The relationship of shutter speeds and apertures to flash

In this information-packed photography class exploring relationships between flash power, aperture settings and shutter speeds, Karl explores four key areas:

  • 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 we cover the following:

  • 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

NOTE: This photography class is available with English subtitles.


  1. 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.

  2. 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.

  3. 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.

  4. 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 .

  5. 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!

  6. 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.

  7. 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.

  8. 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.

  9. 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 🙂

  10. 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.

  11. Hi Karl, my apologies in advance for the silly question; I am still a neophyte. I was wondering why a shorter shutter speed would not allow ambient light in. When you shot the photo of Stephanie at 1/60 of a second, the camera only recorded flashlight. However, if you had shot with no flash at that same speed, the camera would have recorded some ambient light. Probably it would have resulted in an underexposed shot, yet some ambient light would be captured. I must have misunderstood something from your explanation.
    Thanks for the answer and most of all for the outstanding course!!

    1. Hi Max, It would also depend on the aperture. Remember the aperture also dramatically affects the amount of ambient light coming in. So 1/60th at f8 might not let any ambient light in to the camera (in an indoors situation where the light isn’t as bright as outside) but 1/60th at f1.8 would let some ambient light in. The best way to find out is simply do a test shot without the flash trigger to see if any ambient light shows up. Generally speaking though it’s always better to go with the fastest shutter speed you can (that’s called the cameras sync speed) and use that to cut out as much ambient as possible. If you find that even with the fastest sync speed and the desired aperture that you still have ambient light pollution then you must reduce the ambient light pollution.

  12. Hi Karl! Love the way you teach. I just have one question from this class, just to check if I understood everything: If I want to shoot some portraits with movement (someone dancing for example), I can do that with a slow speed on camera if I don’t have ambient light? With natural light I always shoot with high speed, but in studio, is the flash doing that work? Thank you

  13. Hi Karl, the lesson was super clear, I just have one question, what is the difference between High speed sync and Hypersync flash photography? thank you for your time!

  14. Head rush Karl, so easy to understand. I have asked many people to explain this and you made it simple. Thank you

  15. Karl, after watching this whole course, I still have one question (sorry if it sounds little stupid). So I understand that making shutter speed slower in studio while using strobes, just allows more ambient light. But my questions is following. Let’s say you shoot outdoor with 1/10th of even slower shutter speed and hand held, you will most probably get not that sharp images right? so if you do the same but in studio, where is no ambient light, all dark, just a strobe light, but again hand held and slower shutter speed, won’t it have an influence on the sharpness of the image??
    I understand that it’s just burst a of a speed light which is very quick, but if camera is hand held and shutter is still open, won’t it make little blurrier picture? or it will be exactly as sharp as it’s when 1/5th, 1/100 or 1/800… ?
    The reason I’m asking is because I want to understand, in case of shooting water splash or falling object in studio, what real difference will be in terms of shutter speed changes, considering no any ambient light…
    Thanks in advance,

    1. Hi, if you shot in a very dark studio with a fast flash and a slow shutter speed then you could shoot hand held at 1/15th if you wanted to and it wouldn’t make any difference because there was no ambient light to be recorded. The flash would freeze everything but your composition might be poor because you couldn’t see what you were shooting. If it was totally black in your studio it wouldn’t even matter if your shutter speed was 5 seconds long because no light is no light, the only light is the burst of flash which fires with a short duration freezing your subject. However we don’t often work in totally black studios, so it’s always advisable to take a test shot without the flash trigger to see if your camera recorded anything.

      1. Thanks Karl. Just wanted to make sure that I understand the theoretical part correctly, as I don’t have that much experience and tests with studio lights.. Appreciate the answer and your time.

  16. My brain hurts but my heart is singing!

    The insights on both high speed sync and second curtain sync are phenomenal. I am off to test both out. I love the effect of the second curtain sync.

  17. Hi Karl!
    I was wondering… in what cases would I need a faster shutter speed (and as a consequence choose first or second curtain) if the freezing motion is based on the speed of the flash?

    1. Hi HC, you don’t need a fast shutter speed if using high speed flash, you can use any shutter speed (up to the sync speed) even very slow shutter speeds as long as you are shooting in a darkish room.

        1. Where you are shooting in a bright room with lots of other light or where you’re modelling lights are on full brightness.

