DLG PHOTOMETER 2 User manual

Photometer 2 Instruction Manual DLGelectronics.com
1
PHOTOMETER 2
Focal Plane Metering System
For
Large Format Photography

Photometer 2 Instruction Manual DLGelectronics.com
2
CONTENTS
Introduction.................................................................................................................... 3
Introduction to Focal Plane Exposure Metering.............................................................. 4
Using the Photometer 2................................................................................................. 5
Technical And Performance Data................................................................................ 10
Circuit Diagram............................................................................................................ 12
Warranty, Servicing, Repairs and Enquiries................................................................. 13
Specification................................................................................................................ 14

Photometer 2 Instruction Manual DLGelectronics.com
3
INTRODUCTION
Image-plane metering with a large-format camera allows brightness measurements to
be taken at any desired point in the image. This allows exposure to be optimised taking
into account shadow and highlight areas, ensuring that detail within these areas is
captured in the negative. The Photometer 2 provides image-plane metering at an
affordable price in a simple, easy-to-use and robust metering system.
The Photometer 2 comprises a metering unit, a frame (which is inserted in the camera in
place of the film carrier) with integral metering probe, and a connecting lead.

Photometer 2 Instruction Manual DLGelectronics.com
4
INTRODUCTION TO FOCAL PLANE EXPOSURE METERING
A photographic exposure meter measures lighting and indicates camera settings to give
a nominally optimum exposure of the film. Several methods of metering are widely used.
Reflected Light Metering
Wide angle reflected light metering gives an overall reading of the luminance of the
scene and will indicate camera settings such as to render the overall scene average
luminance at a mid-grey level. This is the most common technique and gives good
results with “normal” scenes. However, in an unbalanced scene, with a dominant dark or
bright feature, the exposure may not favour the feature of interest. As an example,
imagine a scene with the mouth of a cave in an otherwise brightly lit daylight scene.
Using camera settings indicated by a wide angle reflected light meter will give an
exposure optimised for the average across the scene including the dark cave interior
and the brightly lit daylight outside. It is likely that the detail within the shadow of the
cave will not be satisfactorily rendered, with the negative underexposed in this area and
failing to show any detail within the cave shadows. Similar situations can arise when
photographing dark objects against the sky, or in a snow scene, or when trying to
photograph a brightly lit subject against a dark background.
Incident Light Metering
Incident-light metering partially addresses this issue by indicating an exposure setting
based on the light falling on the subject of interest in the scene. In our cave example, an
incident light reading could be taken within the cave in an attempt to optimise the
exposure for the shadowed cave interior. However, the incident light reading obviously
does not take into account the reflectivity of the subject.
Large-Format Focal Plan Metering
With large format photography, the possibility exists to measure the actual illumination at
specific points in the image, and to optimise the exposure for features of interest in the
image. Further, it is possible to measure the illumination at various points in the image
where it is desired to get good rendering of shadow and/or highlight detail, and to
optimise the exposure to achieve the best compromise. Furthermore, by determining the
total range of luminance across the shadows and highlights of the image, the film
processing may be optimised to give the best results.
The focal plan metering system lends itself to use of the Zone System, devised by Ansel
Adams and Fred Archer. An excellent description of this system is given in Adams’ book
The Negative (1981).

Photometer 2 Instruction Manual DLGelectronics.com
5
USING THE PHOTOMETER 2
Components of the Metering System
The metering system comprises:
1. The meter
2. Frame, including rear shutter.
3. Sensing probe
4. Connecting cable.
Insert 9V battery type - 6LR61 / 1604A / PP3. The battery compartment is on the rear of
the case.

Photometer 2 Instruction Manual DLGelectronics.com
6
Insert the frame in the camera exactly as you would a film carrier. The metering frame is
designed to the same geometry as a standard film carrier and should engage positively
in the camera. The frame incorporates a slide shutter and this should be behind the
metering probe, that is, it should come between the ground glass screen and the
metering probe. The shutter is used to exclude light from the interior of the camera when
taking readings particularly in challenging circumstances.
Insert the metering probe into the wider of the two slots in the top of the frame, if it is not
already inserted. The sensor should be facing the front (lens) of the camera. If it is not
clear which side is the sensor, the connector block at the other end of the probe should
be on the front side. A white circle on the rear of the metering probe indicates the
location of the sensor.
Connect the probe to the metering unit with the cable.
Turn on the meter and set the film speed (lower left control).
The display indicator will display zero (centre of the display) when the measured part of
the image will give a neutral grey at the exposure settings on the meter.
Slide shutter
closed if
necessary to
exclude excess
light from
camera interior

