The definitive equipment listing for Prakticas on the internet
	Main  |  Camera Bodies  |  Lenses  |  Accessories  |  Photo index  |  Contact Accessories -> Extension rings -> Manual General - The extension rings without plunger - Prolongation of the exposure time - How the automatic diaphragm control is maintained when extension rings without plunger are used - Extension rings with plunger - The lens reversing ring Extension Rings for PRAKTICA cameras and PENTACON super 1. General It is the genuine single-lens reflex camera with which it is incomparably easy to enter the fascinating field of close-ups. In the same manner, in which you are accustamed to do for usual Shots, the unique finder system of this type of camera enables you to check the image, its definition, and its depth of field. These lenses - which can be interchanged - and the focal plane shutter - which is not connected with the lens mechanism - make it possible to extend the lens merely by interpasing extension rings. As is known, such an extension is indispensable if yoU wish to approach the object more than the helical thread of your lens allows. Can you remember the double or tripie extensions of the old plate cameras? With the extension rings (ar the extension bellows) you will obtain the same effect. In such a manner the reproduction of small and smallest objects or details of them in natural size (1:1) or even in a lorger ratio will become possible. Finally, we wish to inform you about some expressions which you will read in the text of these Intructions for Use. "Image distance" means the distance between film plane and lens whereas "subject distance" means that between lens and object. The tables of these Instructions for Use specify the image scale (β') with the use of one extension ring or of certain combinations of them. As in case of an enlarged image distance (i.e. with use extension rings) the brightness of the image will decrease, the exposure time in comparison with normal taking must be longer. Therefore, these lists glve the factors valid for various cases, too. If you are, however, possessor of a TTL-camera, you can save yourself the trouble of computing since the required prolongation of exposure time will be automatically taken into consideratlon by this TTL-metering system even if extension lengthening accessories are used. And these are extension rings available for the PRAKTICA models: Set of extension rings (208 500) comprising three etxension rings without plunger, sizes 7mm, 14mm, and 28mm. To maintain the electric diaphragm control, an additional extension ring (203 540) with socket for the twin-cable release (210 050) is provided. Set of extension rings (208 830) comprising three extension rings, sizes 7mm, 14mm, and 28mm. The plunger is for maintaining the electric diaphragm control. This set of extension rings (208 833) comprises 2 plunger-type extension rings of 14 and 28mm. It fits particularly the PENTACON super. In connection with the Pancolar 55 mm f/1.4 lens all image distances up to β'=1 are obtainable. This set of rings can be used also for all other camera models of the PRAKTICA family. Set of extension rings (208 400) comprising two plunger-type extension rings fitted with an additional means for electric diaphragm control, sizes 12.5mm and 25mm. Though this set is particularly intended for all PRAKTICA models with electric diaphragm control, it can also be used with other PRAKTICA models. Set of extension rings (961 333), comprising two Zwischenringen extension rings with electric diaphragm control and aperture mechanism, sizes 12.5mm and 25mm. This set is intended for use with Praktica B series cameras only. A third-party manufacturer has produced a set of extension rings with sizes of 11mm, 21mm and 31mm for Praktica B cameras. The Close-up Bellows Attachment offers you the possibility of a continuous extension lengthening. 