HS or HSS
What is the Difference?
by Michael Clark
Since the dawn of flash photography there have always been technical limitations that restricted how and where flash could be used to enhance an image. In recent years, there have been a slew of innovations with different flash technologies for both hot shoe flashes and strobes that have opened up never before possible options. These advanced flash techniques are often misunderstood. The aim of this article is to demystify and define the various flash technologies that allow us to shoot at shutter speeds higher than the standard flash sync speed of DSLR cameras.
All flashes, no matter what size or shape, work by storing up an electrical charge and then emitting that charge as a light source through a flash tube.
When the flash is triggered the electrical charge is dumped into the flash tube and ignites a gas. The gas is ionized and thus releases a flash of light. Hence, the flashes we use these days are just a modern version of the old time flashes used a century ago where photographers basically ignited flash powder to create light.
The only difference now is that we can control the amount of light emitted by the flash electronically and with incredible accuracy.
The vertical plane shutter incorporated into most modern DSLRs is composed of two separate parts, the first curtain and the second curtain.
When you press the shutter release the first curtain opens and then the second curtain closes according to the selected shutter speed.
The time gap between the first and second curtain is the shutter speed.
For longer shutter speeds, like a one second shutter speed for example, the first curtain opens and the second curtain closes after the one-second time period has elapsed. In this case, the entire sensor is exposed to the light between the opening of the first curtain and the closing of the second curtain.
For shorter shutter speeds, like a 1/1000 second shutter speed, the first curtain starts to open and the second curtain follows shortly thereafter before the first curtain has made it’s way across the entire sensor.
This results in a narrow slit of light that moves over the sensor, thereby creating a very fast shutter speed.
The highest flash sync speed of any camera is the fastest shutter speed at which the entire sensor is exposed completely to the burst of light. For some DSLRs the flash sync speed is 1/200th second while others go up to 1/320th second.
As an example, with a Nikon D810, the top flash sync speed with strobes is 1/250 second. This is the fastest shutter speed where the entire sensor is exposed all at once. With shutter speeds higher than 1/250 second, the entire imaging sensor is not exposed at any point, which is why you see a black bar in the bottom of the frame if you try to shoot at a shutter speed above the standard flash sync. That black bar is the shadow of the second curtain closing.
Some medium format cameras have leaf shutters that are built into the lens, and which work differently than the vertical plane shutters in DSLRs. These shutters allow for higher flash sync speeds (in some cases up to 1/1,600 second) with no clipping.
When shooting with strobes, the aperture controls the brightness of the light on your subject and the shutter speed controls the brightness of the background.
Hence, if your subject is overexposed you stop down the aperture. If your background is too bright you can choose a faster shutter speed to darken the background or a slower shutter speed to brighten the background.
When shooting outdoors, in broad daylight, being restricted to a shutter speed or 1/200 or 1/250 second means that quite a bit of flash output (Watt-seconds) is required to overpower daylight.
By accessing higher shutter speeds, we can overpower daylight with less power output (or from farther away) and we also have
Working with Hi-Sync flash opens up new doors creatively allowing for full control over the final image when using flash. Not all high shutter speed sync flash technologies are the same and some offer more advantages than others.
As of this moment, there are three technologies on the market that allow for working with flash above the normal flash sync speed of DSLRs.
High Speed Sync is a technology invented for Speedlights, now used by several manufacturers.
HSS works by continuously pulsing the flash at incredibly high speeds creating a stroboscopic effect that illuminates the shutter slit as it moves down the sensor. Because it has to output so many pulses of light, creating essentially a continuous light source for a brief period of time, the actual light output of the flash is quite low and can vary wildly depending on the shutter speed.
HSS also requires a considerable amount of power and eats through batteries quickly.
The upside of HSS is that it creates very consistent lighting across the entire image. The downside is that because the flash is outputting so many bursts of light in such a short period, the flash has to be fairly close to the subject. The light output also decreases with faster shutter speeds and the color temperature of the light may vary as the shutter slit moves across the sensor.
