During the photo shoot with my daughter in the studio I realized something odd. The D800 is supposed to have a minimum flash synchronization time of 1/250s. This is the fastest shutter speed at which the camera can still communicate in time, so that the flashes triggers when the sensor is fully exposed and not partially covered by one of the shutter blades (fast shutter speeds mean, that the second shutter blade is closing while the first shutter blade is still in motion, so that the sensor is never fully exposed. See this highspeed-video from 0 min 36 sec).
With the flash sync time of 1/250 I set my camera to 1/250s and started shooting. And bummer, the bottom part of the image was black. Long story short – I investigated this issue a little further and made test shots, triggering the flashes both with the Yongnuo wireless units and the sync cable which came with my studio flashes. I have used different channels on the RF603 units to rule out interferences with other equipment and also used them on my Nikon Speedlights.
Results see below. Sorry for the tasteless composition, I took what I could find in five seconds 🙂
In this image the flash was triggered using the wireless units. As you can see, the bottom part of the image is black. This means, as described above, that the flashes got the signal to fire too late, the second shutter blade was already closing before the sensor. The Yongnuo RF603 needs the fraction of a second to process and relay the signal, inducing a delayed flash trigger. The result is this black strip.
Cross-check: same camera settings, same setup, flash triggered with a sync cable. Result:
Conclusion: I guess this is the price for a low price – I got the four Yongnuo units for around 55 Euros, which is an excellent deal. The units have a very good build quality, They do not feel “plasticky cheap”, they sit firmly on the hotshoe and the connectors make a solid impression. In the battery compartment are four DIP-switches to select channels – meaning they have 16 different channels on which they can send so that your units won’t interfere with Yongnuo units of other photographers which happen to be nearby.
Anyhow, due to the delayed trigger signal you lose the option to shoot at 1/250 sec when using the RF603. 1/200 sec is the fastest shutter speed you will be able to use. If you can live with that, it’s fine. I suppose that high-end radio triggers like the PocketWizward do not have such a delay, but a PocketWizard also comes with a hefty price tag.