Article: 19390701053

Title: Questions & Answers

Questions & Answers
Popular Photography
H. W., Owen, Wis. I have a camera that uses 35 mm film. Is it possible to expose several frames, remove the film, cut off the exposed section for immediate development, then reload the unexposed film into the camera? I would expect to waste several frames in so doing.

Questions & Answers

H. W., Owen, Wis. I have a camera that uses 35 mm film. Is it possible to expose several frames, remove the film, cut off the exposed section for immediate development, then reload the unexposed film into the camera? I would expect to waste several frames in so doing.

ANSWER: This procedure is not only pos-

sible but is employed by many 3 5 mm users. Total darkness is required while you reload the camera, cut off the exposed film, and place the latter in your developing tank or some other light-tight receptacle. If you have frequent use for short strips of film, why not load empty cartridges with bulk film in the approximate lengths you wish, thus saving time and expense?

C. B. B., Northfield, Minn. How much will light intensity vary from early morning to late afternoon?

ANSWER: Since lighting conditions are subject to great variations your question cannot be answered in great detail here. Light is most intense around noon, when the sun’s rays come closest to being sit right angles to the earth. At sunrise and sunset the rays reach us at an extremely oblique angle, hence must penetrate a far greater portion of the earth’s atmosphere. This reduces the photographic usefulness of the light to a great degree. Long practice is required before the human eye may be trusted to estimate the intensity of early morning and late afternoon sunlight. The tendency is to credit this type of light with too much actinic value, and underexposure commonly results.

W. W., Chicago, III. What is the principle used in the so-called "fixed focus" lenses with which many inexpensive still cameras are equipped?

ANSWER : Fixed focus or "universal” focus

is a theoretical impossibility, but with any lens there is a point beyond which objects have sufficient sharpness of definition to satisfy normal demands. The lenses used on cameras such as you mention are of comparatively short focal length, and the shorter the focal length of a lens the greater will be its proportionate depth of field. Thus it is possible to manufacture an amateur camera which renders ¡ill subjects in reasonably sharp focus beyond a point close to the lens.

H. J. O., Michigan City, Ind. Assume that I am taking a picture of a corral in which are a dozen head of cattle. The steer nearest my camera may be 10 ft. distant, while the one farthest away may be 100 ft. distant (this being the length of the corral). If possible I want the entire herd in fairly sharp focus. Shall I set the camera for 100 ft.?

ANSWER: NO, because depth of field always is greater beyond the point focused upon than between it and the lens. Thus, if your camera is focused upon a point 20 ft. distant, there w ill be more linear area in fairly sharp focus beyond that point than in front of it. In the instance you mention above, you probably will do well to stop down the ions and set the focusing scale between 10 and 50 feet.

B. H. Y., Philadelphia, Pa. For ordinary snapshots under normal outdoor lighting conditions how fast a lens is required?

ANSWER : Excellent outdoor pictures are

made with box cameras using film of average speed. The ƒ rating of the lenses in such cameras is usually between /14 and ƒ 10, the "instantaneous” shutter working at a speed between 1/25 and 1/60 second. With some of the newer ultra-rapid film emulsions you can get good pictures with such equipment under less favorable lighting conditions than formerly.

S. A. N., Detroit, Mich. Please tell me what a fog filter is and how it is used.

ANSWER: Properly speaking a fog filter is

not ¡i filter ¡it all, but is merely a special type of diffusion disc placed in front of the camera lens to produce the effect of fog in ¡i picture. If you are interested in taking pictures in such a manner as to penetrate fog you should study the use of red filters with infra-red film or plates.

D. M. McM., Sioux Falls, S. D. Some time ago in your column you stated that bubbles in a lens have

(Continued on page 109)

(Continued from page 64)

no effect upon the performance of the lens. It occurs to me that these bubbles will absorb some of the light entering the lens, and if this is so why wouldn't the bubbles show up as dark spots on the negative ?

ANSWER: Tt is true that a bubble in the

body of a lens will absorb an almost infinitesimal amount of light. The reason this does not cause a dark spot on the negative is that any such absorption is distributed over the whole image, each portion of a lens contributing equally to the forming of each point in the image.

D. J. R., Oakland, Calif. I am anxious to take some synchronized flash shots of my nephew who is about six weeks old. The baby’s mother is afraid the brilliant flash will injure his eyes. Is this true?

ANSWER: We have employed synchronized

flash in photographing our own youngster since he was eight hours old. with no deleterious effect ; and the doctor under whose care the child lias been advises us that there is no danger involved. Furthermore, we know of several specialists in child portraiture who employ this method constantly, claiming (with some reason) that the flash is far less trying on babies than injudicious use of bright floodlights would be. Do not take more than two or three flash pictures of the baby at a sitting, and be careful to keep the light at least S ft. from the child.

R. S. T., Des Moines, la. Pictures taken with my smal! reflex camera all seem to have a "washedout" appearance at the corners. This is annoying when I want to use the full negative area (6x6 cm), and I am wondering what could cause it. ANSWER: If the corners of the prints are

dark, you may be using a lens shade whose flare is insufficient for the camera, therebycutting the corners of the image. But from what yrou say it would seem that your camera lens simply is not of sufficient focal length to cover the negative completely-. This same effect maybe noted when you attempt to cover a full 2% x3 'A negative in your enlarger, using a 2" or 37' lens.

F. E. E., Watsonville, Calif. How do you make a sunken lens board for a 5 x 7 enlarger? I want to use a 3" lens.

ANSWER: You must devise some method

of mounting your 3" lens closer to the negative carrier than you would mount the average lens used with an enlarger of this size. This will require some experimentation. The "sunken” lens board you mention means a board mounted up inside the bellows of the enlarger so as to bring it close enough to the negative to focus the latter with a 3" lens.

A. G. A., Swissvale, Penna. I have a camera lens that was given me and I cannot tell just what type it is. It is marked as follows: "Century Camera Co., Bausch & Lomb lens, 4x5 Rapid Rectilinear."

ANSWER: The lens undoubtedly is a fairly'

old one. and was manufactured byBausch & Lomb for use with a Century' camera taking a 4x5" plate size. The focal length of the lens therefore probably is in the vicinity of 6". The Rapid Rectilinear lenses are pretty well corrected for spherical aberration but lack the color correction found in an anastigmat. The Century Camera Co. was absorbed many years ago by the Eastman Kodak Co.