lantern slide technics

LANTERN SLIDE TECHNICS I. SOURCE, PRINTING, AND MOUNTING INEXPENSIVE 2" X 2" SLIDES

HUBERT N. ALYEA

Princeton University, Princeton, New Jersey

A LECTURE which is illustrated with out-dated lantern slides cannot be spirited. To replace numbers of slides each year, and still remain

within the budget, a t Princeton we have completely replaced our 31/4" X 4" standard lantern slide collection with 2'' X 2'' slides. These slides are non-break- able; the long axis of the picture may be horizontal or vertical to take full advantage of the subject; projectors are inexpensive and portable; cost of materials for each black-and-white slide, four cents, is so negli- gible that separate sets of slides may be kept by in- dividual lecturers in the same department; and finally, colored slides, a t eighteen cents apiece, make it possible to photograph colored charts, rock specimens, colored precipitates, and so forth.

This article will describe a simple apparatus for copying diagrams, tables, and pictures from texts; and for copying standard 3'/nU X 4" slides onto 35-mm. film, a t a cost of a fraction of a cent per picture. The photographic technic is so simple that an amateur can finish many hundreds of slides in a week.

Source of Pictures.-Rolls of pictures, suitable for mounting in 2" X 2" slides may be obtained from many sources. Among these are: American Microfilms, 6912 Hollywood Boulevard, Hollywood, California; Biblio- film Service of American Documentation Institute, c/o U. S. Department of Agriculture Library, Wash- ington, D. C.; Detroit Film Laboratories, 66 Sibley Street, Detroit, Michigan; Holbrook Microfilms, 33 West 60th Street, New York City; Record Registry Corporation, 912 West Washington Street, Indianapolis, Indiana; Society for Visual Education, 327 South LaSalle Street, Chicago, Illinois; University Micro- films, 313 North First Street, Ann Arbor, Michigan; U. S. Department of Agriculture through Dewey and Dewey, Kenosha, Wisconsin; Visual Sciences, Suffern, New York. In addition, many libraries are now equipped to make copies of source material.

Secondly, ordinary 35-mm. motion picture frames, half the size of Leica frames, may be mounted in 2" X 2' slides.

Colored Pictures from Fortune.-The author has photographed all of the superb colored illustrations on chemical subjects in the magazine Fortune, but finds that only the following photograph well in color. Colored maps, gold, and silver reproduced poorly. Permission has been obtained from the Editor of Fortune and other owners to copy these pictures. The list which follows gives the volume, month, page, and title of the

308

picture. Volume 1: F-91, New York at night. Vol- ume 2: Jy-59, early locomotive; Au-39, dyed shower curtains, include legend; 5-74, tiled Roman bath; 0-78, Frasch process, include legend; 0-82, sulfur cooling; 0-83, Frasch water reservoir; D-74 Princeton chapel window; D-78, souse window. Volume 3: Ap-43, polar- ized light; Ap-59, Dow brine, include legend; Ap-62, Dow caustic, include legend; My-84, U. S. iron map. Volume 4: Jy-55, map U. S. coal; D-65, emeralds. Volume 6: Au-clover, include legend. Volume 8: Jy-95, iron sheet mill; S-23, New York City; 5-104, iron ore loader; 0-108, steel ladler; D-123, iron smelter. Volume 9: F-62, lastex. Volume 10: Au-65, Ni-smelter; N-100, Hg-turbine. Volume 12: S-69, alcoholic sot; S-76, shopgirl's lunch; 0-60, glass bricks; D-146, steel rolling mill. Volume 13: Jan-79, beer cans; Mr-70-71-74-75, plastics; My-87, food calories. Volume 14: 0-29, zopaque, Ti02; 0-123, blast furnace; N-109, photoelasticity; N-112, dyes; D-82, copper town. Volume 15: Jan-67, light buoy; Jan-70, copper mine; Jan-75, copper rod mill; My-106, plastics. Volume 16: Jy-119, iron ore strip mine; Au-50, Kraft paper machine; S-192, 011 stills; 0-30, styrene; 0-131, bo- logna; N-117, colored clothes; N-128, painting restoration; N-130, painting restoration; N-141, circulatory system. Volume 17: F-21, iodine; F-99, grinding wood; My-21, thiokol; My-34, aeroplane; Jn-24, cellophane; Jn-108, plastics; Jn-56, mine headframe. Volume 18: 5-75, cellophane through polaroid.

