Quantum CALCU-LIGHT X Operating Instructions Manual

QUANTUM CALCU-LIGHT X

OPERATING INSTRUCTIONS

1. INTRODUCTION

This manual is yo ur guide to operating the Calcu-Light. Please read it
completely to fully benefit from the unique capabilities of your
instrument.

Refer to diagram 1 throughout this manual. There are two switch
controls, MEASURE and MEMORY. A LIGHT TURRET rotates to
enable either the incident or reflected light meas urement m ode. A
calculator dial provides f-stop, film speed, shutter speed, exposure value
(Ev) and cine (frames-per-second) values.

Diagram 1

2. SETTING FILM SPEED

First, rotate the outer dial rim until the reflected
window. This exposes the film speed dial, in the finger slot, on the right hand side of Calcu-Light.

Next, place your index finger into the slot and your thumb on the dial rim. Squeeze the rim and dial together and turn
them. The ASA and DIN numbers will change to the new values. If the desired value is not reached, reset the rim to
its original position, and again, rotate the rim and dial.

See specifications for the exact designations of film speed "dot" markings.

3. SETTING AND REMOVING LIGHT TURRETS

The standard Calcu-Light turret rotates to take either 30° reflected light or 180° incident light measurements. To
change the mode, l oosen the turret thumbscrew app roximately 4 or 5 turns . Lift and rotate the turret and tighten the
screw.

The selected mode is indicated by whichever turret symbol, reflected
of Calcu-Light. A mark on the instrument housing
light, the lens for reflected light.

The techniques of incident and reflected light measurements are covered in Section 5.

and incident symbols lie on either side of the digital di splay

or incident lies at the front (dial side)

serves as a reminder of the mode. The white dome for incident

To remove the turret turn the thumbscrew counterclockwise until it is free. Any of the accessory turrets described in
section 8 can now be mounted onto Calcu-Light.

4. TAKING A LIGHT MEASUREMENT
Point Calcu-Light in the desired direction and press the MEASURE control. A reading will appear in the display

window. Continue to hold the measure control to obtain updated readings.

Calcu-Light automatically remembers th e last light reading taken. To recal l this reading press the MEMORY
control. The digital light value indicated will not be changed by pressing MEMORY.

Set the digital reading obtained into the dial by turning th e dial rim. Use the incident

window or the reflected
window pointer corresponding to the mode se lected. The calculator dials should now show the correct combinations
of corresponding shutter speed, lens f-num bers, and cine (frames per second) values for the digital light value
indicated. Exposure values (Ev) also appear.

All line marking s on the dials are for one Ev, or stop, apart. Dot markings are 1/3 Ev incr ements, or 1/3 stop each.
The digital numbers of Calcu-Light are al so a sequence of 1/3 stop increments of light value.

Sections 7 and 10 give more detailed information about the digital and dial readouts.

5. EXPOSURE MEASUREMENT

Photographic light readings taken with Calcu-Light are categorized as reflected or incident light meas urements. The
system accessory attachments described in S ection 8 provide for special types of measurements within those two
categories.

Incident readings measure the light received by the subject from the (180°) hemisphere in front of the subject
(towards the camera). To take the reading, use the diffusing dome of the light turret by mounting it over the

mark
on the instrument. Hold Calcu-Light at the subject position and point the center of the diffusing dome towards the
camera position.

Be sure to avoid blocking any light sources. Take your reading and set the dials as previously described.

An incident reading is reliable and accurate because it is a measurement of light from its source, before it is reflected
and modified by the subject. The reading is not affected by the subject's color, tone or other reflectance qualities.
The resulting exposure places tones in the final picture (more or le ss) as they appear to the eye.

Reflected light readings, on the other hand, are essential for either convenience or special applications. They
measure light reflected by a subject in a specific direction. To take a reading use the lens of the turret by mounting it
over the

mark on the instrument. Point Calcu-Light towards the subject from the direction of the camera. You
may measure the subject up close or from far away, but do not block the light sources. Take your reading and set the
dials as previously described.

A reflected li gh t reading is calibrated to an average ton e, defined as 18% grey. A reflected reading of an 18% grey
card will result in the same exposure as an incident reading of the light source. And, the subject will be rendered as
18% grey in the final print.

A reflected r eading o f any s ubject results in an exposure that tends to render that subject as an "average" tone. That
is why reflected readings of predominately bright, or dark, subjects do not generally yield the best exposures. They
must be interpreted and modified. For general purposes inci dent readings are preferred.

Reflected light r eadings, however, are essential when the subject position is inaccessible for incident readi ngs, and
when the subject is itself a light source. They are useful for contrast and zone measurements to within 1/3 of a zone,
or stop.

6. BATTERIES