The Relationship of Shutter Speeds and Apertures to Flash

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

Specifically, he looks at:

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

Karl demonstrates how each of these can work together to influence the final image.

In this photography class:

  • How shutter speed works
  • 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


  1. Hi,

    So basically in regular studio photography, I should never really change my shutter speed more or less than 125?


    1. Hi Dave, if that is your maximum shutter sync speed (that is the fastest the camera can synchronise the shutter with flash) on some cameras it’s 1/125th on others it’s more. But whatever it is you should go with as that is the speed that will still work with your flash and cut out the most daylight or ambient light but not cut out any of the flash.

  2. Hello Karl, I have two questions.
    first, If flash speed is lower than the camera shutter speed, then what happened; is the black line still appear in the image or not?
    second, if flash speed and camera shutter speed are the same at a higher value; then what happened, am I get properly exposed image or image with a black line?

  3. I have a Sony A7R4, when I attach the Broncolor highspeed trigger, the camera doesn’t allow me to increase my shutter speed beyond 1/250. Couldn’t find an answer on the internet, do you have solution for this?

    1. Hi, I can’t see a reason for this. If you are in full manual mode then you should be able to set your camera settings to exactly what you like on any camera?

      1. Ahhh, it’s an option in the trigger itself for HS sync , and not the camera itself. Once I turn on HS in the trigger, I can increase shutter speed in my Sony camera. Thank you

    1. Hi, unfortunately we can’t advise on all camera models as there are too many but if it has that feature then it will say about it in the camera manual.

  4. I want to know whether my flash should use front curtain synchronization or rear curtain synchronization in studio shooting?

    1. Hi, First curtain is usually fine. The only time you need second curtain is if your deliberately trying to emulate movement with flash and continuous lighting.

  5. Karl, in your explanation of HSS, you said the flash duration is longer to allow the “scanning” of the image. What effect does the longer duration have on fast moving subjects as discussed in your previous lesson – or would you not use HSS for fast moving subjects?

    1. Hi, it doesn’t have any effect because it allows you to utilise a faster shutter speed instead, so rather than a standard 1/200th for example you can now attain 1/4000th with the shutter speed instead of say 1/4000th with the flash duration. Although the shutter at such speeds is a ‘slit scan’ the resulting laydown of the exposure on the recording medium is still fast enough to counter the effect of the ‘slit scan’ in most cases. Even if we were using fast flash duration instead the light isn’t an instant of total exposure of flash at that one moment, there is a gradual build to a peak of intensity of light and then a gradual fall of light called the tail but it all happens within the t0.1 measured period which may be as fast as 1/10,000th of a second on some flash systems. My preference is still for fast flash durations rather that fast shutter speeds with HSS as you can usually achieve faster crisper shots for very high speed work but even 1/1500th is fast enough for many things.

  6. I had a lot of doubts about this particular topic and yes i am fully satisfied with the content that it cleared almost all by doubts in this specific section . Thank you very much karl. The way you convey each topics with the simplest way possible i really appreciate that .

  7. Thank you very much, Karl!
    I entered this chapter with tons of question marks on my mind but left with an absolute understanding of lighting, aperture, and shutter speed. I can’t wait to reveal more great educational content!

    I’m very happy with my educational experience on this platform with the affordable prices. Professional presentation and neat content organization.

    Furthermore, I really appreciate the other educational contents you do, like challenges, live shows, and member discounts, along with the customer service provided. Thank you very much, bother!

  8. Hi,
    If I’m using a continuous light, will slowing down the shutter speed also let in more surrounding/unwanted light?

    1. Hi Juneed, yes absolutely because the other light in the room is also continuous, which is why you should work in a darkened room if shooting with continuous light.

  9. Couldn’t you eliminate the effect of ambient light by finding the aperture that makes the room dark (with only ambient light) and then setting the flash to correctly expose the shot at the next higher f-stop?

    1. Hi, you can always affect ambient exposure with both aperture and shutter speed. But and this is a big BUT, you shouldn’t be approaching your photography that way. The aperture choice is itself a creative decision based on the depth of field look you want in an image so that choice should be made first and then stick to it and adjust everything else you can around it.

  10. Hi Karl. Hope you are doing well. I saw in many answers you tell to make a test about cut out the ambient light. For make this kind of test which settings in my camera should I use? Put the shutter in the max flash sync or less? In my case I have the Sony a7III and it would be 1/250. But I saw you used in 1/60 and you cuted out the ambient ligh. And about ISO? For make this test should I keep it in 100? And about aperture exist a value Rule of aperture for this kind of test? Should I put F8 or if I open it more to F5.6 will be a problem?
    Thanks ✌️

    1. Hi Guigo, we cut out ambient light so that it doesn’t add lighting ontop of our flash lighting (unless we want it to). Ambient light is always different brightness depending on if it is daytime, nighttime, morning, weather, indoors, outdoors etc. So there is not a particular shutter speed that is correct for all of them. If you want to cut out the most you can with your camera then 1/250th is the fastest flash sync speed you have so that is the one you should choose. If you want some ambient light in your picture then choose a slower one (by testing it). If 1/250th isn’t fast enough to cut out the ambient light then you would need to think about reducing your ISO or closing the aperture or using an ND filter. In most cases 1/250th will cut out most of the ambient at f11 but not at f4. There is no rule only the settings that work and allow you to do what you need with light, motion and depth of field.

  11. Hi there, thank you for this tutorial, I figured out that my camera can’t do slow shutter speed with a flash unit because it’s missing a pin in the hotshoe (probably), I’m only able to shoot pictures with flash above 1/250th, if I go below that (which I sometimes want for ambient light to come in also if I’m outdoors, the flash unit doesn’t fire, even if I switch off HSS, I hope to get this fixed with another camera soon, I’m using the Canon EOS 250D now, going to buy the Canon 90D in about 4 months, with that I’m using the Godox AD200 in Manual mode.

    Any way I can still get this working with a work around? You said something about ND filters, but I think that answer was because I didn’t explain it right…

    Anyways, thank you very much for this tutorial, learning a great deal this way 🙂

  12. Hi Karl,

    Can high speed sync be used to make up for a long flash duration? For example is f8 1/200 with a light power that has a 1/4000 flash duration the same as shooting f8 1/4000 with HSS if the light were to only have a flash duration of 1/2000? Hopefully this makes sense.


    1. Hi Squiggle, no that makes no sense at all. 1/4000th or 1/2000th is much quicker than 1/200th so those very fast flash bursts happen easily within or inside the time of the flash sync. HSS is a different way of working it usually relies on a longer flash burst of like 1/500th of a second so that you can use a faster shutter speed like 1/4000th so what happens is your shutter speed ‘syncs’ with it but it also cuts off a lot of the flash either side so it looses alot of the exposure which is why I’m not a fan of HSS. Like anything though people overcomplicate things. First of all ask yourself ‘what am I trying to do and what do I need it for’? Then from there you test or work out how to solve it. I see far to many photographers getting lost in the specifics rather than focusing on telling the story with their images, what happens is they concern themselves with the technological aspects to the point that it stops them getting on with shooting and creating. First tell me or yourself what it is you’re trying to achieve and why and then let’s go from there.

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