Once, I received a message from another photographer explaining that he had to use high speed sync in order to freeze motion. In this blog entry, I want to explain that high speed sync or HSS is not the most efficient way to freeze motion with flash.

While HSS is a viable option, it’s not necessary to achieve crisp photography results. You don’t need HSS to freeze motion.

How do we really freeze movement in photography?

Before looking at HSS or your shutter speed, we have to look at the one thing that is crucial to freezing motion and it is light duration or flash duration.

What is flash duration? It is basically a measurement of the amount of time your light reaches a certain percentage of it’s peak power.

Manufacturers such as Godox, Profoto or Paul C Buff uses the T.1 or T.5 to measure how long the light duration is.

T.1 = Flash Intensity when it exceeds 10% of it’s max brightness

T.5 = Flash Intensity when it exceeds 50% of it’s max brightness

A few tips:

1) T.5 is typically slower than T.1 - this is because of the measurement being used. ‘Back in the days’, lighting equipment manufacturers used the two above standards (T.1 & T.5) in order to measure light duration. This was confusing to consumers so the ISO committee stepped in and made the T.1 the official measurement. However, some manufacturer’s like Profoto still show t.5 for their light duration.

2) Let’s remember basic math where 1/15000 is faster than 1/10000. The higher the divider, the shorter your light duration is, the better it will be at freezing motion.

3) Your lights will have a shorter light duration (meaning better) when you use less power. A good example is to look at the Godox ad600 (BM, Pro and all the variant models). At full power, the Godox emits a light at t.1 that measures 1/220. At it’s lower power, the ad600 produces a light duration of 1/10000 (it varies by +/- 100 in different models) which is a lot faster than at full power.

What shutter speed is great to freeze motion?

The problem with HSS comes from tip #1 . While you are using HSS, you typically have to use more power in order to match that shutter speed. It’s no surprise if ever you end up shooting at 1/1 or at ½ if you sync up to 1/8000.

As we now know, shooting at full power makes your light less efficient. While you may actually freeze the subject using the very high shutter speed, you are using your light as it’s most inefficient manner since you are using it at full power.

On top of it, you are also burning your light much faster. Shooting constantly at 1/1 or full power will burn your build and components faster.

A shutter speed of 1/100 to 1/200 you should hit a sweet spot between a closed enough aperture and a light power that is manageable for it’s duration.

Another tip which would be too long to include in the first 3 here is to always before making a purchase visit your light manufacturer’s website and compare the lights at their full and lowest capabilities, it will tell you how will your light generally perform under the manufacturer’s claim.

What I would suggest if light duration is critical to your work is to measure light yourself by either renting or borrowing a unit. Test it a different power settings and if the measurement fits your typical aperture and light distance, then you are good, if not you might want to either adapt your shooting style or find another pack/system for you.

Let’s pick 3 lights I’ve used or seen at worked on set with.

First is the Paul C Buff Einstein 640 which is my main work horse in the studio. A quick visit on the manufacturer’s website will give you the following stats:

Another one is the Profoto 7A power pack (the Profoto 7A pack discontinued but you can get a newer version here)

Note that the measurements are in t.5

The last as we already discussed is the Godox ad600 :

I’ve included here a video of a behind the scenes where I put that theory to the test. To add to this, here are a few of the straight-out-of-camera images and finals.

So I hope this was useful in demystifying that HSS is not really the best of option to freeze motion and that light duration is the most important metric to look into light if you want to freeze subjects. Here are the raw images, crop and the gallery to the end results.

Final images right here:

Happy light duration :)

YvensB

Disclosure : The links included in this blog entry are affiliate links to Amazon.com and Amazon.ca and other websites. Which means that if you click on them and buy an item, I get a small commission for the referral. Prices do not increase whether you click the links above or found them yourselves. Purchasing through those links allows me to publish more content for you!

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