Understanding Flash Duration

When it comes to freezing movement, flash duration is key. Flash duration varies greatly between different types of studio lighting. If you’re looking to freeze movement, it’s important to understand its effects.

Karl explains exactly what flash duration is and the impact it can have on your shot. In a step-by-step demonstration, he shows different studio lights with different flash durations and their ability to freeze movement.

In this class:

  • Why flash duration is important
  • What impact flash duration has
  • When to use fast flash duration
  • Measuring flash duration
  • Practical demonstrations of different flash durations
  • Sync speed vs flash duration

Questions? Please post them in the comments section below.


  1. HenrikSorensen

    Hi Karl and co.,
    Thanks for a great website and community 😊

    I have a few questions, after having read and seen both this video as well as a bunch of youtube videos on freezing movements outside and in studio environment, using a flash.

    I’ve also heard this sentence with “as longs as the flash is the dominent light source” ..it’s the flash that’s actually setting the shutterspeed ! That makes sense, but how do I actually measure that – and know when the flash so to speak “got” the shutterspeed versus the camera ?

    Recently I used my Profoto A1x flash outdoors and wanted to freeze some kids in the fast movements when running in the forest – they were 5-8 meters from me – 1/200 F4.0 and ISO1000 (it was a cluody day) – and the Profoto A1x flash on 4 – as I assumed that the lower power setting the faster the flash duration would be and, therefore freeze everything – but it didn’t …. sigh !
    Am I up against the inverse square law here or in other words – how do I freeze movements 5-8 meters from me and still preserve the ambient light in the background so that doesn’t go completely dark ?

    … and how do I avoid ghosting, because I saw that too ? Is that the camera shutterspeed I need to bumb up then ?

    1. Hi Henrik, the simplest way to check the dominant light source is to take a shot without flash with the same camera settings that you are using for the flash shots and then you can view how much exposure you are getting just from the ambient light. In answer to your second question don’t worry about using them on low power, they should be fast enough to freeze running kids even on high power. The way I work with flash is to establish how much ambient light I want in my shot first by doing some test shots in manual and arriving at the right level of underexposed look that I want. Then I just add flash ontop and adjust the flash power until it looks right.

      1. HenrikSorensen

        Thanks for the reply Karl 🙂 Much appreciated

        How about my question about ghosting when shooting with flash
        “… and how do I avoid ghosting, because I saw that too ? Is that the camera shutterspeed I need to bumb up then ?”

        1. Hi Henrik, yes you can remove ghosting from existing ambient light by increasing shutter speed or reducing the ambient light.

  2. First off Kudos again for this course!! I am a beginner and starting to learn about studio lighting and my question is this, when you set up your lighting like the one you have with your models in the emotion of light segment.. 2 soft boxes for rim lighting, one with the diffusion material for the gradient background and your main light..when you take your shot do they all flash or just your main light? Thanks

  3. Hi, I’m new to photography, I bought a yn685 ii speedlite, can I freeze images with this flash?

  4. 8artpixels

    Hi Karl,

    This video is incredibly great at showing that the 2 Broncolor lights used can freeze some of the fastest moving objects around us. What about freezing liquid splashes, models jumping in the air etc… which is probably what most photo shoots will evolve around ? that obviously will require much lesser fast flash duration. Could you recommend the minimum requirements as far as watts/jouls needed as well as t 0.5 flash duration as most lights other than Broncolor advertise their lights with t 0.5 value in order to be able to freeze those types of motions I mentioned above ?

    And once again, thank you very much for all the content you provide us with 🙏🏻

    1. Hi, my guess is that if your camera can shoot clean images at ISO 400 then you could use as low as 400W lights but I would prefer and extra half stop at least so 600W or more. Then for flash duration for models jumping you’d be looking at about t0.5 1/5000th but for liquids you need faster depending on the scale in the frame. The question is a bit too ‘open’ because how much speed you need depends on how much movement and how much movement isn’t just about how fast the thing is moving, it’s also about how much you are magnifiying the movement, for example a bullet going across a wide angle shot is going to take longer to go across the photo than a bullet going across the photo of a close up shot.

