Praktica BX 20 User manual

Praktica BX 20
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Introduction
Technical features
Guide to individual parts
Preparing to take pictures
Inserting the battery
Checking the battery
Opening the back
Inserting the film
Closing the back
Preparing to shoot
Setting the film speed
Taking pictures
Automatic shutter speed control
Preselecting the aperture
Automatic mode, indication
Shutter release
Locking the metered value
Exposure compensation
Semi-automatic mod e
Holding the camera
Flash photography
Changing the lens
Focusing
Depth-of-field indication
Infrared photography
Release button
Locking the release button
Self-timer
Changing the film
Care of the camera

With the PRAKTICA BX 20 you have bought a high-quality 35 mm SLR camera that combines ease of
operation with a versatility ideal for any kind of creative work.
The shutter speeds are automatically controlled within the range from 1/1000 s to 40 s.(seconds)
In addition, the camera's microelectronics permit the use of fixed shutter speeds between 1/1000s and 1s as well
as unlimited shutter speeds with the B setting. TTL light metering with open aperture and, thus brightest
viewfinder image is made possible by the electronic transfer of the aperture setting from the lens to the camera.
The PRAKTICA BX 20 is also equipped with a system which, if a dedicated computerized flash unit is used on
the camera, measures the light coming in from the flash unit, makes a split second evaluation, and closes the
shutter as soon as the right amount of light has struck the film. It goes without saying that conventional
electronic flash units can be plugged onto the camera as well. Manual corrections of the automatically
controlled shutter speeds are possible for the purpose of deliberate overexposures and underexposures.
LEDs on both sides of the clear and bright viewfinder image indicate the shutter speed to be expected, limits,
mode of operation (automatic or semi-automatic), memory function, exposure compensation and flash readiness
including the O.K. signal for dedicated computerized flash units. The bottom of the finder image provides
information on the preselected aperture and whether the shutter is wound or not. The PRAKTICA BX 20
accepts an auto winder and the wide range of PRAKTICA accessories.
FEATURES
· SRL camera for a frame size of 24mm x 36mm open-aperture TTL metering system
with electronic aperture setting transfer
· automatic electronic shutter speed control (stepless) in the range from 1/1000 s to 40
s
· change-over from automatic to semi-automatic mode possible; fixed speed range from
1/1000 s to 1 s
· electronic TTL metering system for flashes and correct dosage of light for dedicated
computerized flash unit,
X synchronization (approx. 1/100s)
· flash readiness indication (and "flash O.K." signal) in viewfinder image
· LED information on expected shutter speed in viewfinder
· indication of overexposure or underexposure
· aperture setting displayed at bottom of viewfinder image
· shutter "winding" information
· manual exposure compensation of + 2 exposure factors, indication of compensation
by red LED at,, + a
· locking of metered value and indication there of by green LED at "AEL" - (automatic
exposure lock)
· self-timer (approx. 10 s) with starting button serves also as stop-down lever for
depth-of-field checking
· focusing system comprises Fresnel lens with innovative diagonal triple wedge,
microprism ring and ground glass ring
· viewfinder image shows approx. 95 per cent of picture sides

· PRAKTICA bayonet (flange focal length 44.4mm internal diameter 48.5 mm)
· connection for motor winder
· film information holder on camera back
· indication of battery condition in viewfinder
· power source: 6V primary battery (e. g. PX281Mallory) (Webmaster: a note stuck
inside the manual states 4-LR44, 4-SR44 [Silver Oxide batteries - longer lasting] or
PX28 battery [basically two SR-44 batteries in one cell] also a note about a new battery
holder). All of these are common batteries available in large department stores or
camera stores.
· silicon photo element as light sensor
· metering and control range: 0-17 EV at 100ASA and aperture 1.4
· dimensions of body:141mm x 88mm x 49mm
· weight of body without battery: 510 g
Guide to individual of parts
1. Filter thread
2. Unlocking key
3. Self-timer release
4. Self-timer setting /ever
(anticlockwise) stop-down
lever for depth-of-field
checking
5. Frame counter
6. Winding lever
7. Window reflecting
aperture setting into
viewfinder
8. Rewind crank
9. Rewind button
10. Film speed dial
11. Unlocking key for film
speed dial

