Originally posted by geekette Interestingly, I got a Vivitar SL-2 accessory.... I put it on my Vivitar 283, snapped a pic with my pop up flash and the vivitar flash went off!.
Was the pop-up flash in p-TTL mode? It should be unless the lens you were using was manual (or the aperture ring of the lens was not at A). In this case, the pop-up flash would fire 1 strobe at full power.
If the pop-up flash was in p-TTL mode, the remote Vivitar 283 fired with the pre-flash strobe, which was
before actual exposure. Depending on the power setting, the remote flash might re-charge fast enough and fire again with the main strobe of the pop-up flash.
To verify this, repeat the same test, but this time set the camera in 2 sec. delay mode. You will see the pre-flash strobe and the main strobe of the pop-up flash 2 seconds apart.
And/or take a photo in front of a mirror, with the camera and the remote flash visible in the mirror.
If you plan to use the pop-up flash to trigger remote flashes optically, either you need to somehow suppress the pre-flash strobe, or the optical slaves have to have the ability to ignore the pre-flash strobe (unless the remote flashes support p-TTL remote, which does not apply here).