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5.4.6 Guide number indication when using lenses without CPU
Lenses without CPU (i.e. without electronic data transmission) do not transmit
to the camera any electric information about focal length and aperture set-
ting. If such a lens is used on a Group A camera, then the mecablitz will only
receive from the camera the data relating to the film speed in ISO. The posi-
tion of the zoom reflector must be set manually (see 5.7.2). In this case the
LC-display of the mecablitz indicates the guide number for the current setting
instead of the distance (in the given example: guide number 34). The maxi-
mum flash range is the result of the following formula:
guide number
Maximum flash range = ——————————
aperture
Refer to the instructions regarding the flash-to-subject distance in
section 5.5. The guide number is not indicated when the reflector is
folded down.
5.4.7 Meter-Feet changeover (m - ft)
The maximum flash range indicated by the mecablitz LC display can be
either in meter (m) or feet (ft). To change between the two, proceed in the fol-
lowing manner:
•
Turn off the mecablitz by its main switch.
• Keep the “Select” key combination depressed (= “Mode” key + “Zoom” key).
•
Turn on the mecablitz by its main switch.
•
Release the “Select” key combination (= “Mode” key + “Zoom” key).
•
The flash range indication changes from m to ft or from ft to m.
5.5 Determining the maximum flash range with the guide number table
Group B cameras do not transmit to the flash unit the ISO, aperture and focal
length data. Consequently, the mecablitz LC display will not indicate the ca-
mera’s aperture and the maximum flash range. In such an event you can
determine the maximum flash range with the help of the tables listed in the
Addendum.
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Use the following formula:
guide number
Maximum flash range = ——————————
aperture
This formula does not apply to bounce flashes, e.g. when the reflector
is folded down!
Example:
The speed of the loaded film is ISO 100 and the lens has a focal length of
50 mm. The guide number given for this combination in the table in the
Addendum is 34. Set on the camera or lens the aperture f/4, for example. The
above formula can now be used to calculate the maximum flash range:
guide number 34
Maximum flash range = ———————————— = 8.5 m
aperture 4
For the manual flash mode “M” at full light output this means that the dis-
tance to the subject should be 8.5 m to obtain correct exposure results.
For TTL flash mode this means that 8.5 m should be the maximum distance to
the subject. However, to give the camera’s electronic system sufficient scope
for light output control the subject should be positioned somewhere between
40 % and 60 % of the calculated range. For the above example this means a
distance of between 3.4 m and 5.1 m. For close-ups it is necessary to ensure
that a minimum distance of 10 % of the calculated value is observed in order
to avoid overexposure. For the above example the minimum distance is 10 %
of 8.5 m = 0.85 m.
Please note that the maximum flash range is related to subjects with a
25 % reflectivity which applies to most shooting situations. Pronounced
deviations from this reflectivity, e.g. highly or poorly reflective subjects,
can influence the maximum flash range of the mecablitz.
5.6 LC display illumination
Keep the “Mode” or “Zoom” key depressed for approx. 10 sec. to activate
the mecablitz LC display illumination. The LC display illumination is switched
off when a flash is triggered.
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