How Shutter Speed and Aperture Relate to Flash

This illuminating tutorial is guaranteed help you take better photos.

In this information-packed photography class, Karl breaks down the relationships between flash power, aperture settings and shutter speeds.

You’ll learn about:

  • Understanding flash sync speeds
  • The relationship between ambient light and flash
  • The relationship between aperture and flash
  • First- and second-curtain flash synchronization

You’ll learn how each of these can work together to influence the final image.

In this class:

  • How shutter speed works in photography
  • Sync speed vs flash duration
  • Leaf shutter vs focal plane shutter
  • Shutter speed and aperture
  • The impact of ambient light on an image
  • Controlling flash exposure
  • Combining studio and ambient light

If you enjoy this class, check out Understanding Flash Power and Fast-Flash Jelly Headshots.

Questions? Please post them in the comments section below.

Comments

    2. Hi, yes if you jump to the essentials section and the introduction course and ‘how cameras work’ you should find what you need.

  2. The front and rear curtain sync topic makes me naturally ask: Is there a way to have the flash fire in the middle of the exposure in case someone wants a trail with the sharp subject in the middle of it?

    1. Hi, i’m just trying to visualise what you’re thinking…. so if the flash went off in the middle of say a 3 second exposure (at 1.5 seconds into the exposure) and you had ambient light recording the motion of the subject as well then you would have a blur infront of and behind the subjects direction of travel. I can’t see where this would be useful and I’m not aware of a sync setting that can provide this but it’s perfectly achievable manually by removing your flash trigger from the camera and taking the shot as normal but then pressing the trigger manually half way through the exposure.

  3. cdambrosio

    Hello Karl, Does this mean for medium format cameras you set up the aperture and shutter speed to what you want and then adjust your strobe accordingly? So, you can be at f8 at 1/600 and then set your strobe to the power you need?

    1. Hi yes I always shoot in manual and I set my exposure for the ambient light first on how I want that to look and then I add flash and only adjust the flash power to suit. Although you may need to consider what your maximum flash sync speed is, because on some cameras you can use any shutter speed and on others you might be limited to 1/250th of a second.

      1. cdambrosio

        Thank you so much, I just purchased the x2dII after your review of it. I’m coming from a full frame camera and I wasn’t sure how the workflow changed if it does at all when using strobes.

        1. Hi, I’m sure you’ll love the camera. The workflow is the same you just have the benefit of any speed flash sync. It’s worth keeping in mind though that shooting with medium format you work at a slower pace and more considered but that is a good thing.

            1. Hi, so most people that shoot 35mm tend to get in a habit of shooting quite quickly and taking lots of pictures rapidly because those cameras can often do this. With medium format you tend to slow down and think about quality over quantity, it’s a bit like working with film in that you are taking pictures in a more considered way and practising the craft and art of shooting rather than hoping for a result.

              1. that is interesting. I am attempting to work slower even with my canon digital. I have a medium format film camera which is forcing me to work with more intention (film is expensive) which is slowly translating to the digital.

                I am curious as to why a medium format, presuming digital, would make you work slower. I had expected that the habit of shooting quickly was a film v. digital thing.

                1. Hi, a good question but the answer is simple in that MF digital cameras can’t shoot at 10fps. Traditionally they were only capable of 1fps although they have increased now but they are still much slower than 35mm. Also the overall feel, bigger image, higher resolution to zoom in an explore details, slightly bigger cameras and heavier lenses all contribute to the way you approach it. But I guess for me it’s also what I’ve learned yields best results. I’ve shot with every format professionally from film to digital and I’ve realised that a slow more thoughtful approach provides many more successful shots than rushing around trying to photograph everything.

  4. tastrong61

    Correct me if I’m wrong. My understanding of high speed sync was that the flash will fire multiple flashes as the shutter moves across the sensor. The problem is that it takes away power from the flash so other adjustments need to be made if you’re at the limit of your flashes power.

