At the Nikon this works automatically, since they constantly signaled the release readiness. Therefore, could suffer here the battery runtime. As I understand it, Nikon DSLRs do this, however, only during the AF operation (half-pressed-camera shutter).
Since the hot shoe adapter Sony this signal does not forward, is here for fast sync speeds of Half-Press before triggering the test button on the transmitter. Since the unleashed flashes with manual exposure is usually not so spontaneous process anyway, that's still ok. It also works without, but then at 1 / 125s Final.
Although I have even done any comparisons, but from reports of other users I know that the range and reliability will be significantly higher than those of radio triggers that even in the 433 MHz band work.
A few more notes:
In order for the ext. Lightning at the NIKON P7100 is triggered reliably, is to make the internal flash on the menu, but it must be folded out! To get at the Sony SLTs in manual mode a bright viewfinder image, is the "Live View setting" to set in Menu.
I have chosen deliberately for the RX 602 and against the slightly newer and somewhat more favorable RF-603. The latter associations so the sender and receiver in an identical unit. One drawback is there that therefore the recipient is below a hotshoe connector with center contact, and no tripod mount like the RX-602nd The systems are the way NOT compatible radio!
If you, however, only (with built-in receiver for both systems) uses the YN-560-III flash, so perhaps is but a single RF transceiver 603, the effective solution. Because the flash is not so required, so that it is with the lack of tripod mount matter and you only need a single "RF 603 additional transceiver" to buy, rather than a two set.
Both RX-602 and RX-603 combines the two functions of the camera and flash remote trigger, however, brought to two complete sets on different channels set if you want to use both at the same time. For if only one transmitter trigger both receivers at the camera and flash, so the flash would have gone again until the camera shutter had opened. To solve this, you therefore holds a transmitter in his hand and pressed it to the test button. The corresponding receiver is connected by cable to the camera. A second transmitter on a different channel is normally mounted on the camera hot shoe, and the corresponding receiver then fires the flash.
The various offered Nikon sets the way differ essentially by the type of cable for the camera shutter connection. The set offered here, this cable is not included, so this would be to acquire still separately for the camera remote release functionality!
The RF-602/603 does not support iTTL or HSS! Who needs it or wants to should look at the YN-622N instead!