Photometer 2 Instruction Manual DLGelectronics.com
7
Move the metering probe within the image to measure the brightness of the various
features within the image. Adjust the “exposure” settings on the meter as required in
order to keep the display within the required range. The display is marked in whole top
numbers, so that e.g. +1 on the display indicates a factor of two in the brightness and
thus one additional f-stop on the lens aperture or one increment of exposure setting.
Normally, features that are darker than 2-3 stops from the nominal will render as full
black, with no additional detail therefore visible, and features 2-3 stops lighter than the
nominal will render as white, likewise showing no further detail.
The meter incorporates two memories, which can hold the brightness value at two points
in the image while metering a third. This is convenient when attempting to optimise the
exposure across more than one feature in the image. When the “hold” buttons are
pressed, the currently-metered brightness value is stored in the meter in the
corresponding memory.
Turning the on-off-1-2 switch to the hold 1 or hold 2 positions displays the stored
brightness.
A typical use might be as follows.
1. Measure the image brightness in a shadow area of interest. Adjust the
exposure controls to give a reading of, say, two stops down from centre scale
in order to give a dark rendering but still showing some details. Press the
“hold 1” button to store this brightness.
2. Move the metering probe to measure a highlight feature. Adjust the
“exposure” controls on the meeting as required to bring this into the range of
+/-3 on the display.
3. After setting the exposure control on the meter at step 2 above, turn the off-
on-1-2 control to the “1” position and confirm that the previously-stored
brightness in the shadow area is still within an acceptable range. If not, re-
adjust the exposure settings to bring both the highlight area and the shadow
area into an acceptable range.
Move metering
probe as
required
Sensor position
is marked by
white spot on
rear of metering
probe

Photometer 2 Instruction Manual DLGelectronics.com
8
Description of the Controls and Display
INPUT Control
Positions: “Off”, “On”, “Hold 1” and “Hold 2”
“Off” disconnects power and all functions including battery monitor and display light are
disabled.
“On” enables the meter. The meter responds to the light level on the sensor. The display
indicates the brightness of the image relative to a notional 18% grey value for the
Display light
push button
Brightness
indicator
Push to test
battery.
Exposure control –
set the desired
exposure
Range control –set
fractions of second,
seconds, minutes or
hours of exposure
Use the HOLD buttons to
store the current
brightness in memory 1
or memory 2.
On/off switch and input
setting –position 1
displays memory 1,
position 2 displays
memory 2.
Set the film speed
Connection to metering
probe

Photometer 2 Instruction Manual DLGelectronics.com
9
selected exposure setting and film speed. Display pointer to the right indicates brighter
whereas to the left indicates darker.
When either of the “HOLD” positions is selected, the corresponding stored value is
displayed. The HOLD functions memorise the brightness not the display –the displayed
value is adjusted according to the settings of the exposure, range and film speed
settings.
EXPOSURE and RANGE control
Together these enable the exposure time to be selected. The maximum exposure is
approximately 1 hour at 125 ASA.
At very low light levels the meter can take some time to respond and settle to an
accurate reading. Avoid exposing the sensor to high brightness conditions immediately
prior to taking readings at very low light levels, as this slows the response.
Excessive humidity may limit the ability of the meter to read extremely low light levels, In
the event that this occurs keep the meter in a warm dry place for 24 hours and
performance will be recovered.
FILM SPEED
The film speed selection provides for a range of different film speeds from 32 ASA to
1600 ASA. For film speeds not in this range, allowance must be made or the exposure
settings adjusted accordingly.
HOLD buttons
Pressing either of the HOLD buttons memorises the current brightness in that storage
location irrespective of whether the INPUT control is in the ON, HOLD 1 or HOLD 2
positions.
The HOLD functions memorise the brightness not the display –the displayed value is
adjusted according to the prevailing settings of the exposure, range and film speed
settings.
The memory is stored on capacitors in the meter and will therefore drift over a period of
time. The drift may be in either direction depending on the stored brightness. The
specified accuracy will be maintained for a minimum of one hour.
The HOLD functions do not memorise the brightness when the meter is turned off and
initialise on power-on in the region of 1 second exposure equivalent.
BATT TEST
The battery test function is provided as a low battery may give non-obviously inaccurate
readings. The battery should be replaced should the red light illuminate when the button
is depressed.
Display light
A backlight is provided when the red button to the right of the display is depressed. The
light extinguishes when the button is released in order to conserve battery life.