Printing.-Negatives may be obtained from many libraries, or from the copying apparatus to be described. Positives are made from these as follows.

Exposing the Negative.-Two plates 1" X 3OW, cut from automobile windshield glass are taped together along one side. Inside, the bottom glass is painted black to prevent reflection of light. Work under red light. Place a three-foot length of positive 35-mm. film emulsion side up on the black glass. Over this place the negative, of which the positive copy is to be made, emulsion side down. The two films are caught between the glasses as between the covers of a book, and may be aligned by turning the glasses on edge and tapping. Turn on a 15-watt ceiling light for the count of 5 to 15, depending upon the density of the negative. The positive film is now exposed, and ready for developing.

Photographic Solutions.-A developer giving high contrast, a t the sacrifice of grain size, is recommended

for general line work. The following solutions keep indefinitely.

Solution 1. (Similar to Stock Solution A, Eastman D-9 Pracess Developer)

. . . . . . . . . . . . . . . . . . . . . . . . . . Water. 2 liters . . . . . . . . . . . . . . . . . . . . . . . NaHSOa.. 50 grams

. . . . . . . . . . . . . . . . . . Hydroquinone.. 50 grams . . . . . . . . . . . . . . . . . . . . . . . . . . KBr.. 50 grams

Solution 2. (Similar to Stoek Solution B. Eastman D-9 Caustic) . . . . . . . . . . . . . . . . . . . . . . . . Water.. 2 liters

. . . . . . . . . . . . . . . . . . . . . . . . . NaOH 100grams

Solution 3. Bisulfate Hardener . . . . . . . . . . . . . . . . . . . . . . . . . Water.. 2 liters

. . . . . . . . . . . . . . . . . . . Chrom Alum.. 40 grams . . . . . . . . . . . . . . . . . . . . . . . NaHS08.. 40 grams

Solution 4. "Hypo"-Thiosulfate Fixer . . . . . . . . . . . . . . . . . . . . . . . . . . "Water 2 liten

Na~SaOr5Hx0. . . . . . . . . hypo pea or rice crystals. 30 grams

. . . . . . . . . . . . . Na.SOs, anhydrous.. 30 grams . . . . . . . . . . . . . . . . HC2HaOs, glacial. 30 cc.

. . . . . . . . . . . . . . . . . . . . . . . . . HaBO a . 15grams . . . . . . . . . . . . . . KAI(SO,)., 12H90.. 30 grams

*Warm half of the water to 50°C. and dissolve all of the hypo in it. Add the remaining water, followed by the other chemicals, taking care that each is dissolved before the next is added.

Solution 5. Quick Drier Ethyl alcohol (95 per cent.). . . . . . . . . . 900 cc. Methyl alcohol.. . . . . . . . . . . . . . . . . . . . 90 cc. Formaldehyde (40 per cent. formalin). 10 cc.

Solutions 1 and 2 once mixed must be used within a few minutes, and should not be used more than once; solution 3 may be used two or three times; and solutions 4 and 5 can be used repeatedly.

Procedure.-The film is developed in a stainless steel tank manufactured for 35-mm. film. Two strips of film each containing approximately thirty-five pictures may be developed simultaneously by threading them into the reel back-to-back, emulsion sides out. The reel must be loaded under a red light but subse- quent adding of the developer, hardening, washing, and fixing may be carried out in full daylight.

Cool all solutions to lS°C. in beakers immersed in ice. This is important. For brilliant results all developing,

washing, and fixing must be carried out a t 18.0 +

0.5"C. (1) Fill the tank containing the film, with water.

