High speed sync HSS on your DSLR to put it simply is the ability to use flash at faster shutter speeds than the cameras intended manufactured sync speed limit. Most cameras on the market today have a native sync of 1/250th of a second, and anything beyond this limit means your camera is unable to sync with the flash.
How HSS works.
When you take a photo there are a lot mechanism at work inside the unit. What we are going to focus on in regards to HSS is the shutter and how it works.
Native Sync < 1/250th of a sec
There are two shutter curtains that move in really fast to expose the sensor and record the image. The shutter curtains opens and closes at the native sync speed. The flash pop at the start of the exposure. (see front and rear curtain flash) The first curtain opens fully followed by the second closing thus ending the exposure.
HSS enabled > 1/250th of a sec
When HSS is engaged the curtain movement changes. As soon as the exposure starts the first curtain will start moving but the second curtain will not wait for the first curtain to finish, instead it follows creating a slit as the exposure moves down. While this is happening the HSS enabled flash sends a series of pulses to light up the entire exposure as the slit moves down completing the exposure.
You may have noticed this if you shoot with a flash that is not HSS activated the bottom of the image is dark or the whole image is dark. This is because the flash did not sync at this shutter speed.
When to use HSS.
Say you have a bright background and you want use a wide aperture eg. f/2.8 your shutter speed will have to be about 1/800th of a second. Starting with choosing the aperture you are instinctively forced to use a higher shutter speed even if your ISO is at its lowest to get a decently exposed photo.
The camera will switch to HSS automatically or will not allow you to shoot at 1/800th of a second, below is a video explaining how I switched on the HSS function on my NIKON D800
I go through the process of setting my camera into HSS mode and showing a few examples of photographs shot under harsh light. * GEAR USED Flash ORLIT RoveLig...
Why I shoot in HSS mode.
As you may have noticed most of my work is done outside on location and this poses a challenge mostly in the form of too much ambient light, or other elemental forces eg. wind but that’s discussion for another blog post. Any photographer who has ever shot with flash will know it is crucial to retain detail in the shadows and highlights. I do however shoot with natural light in situations where the light is flattering on the subject. But in almost 75% of photoshoots I’ve done weather it be weddings or scheduled gigs they all happen at times not under my control.
HSS has been crucial in such cases. I could control and maintain the detailed look in my photographs even under harshly lit conditions, thanks to HSS I could shoot at shallower depth of fields and balance the ambient light.
Benefits of HSS
Allows you to shoot at sync speeds higher than your native sync limit
Freezing fast action eliminating motion blur and cutting out most of the ambient light giving you control of the amount of light.
You can shoot at wider apertures also allowing for a shallow depth of field.
Most of all it gives you creative control
Camera settings
NIKON D800 1/1000 | ISO 100 | f/ 5