  18. Excellent as usual….I think this is the 5th one I’ve watched in a row! LOL. You stated that HSS is a “work around” for higher shutter speeds. I understand the downside as speed light battery consumption will be quicker. What are the other downsides to it? Color balance issues? Ambient light pollution? Thanks!


    1. Hi Arjun, the main disadvantage is that for HSS to work the flash is actually using longer burn time flash bursts, so usually near full power and there is not much control over the flash power from the flash itself. This has to be done from the camera which reduces the versatility a little.

  19. If a camera doesn’t have a 2nd sync option, is there a way around this? Perhaps and external flash with that setting?

  20. Hi Karl, very clear explanation! Can I confirm that I will also need a HSS enabled flash head aswell as a HSS trigger. So for example I won’t be able to use my old Profoto 600’s to synch above the camera synch even if I swap out my old wireless trigger for a new HSS trigger? Thanks Steve

    1. Hi Steve, yes my understanding is that is correct. I’ve only used HSS once to demo on a broncolor siros ‘how to’ video so I’m afraid I’m not an expert on it. But from what I understand the flash burst actually becomes longer so that light is exposing for the entire time the small slit of 1/8000th passes over the entire sensor. To do this requires the flash in a HSS setting and a capable trigger.

  21. Hi Karl,

    Quick question. I just bought some cheap Interfit studio flashlights with soft boxes. Apparently my camera supports 1/200 sync speed. However, when I choose that shutter speed I can still see the shutter towards the bottom of the image, takes up a bit less than a third of the image. Of course, if I slow the speed down then I don’t have that issue.

    So my question is, am I doing something wrong? The camera definitely supports 1/200 sync speed but it seems I need to make it slower.

    1. Hi Chris, you’re camera is either not supporting 1/200th or the triggering method has a delay problem. I would expect it’s the first, I once had a Canon 5D that was supposed to be 1/200th and I could only ever get it to sync at 1/160th.

      1. Thanks Karl. It seems I have to set mine to 1/125s. There’s a part of me that thinks it’s maybe the trigger as they are not overly expensive lights, this was also on max power so I might try reducing the flash power to see if that makes a difference. Maybe if I try some proper studio lights in the future I might get my answer. Thanks again for responding.

        1. Hi Chris, try an actual sync cable from the camera direct to the lights to figure out if it’s the trigger.

          1. Good point, thanks Karl, that would definitely be the fastest way to check!

  22. Hello Karl,

    I just want to say that I am absolutely flabbergasted by your online training course. It is amazing. I have learned so much in such a short time.
    That is by far the best money I ever spent. Just like you said in your advert, first invest in yourself and then in your equipment..

    Thanks Karl,

    Keep em coming..

      1. Hello Karl, yesterday during my self portrait shoot I ran into the problem you explained in detail regarding flash sync speed. I was shooting with a fast shutter speed to eliminate the ambient light and I just wanted to light up my face with the flash using the inverse square law. During the shoot I just wasn’t able the see the bottom of my face, it was always dark and then it hit me, I remember your course on sync speed. I was shooting at a shutter speed of 400, and then I found out that my max speed without a high speed flash sync is 320. So I adjusted my f-spot, shallow depth of field had no use here as my back ground was all black. And then I got it to work. Thanks again, I would of never figured that out without seeing your course.

  23. Hi Karl, really loving the courses so far thank you! Does changing the aperture to increase or decrease the flash power then have an effect on the depth of field / background blur?

  24. Hi Karl! I hope you & your team are staying safe due to this hard times. Well, I have a question for you. I have a high sync speed trigger (according to manufacturer 1/8000s), do I have to change trigger in order to let some ambient light in or just a slower shutter speed with same trigger will do? Thank you in advance.

    1. Hi, thank you I hope you are well too. This is one of those questions where I’m afraid you will just have to try it and see. Sometimes 1/8000th is going to be much too fast when you are trying to combine flash with daylight because you will loose all the daylight. Other times you may be in the studio only trying to shoot some fast motion and then it will be fine. But the simplest way of finding out is to take your camera outdoors and put it on a tripod, set up your flash and trigger and just play with it and make a note of each result on a note pad while you test a series of shots and then keep those shots on file for future reference. Have an object such in the 3m range and then look at the results of the light on the object and the further (daylight) background at different settings.

