اجهزة عرض الصور الشفافة .. كتاب التحميض والطبع والتكبير

Transparent display devices:

These devices differ in their main design from the devices prepared for 35 mm photo slides, in the following respects:
(a) The lamp is larger in size, and the diameter of the filament also increases.

(b) These devices often do not have heat-absorbing filters, even if the power of the lamp is increased (to 500 watts, for example), but this filter may be found as an additional piece placed under the lamp socket.

(H) It is usual for the condenser to consist of two flat lenses on one side (Plano-convex), and another condenser may be added similar to the above, in order to increase the brightness of the image.

This type of projector has a long square Bellows bellows that connects between the lens and the Slide Carrier, and the bellows is used to adjust the distance, and given that the focal length of the lens usually ranges between 8 to 10 inches; So the blower should be long.

Film Strips:

This name is given to the 35 mm short films (36 images, for example) that carry a group of transparent, positive images with one integrated theme, which are presented one after the other, as a visual aid for visual aids for explanation in scientific and practical lessons or lectures that may require reference to figures Illustrations or photographs, as many industrial establishments and establishments use them as a means of support for their speeches and representatives in advertising, and to explain the advantages and how to use their products in order to facilitate their sale or as guidance on the means of maintaining them...etc.

This type of film has spread in some countries, and institutions have specialized in its production and distribution. It also has libraries that include various educational and cultural topics, distributed widely all over the world. These tapes may be on colored films, or on “black and white” film. If the first type is more capable than the second in fulfilling its purpose in some cases (as if the pictures represent oil paintings or colored works of art), but it is more expensive. In the following pages, we will confine ourselves to talking about the second type only due to its relevance to the subject of this book.

In most cases, the images carried by the tape are transferred from transparent negative images of different subjects, and therefore, when starting to prepare the tape, it is necessary to arrange the subjects of the images according to the sequence of explanation, as it is difficult to rearrange them afterwards unless the tape is cut and re-welded in special ways, which is not always possible. For those with limited capabilities, the degree of contrast of all negative images must be close, if they are printed on one tape, and all images are shown at once, so it is not possible to control the contrast of each image separately. Likewise, it is better that the degree of density of all negative images be similar, or close at least, as it is done in the beginning. The matter is to do one experiment to estimate the duration of nursing. It is easier to match the duration of nursing required for all pictures, and it is much easier to match the area of ​​the negative pictures. And it is taken into account that all the images are arranged in one direction, so that the matter does not need to adjust its position every time, and since some images are transverse and others are longitudinal, so it is also possible to transfer some of them on a smaller size than it, such as 18 x 24 mm (Fig. 109).

And since some of the illustrated topics require a written explanation below them, therefore it must be prepared in advance in a clear handwriting, then photographed on a negative film, then printed on the tape of the film so that it follows the image of the subject being explained. In order to facilitate the combination of the image and explain it once on the display screen, it is advisable to photograph each of them on the smaller size 18 x 24 mm. After filming the tape using the aforementioned methods, it is usually better to increase the degree of its contrast a little so that its transparent parts appear completely white, and the existing parts appear completely black when shown.

Putting film tapes into the projector:

Placing the film tapes in the projector depends on the manner in which they were prepared, and this is what we explain in the following:

(a) If it has been prepared by contact printing or by reducing it by transferring from a larger negative image, its sensitive surface must be facing the condenser in the projector condenser so that the modified image appears on the screen. What was on the right in nature appears on the right as well. on the display screen.

(B) If the tape was prepared using the “reversal display” method, it should be placed with its sensitive surface facing towards the lens of the projector. The correct way to watch the reverse film is to look at it from the back until you see the modified image.

display :
There are two main types of display:

(a) Beaded Screens

(B) White Matt Screens. The characteristics of each of them differ from the other, and accordingly they differ. Others, depending on the validity of each type.
The first type increases the brightness of the image whenever the spectator’s location is close to the optical axis of the lens (Fig. 110). Therefore, the grainy, glossy screen is suitable if the transparent image is displayed in a long, narrow hall, when it is necessary for the spectators to sit in places close to the optical axis of the lens. The matte white screen is more valid in the wide, bright auditorium, when the spectators must sit transversely (Fig. 111).