Photometer 2 Instruction Manual DLGelectronics.com
10
TECHNICAL AND PERFORMANCE DATA
The information contained in this section is for guidance only and represents typical,
rather than the guaranteed minimum performance. It is provided for the guidance of
specialist users with unusual applications and may be disregarded by the majority of
users.
Calibration
The meter has been calibrated to give a negative tone in the centre of the useable
range. Film tests have been carried out to determine the optimum point. See figure.
Note that the film base is not perfectly transparent and typically transmits around 50% of
the light. The test data has been adjusted accordingly, to give 0% for the lightest
possible (around 50% transmission) negative and 100% for a completely opaque
negative.
Measured HP5+ Characteristic
-3
-2
-1
00 1 2 3 4 5
Log Relative Exposure
Log Intensity
Film Base
Calibration Point

Photometer 2 Instruction Manual DLGelectronics.com
11
Spectral Response
Peak response is at 530nm (green). Response at extremes of the spectrum will be
within a factor of two (one stop). In practice in normal situations, where highly saturated
colours at the extremes of the visible spectrum are not normally present, no correction
factor need be applied for colour.

Photometer 2 Instruction Manual DLGelectronics.com
12
CIRCUIT DIAGRAM
+
-
R1 1M VR1
100k
R6
5.1k VR2 10k
Q1 BC548
Q2
BC548
IC4a LF442 R3
43k
R2 6.2k R2
R6
D1D1
C8
0.001
+Vref -Vref
+Vref
TH1
4.7k @ 25°C
-4%/°C
IC4b LF442
+
-
C6
0.1
C7
0.1
IC5a ½ TL062
+
-
IC5b ½ TL062
+
-
IC6a ½ TL062
-
+
R7 10k
R8 10k
R9 10k IC6b ½ TL062
-
+
+Vref
-Vref
1/s
h
1/s
h
+Vref
2000
1
SW2
Exposure +Vref
- Vref
1600
125
25
R12 5.6k
D3 1N914 D4
1N914
R38 2.2k VR3 2k
μA
R37
5.6
C1
100
+9V
+5V (Vref)
C3
10
C2
10
D1
1N914
-9V
IC2
78L05
GND
Batt 0V
IC1
ICL7660
2
4
8
5
IC3
79L05 -5V (-Vref)
Batt +9V
R39 10k
R40 3.9k
R41 10k
Q3 BC548
Q4 BC559
R45 3k LED2
RED
+9V
SW7
Batt. test
OFF
TP1 TP2
R10
R11 20k
R13 130k
R15 20k
R14 39k
R16 13k
R17 9.1k
R19 4.7k R21 3k
R20 3.3k
R22 2.2k
R23a 820
R24b 1.1k
R18 6.2k
TP3
TP4
TP5
R23b 22k
R34 36k
R33 68k
R35 22k
R27 24k
R26 68k
R28 56k R30 330k
R29 220k R31 390k
R32 130k R36 130k
R24a 20k
R25b R25a
3
SW1
10k
125 -0- 125μA
D5 1N4006
ZD1 5.1V
R42 10k
R44 10k Q5
BC559
SW8
R46 2.7k
LED1 GRN
LED3 Display Light
SW4
Film Speed
SW3
Range
+
R5 68k
+Vref
All resistances in ohms. All capacitances in micro-farads.
R46 68k
s/n 005 to 008 Incorporating Changes: 01 –Deletion of C4 and C5 03 –Offset Adjustment Circuit
Offset Adj.
Slope Adj.
1.1k 20k
R43 3k
+
-
R1 1M VR1
100k
VR1
100k
R6
5.1k VR2 10k
Q1 BC548
Q2
BC548
IC4a LF442 R3
43k R3 43k
R2 6.2k R2R2 6.2k R2
R6
D1D1D1D1
C8
0.001
+Vref -Vref
+Vref
TH1
4.7k @ 25°C
-4%/°C
IC4b LF442
+
-
IC4b LF442
+
-
C6
0.1
C7
0.1
IC5a ½ TL062
+
-
IC5a ½ TL062
+
-
IC5b ½ TL062
+
-
IC5b ½ TL062
+
-
IC6a ½ TL062
-
+
IC6a ½ TL062
-
+
R7 10k
R8 10k
R9 10k IC6b ½ TL062
-
+
IC6b ½ TL062
-
+
+Vref
-Vref
1/s
h
1/s
h
+Vref
2000
1
SW2
Exposure +Vref
- Vref
1600
125
25
R12 5.6k
D3 1N914 D4
1N914
R38 2.2k VR3 2kVR3 2k
μA
R37
5.6
R37
5.6
C1
100
+9V
+5V (Vref)
C3
10
C2
10
C2
10
D1
1N914
-9V
IC2
78L05
GNDGND
Batt 0V
IC1
ICL7660
2
4
8
5
IC3
79L05 -5V (-Vref)
Batt +9V
R39 10k
R40 3.9k
R41 10k
Q3 BC548
Q4 BC559
R45 3k LED2
RED
+9V
SW7
Batt. test
OFF
TP1 TP2
R10
R11 20k
R13 130k
R15 20k
R14 39k
R16 13k
R17 9.1k
R19 4.7k R21 3k
R20 3.3k
R22 2.2k
R23a 820
R24b 1.1k
R18 6.2k
TP3
TP4
TP5
R23b 22k
R34 36k
R33 68k
R35 22k
R27 24k
R26 68k
R28 56k R30 330k
R29 220k R31 390k
R32 130k R36 130k
R24a 20k
R25b R25a
3
SW1
10k
125 -0- 125μA
D5 1N4006
ZD1 5.1V
R42 10k
R44 10k Q5
BC559
SW8
R46 2.7k
LED1 GRN
LED3 Display Light
SW4
Film Speed
SW3
Range
+
R5 68k
+Vref
All resistances in ohms. All capacitances in micro-farads.
R46 68k
s/n 005 to 008 Incorporating Changes: 01 –Deletion of C4 and C5 03 –Offset Adjustment Circuit
Offset Adj.Offset Adj.
Slope Adj.Slope Adj.
1.1k 20k
R43 3k
Indicative only –component types and values may differ as part of our policy of continuous
improvement