    I think what you described is Hyper Sync with the longer flash duration. I studied this quite a bit before HSS was introduced because I wanted to control light more when shooting outside. I was looking at a few tutorials which talked about certain packs (portable) like what Speed-o-tron offered at the time and with PCB AB1600 using pocket wizard triggers specifically made to tailor flash duration. What you described right about the 7:00 mark seems like the exact explanation of Hyper Sync. ??? Yes/ no?

    1. tastrong61

      ps. Broncolor may work differently but it would still classify as Hyper Sync if my understanding is correct. Just trying to learn.

  5. HI,

    Does the new global shutter system in the Sony a9 eliminate the issue with flash sync or is it a new workaroud?

  6. Hi Karl, how does the first curtain / second curtain work on cameras that only have digital shutter and are not mechanical ? Thanks.

    1. Hi, first or second curtain simply refers to when the flash will be fired, either at the start of the exposure or at the very end of the exposure so this is just controlled electronically so should make no difference whether it is a mechanical or electronic shutter.

  7. I was told that when working indoors, he first step is to set the camera so that the ambient light is removed, so take a photo at F8, SS 100, ISO 100 and that photo will be black. From there turn on your flash and you can start taking photo’s. Do you need to do this?

    1. Hi, as often is the case it depends on circumstances as occasionally you also want to include some of the ambient light in the scene too. However I always think it is good practise to understand how much is ambient and how much is flash. A good example of this can be see in this class where I have to mix both but also need to establish which is which: https://visualeducation.com/class/environmental-portraits-carpenter/ – The settings you mentioned above would be a middle of the range starting point as ambient light can vary greatly. I tend to decide what I need my aperture to be for creative depth of field reasons first and then shoot at varying shutter speeds and ISO to establish what the ambient light levels are. If you restrict yourself to f8 straight away then you’re also restricting your creative decisions for depth of field. Once you’ve established your DOF and aperture you then work everything around that whether it’s an increase or decrease in shutter speed, a decrease or increase in ISO or even adding ND filters to your lens. The class I mentioned above will give you a good idea of how I deal with these sort of problems.

  8. Hello Karl,

    I have a question: When I use my godox V1 as an optical slave to shoot with my Canon T3i I cannot go above the 1/250 sync speed (I do not have any trouble when the flash is attached to the hot shoe). Is this because of the optical trigger? How can I fix this?

    Thank you!

    1. Hi Ramina, I’m afraid the working specifics of different flash systems is not something I can answer as many of them are different. You would have to consult your user manuals or the manufacturer for that sort of information. As you know we teach techniques, lighting, visualisation and the art of photography. The limitations you are experiencing will be a solvable as it would be very strange for a system to prevent you from choosing whatever shutter speed you want if you are working in manual mode.

      1. Thank you for your reply, Karl. I have this limitation even when I only use my camera’s pop up flash, It does not let me go beyond the max sync speed in full manual mode. So I think when I use the pop up flash as an optical trigger my camera still applies the same limitations because the pop up flash is firing to fire the external flash. Thank you again.

  9. I’ve always had the issue of experiencing a cap on my shutter speeds when I was connected to my FJ400 strobe. Despite being in HSS mode on the trigger, strobe, and in camera, I could adjust my shutter to 1/250 or higher, but the camera would automatically readjust to 1/200 once I engage the shutter to take the photo. Not sure why this is. I currently use a Canon R6II but also experienced this issue when I used my previous Canon Rebel T8i model

    1. Hi, if you are in full manual mode on your camera then this shouldn’t happen as the camera should give you total control, it may be that there is a sensor on the hot shoe where the trigger or flash goes that over rides this but that would defeat the purpose of having a full manual mode. Check in the camere menu settings if there is an over ride for flash sync speed.

      1. Wow I tried the same thing with a speed lite instead and didn’t have that issue. The FJ-X2m flash trigger must not be registering with my camera. Will research if there is any other accounts of this issue online.

