Topcon RE GN Topcor Lens User manual

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                           TOKYO KOGAKU KTKAI K.K.

RE GN TOPCORLENS
The RE GN Topcor M SOmm f/1.4 lens    the subject is focused. The frustration
(andthe RE GN Topcor 5Omm tlLS lens)    of having to calculate the correct  f I
have been designed as universal use   number for the focused distance,as in
standardlensesof the highest perform-    the case of other lenses,has been com.
ance and are representativeof the high     pletely eliminated from flash photog-
Topcor quality in  optics.  Both are    raphy, and, together with  the Auto
modifiedGausstype optical designsfor    Winder, brings greater mobility to the
obtaining superior optical performance   photographer.
and depiction.
                                      Both standard lenses are designed to
However,one of their most outstanding    give you greater satisfaction in every-
f eatures is automatic  f lash settings,   day photography but especially when
obtained simply by setting the guide    taking snapshots and candid shots. in
number of the flash bulb or electronic    availablelight and at night, as well as
flash unit to the GN scale-which auto-     for photographingchildren,animals,in-
matically sets the correct aperture as    sects and other moving subjects.

SPECIFICATIONS                NOTE:
                                                    1.  Bracketed specifications are for  the
Focal length          5 0 m m              50mm f/1.8 lens.
Maximum aperture       t lL.4 (tlr.8)              2.  The reading direction of the distanceLens composition    7 elbments5 groups                                                scale has been reversed,compared to                        (6 elements 5                                               previous TOPCOR lenses, in order to                     groups)                                                 give  it Flash-Maticoperation.Lens diaphragm
  Type                Fully automatic          The depth of field scale has also been
  Exposure  meter   Full aperture expo-        eliminated for the same reason. How-
   couplling          sure measurements        ever, the actual depth of field can be
  Scale             L.4-L6 (r.8-22\          checked visually by using the depth of
Angle of view                                          field preview lever and, therefore, its
  Diagonal          4 7 "                        elimination is not important. For pre-
  Horizontal         3 9 0                        cise depth of field settings, moreover,
   Vertical           260                       the depth of field table can be utilized
Guide number scale  GN 10 to 80 (meter)       as in the past.
               GN 32 to 250 (ft.)         The aperture ring click-stopswhen used
Filter mount          6 2 m m ; O . 7 5 m m          independently,but automaticallyloses
                       pitch                             its click-stopswhen coupledto the GN
Lens hood          Bayonet type (same        scale, in order to move smoothly to-
                    as f/l.8 lens)             gether with the interlocked distance
Lens cap         65mm push-ontype        focusing ring.
Size            67mm dia.x 44mm
Weight             350 gr. (290 er.)

GUIDENUMBER                       bulb being used at the distance focused                                      and thus  is handy for use with regular
The guide number is based on the shutter    Auto-Topcor lenses.
speed and film speed being used and is                                                      ln the case of the RE GN Topcor M 50mm
usually found in the  instruction sheets                                                   f/1..4 lens and RE GN Topcor SOmm f/1.8
furnished with the flash bulbs, as well as                                                lens, however, a much faster and simpler
instructionssupplied with electronic flash                                       system has been developed right on the
units.                                             lens so that the correct f/number is set
The guide number thus obtained is very     automaticallywhen the distance focusing
important for  f indingthe correct aperture     ring is adjusted, by simply using the GN
or f/number to be used with the distance    (guide number) scale and its GN lock.
that the flash gun or electronic f lash unit
is used from the subject being illuminated.  GN SCALE
(When the flash gun or electronic flash
unit is used on the camera, the focused   The GN (guide number) scale has two rows
distance or camera-to-subject distance is     of  numerals. The top  row, which has
also the flash-to-subjectdistance.)          orange-coloredfigures, is for use with the
                                                British system,when focusingin f eet, while
The guide number is important because    the bottom row, which has white-colored
the exposure meter cannot be used for    numeralsis for use with the metric system.
taking a readingwhen f lash illuminationis    Both scales are for use with a  f ilm speed
being used. When the TOPCONFlashGun     of ASA 100 or equivalent.
is used, the Flash Calculatoron the back
of the gun may be used for quickly and    The top row has the following guide num-
simply f inding the suitable aperture for the     bers:

4

25O, (22O), 180, (153), L25, (LtO),90, (77),    Set the dial for ASA 1OO and check the
      63, (54), 45, (38) and 32.                     aperture/flash distance combinations indi-
                                               cated by the dial. For example,the dial     The bottom row has the following guide                                        may show that tl4 should be used for a     numbers:                                                     flash distance of 7 meters, in which case,
       80, (67), 56, (49), 40, (34), 29, (24), 20,     the guide number would be the product
*      (L7), L4, (12) and 10.                           of the aperture and flash distance,or 4x
                                                  7 : 2 8 ,     The numerals in brackets are the values
       of those dots between the unbracketed    Set the GN 28 (meter) to the GN scale, in
     numerals (which are those actually en-     the usual manner, and Flash-Maticopera-
     graved on the GN scale.                      tions will be poss'ibte'g)ul?uguJ
           lf the guide number indicatedfor the f lash
      bulb or  electronic  f lash unit does  not   AUTOMATICFLASHSETTINGS      coincide with those on the GN scale, set
           it to the nearest guide number on the    As noted, find the guide number for the
      scale.                                        flash bulb or electronic flash unit from
                                                        their instruction sheets and set  it to the
    FINDINGTHE GUIDENUMBER     GN scale. In other words, adjust the GN
                                                 scale (which is on the distance focusing
           lf information on the guide number is not     ring) until the required guide number is
      availablein the instructionssupplied with     opposite the red index dot on the GN lock.
      the electronic flash unit, use the Flash   When aligned correctly, slide the GN lock
      Calculatordial for f indingthe guide number    towards the front end of the lens and, if
       of the equipment.                         alignment is correct, it will lock into place.

Locking the GN scale means that adjusting the distance focusing ring now will result in
adjusting the aperture ring, also, which has, in the meantime, been released from its
click-stops and will rotate smoothly together with the focusing ring.
As can be checked by adjusting the focusing ring, locking the GN scale prevents the
focusing ring from being rotated beyond certain limits, or, in other words, beyond the
flash range, although all the f/stops can be used, as in the following examples:-
    Guide Numbers         Apertures              Focused Distances
    1O (meter)                   tlt.4 to tlL6          7m to O.7m
                                 (f/1.8 to tl22)           (5m to O.6m)
    80 (meter)                  tll.a b   f 116          57m to 5m
                                 (f/1.8 to tl22)          (4Om to 3.7m)
Remarks:                    USINGOTHERFILM SPEEDS
lnformation in brackets are for the f/1.8
lens.                                  As noted, the GN scale has been calibrated                                                                                                                  iJ                                                   for ASA 1OO film, whereas films, both                                   IWarning                                                                                                                                                                                                                                                                                                                                                                                                                                                     I                                             color and black-and-white,are availableinAutomatic flash settings are not possible                                  many other speedsor sensitivities,as well                     Ifor off-the-cameraflash illumination and                                          as being indicated in other standards.bounce  lighting, because the    f lash-to-
subject  distance and   f lash-to-ceiling-to-  The following conversiontable should be
subject distance respectively are not the    used for finding the equivalent ASA 10O
same as the camera-to-subjector focused    guide number when the guide number for
distance.                                  another film speed is indicated.

6

For example,if the guide number for ASA   FINDINGYOUR GUIDENUMBER       25  film  is 45  (ft.), with the electronic
        flash unit being used,then find the equiva-   You may not be satisfied with the flash-
 r&    lentnumerals,GN (meter)or 74.  Next,f rom movethe  tophorizontallyrow  of     illuminatednumbers indicatedphotos bytakenthe manufacturerwith the guideof
       across the ASA 25 row  until you reach    the f lash bulb and/or electronic f lash unit.
        14, then move down towards the row for     This may be the case becausethe guide
      ASA 100 and the figure intersected will    number is normally based on the use of
       be the required guide number  f or  set-    an efficient ref lector in a room of averageFE
        ting to the GN scale, or 28, in this case.    size and brightness and  because the
        (Actually, you can refer to the top rows    maker's idea of an appropriately exposed
       once more, as  it  is much nearer in this     shot may ditfer slightly from yours.
        case.)
                                                                                              lf you do most of your shooting in rooms
        Or, if a GN 20 is indicatedfor DIN 18 film     smaller or larger than average,or brighter
       speed, move across the DIN 18 row until     or darker than average, or  if you prefer
       you reach 20 and then move down to the      slightly more exposed or under-exposed$      ASA 1OO row, which will show you that     shots, then try  f lash shots with your own
       your required GN is 28.                    personalguide number for your electronic
      Once the equivalentASA 1OOguide number         f lash unit or   f lash gun (the same bulb
                                              must always be used).       has been obtained, further operations are
         identical to those explained for the ASA    To  f ind out your own guide number, place
       100 film speed.                            your camera at 5 meters, or the distance
                                              most likely to be used by you, from the
                                                      subject, in the type  of room  that you

expect to take flash shots most often.
While a slow color film would be best,
load the camera with the film that you
expect to use, and make a series of  test
shots, starting  with  the recommended
guide number and then bracketing your
shots on both sides of  the  "correct"
f/number, varying the exposure by two
stops over and one stop under.
Upon developing the film, choose the shot
that  pleases you  the  most and check
your data for the f/number used for that
shot. Your own guide number can then
be calculatedby multiplyingthe  f lash dis-
tance  (camera-to-subject  distance with
f lash on the camera) by the f/number
used. Thus, if the distance used was 5
meters (as in the example above, and the
best photo was taken with f/4 lens open-
ing, your personalGN will be 20, for the
film used.


                                                                                      Printed in Jopon 7304E'1578-5lAS