Appendix: Adjust back focus
Back focus refers to the distance from the rear lens element to the camera focal plane. It is
only necessary to adjust the back focus if the lens of the camera cannot hold focus throughout
its zoom range.
Required tools
● Back focus adjuster (in the BC840 camera package)
● Test chart / contrasting object
To adjust back focus
1
Set the camera on a stable mount at least 75 feet (23 metres) away (or as far as
possible) from the test chart or object.
2
Make sure the iris is wide open and keep the lighting as low as possible.
3
Adjust the focus to infinity, indicated on the camera by the ∞ symbol.
4
Turn the zoom to the extreme telephoto position, and then focus on the subject.
5
Set the zoom to the wide-angle position.
6
Loosen the retaining screw of the back focus ring with the supplied back focus adjuster,
and then adjust the back focus ring to sharpen the picture.
7
Repeat steps 3 ~ 6 until the focus remains consistent throughout the zoom range.
8
Tighten the retaining screw of the back focus ring to fasten the ring.
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