  10. Another observation is that HSS works differently in different camera systems. Canon is very primitive because is elongates the flash duration as you explain. However Nikon HSS is the most sophisticated and adopted by Leica. The HSS flash output is in pulses so requires a lot of power. The faster the shutter speed, the more power you need for more pulses.

  11. Probably the best explanation on the world wide web.
    Just one issue. Focal plane shutter only travels forwards. This means both curtains travel in the same direction. So waving the black card apart from each other is not correct because they are moving is opposite directions! Also most focal place shutters run horizontally not vertically. Only later cameras had vertically running focal plane shutters.

  12. Hi Karl,

    I have a question regarding the flash function settings. Are options for first and second curtain flash synchronization available in Nikon Camera as well or not?

      1. mahdi2mf

        Hi Karl, Thanks for the lesson. Where are those options in the Sony Alpha 7 IV? also, Can I try that technique with Siros S?
        In my camera flash mode, I have fill flash, rear flash, and slow flash, and I think they are the same modes with curtain flash synchronisation in Canon, but the results are not the same.

  14. Hi Karl, a rather theoretical question. Why is it the case that the camera sensor only catches flash light within the sync time and none of the ambient light? Would that be different, if the ambient light would be brighter than the flash? Cheers, Gerald

    1. Hi Gerald, it does capture the ambient light as well it just depends how much ambient light there is and if it’s strong enough to record.

  15. HI,Karl
    Is it technically difficult to support Google Translator?

    Because of the language barrier, it is difficult for me to understand all lecture content.

    The integrated translator does not deliver the correct language, but it helps to understand the lecture content.

    1. Hi, yes ISO is the base of the exposure level, the sensitivity of the recording material. But generally speaking in a studio environment when we have all the light available to us then we put ISO at 100 or 64 to ensure the cleanest possible images. But if your lights are a bit weak then you can increase ISO to compensate.

  17. Hi!
    Super informative as always!
    When working with fast shutter speeds, as you menthion in the video – e.g so fast that the shutter curtains are following each other and letting light in as a they go down/up – can this effect my choise of focus area and/or metering mode?

    1. Hi Jesper, thank you. No it doesn’t affect your choice of focus area or metering mode as those functions take place before the shutter moves.

  18. Hi Karl,

    Which shutter speed is recommended to achive the blur effect while using the rear sync flash?

    Best regards.

    1. Hi, it would totally depend on the speed of the movement of your subject. I think in this example I mentioned the shutter speed but can you remind me at what time in this video you are referring too please.

  19. Karl,

    It appears that you use 1/160 shutter speed on most of your shoots. Since sync speed is less of an issue on medium format cameras, how did you decide on that speed?

    1. Hi, the only purpose of ‘sync speed’ other than allowing the camera to time correctly with the flash is for the sync speed to be fast enough to cut out any ambient light that you don’t want. Often at f11 or f16 the amount of ambient light would be so low I could choose a sync speed of 1/50th and wouldn’t see any difference. The cameras in this video were 35mm with a maximum sync speed of 1/200th, however I’d noticed a problem with the sync on one of them as I had a shadow line from the shutter appear at 1/200th so I dropped to 1/160th to solve the problem. On medium format yes you are correct I could sync up to 1/2000th if I needed too. The times when that is useful (as you will see in some of our other classes) is when you are shooting fashion with flash outdoors in bright conditions, then that faster sync can allow me to cut most of the daylight out if I want to and have the scene look underexposed but the flash at the correct exposure. I show a way around this for 35mm cameras in another class by using ND filters you can see that here: https://visualeducation.com/class/simple-fashion-on-location/ As the shutter speed doesn’t affect the flash exposure (if it’s within the sync speed) then the only thing you ever need to know about sync speeds is ‘can it cut out enough of the ambient light that I don’t want?’ if it can then that’s all the sync speed you need. If it can’t then can you shut the blinds, darken the room, turn your modelling lights down or wait until later in the day? It’s the fundamentals of what a sync speed is meant to be doing that is the most important and that is cutting out light other than the flash.