  25. Hi Karl,

    As I am trying to understand more and more about lighting and all, after watching this particular one I just wanted to ask a general question.

    Would it be better and more effective if I shoot with a Mirrorless camera instead of a DSLR camera when it comes to working with a flashgun or in the studio? The shutter speed mechanism that you mentioned in the video and explained that it does the scanning process when using flash and as you know mirrorless cameras have no mechanism built by the sensor and should be able to work much quicker or the Mirrorless cameras have a fixed sync speed as well and work pretty the same as DSLR’s?

    I hope I am making sense on my question!

    Cheers from New York :))

    1. Hi Albion, whether it’s mirroless, DSLR or medium format the only thing you need to check is the specification for the ‘maximum flash/shutter sync speed’ this will be noted as something like 1/250th of a second. Various cameras and brands all have different maximums. The faster it is then the more ambient light it can cut out, flash value isn’t affected by the shutter for the most part because the flash is over to fast. So just look out for the specs on the sync speed, some mirroless have quicker ones, but then some medium format DSLRs have even quicker. Cheers Karl.

  26. Hello Mr. Karl

    First of all, I admire your work for the last 9 years, and iv been following the same for a long time.

    Recently I have purchased the educational part of your program, just to fulfill some advance knowledge. I have purchased Eos R which I find in relation to this video ( from min., 6+) were you addressing curtain behavior on fast shutter speed in relation to FFD.

    So, my question is, does this rule applies also for mirrorless cameras as well as the curtain system?

    Thank you in advance.
    Best regards


    1. Hi Goran, I’m sorry I don’t quite understand your question. Some mirroless cameras have a faster shutter sync speed than normal DSLRs as they can utilise and electronic shutter function rather than a mechanical one. Is that what you meant?

      1. Hi Karl,

        Sorry for my poor description, but yes, as you wrote down, this is exactly what I was thinking to get as an answer.

        Thanks again for your time and help.

  27. Hi Karl,

    Excellent video very useful information.

    I’m due to go and photograph an indoor athletics training day. One side of the gym is all windows so to try and balance that ambient light I’m using dual speedlites on the opposite side. Hoping to use HSS with a fast shutter speed but would ideally like to keep my aperture quite low to really keep the focus on the subject.

    However I’m worried that what I want and what I might have to do to compensate will affect my images. For example high shutter speed and low aperture will ultimately remove any ambient light and I’ll end up with images that looks like they’ve been taken in the dark with a flash. Am I correct in thinking that pushing up the ISO and lowering the power of the flash would be one way to balance this out?

    Ideally I’m hoping to working with 1/1250 and F/4 depending on the day will depend on how much my flash will need to compensate for the ambient light.



    1. Hi Charles, yes pushing up the ISO and reducing the flash will be an option as would opening the aperture more and reducing the flash or simply reducing the shutter speed if that’s an option and then you don’t need to reduce the flash as the flash exposure is only linked to aperture or ISO. Other ways of thinking about controlling light in such situations is can the daylight be reduced with blinds, gels etc (sounds unlikely in this case but worth keeping in mind).

      1. Thanks Karl,

        Hopefully I’ll get away with keeping my ISO low and try to take my shutter speed down as much as possible. My Canon lens is 200-400 F/4 so unable to go wider however I’ll take my 70-200mm F/2.8 in case I’m struggling and I’ll just have to get in closer.

        Many thanks for your reply very helpful.


  28. Hello Karl sir,
    As you said we have three options to increase the exposure of shot 1 is aperture 2 is flash power 3 is flash distance. Did we increase the exposure of shot using zoom function of flash ?

    1. Hi Mandeepsingh, most studio flashes don’t have a zoom function (only speedlites do) of course if we use any modifier (including the zoom on a flash) then we are able to funnel or direct more light into one spot than with another modifier and as such there will be more light available in that area and an increase in exposure, So the same flash with a softbox will have less light than the same light with a Para 133 in the focused position but obviously the look of the light will be very different for each. In fact last nights live show on umbrellas demonstrated this quite effectively.

  29. Hi Karl
    When using the flash should we always use ‘flash’ as white balance? This is really interesting course as I did not see any course explaining in detail like this. I have to take notes and explore.

    1. Hi, Yes when using flash set the white balance to flash or if you know the exact Kelvin temperature of the flash then set it to that with manual white balance K setting.

