Understanding Flash Duration

Want to freeze 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.

Here, Karl Taylor 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. I’m trying out a Broncolor Siros 800 S with an l40 reflector, for its action-stopping speed by photographing a fan, similar to the test here. In “Speed” mode at its lowest power setting of 2, I can’t get the fan to freeze like you did here. And, at f/8, the shot is underexposed and movement is blurred. Any clue as to what’s wrong? I double-checked the all the settings on the strobe and they look correct for freezing action. This is supposed to work, I should be able to freeze the fan, yes?

    The studio is dark to prevent ambient light influence, and the distances of the strobe and camera to the fan are about 6′, similar to the test here. Camera is locked-down on a stand, and set at 1/160 of second, f/8, manual mode, and 100mm lens is focused manually.

    The fan I’m testing quite possibly is spinning faster than the one in this test , however –

    Next, I tried the same test using a PCB Einstein in “Action” mode. I have the power at half-power, with plenty of room to go lower and open f/stop more if needed, yet I’m able to get f/8 , correctly exposed and the fan is frozen and sharp!

    I’m triggering both wireless, the Siros, using the Broncolor RFS 2.1 trigger and Einstein, using their PCB Wireless transmitter.

    Either the Einsteins are far superior at freezing action, or I’m doing something terribly wrong! Does anyone have a clue what I could be doing wrong if anything at all?

    1. Hi Ivan. The Siros should freeze that no problem? Are you sure you didn’t have any ambient light pollution causing ghosting?

      1. Hi Karl,

        Thanks for the reply! I agree, the Siros should be able to freeze the fan movement! And, at this price point, it should be a superior lamp head compared to the Einsteins.

        Perhaps it has something to do with the “speed” setting on the Siros unit. It could be faulty, or the unit may need a firmware update. Or, could it be an issue with the wireless trigger or not syncing with the camera correctly. I’m at a loss but I’ll try to figure it out. If else, it’s good test of this gear.

        I’ll check to see if the Siros needs a firmware update, and if so, I’ll do that next and see what happens.


  2. martin.ludvik

    Hey Karl, thank you for your work! I have a question regarding high speed sync. How would high flash duration with standard shutter speed compare to high speed sync and a fast shutter speed in regard to stopping the blade and sharpness? Thanks in advance

    1. Hi Martin, only shutter speeds of 1/8000th of a second would get close to freezing this speed of movement. Some flash systems allow for HSS so that you can use them with the shutter speed of 1/8000th but it is more restrictive on the control you have over the flash output power.

  3. I love your instruction, and you are very good at demonstrating the theory. I’m wondering if the only real way to discover a light’s flash duration is to do the test you just did. I noticed your shutter was at 1/160. So when I read this information – “Flash duration of 1/1,042 to 1/40,000 second depending on output setting” for a speedlight, or this – “Flash Duration: 1/220 to 1/10,100 Sec” for a monolight – is that telling me that the duration is such that it would look AS IF I had been using a shutter speed that fast? And in this case, the speedlight would have a faster duration that the mono head.

    1. Hi, yes you are correct. A fast flash duration essentially replaces a fast shutter speed as long as your shutter speed is fast enough to cut out any ambient light from the room etc. It’s best to work in a low light enviroment though and rely just on the flash to do the freezing. Yes speedlites can be faster but they are much lower in power.

      1. Thank you so much! I teach at a small community college (2 year program), and my students are big fans of your YouTube videos. Thanks for being so generous with your knowledge!

  4. Hi Karl,
    My latest tests lead me to believe that it is an issue with the triggering system. I can get a nicely exposed picture at 1/1500 of a second and completely black at 1/2000th.
    I have the canon version of the trigger. I’ve ordered the Nikon version (it seems hasselblad uses there protocole) to see if I get better results and will let you know.
    Can’t test with a sync cable because for some inexplicable reason they removed the 3,5 jack on the X2D 😩.

    1. Interesting. Yes they use a Nikon protocol hotshoe but I’ve never had any problem with the broncolor RFS2 trigger on the hotshoe for my bron lights?

  5. Hi Karl,

    Thank you very much for the great video as usual. I have a question regarding flash duration and something I can’t figure out on my own.

    Lets say I set up my flash system to a very fast flash duration (Godox ADL600Pro) that go down to 10000th of a sec. Provided I am on a very low ambiant light with a setting of 1/500 on my camera I get a certain exposure. If I increase my camera speed to say 1/2000 the picture is darker than the previous one.

    Given that ambiant light is not an issue (I get almost a black picture with 1/500 if the flash is off) and that flash duration is much shorter than the camera speed.. I can’t figure out why the picture exposure is different..

    Sorry if this is a stupid question but I would love to hear your explanation.