12. Memory and battery
check key
13. Aperture setting ring
14. Focusing ring
15. Depth-of-field scale and
infrared index
16. Lens positioning
mark
17. Lug for carrying
strap
18. Rewind release
19. Index for automatic
mode
20. Shutter release lock
21. Shutter speed dial
for "auto" and fixed
shutter speeds
22. Shutter release
with socket for cable
release

23. Hot shoe with center
contact
24. Center contact
25. Coupling point for
computerized flash unit
26. Indicator of exposure
compensation with index
27. Camera back
28. Film take-up spool
29. Film sprocket
30. Shutter blades
31. Film cartridge
compartment
32. Eyepiece with
accessory holder
33. Memo holder
34. Lid of battery compartment
35. Tripod socket
36. Guide way for motor winder
37. Coupling for motor winder
38. Catch for motor winder
39. Contacts for motor winder
40. Mark (for insertion of battery
compartment lid)

Inserting the batteries
A 6 V source is required to power the whole electronic system. It may be an alkali-manganese, silver oxide
(SR) or lithium battery.
We
bmaster:
On the left is an example of two PX-28 batteries from a Ricoh
manual. This is how the batteries should go looking down at the camera. Not
sure where the positive marks are on the body so this could be backwards. If
using 4-SR44 batteries you should have two bumps going in one direction and
two in the opposite.
Four button cells (e. g. LR 44) in a battery case (order no. 961 363) will also do. (the bumps on the batteries are
the negative sides, the two bumps should go in the same direction)
Under normal conditions, a fresh battery lasts for about 2 years. To insert the battery, push the battery
compartment lid (34) in the direction of the arrow and swivel it out Wipe the contacts in the battery
compartment and those of the fresh battery with a dry cloth. Press the plus pole of the battery against the spring
contact (polarity marks in the battery compartment) and tip the battery in. Close the lid and let it click in.
The contacts of the battery and in the compartment should be checked from time to time, and cleaned if
necessary. Low temperatures have an adverse effect on the battery; it should therefore be suitably protected in
cold weather.
If the camera is not used for an extended period, the battery should be removed.
Checking the battery
The shutter must be wound. Press shutter release (22) and then memory key (12). If the LED indication is bright
the battery still has a sufficient power reserve. When the battery is spent, the LEDs on the right side of the
viewfinder image will go out. The battery condition can not be checked in the B and setting.

Opening the back
Pull the rewind button (18) up as far as it will go to unlock the back Open the back completely the frame
counter (5) will automatically return to the starting position.
Inserting the film
Before the film is inserted the shutter speed dial should be set to a fast fixed shutter as otherwise a slow shutter
speed may be formed in the "auto" mode. The winding lever is blocked until the shutter has completed
operation. Do not use force! An undesired slow shutter speed that may have formed in the "auto " mode can be
cut short by changing from "auto" to B. Such a slow speed is also obtained in the "auto" mode when the shutter
is released without a lens being connected to the camera.
Put the film cartridge into the cartridge compartment (31). Press the rewind button (9) back in all the way;
turning it if necessary. Insert the film leader at least 1 cm into the slit in the take-up spool (28). Carefully
operate the winding lever until the teeth of the film sprocket (29) engage in the film perforation.. Swing the
winding lever fully out and let it return. Release the shutter.
Closing the back
Press the middle of the lock side of the back against the camera body until the lock is heard to engage.

