Weston Model 715 BOLEXMETER User manual

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                           THE CORRECT WAY TO HOLI)       IMPORTANT
                                  YOTIR BOLEXMETF]R
  Keep  the  glass window   over  the   cell  open-
ing  clean.
  During   dry   cold  weather   the  glass  on  the
instrument    is  likely   to  become  eleotrified  by
contact   with   the  hands   or  clothing.    This   at-
tracts  the  pointer  and  gives  erroneous  read-
ings,  but  the charge  on the glass can be  easily
eliminated   by  breathing  upon    it.
ZERO  SETTING  OF INSTBUMENT   POINTER
                                        "electric  When  no  light  reaches  the              eyet'  in
the  back  of  the  Meter  the  instrument   pointer
should  rest  directly   over  the  zero  position  on
the  scale.
    If  this   is  not  the  case, and  there   is no  elec'
trostatic   charge  on  the  glass  (see paragraph
above),  then  the  pointer  can be  readily   set to
its  zero  position  by  slightly   turning   the  screw
located  Ct  ttre  right   of  the  meter  scale-
  When  making  this  correction  place the meter
back  downward  on some opaque  object'  as a
card  or a book  so as to exclude   all  light  from
the  photoelectric    cell,  and  hold    it  at  an  ang:le
of  about  46o.
                 Copyright  1940

                                                                                  on  )'our  camera.          AMERICAN BOI,EX CO.           )'ou  u'r;ulrl  shacltr the  lens                                                                          \\'ithout   this  prccauti{)n,  all  crl'oueous r.eading
                                                                      nral' bc obtuincd.  l.he mett'r urcirsures all light
           A D D I T I O N A L  C O P I E S O F T H I s                          u'ithitr an  lrngl(' ol'  l5'  rtJ)or,'c,Itelol'  nncl'-to
                                                                       citlrcr si<lc ol' tlrt.  lirrt' ol' siglrt.           tsOOK  FIFTEEN  CENTA  EECTT
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        HOW TO OPERATE YOUR BOLEXMETER

WITH YOUR CINE' CAMERA
  When  using  thp  BOLEXMETEIi    in  conjunc-
tion  with   your  BOLEX   cin6  camera,  simply
select the proper  meter  scale  to  suit  the  light
conditions,  aim  the  meter  at  the  scene to be
photographed  and  obtain  a relative  brightness
reading.     If  at  all  possible,  close-up  readings
should  be  taken   directly   from   the  principle
objects  in the scene. However,  for  the majorlty
of  scenes, an  over-all  measurement  from   the
camera'  position   will  be  satisfactory.   \Mhen
taking  close-up  readings  measure  the  darkest
and  brightest  obj ects in  the scene to be photo-
graphed  and  set  the  arro\^r  of  the  exposure
guide  miclway   betrnreen these  two  m,easured
values.   This   will   give  an  average  relative
brightness  reading.
   I.,et us assume  that  the  relative  brightness
re'ading  obtained   (over-all   or  average)   is  22,
and the speed value  of the film used is 8. With      WITH YOUR CII{E' CAMERA
this  speed  value  set  in  the  window  marked      FOR SINGLE EXPOSURESoo\\"eston          Speed.", rotate  the  upper   dial  of  the
exposure  guid e  until  the  arrow  points  to  the          A motion  picture  camera  is essentially a  still                      "Relzrtive                                                     camera  'which takes a number   of  still  picturesligure  22 on  the                               Brightness"   scale.
 ( See  illustration.   )   Opposite  the  value  corre-                  itr  rerpicl succession.  The rloLEX  cin6 bamer&,                                                                          for  exnrnpl€, u'hen operated  at a camera speedsponding   to  the frames  per  second" for  rn'hich                                                                        of 16 frames  per  second  is  actually  taking  16
the  camera   is  set  will  be  found  the  correct                 still  pigtures  in  olle  second.rvith  an  exposure
f  : stop to be used.  (Values  of frames  per sec-           time  of  7/30  of a second each.  At  a sp-eed of
ond  are  the  figures  on  the  red  background.)                :i2 frames  pe{ second the exposure time- is l/60
For example,  for  a camera speed of 16 frames              of a second  for  each picture,   etc.