  30. Hi Karl, essentially bottom half of the image is completely black so is a sync speed issue however when I’ve used other triggers / lighting in the past I’ve taken shots over the 1/200 sync speed in HSS mode with my Canon 5DIV. Does the slightly older scoro not support this or would it have been something going on with the trigger or something else going on like a setting I’ve missed?

    1. Hi Cameron, the older Scoros don’t support HSS as far as I’m aware. But if you are shooting indoors then the using 1/200th sync shouldn’t be a problem as long as your ambient light is not too bright. All the shutter speed is doing is cutting out daylight or ambient light. The flash is doing all the ‘freezing’ of moving objects so it doesn’t matter what shutter speed you are using if you are shooting in a darkened studio.

  31. Hi Karl, I was trying to balance out ambient (backlit natural light with model beside a window cove) and use the strobe as fill light. I’d rented a scoro a4s and no matter what I tried was getting the banding of the mirror with higher shutter speeds. I thought that model of scoro even though not the latest version thought this would work? Am I missing something here or is it just not an option with that one and have to be the latest version? I did try the ‘speed’ setting so power was T0.1 as well.

    1. Hi Cameron, without seeing what you are talking about it is difficult to understand what you mean? But it sounds when you use the word ‘banding of the mirror’ that you went above your camera’s maximum sync speed and ended up with a band of light across the image. First of all we’d need to know which camera you were using, if it was a conventional DSLR then it is likely that the maximum sync speed is 1/200th of a second and if you went above this you encountered a problem.

  32. amazing,
    love your patience to explain all those things, you just got my lifetime subscription.

    also love your broncolor setup but is a bit out of my range so i will settle for ELC Hd pro setup.

    but please help me understand if i get it right.

    flash duration controls motion blur. so if i want a water freeze can i use a shuter of 160 and a very fast flash duration?

    but if i want to freeze water in strong ambient lighting then i need to also shorten the shuter to reduce the ambient so only then i need a hispeed sync.. right?

    cause the way i understand now,
    the shuter is 1/160 but because the flash only take like 1/4000 it only exposes the sensor for 1/4000 right?

    i dont know if i make so much sense

    ok, back to videos 🙂

    1. Hi, and thank you so much for your support! Yes you are right on all counts as you described. So if you have too much ambient/natural light when doing water splash shots then your 1/160th may not be a high enough sync to cut the natural light out. One option would be to add an ND filter to cut out natural light and increase the flash power to overcome the ND filter. A better option would be to darken the room, turn of interior lights, close blinds and keep modelling lamps on low.

  33. I was always thinking the siros would be affordable cause he makes it sound affordable but quite the opposite. 2’000 USD

    1. Hi Liam, I think it works out less than that on the kit prices but my descriptions are based on a comparison basis with other brands like Profoto. If broncolor is out of your budget then Elinchrom might be an option for you but without as fast flash durations.

  34. Hi Karl and the team!) Thank you for that tutorial, I’ve seen it for several times but still can’t understand one thing – my camera sync speed is 1/160 and that means I can’t use speed like 1/500 because of synchronization problem, but may be I can use long exposure so that the whole sensor may be lit with strobes? Like- open shutter, then flashburst, than close shutter? That way I can freeze fast mooving object and use strobes if I have no ambient light, am I understanding it right? The only problem I see here is that I’ll have to trigger flash lights separately…

      1. Hi Karl, sorry for my English)) I ‘ve failed to explain my question. I understand it is the flash that freezes mooving objects, but here you are speaking about flash synchronization problem. But if we shoudn’t consider shutter speeds : 1 why it is a problem? I can use any shutter speed as my mooving object will be freezed by flash anyway. 2 why all the cameras have different numbers of x-synchronization(and medium format synchronizes even faster) if we may not consider shutter speed at all when using flash?