Photometer 2 Instruction Manual DLGelectronics.com
13
WARRANTY, SERVICING, REPAIRS AND ENQUIRIES
The meter is guaranteed against manufacturing defects for a period of one year.
Register with us by emailing us with your contact details, quoting your meter serial
number (found inside the battery compartment) to extend your warranty to three years.
In the event of damage or defects, please contact us at [e-mail],
or write to us at DLG Electronics, 138 Osmaston Road, Derby DE1 2RF, UK, or contact
your local distributor. For units outside warranty we can offer cost-effective repair,
refurbishment or replacement with a refurbished model if you return your damaged unit.
Please do not send us your meter until you have contacted us.
We welcome any feedback, comment or suggestions on our products. Please contact us
at [e-mail] or use the feedback form on our website
dlgelectronics.com.

Photometer 2 Instruction Manual DLGelectronics.com
14
SPECIFICATION
Exposure Range:
1/2000 second to 1 hour at 125 ASA
Film Speed settings:
32, 40, 50, 64, 80. 100, 125, 160, 200, 400, 800, 1600 ASA
(16, 17, 18, 19, 20, 21, 22, 23, 24, 27, 30, 33 DIN)
Display Range
± 6 stops either side of selected setting.
Accuracy:
± ⅓ stop* (1/s and s ranges only)
“Hold” duration:
¼ hour to ⅓ stop minimum.
Peak Spectral
Response:
530 nm
Power consumption:
10 mA approx, battery monitor and display light off
Battery type
PP3
Battery reverse
connection protection:
Yes
Settling time:
<1s, exposures 1/2000s to 1s at 125 ASA
<10s, exposures 1s to 1 min at 125 ASA
<1min, exposures 1 min to 1 hr at 125 ASA
Sensor
Resistance
Weight
12 oz. approx
Dimensions:
Meter Unit: 4½” x 6” x 1⅝”
Metering Probe: 10½“ x 3/4” x ⅛” approx
Frame: - to suit camera format.
_________________________________
Document reference DLG-PM2-001 v4
© D. Gooding 2017

Photometer 2 Instruction Manual DLGelectronics.com
15