Minolta Auto Spot 1 degree User manual

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  Minolta Auto-Spot 1 " is a high-perfomance,  spot-reading photo light meter with a CdS cell. which
  is best suited for use by professional photographers, movie cameramen, and other light measuring
  experts. This spot meter has outstanding features, as listed below:
  1. Superb Accuracy
 Accurately marked light measuring range (1 ")
 Although this meter has a very narrow field angle of 1 ", its light measuring angle is very accurately
 marked.
  Flareless spot mete r
 This spot meter accurately measures light within its measuring range.
 The measured value of the light is not affected by any stray light beyond its field-
  2. Easy to Operate
 Easy to operate automatic spot meter
 To operate the meter, after ASA film speed has been set, just press the main switch button and read
 the exposure scale after they no longer rotate. When main switch button is released the exposure
  scale will lock permitting you to select correct shutter speed and lens aperture for proper exposure.
 This spot meter eliminates the trouble of operating a complicated calculating scale. The circuit
  starts the motor which, in turn, drives the scales in the viewfinder. Then the scales automatically
  indicate the  f -number, exposure values and the shutter speed best suited for the subject.
 The viewfinder shows a bright and highly magnified erect image
 Due to the use of a full mirror the viewfinder receives 100% effective light.
                            www.butkus.us

It therefore gives a high amount of brightness to the viewf inder system. This relatively high transmis-
     sion of light into the finder system permits the image to be magnified 4X.
    Bright scale illuminating lamp built in for reading the scales in the dark
   A bright lamp in the viewflnder enables you to read the scales clearly even in dark places
     3. High Reliability
'    Metallic body
    This meter is made mostly of die-cast aluminium and other metals. This makes  it highly shock-resist-
     ant.
    Completely hermetic semicondutors
     This CdS cell is of a highly stable metal sealed type. Transistors, diodes, and other circuit parts are
     completely moisture-proof. Six of the eight transistors are of the disc type, made*of silicon, so that
     they are specially stable.
    Printed circuit
    The printed circuit is highly resistant to vibration
    Stable electronic circuit for normal operation
    Temperature variations usually change the properties of the transistor. This meter, however, has
     highly stable transistor circuits over a temperature range +45'to -10'C. Because a bridge circuit
    and a voltage regulating circuit are used, protection against voltage variation can be asured. As long    t
     as checker lamp is kept "on", this meter functions well under most any conditions.
    Folding rubber hood
    The lens barrel is protected against damage, by its cover, a folded-type rubber hood. The eyeprece
     also has a rubber hood.

1. Detecting Circuit
  The bridge circuit consists primarily of a CdS resistor and a
   variable resistor. The amplifying circuit and the motor are
   placed in the position corresponding to the galvanometer.
  When the balance between the values of both the CdS
  and variable resistors is lost for any reason, current runs
  through the motor. Then the variable resistor, interlocked
  with the motor. works until the balance is restored. This
  spot meter is characterized by the coupling of the motor
   revolutions with the scales in the viewfinder.





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2. Optical Systems (for Viewfinder and Measur-
ing Light)
The light reflected from the object enters into this spot
meter through the lens L1. In this case,2Oo/o of the light
is reflected on the total reflection mirror A. and turns into
an erect image through the Porro prism P.  Then the
image appears on the scale glass F and reaches your eye
through the eyepiece L2. As the mirror A is big enough for
your eye, all the light for the viewfinder reaches your eye.
The viewfinder, therefore, looks very bright. 75o/o of the
light passing through the lens L1 hits the reflection lens
C and the mirror B. Then it is focused on the opening
(1 ') of the slit S and reaches the CdS cell.
As the scale glass F and the slit S are optilally conjugated,
light focusing on the viewfinder screen is the same as that
on the slit S.                                                                                               I
3. No Flare Noise Effects 6rf  K u c. ct f
Special features of this spot meter include: 1) it has no
halfmirror; 2) focusing can be done at 1 m (3.3ft); and 3)
harmful rays are prevented from entering. Even when
there is a very bright flaring light outside its  f ield,'it
remains unaffected by the light. In addition, the lamp
illuminating the scales and light passing through the
eyepiece have no effect on its functions.