Preparing to shoot
The winding lever (6) may be swung out a little way without starting the winding procedure. This readiness
position increases the handling reliability when taking rapid picture sequences. Swing the winding lever as far
as it will go, return and press the shutter release (22). Repeat the procedure and continue to do so until the
automatic frame counter (5) indicates frame 1.
Information on whether the shutter is wound or not is given at the bottom of the viewfinder image:
* aperture reflected into viewfinder appears red -shutter is not wound
* aperture reflected into viewfinder is colorless -shutter is wound
Proper film advance can be checked by making sure the rewind button (9) rotates as the winding lever (6) is
moved.
If you shoot with a winder attached to the camera refer to the instructions for use of the PRAKTICA winder
made by VEB PENTAGON DRESDEM We shad not be liable to you for damage caused by using a winder of
different make.
Setting the film speed
Press the unlocking key (11) and turn the film speed dial (10) until the film speed given on the pack (ASA
value) matches the index of the compensation indicator (26). The flap from the film pack can be put into the
memo holder (33) as an additional aid to the memory.
Automatic shutter speed control
In the "auto" mode, the PRAKTICA
BX20cperates automatically in a stepless
shutter speed range from 1/1000 s to 40s. The
shutter speed is electronically controlled in
consideration of the lighting conditions, the
preselected aperture and the film speed.
LEDs at the edge of the viewfinder indicate
the controlled shutter speed. Should the
shutter speed range be exceeded, OVER or
UNDER is indicated.
The TTL metering system automatically takes into account all factors influencing the exposure such as focal
length of the lens, filters and extensions.
If lenses with the 42x1 PRAKTICA thread are used with an adapter, light metering is automatic at working
aperture.

Preselecting the aperture
The desired aperture is set against the mark on the lens by fuming the aperture setting ring (13). The set aperture
is displayed at the bottom of the viewfinder image.
If lever (4) is moved in the direction of the
arrow, the diaphragm is stopped down to the
aperture set, and the depth of field can be
assessed in the viewfinder.
Automatic mode, indication
Set the shutter speed dial (21) to "auto". The
electronics are switched on by slight pressure
on the shutter release (22). In the viewfinder
image the shutter speed calculated by the
automatic system is shown by an LED
display. If it appears unsuitable for the
subject, it can be corrected by selecting
another aperture. LEDs are allotted to
selected speeds between 1/1000 s and 8 s,
with intermediate values being indicated by
the simultaneous lighting of two adjacent
diodes.
Shutter speeds between
8s and 40s are indicated
by the permanent lighting
of the UNDER LED,
while speeds outside the
1/1000 s to 40 s range are
indicated by the flashing
of the LED at OVER or
UNDER. In this case the
shutter is set for 1/1000 s
or 40 s. If shutter speeds
of 1/15 s and slower are
formed, the use of a
tripod or other steady
surface is recommended.

Shutter release
After shutter speed has been checked in
the viewfinder the shutter is operated by
fully depressing the shutter release (22).
When pressure is removed from the
shutter release the electronics are
automatically switched off.
With slow shutter speeds the removal of
pressure from the shutter release does
not affect the exposure procedure. In
this case the electronics are switched off
when the shutter cycle has been
completed.
If the cycle needs to be broken off prematurely with a very long shutter speed (e. g. after an accidental shutter
release), the shutter speed dial (21) should briefly be turned to B.
Locking the metered value (exposure lock - AEL)
If the subject features extreme
contrasts (e. g. people wearing dark
clothes in sunlit snow or a light-
colored object in front of a dark
background), the exposure value
can be determined by individual
metering of the most important
element in the picture from close
up. The value obtained in the close-
up measurement is stored, and the
image section can then be changed
without another shutter speed being
set.
To store the metered value first depress the shutter release (22) slightly (camera is wound) to initiate the
metering process, and then briefly press the memory button (12) to lock in the metered value (LED at "AEL" is
lit).
No new measurement is made before the shutter is released, and the shutter speed will correspond to the locked
value. The locked value is erased when pressure is removed from the shutter release and the electronics are
switched off.

