The HS head is specifically dedicated to Hi-Sync.
The HS head is specifically dedicated to Hi-Sync photography. The long flash duration allows for the best possible Hi-Sync lighting options, along with the use of the EL-Skyport Plus HS transmitter to sync at high shutter speeds, which are normally limited to 1/200th second.
At full power on an ELB 400, the HS head offers at t0.5 a flash duration of 1/550th second, which is optimized for the least amount of gradation when shooting in Hi-Sync mode. This flash head is also designed to work at virtually any power setting and still provide very evenly lit Hi-Sync exposures. If you are looking to shoot at high shutter speeds using the Hi-Sync technique, this is the flash head you want.
The image below was captured using the Hi-Sync mode with a shutter speed of 1/1250th second. Using such a high shutter speed completely freeze the subject, with no motion blur at all. The BMX rider is tack sharp. Contrast this with the mountain biking image above to see how the Hi-Sync (HS) flash head can stop motion fully compared to the Action head.
In addition to shooting action, if you want to create portraits with a very shallow depth of field, the HS flash head opens up a whole new world. You can basically choose any aperture and any shutter speed and dial the ELB 400 power pack up or down to control the exposure. Because of this, it is possible to shoot portraits at small apertures like f/1.4, f/2 or f/2.8 without the need for diffusion or neutral density filters. The image below is a good example of this option. The aperture used for this image was f/2.2 with a shutter speed of 1/8000th second.