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4. Scales
   Tl-ie scales are set in the viewfinder: (See the chart of the
  finder scale)
  EV:AV+TV: BV+SV
  Where EV: Exposure Value
       AV: Aperture Value
       TV: Time Value
       BV: Brightness Value
       SV: Speed Value





  When SV and AV remain constant in the above formula,
  TV is determined according to BV. In this spot meter,
   all values are indicated in the viewfinder in combined
  from through the interlocking of fhe motor with the time
www.butkus.usscale. The speed value can be adjusted with the

          5

ASA knob over a range from 3 to 25,000.
5. Power Source
The light measuring power source is a-9 V manganese
battery (Mallory M-1604 or ebuivalent). When it is used
 f requently its voltage grpdually decreases. A Zenner diode
therfore, is used for the Voltage regulating  circuit.
The circuit. together with the bridge circuit, contributes to
the stable light measuing performance of this spot meter
almost irrespective of voitage variations-from 6 to 9 V.
The battery can be checked with a lamp. When the battery
voltage drops below 6 V, the lamp does not light up.
When the voltage is 6 V or more, however, the lamp lights
up brightly. The lamp enables you to Tlnd whether you
need a new battery or not.
The lamp illuminating the scales in the viewfinder is a
1.5 V of the AA size. Be sure to replace the lamp with a
new one when you can no longer see the scales clearly.
                                  \"v rt Y;6. Battery Life    $-' ^
The 9 V battery can be used ior a total of '100 minutes.  lf
ybu use it frequently, however, prepare a spare one for
safety's sake.


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Preparation for measurennent


                            (1) Adjust visibility"
                          Look through the viewfinder, and turn the eyepiece until you see
                                          a ll the sca les clearly.



                           (21 Extend the hood. (Fold it up after use.)



                                                                                                                                                                                                                                                                                                                                                                                  t
                            (3) Adjust the film speed.
                         The lowest scale in the viewfinder is the ASA scale.
                           Turn the foremost ASA setting kr. rb, and set it to the ASA number
                                 of the  f ilnr you are using.
                                          (lf you cannot see the ASA scale clearly, first adjust yoLrr visibility
                                 to the scale. Then set the knob to the ASA number of your film, and
                               adjust your visibility again to both the diaphragm and the shutter
                           speed scale.)
                            For conversion between DIN and ASA number, refe.r,to the ASA/
                        DIN conversionwww.butkus.ustable at the bottom of the grip.

(4) Gheck the power battery voltage.
                              Press the main switch button and the checker button beside the
                                 vlewf inder at the same time.
                          Then the lamp above the checker button lights up.
                     Now all preparation are finished.



Measurement

                                       (1                                  ) Aim at the subject.
                       The circle at the center of the viewfinder indica#s the light fieid
                              (measuring area).

                      CAUTION : Do not try to view the sun with the meter lest the direct
                                 sunlight should burn up the sensitive mechanism of the meter.

                            (2) Focus on the subjcet.
                             Turn the lens barrel until subject to be measured appears sharp in
                                viewfinder window.
                                                            l0

.(3) Press the main switch button.
When the main switch button is prBssed, the illumination lamp
lights up and the exposure scale moves in the viewfinder and stops
at the point correspond!ng to the luminance of the subjcet. (The
scale remains stationary even after you remove your finger from the
b utto n. )



(4) Read the scale.
Read the combination of the f-number and the shutter speed, or
the luminance guide number.



(5) Indication beyond the measuring range.
You can find the luminance of the subject according to the indication
of the EV pointer in the viewfinder and the measuring range of the
mark.
The accurate luminance of the subject can be measured if the EV
pointer stays inside the measuring range. But it cannot be measured
if the pointerwww.butkus.usmoves beyond the range.
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(6) How to use the ND filter.
                             The ND filter (16X) is available for extension of the measuring range
                           on the high luminance side. With this filter, you can measure the
                                 luminance of the subject up to BV 16 (equivalent EV 21 for the ASA
                              100 film). In this case, a four-step correction is needed for reading
                                  the scale.

                                  (7) Calibration table
                          Vou can get the accurate calibrated value of your meter according
                                   to the calibration table packed with the meter.
                           By using the table, Foot-lambart value can be get from a crossing
                                  point of a guide line of the luminance guide numbgy (indicated by
                                  the EV pointer set for ASA 100) and a calibrated curve.F

F                              (8) Compensation of luminance changes due to magnifica-
                                 tion change.
                               Compensation figures have been placed on the lens barrel of the
                                  meter, for purposes of obtaining more accurate exposures. To     r
                                      correct for this change,  it is necessary to add compensation number
                                    to luminance guide number.



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