  20. Hi Karl. I’m just a bit confused here, if I’m deciding to use some ambient light say for an outdoor shoot and wanted to add some flash. If there was some fast action needed to be caught. Would hss work or would the flash cause any issues as what I’m understanding is it would take longer (the burst) of course I fully understand if I was completely cutting out the ambient light but if I was to have both for action shots. Would the high shutter speeds in HSS catch the moment… of course I know without the flash yes it would as it’s a high shutter but just wondering would flash cause any surprises with motion… this may be a silly question but I’m just trying to understand how it works as opposed to just shooting and then saying great stuff it worked. Thanks, Brad

    1. Hi Brad, I’m afraid your question isn’t quite clear but I’ll do my best to put some answers down.
      1. Generally speaking a burst of flash is faster than most shutter speeds and certainly faster than the usual 1/200th sync speed of many cameras.
      2. On cameras with HSS or medium format cameras you can shoot at higher sync speeds so that you can cut out more ambient light if you need to, as explained in this video at higher shutter speeds the shutter is now working as a ‘scanning slit’ across the sensor on the 35mm cameras (not on Medium Format cameras) and as such the flash burst has to last for the entire time it takes the ‘scanning slit’ to pass across the sensor – this is how HSS works, therefore essentially your flash burst ‘appears’ equivalent to the shutter speed you selected.
      3. In situations where there is very little ambient light then you can rely on the flash to do all of the ‘freezing’ for you as there is not enough ambient light to really affect or cause any ‘ghosting’- see some of my fashion on location shoots/classes in Iceland where the model is running in the green dress.
      4. There would be no surprises with HSS, the amount of motion captured would be the same as the shutter speed would capture ordinarily. The downside of HSS is that you have less control over the amount of flash exposure level but this isn’t usually a problem.

      Please see the other chapter in this section on ‘Flash duration’. Kind regards Karl.

  21. Hi Karl,

    This knowledge is so interesting and fascinating to me, but it’s also a little bit confusing.

    So I can see from all the demonstrations that flash has the ability to freeze motion, but I also know that shutter speed affects motion blur in pictures and can also freeze motion.

    Can please clarify the difference between freezing motion with a flash and with the shutter speed.

    1. Hi Michael, you can freeze motion with your shutter speed if it is continuous light and it is bright enough. You don’t need a fast shutter speed with flash because the flash will freeze the motion and the problem is the camera getting it’s timing correct to trigger at the same time as the flash and this is limited by the flash sync speed which was explained in this video, I hope you watched that part?

    2. BastianLai

      Hi Karl,
      Is it possible to obtain a first curtain and then a second one later at the end ?
      Thank you.

        1. BastianLai

          Hi Karl,

          I am expecting to get a precise & clear face at the beginning then the head movement to obtain the blurred effect & finally a 2nd flash which is required to obtain another precise & clear face at the end of the movement ..so my idea was 1st flash- blurred movement – 2nd flash.,..but I may have misunderstood sthg.
          Thank you for your time & explanations

          1. Hi, then there are two options you need to shoot in an almost dark studio and open your shutter manually, fire your first flash manually, turn your continuous lights on and then fire your second flash manually. Alternatively you can have the camera trigger the first flash for you by using the camera in ‘B’ mode and the flash will fire at the start and then when you let go of the shutter just before you will need to fire the flash manually with another trigger.

  22. Hi Karl,

    Can I replace a fast flash duration of 1/8000 of a second to freeze a motion with a flash in HSS mode with a shutter speed of 1/8000 of a second and still freeze the motion?

    Thanks,
    Jyothi

    1. Hi, yes but there are limitations in both the amount of flash you will actually have in terms of power and this isn’t a reliable way to work if you are serious about fast flash work in the longer term.

  23. Hey Karl!! Wow I am learning so much from this class, thank you for everything you have put into it. My question is for the external speed light control setting, I’m not finding that in my camera anywhere. I shoot Sony A7iii and I’m not finding anything on YouTube for it. I have a strobe Einstein 640w with a trigger and receiver, do I need something special to be able to do the 1st and 2nd curtain shots? I cant seem to find the settings your changing in your camera, thank you!!