2. The extension rings without plunger These rings are screwed between lens and camera. Depending on the desired image distance they are used separately or in combination. For these extension rings the electric diaphragm control mechanism is shut off, while the automatic system can be maintained effective. Please have a look at section 4. The lens is stopped down as decribed below: a) Lenses fitted with spring diaphragm (SB): Force the diaphragm clamp ring towards the camera and allow it to click in at the desired diaphragm numeral. b) Lenses fitted with automatic pressure diaphragm (ADB): Set the diaphragm numeral by turning the diaphragm setting ring. c) Lenses fitted with preset or manually set diaphragms are operated on as usual. Focusing and choosing the image section as well as checking the depth of fleld is in the finder of the camera. Focusing is best made by changing the subject distance. When a tripod is used, this distance variation is facilitated by a focusing slide. 3. Prolongation of the exposure time As compared with the values read on the exposure meter the time of exposure must be prolonged since close-up require extension lengthening accessories. Table 1 below lists, therefore, exposure values for the image scale (β') as well as prolongation factors (v). Table 1 Extension rings in combination with the standard 50 mm lens Ring no. Depth of ring (mm) Image scale (β') Size of object area (mm) Subject distance (mm) Exposure factor (v)   no ring - 0.14 - 172 x 257 - 407 - 1.3 1 7 0.14 - 0.28 172 x 257 - 86 x 128 407 - 228 1.3 - 1.6 2 14 0.28 - 0.42 86 x 128 - 57 x 86 228 - 169 1.6 - 2.0 1+2 21 0.42 - 0.56 57 x 86 - 43 x 64 169 - 140 2.0 - 2.4 3 28 0.56 - 0.70 43 x 64 - 34 x 51 140 - 122 2.4 - 2.9 1+3 35 0.70 - 0.84 34 x 51 - 28 x 43 122 - 110 2.9 - 3.4 2+3 42 0.84 - 0.98 28 x 43 - 25 x 37 110 - 100 3.4 - 3.9 1+2+3 49 0.98 - 1.12 25 x 37 - 21 x 32 100 - 95 3.9 - 4.5 The next table shows the values for image scale and prolongation factor for the cases of extension rings used in combination with additional lenses. Table 2 Extension rings in combination with supplementary rings   Focal lengths of lens (mm) Ring no. 35 75 and 80 100 135 (β') (v) (β') (v) (β') (v) (β') (v) 1 0.20 1.3 0.09 1.2 0.07 1.3 0.05 1.2 2 0.40 1.6 0.18 1.4 0.14 1.5 1.10 1.3 1+2 0.60 1.9 0.28 1.6 0.21 1.8 0.16 1.6 3 0.80 2.3 0.37 1.9 0.28 2.2 0.21 1.8 1+3 1.00 2.6 0.47 2.2 0.35 2.5 0.26 2.0 2+3 1.20 3.1 0.56 2.4 0.42 2.8 0.31 2.3 1+2+3 1.40 3.5 0.65 2.7 0.49 3.3 0.36 2.5 Example: For the diaphragm numeral just set your exposure meter will indicate an exposure time of 1/60sec. resulting in an image scale of β'=0.4. When utilizfng the normal focal length (f=50mm) you will read from the first table the prolongation factor v=2, and computation will be 1/60sec. x 2=1/30sec. Cameras fitted with the TTL-metering system need no conversion of exposure time as the correction is automatically taken into consideration by this system. We recommend not to apply extreme wlde-angle lenses far close ups. This is the reason why the second table does not list values for focal lengths less than 35mm. 1 Extension ring No. 1 (208 510 - 01) 2 Extension ring No. 2 (208 510 - 02) 3 Extension ring No. 3 (208 510 - 03) 4 Extension ring No. 4 (210 540) 5 Release button of twin-cable release (210 050) 6 Knurled screw of twin-cable release 7 Button 8 Counter nut 9 Threaded sleeve 4. How the automatic diaphragm control is maintained when extension rings without plunger are used When the extension rings without plunger or the close-up bellows attachment are used, the automatic diaphragm control is at first shut off. To maintain, however, the above function as has mentioned above, for close-ups the special extension ring No. 4 (208 540) with cable release socket and the twin-cable release (210 050) are applied. The additional ring No.4 should always be directly attached to the lens. It is fitted with a mechanism for operating the automatic diaphragm control which is actuated via a cable release to be screwed into the nipple on the ring. A twin-cable release is required to operate the shutter release of the camera together with the automatic diaphragm control mechanism. The short cable release is to be screwed into the release button of the camera while the long one is inserted into the nipple of the extension ring. Before using this combination for the first time, you should once adjust the cables connected wJth the used lens of the camera in such a manner that at firt the diaphragm and subsequently the shutter are actuated when the release button (5) of the twin-cable release is being