Notes on Tables	Extension Increase	Explanation of tables (partly scanned as image)
Exposure Factor	Table 1 - 50 mm. and 58 mm. lenses (scanned as image)	Table 2 - 100 mm. and 135 mm. lenses (scanned as image)
DIN-Patterns table (scanned as image)	Bottom of page

The following tables contain all data for close-ups with lenses of 50, 58, 100, and 135 mm. focal length and facilitate the selection of the extension increases. The tables give calculated values which may differ a little from the real values because of the admissible tolerances of the focal distances of the lenses. However, these small differences can be neglected when applying the tables to any kind of regular work. The figures of the tables are for the lens set at infinity. Intermediate values are found by focusing at shorter distances (means lower figures in metres). By adding tubes you will get greater enlargement on the negatives, according to the length of extension. Extension Increase i.e. the total length of the bayonet rings and tubes of the same length as the focal distance = pictures 1:1 on the negative of double length of the focal distance = double magnification on the negative of triple length of the focal distance = three times magnification on the negative of quadruple length of the focal distance = four times magnification on the negative of quintuple length of the focal distance - five times magnification on the negative, etc. Scale of reproduction = ratio of subject to image e.g. 1:1 = 1.0 means subject and image are of same size; 1:2 = 0.5 means the image is half as large only as the subject; 2:1 = 2.0 means double size of image = two times enlargement Picture size of the subject means, how much of length and height of the subject is covered by the film. Here, partly, round figures in millimetres are quoted. Exposure factor When working with increased extension, the exposure time must be longer, for there will be a diminution of light with the increasing image distance. Therefore, the exposure time for a certain diaphragm opening must be multiplied by an exposure factor corresponding to the extension increase. When focusing at short distance with the lens helical focusing mount alone there is a small exposure increase only that can be overlooked, but with longer extensions it has to be calculated according to the following formula: exposure increase = ( image distance/focal distance) squared Example: Extension increase with the Pair of Bayonet Adapter Rings and all 3 Tubes (= 60 mm.). Length of the image distance = lens focal distance e.g. f=50 mm. + extension increase e.g. 60 mm. - 110 mm. The focal distance is 50 mm. in length. 110 : 50 = 2.2. 2.2 multiplied by 2.2 = 4.84. Thus, in this case, the exposure factor is 4.8, in other words the normal exposure must be multiplied practically by 5. Increases of extension can also be used with other lenses not yet mentioned. For a certain scale of reproduction you will attain, when using a wide angle lens, a shorter subject distance, and with a long focus lens, a longer subject distance than with a normal lens. Both cases are possible in practice. Focusing is done on the ground glass screen as usual. Close-ups with great magnifications of the subject require relatively long image distances and short subject distances. Our lenses are, however, corrected for the reverse ratio, that is long subject distance and short image distance. Therefore, we recommend for close-ups with magnifications of more than 2.5 times, to use the lens in reverse position i.e. with its back turned towards the subject and the lens front facing the film. A reversal ring is required for this. When using the lens this way, there is no possibility of helical focusing, therefore, critical focusing is done by slight changes of the camera position. For taking pictures with over 5 times magnification we recommend the Microtars. As special lenses for macro-photos, they must, of course, not be attached inversely.     Top of Page

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