This moistens the film so it takes up developer evenly in the next step. Pour out the water. (2) Mix equal quantities of solutions 1 and 2 and pour the mixture immediately into the developing tank containing the film. (3) Exactly two and one-half minutes after the developer strikes the film, begin to empty the tank quickly. (4) Immediately refill the tank with solution 3, without stopping to flush out the developer. Solu- tion 3 arrests development, neutralizes the residual al- kali, and hardens the film surface. Leavein this hardener for threeminutes. (5) Wash twicewithwater. (6) Pour in fixing solution 4 and fix for ten minutes. (7) Finally wash in running water for a t least half an hour.

The negative may be dipped into solution 5, gently sponged to remove excess water, and dried in front of an electric heater in a few minutes. However, for the final positives it is better not to hasten matters, but to merely sponge the film, and hang i t up to dry without the use of alcohol or heat.

Mounting, Filing, Projecting.-Each frame in the positive is cut out, rubber-cemented between a labeled paper mat, and bound between 2" X 2" glass. These are best filed in a tray-type biological slide cabinet, where each picture may be seen without removing from the tray. This is preferable to filing upright, as in the usual slidebox.

Projectors of many kinds are available, ranging from $15 100-watt projectors, to $150 750-watt auditorium lanterns equipped with interchangeable lenses to accommodate both 2'' X 2" and 3'/4" X 4" slides.

Looking Ahead.-Exchange of 35-mm. negatives between schools, and weekly issuance of timely film- strips for use in general chemistry will be welcome lecture material. Use of fine-grain developers already provides artistic 2" X 2" slides with perfect definition. Smaller schools with limited budgets will find an im- mediate saving in their adoption. When larger in- stitutions awake to the possibilities of these slides and provide projectors for visiting lecturers, the old- fashioned lantern slide will he relegated to the past along with the horse and buggy.

11. AUTOFOCUSSING COPYING DEVICES

Apfiaratus for Copying Pictures.-Apparatus in Fig- ure 1 copies black-and-white or colored pictures from hooks and magazines. Its features are (1) a picture is automatically brought into focus in a few seconds, show- ing the picture exactly as it will appear in the slide, without the use of a ground-glass focussing device; (2) difference in thickness of books is taken care of; and (3) the curve near the binding of the book does not bring one side of the picture out of focus, as often occurs in copy work.

. . OPening a p ~ e o ~ i n g menlory fronl p h r o w orinling.

Mark in mask obovc lens [ o h r 12- on and line Timc no. i n inches calla, nrm. rollor) Leico d*owinpr Pictures

0 6Vn X 4V4 0 12-mm, collar. f:9 '/a rec. ' / z see. no imot lens

1 481, x 311. 1 I f:g v. see. ,/I see. 2 4'/. X 2v. 2 2 f:9 I/, see. a / . s c . 3 3 X 2 Lower rod 3 1:s '/. rec. 1 sec.

until head rests oo collar

The figure gives speafications for a Leica camera, bers 1, 2, and 3 and the brass masks tabulated on model E or F ; but by simply altering the screw which page 309. holds the camera and the position of the graduations The picture to be photographed is placed on the on the square tubing above it, the apparatus can be wooden table. The appropriate mask is selected, its used with any other 35-mm. camera such as the Con- square brass rod inserted in the hole, and the knurled tax or Argus. Items not shown in the specifications nut supporting the vertical optical bench is turned to follow. The screw which holds the Leica camera is lower the mask firmlv uDon the ~icture. If. for examnle.

not attached to the square rod, but to a side-plate jut- ting out from it. Permanently fixed so as to project two inches in from each side of the board, and fourteen inches above it, is a 100-watt bulb, shaded from the camera lens. Exposures stated in this article are for this 200-watt illumination. Leica owners will use a 12-mm. collar for all pictures, together with supplementary front lenses by Ernst Leitz Wetzlar num-

- * . . mask numbk 2 is selected, then screw- ing in supplementary front lens number 2 and elevating the camera to number 2 on the square supporting rod will bring everything that appears in the opening of the mask exactly into focus; and this will appear on the finished slide.

While extraneous printed matter appearing within the mask can be blocked out with 5 X 8 cards, we have found i t simplest to mask the final positive with black cellophane in its 2" X 2" paper mat. Use exposures indicated above. With colored film, such as Kodachrome A, exactly the same procedure is adopted. However, exposure times for colored film are so critical that it is advisable to take two frames of each picture, varying the exposure about three-fold, and discarding one of the finished frames.