    Thanks very much in advance,


    1. Hi, thank you for your comments.
      1. Does your Godox go to 1/10,000th at t0.1 or t0.5 (if it’s t0.5 then it’s actually only really about 1/4000th at t0.1)
      2. The only explanation based on the information that you have provided are the following. a) your camera can not synchronise with flash at the shutter speed you selected, for example you are exceeding the flash sync speed. Or b) the flash duration is longer than the shutter speed you selected and you are cutting some of that duration off and therefore losing exposure. My guess is it’s (a) (unless you are shooting with a leaf shutter and a medium format camera) as there are not many cameras that can synchronise at those faster shutter speeds.

      1. Hi Karla,

        Thank you for getting back to me.
        1. It is t0.1 from what I can remember but I’ll double check.
        2. Using the X2D so flash sync speed should be ok.
        I’ll run more tests and get back to you. I want to get to the bottom of this.

        Thanks again.

        1. Hi, if you are on the X2D then I can’t understand any logical reason that this would happen. Also check your flash trigger and that it is suitable for flash sync. From a physical point of view the only reasons it could be happening were what I previously explained so test those first and then let me know. Cheers Karl.

  6. This was a really interesting demonstration! Adding a speedlite in the comparison would have been the cherry on top, but I understand that in this setup they would be too weak to illuminate subject 🙂 Inspired by this, I will try to make my own test. I often do hand-held macro photography in the field at high magnifications, which also involves very fast movement within the frame. Speedlites are more practical for this type of activity, and they have massive amount of variation in flash duration at different power levels, probably much more significant than with pro studio lights. I usually stay away from powers higher than 1/4-1/8 because the motion blur could actually show up in the image above life size magnification. For this use having a stronger speedlite could actually help to keep duration down for same output.

  7. David

    Hi there Mr. Taylor!

    I am thinking about getting together a little first studio on a budget, but also don’t want to go with the cheapest options for the most crucial elements. In another video of yours you said 4 is the go to as a minimum number of lights. I thought of buying the Godox AD600Pro for the key light, and I wondered weather all 4 has to match it’s specifications regarding flash duration for example to get the desired results. For instance if I would like to freeze some highs speed phenomenon e.g. a tennis ball covered with flour and hitting the net of the rocket which I think I saw in your gallery, do I need all the lamps directed on the subject to have that capability of an extremely short flash duration? And also could you answer the same question regarding the background lighting. I thought of buying that AD600Pro where necessary and going with the much cheaper DP600III or DP800III where it is enough, and from there climb up to the Broncolor in the future 🙂

    In addition if you could mention some similar situations where you think that it is crucial to invest more and some accessories where I may be ok with the budget friendly options.

    Sorry for that 3in1 question 🙂 This is my first one. I will try to keep them shorter in the future.

    Thanks in advance. Your educational material is extremely helpful.

    1. Hi, yes if high speed work is required then it is better for all four lights to be operating at high speed otherwise there may be ‘ghosting’ even from the background lighting. 4 lights is my minimum recommendation for a professional studio but you can still do a lot with 2 or 3. There are many accessories that can be purchased on a budget from third parties, for example I use a third party Beauty dish, alot of my lighting is from home made scrims etc etc. If you watch more of the classes you will see this in some of them. All the best Karl.

      1. David

        Hi Karl, thank you for your detailed answers. I have a follow up question to that as i am very close to actually buying my lights. Is it important to exactly match the flash duartion for each light source, or it just that they must be high speed. Im asking this because i don’t know if there is a way to manually set the flash duration of the lamp. So far what i have seen, it looked like it is just the highest speed it can produce at a certain power setting. So for example as far as i understand if i have a 600ws light and a 400ws light they will result in a different flash duration when generating the same brightness because one should be closer to its edge. So i would guess either there should be a way to manually set the 600ws light to a lower flash duartion to match the 400 or, the lamps should be the same model, which somehow doesn’t sound right 🙂 My best guess would be that flash duration just doesnt matter as long as it is above the level that freezes the motion, and different durations above that wont cause any anomaly on the image.

        Best Regards,


        1. David

          Actually, i just wrote this above question before i started to watch the flying tea video, and that answered all my questions. You can set the flash duration manually, and they don’t need to be exactly the same as long as they are fast enogh to freeze motion. Thanks Karl 🙂

        2. Hi David, only the very top end flash systems (usually packs like the Scoro) allow you to select the flash duration, but in doing so it may also have to adjust the flash power to match your requirements. For example I can’t get 1/10,000th t0.1 if I’m at power 6, it won’t let me select that until I drop to power 4.9. However I regularly mix different flashes and different flash durations without any problem. As long as the slowest one is fast enough to freeze what you need you will be fine. See the class where I throw yellow paint over a model, I’m using speedlites, flash and all sorts of stuff.

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