How is a fish-eye lens different from an ordinary wide-angle lens?
A--First, it has a much wider angle of view than even an extreme wide-angle of conventional design. A true fish-eye lens has an angle of view of 180 degrees. In addition, with a fish-eye lens, straight lines curve outward the further they are from the center of the image, and finally a true fish-eye lens produces a circular image within the film frame.
Q--Should a lens need overhauling and do lenses need to be tested periodically?
A--There is no reason why a lens should need any attention unless it is dropped or damaged, although the focusing ring may need tightening if it gets heavy use. The iris mechanism can sometimes become faulty and it is a good idea to check this occasionally. A lens with a leaf shutter should be checked for accuracy and cleaned periodically.
Q--It is amazing to me how a piece of acetate film can produce color. How are the color images introduced to the film?
A--Color film consists of three separate emulsions coated on top of each other, each made sensitive to one particular band of the spectrum, red, green and blue. These are in turn coupled to the appropriate dye color, which is the opposite or negative of the original color: red is recorded as a mixture of a green and blue called cyan, green as a mixture of red and blue called magenta, and blue as a mixture of red and green which is yellow. On processing, the image represents a negative version of the subject in both colors and tones. This is then printed on a similar emulsion on an opaque base to produce a color print in the original tones and colors.
Ed Harn is general manager of Standard Photo Supply. Questions of general interest about photography can be addressed to On Cameras, Chicago Tribune, 435 N. Michigan Ave., Chicago, Ill. 60611. Unpublished questions cannot be replied to individually.