Setting The Head Offset - evertz 4025 Instruction Manual

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4.1.5. Setting the head offset

The ARRI timecode reader head contains both the Timecode and Keykode
sensors, and is mounted on the telecine several frames before the film
enters the gate. There are two settings in the 4025 which are used to
compensate for the head offset. This could be expressed as follows:
TC Offset = KK Head Offset + ARRI Offset
The KeyKode reader head offsets are also used adjust the nominal
timecode head offset. As such, there are separate Keykode head offsets
maintained for each film gauge and transfer rate supported by the 4025.
(See section 3.5.4 for information on calibrating the KeyKode head offset).
The KeyKode head offset should be set before proceeding, as it is used for
both KeyKode and film timecode offset calculations.
Another register, known as the ARRI OFFSET is accessible from the front
panel. When the 4025 generator is in one of the ARRI timecode modes,
the ARRI OFFSET register is accessible by pressing the OFFSET key on
the front panel. This register is a measure of the difference in position
between the Keykode, and timecode sensors. There is one ARRI offset
value for 16mm film type and another for 35mm film type.
To check the accuracy of the timecode head offset, select one of the ARRI
modes from the GEN ASSIGN menu. Turn ARRI Jam Off using the Jam
key. Park the telecine on a reference frame of film.
timecode number for the reference frame into the generator time as
described in chapter 3 of the 4025 manual. A simple way of identifying the
timecode number of the reference film frame, is to use a piece of film that
has a timecode smart slate in the picture area. This smart slate should be
showing the same timecode numbers as were being used in the film
camera. (Note that this method is subject to the accuracy of the smart
slate display.)
Turn on the ARRI STATS display (using the KK STATS menu item of the
Toolbox) and put the telecine into play. The AERR value should be either
0, 1, or -1. Press the OFFSET key on the 4025 front panel to display the
ARRI OFFSET register. Press the vertical arrow keys (", #) while holding
down the SHIFT key to trim the ARRI OFFSET register. As you adjust this
register, the AERR value on the ARRI STATS display should become 00.
The ideal situation is that the ASFERR value on the ARRI STATS display
should also become 00.
Model 4025 Film Footage Encoder Manual
means that differences in the user bits caused the re-jam
(minus sign) means that ARRI Jam is Off.
means that ARRI timecode is missing.
Enter the film
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