    1. Hi, glad you are enjoying the classes. What do you mean by the speedlite control setting? When you put a approved speedlite on the hotshoe the camera should see it is there? You then choose to use the speedlite in manual power or TTL and you set your sync speed ect. If you are using a trigger there is nothing to set you just use your camera in manual mode and the trigger will fire when you press the shutter button and you control your studio light on the studio light. For things such as first curtain or second curtain sync (sometimes called rear or front) you will find a setting in the camera menu to choose which one.

  24. Nick

    HI Karl. 1st off (& most importantly) – these courses are absolutely 1st class, thank you I’m learning soooo much!! 🙂
    My question is around shutter operation at speeds faster than the camera’s sync speed when you get the sort of ‘scan’ effect over the sensor. As the speed the 2 parts of the shutter can move is clearly limited by the mechanical aspects of the camera I understand why this is required. What I was wondering is at shutter speeds faster than the sync speed does the time the shutter is actually ‘working’ remain fixed at the ‘sync speed’? ie the reduction in f stop being linked to the reduced time each part of the sensor is being exposed to light? For example: if the sync speed is 1/250th sec, at that speed the whole sensor is essentially exposed in one go to the image for 1/250th second (in the same way it would be exposed for 1 second at a shutter speed of 1 second). Then at 1/500th sec the shutter scans over the sensor, still taking 1/250th second to cover the whole sensor but because of the ‘slit’ size each part of the sensor effectively only receives 1/500th second of light. Hope that makes sense…I’m a proper newbie so still wet behind my ears I’m afraid! 😉

    1. Hi, no if you go above your camera’s official sync speed when using flash you will have a black stripe across your image.

      1. Nick

        Thanks Karl. Fully understand that bit (getting a black stripe with a flash) – the question was around the time span the shutter is actually in operation, with or without flash….so the thought that the exposure of the sensor is shorter at speeds faster than sync speed (with corresponding f stop reduction) but the time it actually takes to expose the whole of the sensor remains at that of the sync speed. Sorry, I’m not really explaining myself very well.
        For example:
        – 1/250th sec (= sync speed): whole sensor exposed at once for 1/250th second
        – 1/500th sec: slit scans over the sensor. Size of slit means each part of the sensor is exposed to 1/500th sec light. Total time to scan the sensor from top to bottom = 1/250th second
        – 1/1000th sec: smaller slit scans over the sensor. Reduced size of slit means each part of the sensor is exposed to 1/1000th sec light. Total time to scan the sensor from top to bottom = 1/250th second

        Cheers Karl,
        Nick

        1. Hi Nick, what makes you think that the total time the sensor is scanned from top to bottom remains at 1/250th of second even on faster shutter speeds such as 1/1000th? I also don’t understand what you are trying to ascertain in terms of the usefulness of this, if for example the flash burst lasts for only 1/2000th of a second and bursts during the period of a slit then of course we have a black line. There are other technolgies, for example leaf shutters in medium format lenses work in a different way which means I can sync at any speed on most medium format cameras as there is no slit and the whole sensor is exposed whilst the very brief flash burst goes off. There is also something called HSS which through clever trigger timing of the trigger and forcing the flash to burst for very long durations (longer than the time it takes for the slit to move across the whole sensor) then you can actually work with shutter speeds higher than the sync speed. For example with some HSS you can shoot at 1/4000th of a second but the timing of the flash burst lasts longer than the entire scan so during it’s whole pass over the sensor there is still light coming out of the flash, however this results in often weaker recorded light due to the small slit and the flash power has to be increased to compensate which is often OK because at full power most flashes are on there longest duration but this is usually still around 1/1000th of a second so they have to be forced into bursting light out for a longer period. It’s quite a complicated process but what I’m trying to understand here is what it is you are trying to achieve? If you want faster sync then HSS or medium format are your only off the shelf choices to not get a black stripe across the image. Some mirrorless cameras can sync at 1/320th because they are recording electronically with a timing cut off of the sensor rather than just a physical shutter.