pressed slowly. For this purpose, at first you slacken both the counter nuts (8) and screw in and off, resp. the threaded sleeves (9). Camera and diaphragm, resp. are the earlier released the more the sleeve has been screwed in. After adjustment both the counter nuts (8) are tigthened again by retaining the threaded sleeves (9). When long exposure times are required, the shutter release can be locked by tigthening the knurled screw (6), and only after slackening this screw. The shutter ist shut down again. When both the buttons (7) are pressed simultaneousely, the metal cap, which houses both the threaded sleeves and the releases, can be drawn off the body of the twin-cable release. In this manner it is possible to exchange the cable release. Table 3 below lists details about the necessary prolongation of the exposure time when the special extension ring No. 4 is additionally used. TTL-cameras need no correction of shutter speed. Table 3 Extension Rings No. 1, 2, and 3 with Special Extension Ring no. 4 in combination with the standard 50 mm lens Ring no. Depth of ring (mm) Image scale (β') Size of object area (mm) Subject distance (mm) Exposure factor (v) 4 14 0.28 - 0.42 84 x 128 - 57 x 86 228 - 169 1.6 - 2.0 1+4 21 0.42 - 0.56 57 x 86 - 43 x 64 169 - 140 2.0 - 2.4 2+4 28 0.56 - 0.70 43 x 64 - 34 x 51 140 - 122 2.4 - 2.9 1+2+4 35 0.70 - 0.84 34 x 51 - 28 x 43 122 - 110 2.9 - 3.4 3+4 42 0.84 - 0.98 28 x 43 - 24 x 37 110 - 100 3.4 - 3.9 1+3+4 49 0.98 - 1.12 24 x 37 - 21 x 32 100 - 95 3.9 - 4.5 2+3+4 56 1.12 - 1.26 21 x 32 - 19 x 29 95 - 90 4.5 - 5.1 1+2+3+4 63 1.26 - 1.40 19 x 29 - 17 x 26 90 - 85 5.1 - 5.8 5. Extension rings with plunger These extension rings are fitted with a plunger which maintains the connection between camera and plunger of the lens. Consequently, the special extension ring No. 4 with twin-cable release is not necessary. If these rings are of equal dimensions as the extension rings without plunger, details of the first two tables will apply for image scale and extension factors while the values for plunger-type extension rings with electric diaphragm control (208 400) of the 12.5mm and 25mm sizes are read from the next two tables. The above figures are valid for the infinity setting of the lens. Table 4 Extension Rings with plunger for electric transmissio of the diaphragm values in connection with the standard 50 mm lens (long extension) Ring No. Depth of ring (mm) Image scale (β') Size of object area (mm) Subject distance (mm) Exposure factor (v)   no ring -0.25 - 96 x 144 - 250 - 1.6 1 12.5 0.25 - 0.50 96 x 144 - 48 x 72 250 - 150 1.6 - 2.3 2 25 0.50 - 0.75 48 x 72 - 32 x 48 150 - 115 2.3 - 3.1 1+2 37.5 0.75 - 1.00 32 x 48 - 24 x 36 115 - 100 3.1 - 4.0 Table 5 Extension rings in combination with supplementary rings   Focal lengths of lens (mm) Ring no. 35 75 and 80 100 135 (β') (v) (β') (v) (β') (v) (β') (v) 1 0.36 1.5 0.17 1.4 0.12 1.4 0.09 1.3 2 0.72 2.1 0.33 1.8 0.25 2.0 0.18 1.7 1+2 1.07 3.8 0.5 2.3 0.38 2.7 0.28 2.2 6. The lens reversing ring The lenses used in our cameros are designed and optically corrected for wide subject distances and narrow jmage distances. For close-ups exeeding an image scale of 1.5 the lens must, therefore, be reversed as contrary conditions apply (i.e. the lens must be screwed in with Ihe front lens directing to the camera). The lens reversing ring which thus allows attachment of the lens at the set of extension rings has on its one end the camera thread (M42x1), to be screwed into the extension ring, and on the other end the filter thread of the lens, being M49x0.75 for most standard lenses (208 580), and M58x0.75 for the Pancolar 55mm f/1.4 lens (208 582). To actuate the spring diaphragm and the automatic pressure diaphragm, resp. of the lens the special extension ring No. 4 with twin-cable release is necessary. But you can also shut off the automatic mechanism by means of an extension ring without plunger. The rings are screwed into the thread directing to the subject. We request you to observe all recommendations given in this leaflet. Objectionable operation of the devices may da damage the removal of which is beyond our warranty. Improvement of the devices may lead to slight variation from this leaflet. Back | Index | Top