For wedding or portrait photographers, who generally have the flash close to their subject, HSS is a very good option.
For those who need more versatility, HSS has quite a few limitations in terms of light output and the amount of power needed to drive the flash head continuously.
HyperSync is a technology created by Pocket Wizard® and implemented in their ControlTL transceivers. When using HyperSync the flash acts normally and fires off only a single burst of light.
With HyperSync, the flash is triggered before the shutter fires and requires incredibly precise timing to make it all work. Essentially, HyperSync is taking a slice out of the brightest part of the flash output. Only a portion of the light emitted from the strobe is used to light the image. HyperSync works best with flash heads that have a long flash duration – anywhere from 1/1,000th second or slower. How well HyperSync works is highly dependent on the camera and flash combination used.
The benefits of HyperSync are the ability to sync at shutter speeds above your normal sync speed, freeze motion, and the ability to overpower the sun from phenomenal distances. Using Hypersync can also be used to create a narrow depth of field using large apertures.
The downside of HyperSync is that in some instances and with some cameras there can be significant gradation from the top of the image to the bottom of the image.
Also, HyperSync works better with some cameras and flash systems than with others. HyperSync is designed to be used with strobes at their highest power settings, which is a limiting factor, and it requires considerable experimentation to figure out because a light meter cannot be used to read the light output.
In my experience, HyperSync works best with Nikon cameras using a limited range of shutter speeds. With a Nikon D810 and D4, shutter speeds between 1/640 second up to 1/1,600 second lead to the best results. Above 1/1,600 second more obvious gradation becomes a problem and clipping can be also an issue depending on how you have the transmitters set up. HyperSync also requires a fair bit of “playing around” to find the best software settings for the transceivers.
Hi-Sync is the new kid in town. Technically, it works in the same manner as HyperSync, but because Elinchrom has built it into the Transmitter PRO transceiver and dialed in the timing exactly for their strobe units, they have perfected it on a level that solves many of the issues with HyperSync.
Hi-Sync also triggers the flash before the shutter fires and uses a normal flash mode. It is designed similarly to HyperSync in that it works best with a slower flash duration. When used with units that have a faster flash duration there will be a lot less power that can be accessed and probably banding at higher shutter speeds.
In my testing so far with the Transmitter PRO and the new ELB 400 HS flash heads, which have a flash duration of 1/600 second at full power, there is no banding or gradation that I can see all the way up to 1/8,000 second. HS technology is a godsend for sports, action or adventure photographers because it offers a reliable way to shoot with high shutter speeds and work with strobes from considerable distances.
Any photographer photographing anything that moves, either inside or outside of the studio, would reap the benefits of using Hi-Sync.
The benefits of Hi-Sync are the same as with HyperSync: the ability to sync at shutter speeds above your normal sync speed, freeze motion, and the ability to overpower the sun from phenomenal distances.
Hi-Sync is easier to use and much more reliable than HyperSync ever was in my experience. Hi-Sync can also be used to create a narrow depth of field using large apertures.
The downside is that a light meter can’t be used to determine the correct aperture for exposure. Using the Histogram and the rear LCD display on the back of the camera will be the best guide for exposure settings.
Hi-Sync also offers more options than any other flash technology because you have more light output at your disposal and no gradation. For battery-powered strobes, Hi-Sync uses much less power than HSS because the flash head is firing normally. With Hi-Sync it is also possible to turn the power down and continue to use a fast shutter speed.
THE HI-SYNC EXPERIENCE
"Whether or not this product is "game-changer", I leave to the masses to decide." Read Michael Clark's experience using the new Transmitter PRO with Hi-sync feature.
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Learn how to shoot Studio & Location in Hi-Sync with a Transmitter PRO and check out the results as Joe Brady goes in-depth using this exciting feature.
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