Apparatus for Copying 2" X 2" from 3'/&" X 4" Slides.-A change from 31/4" X 4'' slides to the 2" X 2" size is inhibited in many univer- sities by their possession of a large library of the older type of slide. However, with the apparatus in Fig- ure 2 a collection of a thousand large slides can be duplicated as 2" X 2" slides within less than a week; and a t a total cost for materials of about forty dollars.

The lamp of an Agfa negative viewer (cost, two dollars) is replaced by a board canying a ring of eight Christmas-tree bulbs, the frosting of which has been wiped off with meth- anol. A ground-glass plate, and an opal-glass cover complete this source of even illumination. On top of this fits a wooden block, canying a 35-mm. camera a t a fixed distance above it.

To copya slide,merely placeitover the holein themooden block. switch S tunline on the bulbs. and cxmse at f .8 for - the count of ten. Develop seventy negatives a t a time, making positives, mounting and projecting as described above. (See Part I of this article.) If too much contrast results in developing, dilute the mixture of solutions 1 and 2with an equal volume of water, keeping everything else the same. Specifications given in the figure are for a

Leica model E or F, with a 22-mm. collar; but of course visiting lecturers, and the box base furnishes even with slight alterations any other camera may be used. illumination for mounting slides or viewing them in

The apparatus may be carried about the campus to the dark auditorium before projection.

111. AN AUTOMATIC SLIDE-CHANGER

With this apparatus the lecturer, by pressing a button on the lecture table, changes slides in the projection lantern a t the rear of the room. A good lecture is thereby spared upside-down slides, shouts to the

Ladern Slide Copying (\ttechm.nt

fop Leics Camem Scale m insher.

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assistant, or thumps for the next slide. The attach- ment is adaptable to either 3 ' / r W X 4" or 2" X 2' slides; and we have been using slide-changers for both types of slides for three years.

Pushing Mechanism.-Cogs inside an old Minneapo- lis-Honeywell furnace regulator, Type D, gear set 30 seconds, were reversed to speed up time for one revolution to six seconds. The motor is plugged in on 110 volts A.C. The button and cord from the lecturer's table is attached to two posts on the motor

casing. Momentary pressing of the button completes a 12-volt circuit which starts the motor. Depending on which of two contacts are used, the motor will make either a full or a half revolution.

Slide Holder.-The slides to be fed into the mechanism are stacked in rack A. For 2" X 2" slides the rack may be inclined; and a weight placed behind the slides will feed them into frame B. For 31/r" X 4" slides friction was found too great for a gravity feed, and

tension by rubber bands, more flexible than springs, was employed. The rack holds about twenty-five slides.

First Slide.-A long arm from the motor rests against the first slide in frame B; and when the motor turns, the slide is pushed over into frame C. Cis in the beam of the projector, so the slide appears on the screen.

Next Slide.-Meanwhile the motor has completed its revolution; the second slide has been pulled up from rack A into frame B, and the pushing plate is back in its original position but now resting against slide number two. Again the lecturer pushes the button; the motor starts and the arm pushes slides from frames B and C into frames C and D, respectively. Slide number two is now in C and appears on the screen. Slide number one has reached D and is pushed down the chute into the box by means of a little pusher in D, actuated by an extension of the slide-pusher.

Dual Control.-If many slides are to be shown, the projector light is left on throughout the lecture. In that case, the button and cord from the lecture table is attached so as to obtain the motion described above.

However, if only a few slides are to be used, the cord is press pushes slide number two into frame C and turns attached to the posts which give half a revolution. on the light, and so on. Then an eccentric wheel, placed on the motor axis, is No attempt has been made to give actual dimen- used to raise and lower a mercury-in-glass contact sions, since they will have to be adopted to each pro- tube, carrying the projector current. The first press jector and furnace regulator.' of the button turns on the light and shows slide number of equipment for making 2v 2p slides may be obtained one. The second press turns off the light. The third from Dr. Alyea.

lantern slide technics

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