      1. 8artpixels

        This shouldn’t be called Karl Taylor Education but Karl Taylor University !!! It’s impressive the knowledge you have and how you share it in such an easy way to understand🌟

        Today I went and collected my new camera and lenses from the most professional shop in the region that’s been around for the past 35 years and one of the employees told me how the next 48 mega pixels iPhone will shoot same quality pics and have just as good resolution as the Sony a7r iii that I just bought due to it being 48 mega pixels as well and I proudly explained to him how the 48 mega pixels from the iPhone isn’t quite the same as the 48 mega pixels on the Sony a7r iii thanx to your class on resolution and megapixels 😉

        Have a great day Karl,

  5. dkari

    Hi Karl,

    I don’t know how to explain my enjoyment level because I’m here and part of your students. I watch your videos for at least 2-3 hours daily. It is beyond amazing and so informative.

    I have AlienBees flashes (400,800,1200), which are unsuitable for freezing movement.
    Two questions:
    1- Any suggestion for something budget-friendly ( actually Very friendly😂)
    2- Do I need a speed trigger for my camera ( 5D M2 and R)?

    Again Thanks, and keep doing the fantastic job.

    1. Hi glad to have you here and happy to hear that you are enjoying the platform.
      A. Alien Bees are usually good on fast flash duration?
      1. I thought this was Einsteins Alien Bees? Otherwise the most affordable fast flash duration untis are from Godox
      2. No, you would just need a normal trigger or a sync cable.
      Cheers Karl.

  6. hi carl i just signed up for your course today im really excited ive learnt a lot already , but my question is …..are flash lights or speed lights better than continious lighting or would i say more preferred when it comes to product photography?

    1. Hi, thank you for joining us. You will learn lots more by watching the classes but to answer your question, studio flash lights are the best solution for everything.

  7. HenrikSorensen

    Thank you so much for explaining this Karl – I haven’t had any need for doing this for now I understand the process – and that I should yurn down the output on the flash to get a fast flash …..
    But, I’ve got Elinchrom 250 (actually 5 of them) and the lowest output is 1.3 and thats not quite enough to freeze my fan (almost the same as you got) …… but almost – at least the propellars are still and my mark is a bit blurry …. I suppose thats because thats the limit of what Elinchrom 250 can do in regards of fast flash ?

    Have I understood this correct ?

    1. Hi Henrik, yes you have understood it correctly. There are some flashes with faster flash durations, also speedlights on low power have a very fast flash duration which is what I used to use in some of the earlier classes on splash and paint shots that you will find here on our platform.

  8. Hi Karl,

    1. When you said “fast flash duration” it is same as “high speed sync” (HSS). Just trying to understand the terminology.

    2. How to know if flash duration is calculation over t0.5 or t0.1 for the flashes below. I checked on godox website too but I could not find out. Thanks


    3. Do I really need 600J or can I get away with Godox AD200 Pro which has 200J with flash duration of 1/220-1/15380 at t0.1 (For Godox AD200Pro the spec sheet from their website sait it is t0.1)


    1. Hi:
      1. No fast flash duration is different to HSS, HSS uses a trick of longer flash duration but combining it with faster shutter speeds but it is not as good as actual fast flash duration
      2. It should always say in the specifications if it is t0.5 or t0.1 – if it doesn’t say then assume they don’t want to say so it must be t0.5
      3. 200J is a bit too weak for studio lighting in my opinion. 600J would be the lowest I would go generally speaking.

  9. Hello Karl,

    I subscribed to this course today and just watched 4 of your classes and it’s so informational!
    I have a question.
    I’m looking to buy a strobe light possibly Godox and I’m a little confused.
    The specs I checked for 2 particular models include a power range of
    a. 1/256 to 1/1
    b. 1/16 to 1/1

    What does this mean exactly?

    1. Hi, glad you are enjoying the classes. So the option A you mention can go from full power to a much lower power that option B. 1/1 means full power, 1/16 is one sixteenth power which is 4 stops down from full power (remember each fstop is either half or double the previous one, see our Essential section Intro class for a full explanation). The option A can achieve 8 stops down from full power.

      1. Understood!
        Need to know one more thing.
        For 3 different products in strobe lights, the specs say:

        1. Flash Duration: 1/800 to 1/2000 Sec
        2. Flash Duration: 1/220 to 1/10,100 Sec
        3. Flash Durations: Short as 1/10,000 Sec

        What does this mean?

