All of the R-series bodies except the R50 work normally with ‘old’ flashes (everything but the EL-5 and EL-10). However, the connection between the flash and the camera will not be weather-sealed (even though the 580/600 flashes have sealing), for a sealed connection you need the AD-E1 adapter. If you have an R50, the AD-E1 lets you use an old-style flash with it.