AVO exposure meter User manual

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  "AVO"THE
EXPOSURE METER
    sv      16
Imstructioms
   for use


        BitTtsH 1'tA0E

I
       "AVO"The
   EXPOSURE  METER
                          (Pro,.  Pr;tentetl)




trIanufactured bv:'
THE AUTOMATIC COIL WINDER & ELECTRICAL EEUIPMENT CO' LTD
       WINDER HOUSE, DOUGLAS STREET, LoNDON' S'v\/'l
                               Tcl'efhottes : V'ic!oria 3404'7
coNTRAcToRs To: The Admiralt', war office' Air Board G,P.o., India office, Crown
     Agents for the Colonies, and the prlncipal Telephone Companies throuS,hout the world'
                        fhe word "AVO " is our registcred rrade Mark'

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                Method " B "
                       When it is desired to use a definite stoo
                      and consequently  to  ad.just the exposure
                              time to suit, the l<nob should be rotated until a
                                 suitable arrow points to the required " f "
                           value. In general,  it  is advisable to use the
                            arrow which allows the meter to give the
                              largest pointer indication. The exposure
                          time should then be read on the same
                           coloured scale as arrow chosen, while the
                          meter is directed towards the subiect.


                          Diagram 4"
                                Rotote knob in c!ockwise direction until
                                pointer indicates  eitfier full scole or moximum
                               deflection, considering light conditions, with
                              meter pointed towords subject.
                                Reyerse movement of knob until one of
                              the orrows orrives at the stop it  is desired to
                              use .' e.g., f 4 in cose shown.
                       As block arrotr is pointing to f4,  reod
                                                                1  i 25 sec. on black scole.DirrglanL 4                  exposure time of

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                Other Cine Cameras
                              For cines having different shutter speeds,
                              or for slow motion photography,   it is necessary
                           to use Method A, the knob being adjusted
                               untll the pointer indicates the shutter speed
                            of the camera on the most suitable scale,
                          and then reading the stop value to be employed
                       as degcribed.                                                                                                                  If
                         Dlagram 6,
                                Suppose shutter speed is I 64 sec', odiust
                            as in Method A so thot pointer is in o position                                                 {;                              corresponding to 'l'64 sec (os illustroted) on
                                black scale, and reod stop shown on black orrow'
                                               lf  lisht is very weak, use red scole ond red
                                orrow,


Di.TgtanL 6

GENERAL NOTES           arlandrcapesfoliage, withor withaveragefigures,forcground,open 3tr€etruch
    When pointing the meter towards    scenes, bulldings of normal colour, and
   the subject,   it  .is advisable to   tllt    it    in general, scenes where there is about
   rlightly downwardr  if there  is a likelihood    equal amount of light and shade without
   of  direct  light  from  the  rky  or  sun    excessive contrast.
   rhlning on the cell, since th€ exporurc       For distant landscapes or scencl of
   should be made to suit the chadc rather    small contrast in brightn€ss, exposure3
  than the high lights.                         of  half  norrnal may be  given  with
     The possibility of loss of speed due to    advantage.
   the film being kept unexposed for a pcriod        Portraits and groups, scenes of deep
   of time should be allowed for.                  contrast, such as in narrow streetsrunder
          It must be undcrstood that the shuttor   trees and so on, require two or throc
  speed values shown on the camara are fixed.    times the normal exposure to bring out
  Intermediate positlonr between adiacent    the shadow detail.
   indicators must not, therefore, be  used.         This correction for sublcct may, if desired,
  Should the exposure time lndicated by the   be carried out on the diaphragm of the
  meter fall berween two such shutter speeds    camcra instead of the shutter.
  on the camera, one speed should be selected,         Successive stops marked on th€ mctcr
  and slight adiustmcnt of the iris diaphragm     (ln clockwise direction) when applled to thc
  made to compensate for this,                  camera admit twice as much light so that for
       Since it is morc important to makc the   photos of strong contrast thc next larger
  exposure suit the shadc than the brlghter    stop than indicated may be used and for thoso
   portions of a scenc, lts character will, there-    of weak contrast, the next smaller.
   forc, have some bearing on the best exposuroi   Extension of normal  limitr.'  for any given light. This being thc case when              lf at any time  it  is dcsired to takc a
  phcltographing oblects of deep contrast, a   time exposure using a smaller stop than
   longer exposure will bc required than wlth    indicated by the green arrow, the correct
   obiects oflight contrast, although the averago    value can be obtained by doubling the timc
  amount of light coming from the subiect as    indicated, for each smallcr stop shown on the
   r whole, in both cas6s, may be the same.      meter, c.9., supposc the meter indicatcr
     The exporure rhown by the meter  ir   5 secs. at f11, then it would bc'10 sccs.,
  for  ell normrl  .ublcctr.  Thic includo     20 recs., 40 secs  . at 11 6, 122 end f32 rcrpectivcly.