        1. Hi, if you watch this video it should explain it quite clearly with the resulting images that are shown. Basically the flash duration is how long the burst of flash lasts for, the shorter the time such as 1/10,000th of a second then the easier it is to freeze sharp very fast moving subjects in the studio such as flying liquid.

  10. Hello Karl, I heard that HSS when you increase ISO and shutter speed up to 1/8000th then you lost quality of photos ..? and another question when I want to save energy of HSS light then I think is better to use shots by speed up to 1/8000th because is shorter time of energy. And last question how to use physic about ambient light with HSS when I set up between140th up to 200th the ambient light it shouldn’t show up or….? what is correct please?

    1. Hi Romhan I’ve copied your comments and respond to each below:

      ‘Hello Karl, I heard that HSS when you increase ISO and shutter speed up to 1/8000th then you lost quality of photos ..? ‘
      A: There is always a loss in quality when you increase ISO but shutter speed has no impact on quality in this respect

      ‘and another question when I want to save energy of HSS light then I think is better to use shots by speed up to 1/8000th because is shorter time of energy.’
      A: I don’t understand what you mean by ‘save energy’ in this respect. Usually HSS uses high output bursts of flash that last longer so that the ‘slit’ of the fastest shutter speed exposes the whole sensor as it scans across it.

      ‘And last question how to use physic about ambient light with HSS when I set up between140th up to 200th the ambient light it shouldn’t show up or….? what is correct please?’
      A: This question isn’t clear and it seems you haven’t understood the relationship between ambient light and flash and shutter speeds. Please watch this chapter as it will help you understand the relationship between them – https://karltayloreducation.com/class/shutter-speeds-and-apertures-to-flash/ I think you also need to watch the other classes in this section as they are all designed to cover these points step by step.

      1. Thank you for respond, i thought a little different so it is said when you use HSS for-example f1,2 and 1/8000th and you want change light you have to set up only flash power, aperture or moving light and shutter speed does not affect on that… i know about scanning how it works.. so but what is different between 1/8000th an 1/250th ? I think by HSS you lost energy of light / up to f3 stop so when you set up to 1/8000th that is more quicker and then you safe time and energy of light …maybe f1 stop and quality of photos ..?

        1. Hi Romhan but on faster shutter speeds the slit is thinner so less light has the opportunity to reach the sensor? The quality is not affected if you have enough light.

    1. Hi, no you only need a fast enough shutter speed to cut out ‘light pollution’ from other sources other than the flash. Then you let the flash do all the freezing. If you were shooting in a completely dark room you could use any shutter speed even 2 seconds as there is no light pollution only the flash.

  11. Hi Karl, I’ve been enjoying your content and the information on the videos is great. I’ve got a question: why does a “fast” flash duration (as shown on the last example) “freeze” motion on a speeding fan on a shutter speed of 1/160th of a second? Is there something on the flash duration itself that creates this on the image, even on slower shutter speeds?

  12. When you switched to the second light, you had to move the flash up to power 3 and you got a slight blur.
    Based on your earlier discussion, did this lengthen the flash duration? If you had left it at power 2 and increased ISO or aperture to achieve exposure, would the yellow tape have been sharper?

    1. Hi, I’m very keen to answer your question. Please could you indicate at which time in the video you are referring to and I’ll come back to you with an answer.

  13. Hello,

    I am new to photography and I am so glad I am a member. I am interested maternity photography and I would like to know what flash duration is needed to freeze fabric in motion? A friend gave me an Alien Bees 800 (T.01 1/1100 to 1/500) and an Alien Bees 1600 (T.01 1/600 to 1/300). Can I freeze motion with these lights?

    1. Hi Glad to have you aboard and thanks for joining us! Yes the alien bees are pretty quick lights so you should be fine. But the question of how fast do the lights need to be comes down to how fast the movement is and that also comes down to how much magnification there is in the shot. For example think of movement relative to the picture area; someone may move very fast but if that movement is on a full length or wider shot then the apparent speed of the movement is less than if it was a closeup shot because the apparent movement has less distance to travel across the picture area if you know what I mean. All the best Karl.

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