per  second,  with   the  above  assumptions,   the                                                                            'fhecorrect  setting  would  be  f  : 8.  Other combina-                  exposure  guide  of  the BOLEXME'IER    is
tions  of  camera  speeds and    f  :  stops  can be          designed  so  that  u'hen  you  use your  BOLEX
used  to  suit  the  action  of  the  picture  being            cin6 camera  for  single  exposures, as  directed
taken.    Iror  a speecl of  21 frarnes  per  second,              in  the  camerA  instruction   book,  correct  expo-
urrder  the  above  assumptions,  you  rn'ould  set           sure  settings  can  be  obtained   in  the  same
your  camera  to an   f  : stop of 6.3, for  a camera             inallner  as described above for  motion  pictures.
speed  of 32 frames  per second use  f  : 5.6, etc.            rn  this case instead  of  usirrg frames  pei  second.,
I,he instruction  book  furnished  by  the camera            shutter  speeds should  be  evaluated   in  actual
illanul'acturer   should  be consulted  u'ith  regard            time   in  secorlds.  See table  on next  page  for
to the use of  the  various  camera  speeds.               camera  settings corresponding   to shutter speeds.
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  Speed Control    Shutter Speed  Bolexmeter
  Knob Setting   (Exposure-secondsTime)     Se,tting (Frames per sec.)                 (Time-Sec.)
        8              7/20          *7/76
       16             7/25           7/25
       24              7/30           7/30
       32              1/50          7/50                                            't7/60       64             7/go
   * It   will  be  noted  that  exact  rneter  settings
ar"e not  available   for'   I and  61 frarnes  per  sec-
ond,  but  the  resulting   error   is  less than  the
eguivalent   of  7/3  of an   f  : stop which   is negli-
gible  even  for  color  $'ork.
WITH YOUR STILL CAMIIRA   'r'he       procedure    for   determining    the  correct
cxp_osure fnr   still  carnera photography-described.  -aboveis essen-
tially   the  same  as  that                           for
cin6  work.    Select  the  proper-airn    meter  scale  to
suit  lighting   conditions,        the  meter   at  the
scene to be pho'tographed  and  obtain  the  rela-               sirecl.    rf  motion   is  to  be  check€d,  select  a
liy"   brightness   reading.   Whenever   possible,                I'ast available   shutter  speed and  the  calculator
take  close-up  readings  from   the  main   obj ects                 rvill  indicate  the  correct-  f  : stop.  For  example,
of  the  scene  to  be  photographed.      rf  this   is                      if  the  action   is  such  that  7/700  of  a  second
not  possible,  an over-all  rneasurement  from  the             shutter  speed  will  check   it,  the  proper-ass-umptibns,aper-caurera  position    u'ill  be  satisfactory    for'  the             ture   setting,   under   the  above
majority     of  scenes.  When   takingj   close-up            would" be  f z_1, or,  for  a shutter  speed  of  l/206r_eadi_ngs, measure   the  relative   brightness   oT          use  f  : 2.8.-  rf  great  depth  of  focus  is  desired,
the  darkest  and  brightest   obj ects  in  the scene           as  in  landscape  pictures,  select a  small  aper-
to be photographed  and  set the  arrow   of  the             tute  (large   f  : number)  and the  calculator   witt
exposure  guide midway  betlveen  the' two meas-             indicate   the  correct  exposure   tirne.   For  €X-
ured  values.   This  rvill  give an average  relative              arnple,  i_f you  lylsh  to use an aperture   of   f  : 25,
brightness  reading.                                              with  -light  conditions  and  lilm  speed as above,
                                                                 the  shutter  should  be  set  for  a speed  of  1/z   f-,et us  assume  thert  the  relative   brightness                                                          sucond, etc.reading   obtained   (over-all   or  average)   is  18,
and the speed value  of the particular   lilm  being                               USE OF FITTERSused  is  24.  With   this  speed  value  set  in  the                  "Westonwindorv   rnarked                             Speed",  rotate   the           When  photographing   with  a  color   filter  over
upper   dial   of  the  exposure   guide   until   the            the camera  lens   it  is usually  necessary  to  in-
arro\v  points  to  the  figure  18 on the  'oRelative           crease the exposltre.  A simple means  of allow-
Brightness"  scale.  (See illustration.)   Any  one            ing  for  this  is  to  divide  tha  speed of  the  film
of  the  combinations    of    f  :  stops  and  shutter                   lly  the  fi_lter factor  and  reset  the  Iilm  speed in
speecls now  appearing   opposite  each  other  on            the  x'inclow   to  this  new  rilrmber  and  proceed
the  upper  and  intermediate    dial   scales, can           as  if  no  filter  were  used.   F'or instance,   if  you
lle used.                                                                    lrq  using_ a  film_ _with  a  speed  of  16 in  day-
   'fhe                                                                          light,  ?nd  a 2x  filter,  then,  16    .  by  Z  -   g-       combination   of   f  : stop and  shutter speed            reset the  lilm  speed  to  8.    If  you  are  using  a
to be used depend.s upon  whether  motion   is  to           4x   filter,  then,  16    .  by  4 _   4-in    this  case
be gheeked  or  whether  depth  of  focus   is  de-            reset  the  film  speed  to   ,I.
