I attached
Sigma 610 Super flash unit to
Pentax K-3 body.
There is near-infrared pattern sent by flash unit, provided we set camera for
single autofocus (
AF-single) or
auto autofocus (
as this is not working when in AF-C continuous mode), and one uses optical viewfinder.
When LCD viewfinder is in use,
K-3 sends its own green focus-assist light from the on-camera LED. The pity is on-camera LED beam interferes strongly (
is shadowed) with lenses' shades, and even with unshaded bigger lenses (
i.e. 200mm/2.8).
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Originally posted by Class A newer cameras cannot use the AF-assist light on older Pentax flashes, even though all these products are supposed to support P-TTL