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Topic: |
Modifying the
TC-80N3 Intervalometer to disable the auto focus activation function |
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Author/Copyright: |
John Jovic |
The TC-80N3 (Timer Remote
Controller) activates the
autofocus on a camera a short period prior to actually tripping the
shutter. It's the same as pressing the shutter release on the camera
half way to trigger the AF and metering functions without firing the
shutter. The effect of this is that its prevents the camera from
displaying the histogram after a shot has been fired where the interval
between exposures is fairly short, about 5 seconds or shorter. It is
important to be able to see the histogram to keep track of exposures and
so that adjustments can be made when needed, especially when doing
day/night transitions (sunsets). If you can't see the histogram then you
can potentially make exposure errors without being aware of them until
it is too late.
The TC-80N3 has a single wire which performs the AF function and this
wire can de disconnected to stop the AF function. This AF function also
acts as a 'wake up' signal to the camera so this function would cease to
exist if this modification is performed.
The modifications described below show how to disconnect the correct
wire to disable the TC-80N3 AF function. If you do choose to try this
then do so at your own risk.
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Open the TC-80N3, removing the 3 small screws on the
back, then carefully wedge the plastic cover apart using a flat
screw driver. It's easy to open and close up again but be careful to
note the orientation of the battery so that it can be fitted
correctly. |
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The cable connecting the camera to the TC-80N3
intervalometer is a simple 3 wire cable which is soldered to the
printed circuit board (PCB). |
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The red wire is the
shutter release, the white wire is the focus activation trigger and
the black wire is the shield or earth. |
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Cut or desolder the white wire. If cutting then be
very careful that you don't leave small fragments of wire on the PCB
which could cause a short of some kind. If you intend to reconnect
the wire at a later stage then it may be easier to do so if the wire
is desoldered instead of cut. |
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Cover the cut wire with
electrical tape or heat shrink so that it doesn't short on anything.
Also take care to position it so it doesn't foul anything. |
Re-assemble and test.
The modified TC80-N3 was tested with a 1dsMk2 and a 40D shooting in RAW
mode. Both comfortably displayed the histogram when 2 second exposure
intervals where used on the intervalometer. The 1dsMk2 briefly flashed
up the histogram display at 1 sec intervals initially but not after the
buffer started to fill which delayed the histogram too much.