Better duplicate transparencies

BETTER LORNE

DUPLICATE

E. MACLACHLAN,

TRANSPARENCIES

D.D.S.

Ottawa, Ontario, Canada PHOTOGRAPHY is playing an increasingly important part in clinic and lecture work and in patient education. Many of the professional man’s transparenciesused for these purposes are invaluable and often irreplaceable. It is of inestimable value to have duplicates of them. A simple do-it-yourself method will be described by which the original transparency can be not only duplicated but improved in the process without injury to the original. Photography is one field in which doing it yourself often yields better results than having someoneelse do it for you. Anyone who has a camera with a 50 mm. lens (approximately) plus a 105 mm. or 135 mm. lens with extension bellows or extension tubes and an electronic flash can produce excellent duplicates with a little practice and patience. Many dentists already have some or all of the necessary equipment. It is a simple, not a difficult, procedure. It is merely a matter of photographing a color transparency. With an electronic flash assembly, roentgenograms and black and white transparencies can be duplicated in a single operation. The camera is placed on a firm support. The transparency to be duplicated is firmly mounted between the camera and the electronic flash. The’ electronic flash makes it possible to have a constant light source (about l/1,000 second) closely approximating daylight in quality. When floodlights are used for duplication, they lack proper color balance, heat the transparency, are subject to voltage changes, and deteriorate with use. The focusing light source is an electric light bulb (nonglare type) placed temporarily behind the transparency to be duplicated. Much can be done, during the process of focusing, to crop off any undesirable area away from the center of interest or around the borders of the picture. (Clear plastic lip or cheek retractors are desirable in making the original pictures, since they show the natural tissue color and do prevent the disturbing, brilliant reflections that come from metallic instruments.) Compensation in the exposure must be made, because an extension tube or extension bellows increasesthe distance between the camera lens and the film and since the intensity of light varies inversely with the square of the distance. This is called “the exposure increase factor,” and it is supplied with every close-up lens table. It appears on the track of the extension bellows.

C

OLOR

CROPPING

AND

MAGNIFYING

Cropping a transparency magnifies the center of interest. This differs from straight duplication only in the length of the lens used (Figs. 1 and 2). The original Read before

the American

Denture

Society

in New York, 1170

N. Y.

;pre, ‘6”

BETTER

DUPLICATE

1171

TRANSPARENCIES

slide (Fig. 1) was mounted (as in Fig. 3) in a 2 inch by 2 inch opening in a IA inch plywood (flat black) mount approximately 8 inches wide and 12 inches high. The electronic Aash was placed 12 inches from the back of the transparency. An Exakta camera with a 58 mm.“lens on a Novoflex extension bellows was focused on the front of the transparency on the center of interest, which is the incisal edge of the two lower cuspids. The lens is approximately 2 inches from the slide. To produce the amount of magnification obtained in the enlarged duplicate (Fig. 2), the exposure increase factor on the Novoflex scale was 7x. Stop f. 5.6 was used with Daylight Kodachrome film. Anscochrome and Ektachrome, ASA 32, would require a stop of between f. 8 and f. 11.

Fig.

Fig.

I.-The

original

Z.-The

duplicate

slide which

is shown

in position

of the original slide, cropped the center of interest.

for duplicating

and enlarged

in Fig. 3.

to emphasize

1172

MACLACHLAN

EQUIPMENT

A Mighty Light Electronic Flash, an opal glass in frame, a transparency in position, an Exakta camera with a 58 mm. lens on a Novoflex extension bellows mounted on a tripod are shown in Fig. 3. This setup, with the addition of a nonglare electric light bulb (not shown), is used in focusing. At this point, the decisions are made as to the area of the transparency to be duplicated and whether it is to be cropped, reduced, or enlarged. Fig. 4 shows the same equipment as in Fig. 3 with an opal glass hanging on the plywood mount between the transparency and the flash. After the equipment is set up, a basic exposure is established. By use of a 58 mm. lens on a Novoflex extension bellows, I have found the data in Table I to be satisfactory guides. In making a duplicate transparency the same size as the original, that is, 1 :l, place the light 12 inches behind the transparency and make three test exposures. An electronic flash with a guide number of 60 to 70 for Daylight Anscochrome or Ektachrome film should give one correctly exposed duplicate among the three exposures at f. 11, f. 16, and f. 22. I use the Mighty Light DeLuxe Electronic Flash, which has for Daylight Kodachrome a guide number of 40 to 50 and for Anscochrome and Ektachrome, 65 to 80. If, for example, f. 16 gives the best duplicate of the same size, when focusing for double magnification use one stop larger and when focusing for one-half reduction use one stop smaller. If only duplicates of exactly the same size as the original are required, I suggest the use of the Medical-Dental Photo Company’s new Slide Duplicator, otherwise known as The Copy Cat. In duplication, only the electronic flash must illuminate the master slide at the moment of exposure ; avoid light from any other source. Care must be taken also to avoid “bounce light” produced by the flash on the immediate surroundings.

Fig. 3.-The

equipment

used for duplication,

with

the opal glass not in position.

Volume Number

10 6

BETTER

Fig.

4.-The

equipment

DUPLICATE

with

TRANSPARENCIES

the opal glass in position,

ready

for the exposure.

For example, a yellow room would produce yellow duplicates. Cover all the area between the flash and the slide with a cardboard carton painted flat black inside or with paper flat black in tone on the table and a large sheet of the same held over the flash-to-slide area. A successful enthusiast has found that an off-white (oyster shade) paper gave the best results for accurate color reproduction. Another interesting experiment produced seven different variations of color in duplicates by bouncing the light off seven different shades of paper. CORRECTIOKS

It is often very disappointing to find that a very important and irreplaceable original transparency has been either underexposed or overexposed. Either of

APERTURE FORKODACHROME DAYLIGHTFILM(ASA 10)

EXPOSUREFACTOR

32)*

..-!-

--___~

12x 10X 9x 7x 6x

I

5X

4x 3x * A single stop.

i APERTUREFOREKTACHROMEOR ANSCOCHROMEFILM(ASA

+ equals

f. f. f.

3.5 4 4.5

f.

5.6

I

1. 5.6-c f. 5.6/+

I:,p f: 11.5

approximately

one-third

of a stop:

++,

approximately

two-thirds

of a

1174

MACLACHLAN

J. Pros. Nov..Dec.,

Den. 1960

these conditions can be corrected to a marked degree by making a duplicate. If a transparency is darker than average, use a larger aperture ; if it is too light or overexposed, use a smaller aperture or increase the flash-to-film distance. The proper exposure is a matter of judgment and experiment. If the color is slightly off, it can be corrected quite simply by sandwiching or superimposing a soft gelatin sheet called Addacolor* in the mounting, selecting the color which will correct the fault. If the transparency is over-all blue, use yellow; if it is green, use red; if it is yellow, use blue ; if it is red, use cyan. When making duplicates, it may be necessary to use filters for proper color rendition. The right filter to use is a difficult problem and can only be decided upon by experiment. An Ansco UV/15 filter is helpful with films which have a tendency to accentuate the reds. 55 SUNSET BLVD. OTTAWA 1, ONTARIO

*Lou

Bertz

Specialties,

Hollywood,

Calif.