Exposure compensation
Another way of influencing
the exposure individually is
by using the exposure
compensation system (10,
26). Such compensation is
necessary when the
character of the object varies
greatly the norm, e. g. with
dark objects in front of a
light background (+1, +2)
and with bright objects in
front of a very dark
background ( - 1, - 2).
Lift the film speed dial (10) and turn the exposure compensation indicator (26) to the desired value.
An LED (+/-) on the left side of the viewfinder image indicates that the shutter speed is overridden. Starting
from the initial position the shutter speed is reduced in the ,,auto" mode by 1 or 2 exposure factors when the dial
is set to + 1 or +2, respectively. The speed is correspondingly increased when the dial is set to -1 or -2. The dial
can be set to half factors. At the limits of the film speed range - 12 ASA and 3200 ASA compensation by two
factors is also possible.
However, the compensation cannot extend the shutter speed range beyond the speeds of 111000 s and 40 s.
Remember to return the dial to the neutral initial position after exposure-compensated shots. The LED (+) will
then go out.
Semi-automatic mode
If you want to shoot at a particular shutter speed, for reproductions or scientific work for example, set the
PRAKTICA BX 20 to semi-automatic mode. Fixed shutter speeds from 1 s to 1/1 000 s and the B setting for
any length of time are available. Select the speed you want using the shutter speed dial (21) this automatically
changes the camera operation to semi-automat/c mode. As with automatic shutter speed control, the camera's
electronics are switched on by gentle pressure on the shutter release.
The shutter speed can again be checked using the LEDs in the viewfinder: While the LED corresponding to the
set shutter speed flashes, the shutter speed required by the lighting conditions, the film speed and the selected
aperture is shown at the same time by a steadily lit LED (two adjacent LEDs light up for intermediate speeds).
To match the two, alter the aperture or shutter speed until the LED is lit steadily. There is no LED display for
the B setting. The fixed shutter speeds will not be changed by the described correction procedure.
Holding the camera
The illustration shows the best position in which to hold the camera. It should be held steadily and tightly, the
elbows should be supported against the body. In this way blur free pictures will be achieved.

Flash photography
If the available light is insufficient for handheld shots (e. g. indoors) or if the subject has to be additionally
brightened up, flash should be used. All fitting electronic flash units can be used, computerized or not.
Just push the flash unit onto the hot shoe (23); the electrical connection is thus made.
For electronic flash without computer control set the shutter speed dial (21) to . The speed will then be
1/100s.
If a dedicated computerized flash unit is pushed onto the hot shoe and the shutter speed dial (21) set to "auto",
an LED at the viewfinder edge ( ) will signal flash readiness, and the "auto" indication will go out. Flash
readiness will also be indicated in the case of a computerized flash unit when the dial is set to ..
Correct exposure is guaranteed by the camera's TTL light metering system: the reflected flash light passes
through the lens, is evaluated by the camera computer, and the flash is cut short at the right moment via the
cableless hot shoe connection - genuine automatic TTL metering also for flashes.
The "flash O.K." signal (film is correctly exposed) is derived from the flash readiness indication. If the LED
at lights up again immediately after exposure, the correct amount of light has struck the film. The O.K.
signal of the flash unit should be observed in cases deviating from the norm. Flash readiness is retained even if
the memory key is pressed and the green LED at "AEL" signals the locking of the metered value. Exposure
compensation signaled by the LED at (+ / -), is taken into account by the automatic flash system.
To avoid incorrect exposures with flash when the surrounding light is bright, check by switching off the
computerized flash unit that the shutter speed corresponding to the surrounding light is slower than 1/125 s. See
also the operating instructions for the flash unit for detailed information. Changing the lens
Press the unlocking key (2) and turn the lens anticlockwise as far as it will go. Remove the lens from me
camera.
Insert the PRAKTICA lens in such a way that the red marks (16 and 2) on the camera and lens are opposite each
other. Press the lens against the camera body and turn clockwise until the locking pin is heard to engage.

