Ombrux light meter User manual

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                                                                                              use            Description:               that way that the 1'ellowwww.butkus.usdirections for                                                                              apparatus,                                           given                                                                                                   is                                                    Ombrux                                                       each                                                  with                                                                                        put -                                                                                              service                                                                                    within the                                                                    contained                                                               state                                                        as                                                  ln folded     The Ombrux photometer consists of a
                         measuring                                        instrument,             moving'coil   high-class
                     front   having a narrow                         face fitted with                                 a lens  case                                                 case -in betweensuch a waythe instrumentthat it projeclsand beyondthe servicethe
    at the back of which there is a photo-cell. This  the upper part of the lens in a frontal direc-
   photo-cell will, when exposed to the light,  tion, thus strading the lens against the direct   without connection wlth any outside cur-  rays of the sun light.
   rent circuit, generate a photo current which    The needle of the measuring instrument  waxes stron$er, as the degree of illumi-  travels over two scales calibrated to indicate   nation increases and may thus be used to  the time of exposure directly. In a very bright   ,t   dlrectly Indicate the llght Intensity. The in-  atmosphere the time of exposure is read from   strument, therefore, requires no battery and  the upper scale. With weaker light. particu-   the user does not run the danger of being  larly in the case of interior work, the travel   hampered in his action by the failure of any  of the index hand is small. By pressing the   auxiliarv unit.                              red button on the meier, the sensitivity of the       In order to limit the measuring of the lu-  Ombrux is increased 40 times. The time of   minal conditions exactly to the same pictorial  exposure is now read on the lower red scale.  .!   angle as that grasped by the normal photo-   gaphic camera, the lens of the exposuremeter    The Scale: Everv position of the index   rs of paramount importance. B.y eliminating  corresponds with a certdin period of exposure,   the influence of foreign light rays outside of  the values of the scales referring to standard                                                                                                 1303H.   the photographic  field, the possibilities for over-  diaphragm aperture f/8 and 230 Sch.:
             are                  likewise   exposures                             eliminated.                                                &D.,2790Watkins,343 Wynne, +-*    0 Din. For             cases,                         photographs against                 where      In all
   light are taken, the lens of the exposuremeter,  different conditions the conversion factors will
   :iust as the obiective of the camera, must be  be found on the tables in the upper part of the
   protected against all directly falling in light  leather case, which indicate the corresponding     ra1's. This can be obtined in the easiest manner in  times of exposure.
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t      fnstructions for use..
   Get the camera ready for the exposure
in the usual way and determine with the
Ombrux the brightness of the object to be
taken. To this end aim with the lens of the
instrument in the same direction as the lens
of the camera and read the time of exposure
from the scale. This way of proceeding is
recommended, in order to actually catch the
intensity of light prevailing at the moment of
exposure, since   for instance with a cloudy                 -              be rather abrupt fluctuationssky-there may
of the light intensity.
   The angle of image comprehended by the
instrument is about 450 in vertical and about
700 in horizontal direction. In order to avoid
failures in measuring the exposure values, such
as are likely, when working against the light
by sun rays striking the photo-cell directly or
by taking too much sky, it will be well to cut
out a large portion of the direct sky light by
slightly inclining the instrument downwards be'
fore taking a reading.