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   T]SII{G THE BOLEXI}IETER                                                      camera,  under-exposure  Or  oyer-exposgr_e iS
                                                                 consistently   obtain€do  change  the   ernulsion     WITH COTOR FILM                                                    speed setting  as follows:   For under-exposure
TAKING METER READII{GS                    (dense btues)  try  the next  lower _speed value.                                                         For  over-exposure  (weak,  thiir  colors)  try  the   (lolor  fihn  has  less latitude  than  black  anrl                                                           next  higher  sPeed value.u,hite  fihn  and  for  this  reason   it  is  essential
that  the exposure  for  color  filrn be dc'termined           These changes in  fllm  values  artlficially    cor'-
 u'ith   grezrter  exactness  than   for  black   ancl            rect the €D(pos-ureto compensate  for  equipment
n-hitc.   \A/here extreme  contrast  is encountered             erro"s.   Ttiey-    should not be inte{pretedi as fep-
:lnd  detai I  is desired on €r particular   obj ect,  it           resenting   aituat  changes  fur  the  film  speed is advisable  to  take  a  close-up  reading  from                     'fhis                                                 rating.th_nt obj ect.            is  especialli   ad,visahle  for
col or photography   rvhere the  brightness   of  the
main  object                   is                 considerably                                    different                                         than                                'When                                                 the       PAIYORAIVTINGWITH Abriglrtness               of                 the                      bgcl.ground.                                             photo-
graphing  a person.  hold  the  rneter  rvit6in  1g        CINE' CAMERA
to 20 inches of the face, or, in general, not over            Panoraming  over areas where there  is a wide
tn'ice  as  far  from  the  ob j erct is  tho  u,iclilr  o{             variationJf-friggtness        requires  c_onsiderqablethc  obj ect.                                                           care when  usingi color  fflm.   For  best  results
                                                                                                                    it  is adviJable  t5 take separate-       readings  9f  tlreLIGHTII{G                                                                                         l"igfrf   tndnark     areas.  T11pnr when  actually
   Irlnt   I ighting   is  r'(]conlnrcndrrrl :rt  all  times              dkl"t    tne pictureso change the camera -f : stop'
u'hen using color  film.  Although  contrasty  ex-          aJ in[icaieh  bV Ure meter,  for-each   different
posur(ls rvill produee trrlensing effects rvith black            set of  conditions.lrnd u'hitc  fiIm, excessive contrast on color' film
resul ts   irr poor  renditian   of  col ors.   Or.rtdoor
c_olor pig_tur"esshcluld be taken on clear, bright
           Ifor  incloor   \\/ot.l{, carefull.y  plan  {heItayl,
lightirr_g so thnt   it  is d ifluscr-l evenly anrt  flatly
o\:()r thc   sullj ect.
ACCURACY OF EQUIP]VIENT
   lests  on  color  filrn  have  proven  that  expo-
sures must be correct  to  rvithin  one  f  : stop in
order  to  obtain  correct  color  rendition.   Horv-
over,  thc _itccuraclr of  even the  highest  grade
photographic   equipment,   including   Iens-- di:r-
phragrns,  camerrr shutters and  exposrlr"e rneters,
rrray vary  in  each case as much  as 7/3  oI' an
[ :  stop.    rf  al I  thr:  errors  a re such  tb at they
cancel, no  harrn  is  done.  But when  they   ait
tend  torn'ard over-exposure  or  under-exposure,
some me,ans of compensation  should be applied.
ohanging_ the film  speed setting  of the exposure
meter  rvill  in  the  rnajority   of cases cornpensate
ior  these  cquipment   errors.      ff,   r'r,ith your
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