          1. Nick

            Many thanks for taking the time to reply Karl, it’s very much appreciated.
            It wasn’t so much what I was trying to achieve as to whether it was in fact possible or even worthwhile using faster shutter speeds than the sync speed to freeze motion (without flash) if faster shutter speeds were, by design, simply reducing the overall light exposure rather than the time the sensor (in totality) was being exposed to the image. My interpretation of your response is that this is the limitation of a ‘standard’ camera and the only way to get truly sharp freeze motion shots would be either to use a flash (and appropriate shutter speed to overcome any ambient light) or to use a medium format camera which would allow ‘true’ faster shutter speeds.
            Many thanks again Karl.
            Nick

            1. Hi Nick, what you are saying here is partially correct however if you have enough light such as very bright daylight or extremely bright artificial continuous light such as HMIs then it is possible to shoot with your fastest shutter speed such as 1/8000th on some cameras and freeze very fast movement such as birds in flight, helicopter rotor, liquid flying through the air etc etc but of course as you already understand the faster the shutter speed the less light being exposed on the sensor so you need a lot of light or a bigger aperture or higher ISO to compensate and you may not want to do those things. In a studio environment we don’t worry about the shutter speed to freeze things, instead we use a very fast burst of flash instead which on the fastest studio flash can be a fast as 1/10,000th of a second, this light is also usually brighter than continuous light so we just use the 1/250th of a second sync speed and then the whole sensor is exposed at once and that sync speed is usually fast enough to cut out any ambient light from your modelling lamps or interior lighting especially if your are at f11 or smaller.

          2. Nick

            Sorry – missed the 1st bit. I thought the seed the camera could physically move the shutters hit a wall at the sync speed…if you’re saying that the time to scan the sensor increases at increasing shutter speeds beyond sync speed (rather than simply decreasing the width of the slit) this makes sense and answers the question!
            Cheers
            Nick

  25. Hi Karl, Frist off I just your got classes, I find it VERY informative and amazing of all the knowledge at my fingertips. I might be jumping ahead of myself , but can’t you also adjust the the flash exposure by adjusting the ISO if need be. Such as going from ISO 100 to say ISO 400, which would be 2 stops.

    1. Hi, thank you and glad to hear you are enjoying the classes. Yes you are probably jumping ahead as that would have been covered in earlier classes. As a rough guide our learning levels go sort of left to right in the menu and left to right in the thumbnails, so if you skip a thumbnail or level then you may miss information that has been covered in an earlier class. We welcome any comments and answer all training related questions in the comments sections below each video (as you can see) often though questions are also asked that are then covered in the very next class. All the best Karl.

  26. This class was amazing. Karl I don’t know how to configure my sony alpha 7 camera so that it does the flash at the beginning or at the end.

    1. Hi, in your menu settings you should have something called first curtain sync or second curtain sync or it might be called front or rear. It should be in the flash sync settings if it has that ability.

  27. Hi Karl,
    Thanks! I understood the relationship between the ambient light and shutter speed. Basically if I leave the shutter speed longer, it will let more ambient light in. I re-looked at the video and understood this time.

    Thanks for the help! Loving the classes.

    Venu

    1. Hi Tummavg, I think I’ve already asked you to watch the following classes which should have given you the answer as the answer is in the classes? Are you watching these classes properly?
      https://visualeducation.com/class/shutter-speeds-and-apertures-to-flash/
      https://visualeducation.com/class/measuring-light-and-achieving-correct-exposure/
      Once you have watched the classes above then this section of classes https://visualeducation.com/section/environmental-portraits/ will make more sense to you and they cover various situations where you would need to sync your flash at different shutter speeds based on the surrounding ambient light. Do not watch these classes first, please watch the other 2 classes first as it appears you are missing some valuable information.

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