By using the PRAKTICA adapter all original PRAKTICA lenses with the M 42x 1 thread can be connected.
Lenses of other makes with the M 42x 1 thread must be suitable for PRAKTICA cameras and equipped for
metering at working aperture.
The PRAKTICA BX 20 also works automatically with screw-thread lenses, the only difference being that the
light metering is made at working aperture.
Focusing
Focusing is possible with the triple wedge system, the microprism ring or the ground glass ring.
1. Triple wedge
The wedge system allows highly accurate focusing. Optimum sharpness is achieved when the contours and lines
flow naturally. Incorrectly aligned edges indicate that the image is out of focus.
2. Microprism ring
The image is correctly focused when the image inside the grid is c/ear and flicker free.
3. Ground glass ring
Especially useful in photomacrography and photomicrography and when using lenses with a small relative
aperture (greater than 4). The image must a p pear clear and sharp in the ground glass ring.
Depth-of-field indication

The limits of the depth of field for the selected
aperture can be read off from the depth-of-
field scale (15) on me lens. Example: distance
3 m, aperture 8 - depth of field ranges from
around 2 m to 5 m.
Infrared photography
Infrared photography requires a slight correction to the focusing: match the distance determined in focusing
with the infrared index (see arrow) on the lens. Release button
For ease of operation several functions have
been combined in the shutter release (22).
When the camera is wound, gentle depression
of the shutter release until pressure is felt
switches on the automatic system and the LEDs
for shutter speeds or flash readiness (with
special flash units). Further pressure will release
the shutter.
Locking the release button
Accidental shutter release and unnecessary use of power as a result of unintentional pressing of the shutter
release button when the camera is wound or not can be avoided by locking the release button.
To this end, the lock (20) below the shutter speed dial is fumed in the direction of the arrow. To unlock turn in
the opposite direction.
Self-timer
Advance the shutter, swing the self-timer
winding lever (4) in the direction of the arrow 1
as far as it will go, and release by pressing
starting button (3) as shown by arrow 2. The
delay period is approximately 10 s. Do not wind
the shutter while the delay mechanism is
running.
If a motor winder is attached to the camera and switched on, several frames can be exposed during the delay
period with fast shutter speeds. If this is not desired, the motor winder should be switched off.
To avoid incorrect metering in the automatic mode the eyepiece should be covered with the eyepiece coyer
supplied.

Changing the film
The frame counter (5) indicates the number of frames which have already been exposed on a film. If all the
frames on a film have been exposed (red mark at 20 or 36), change the film.
Press in the rewind release (18) until it locks, fold out the rewind crank (8) and turn in the direction of the arrow
until increased resistance followed by easy movement indicate that the film has been fully rewound. Pull the
rewind button (9) all the way up to unlock the back. The film cartridge can now be removed. Do not change the
film in bright sunlight
Attention! If more frames are exposed than are indicated on the film pack, it is possible that the winding lever
cannot be swung all the way. Do not use force. Rewind the film as described above, then swing the winding
lever fully out.
CARE OF THE CAMERA
· Protect the camera from impact, dust and moisture.
· Clean the cartridge and spool compartments, the film track and the back from time to time with a soft brush.
· Do not use organic solvents such as spirit or varnish thinner to clean the camera.
· Do not expose the camera or lens to aggressive vapors.
· Remove fingerprints from the lens and eyepiece surfaces with lens cleaning paper.
· Do not touch the mirror, field lens or shutter blades. Such contamination can only be removed by a service
workshop.
· Use an optical brush for dust removal, or blow out
· Do not expose the camera to very high or low temperatures for lengthy periods. Avoid, for example, placing
the camera in a car window in direct sunlight
· The camera should be suitably protected from extreme cold.
· When using the camera near the sea or on the beach, protect it from salt water, spray and sand.
· Avoid sudden changes in temperature. These may lead to the formation of condensation and thus to corrosion
damage.
· Never attempt to make your own repairs to the camera. Consult a service workshop where necessary.
THIS IS NOTED ON AN EXTRA PAGE ADDED TO THE MANUAL Your PRAKTICA BX 20 has an
improved battery compartment lid.
Please note the following when inserting the battery:
Push the lid (34) in the (changed) direction of the arrow and open it.
Close the lid after battery insertion and lock it.
Please note carefully all the instructions contained in this booklet. Incorrect handling of your camera can lead to
damage not covered by our guarantee.
Further development of the PRAKTICA BX 20 may result in some aspects of the camera deviating slightly
from those given here.