        1. Hi Anna, the synchronisation comes down to the type of shutter. Medium Format cameras use a leaf shutter which is inside the lens and work a bit like and aperture and with a leaf shutter it can sync at any speed. Most DSLRs use a focal plane or electronic shutter and they usually sync at a maximum of 1/160th to about 1/250th on some models. The higher the sync speed then the more ambient (existing) or daylight we can cut out if we leave the shutter speed to low, say at 1/30th then we will get light pollution from the ambient light on top of the flash light which is not pleasant in most cases. This video will help you understand more:

          1. Thank you, Karl 🙂 That was the missing part for me- cut out of ambient light!

  35. As well as struggling with low light etc., (whichj thanks to your tutorials has become a lot less confusing) the ther issue I had was exactly what you showed with the Speed Light and black are in some of my images now I know what they are nd how to remedy .. Thanks Karl

  36. Karl. I wanted to point out something about your explanation on how the shutter opens and closes. At least specific to the Canon 5DMk3 and Mk4. (And I think this goes for all Canon DSLR cameras)
    You had shown two different “shutters” with both of them covering the sensor, and that when the shutter opened at lower speeds, they both unblocked the sensor together, then closed together after the exposure. Then you mentioned at high speeds (i.e. 1/500 or faster) that the shutter changed it’s operation to a “scan” from top to bottom. This is actually incorrect. There are dozens of videos out there showing the Canon shutter operation and they all show the same thing. Curtain #1 covers the sensor at all times. When the camera is triggered, the mirror flips up, and then curtain #1 drops down, exposing the sensor. When the duration is over, (assuming speeds under the HSS limit of the camera, 1/200 for the Mk3 and Mk4) then the second curtain drops, covering the sensor. The mirror drops down, and the curtains reset to 1 covering the sensor and 2 raised up out of the way. HSS doesn’t change the way the curtains move though. It simply makes the 2nd curtain drop down faster behind the 1st curtain. (as you show in your demonstration)
    So really the shutter doesn’t change completely the way it exposes the sensor, it just changes how quickly the 2nd curtain covers the sensor.

      1. That was the same video I had seen before. Maybe it was just in the way I saw you explaining it at first, you had two “cards” covering the sensor. Then you showed that when it opened at slower shutter speeds, both “cards” or shutters moved out of the way at the same time, then both closed over it at the end of the exposure. But that isn’t how the Canon shutter works. Both curtains do not cover the sensor at the same time, and both move away together at lower shutter speeds. I am referring to how you were showing it in this video at 4:20 in. I am sure it is just a matter of how you were showing it made me think you were saying that both shutters cover the lens at the same time, then both move away at the same time, at lower speeds. You explanation at high speeds of course is of course correct.
        Please understand I am not trying to act like I know more than you. You have years and years more photography experience than I do. I simply wanted to clarify how at least on the Canon DSLR camera, the shutters operated on lower speeds (under 1/200 second)

        1. Hi William, no worries. It’s also worth considering that not all shutters work the same too. More cameras are introducing ‘electronic shutters’ as part of the capture process which rely on the sensor doing a scan and then in medium format the shutter is in the lens much like an aperture.

          1. Medium format camera’s are well out of my current budget for sure, but I would love to get one some day. What is your take on the Sony mirrorless cameras? (If that is not too in depth of a question to ask)

          2. Hi William, the picture quality is superb it just comes down to whether you are OK with electronic viewfinders. I still find them difficult to get used to.

  37. I only have some overhead lights in my garage “studio”. Is there any significant difference in image quality between raising my shutter speed to kill the ambient light and just turning off the lights? (Other than being able to see what I’m doing)?

    Thanks for such a terrific site. As a newcomer to product photography and flashes in general your hard work is very much appreciated.


    1. Hi Dave, thank you for your kind comments. With regards your garage overhead lights, if you take a test shot without your flashes connected and using your maximum shutter flash sync speed for your camera you can then examine the test shot and see if the garage lights show up at all in the picture. If they were going to show up it would be in gloss highlight reflections, so put something glossy in for the test. If they don’t show up then you’d have no problems apart from them possibly influencing your thoughts about the lighting on the subject when you are setting up. Cheers Karl.

  38. Hi Nik, yes the answer above mostly covers it but in addition TTL metering (which I don’t use) doesn’t work with second curtain sync.

  39. Hi Karl,

    I think you may have answered this above, is there an example of where First curtain sync is better than rear or second?

    It seems that cameras default to first so I think there must be a reason for this.

    Many thanks


  40. hi sir what is the correct advantage of first curtain synchronisation.

    I mean when it can be used appropriately

    1. Hi Rao, there is no advantage or disadvantage if the shutter speed is high or the subject is not moving. Second curtain is only an advantage on a moving subject but it’s not a disadvantage on one that is not. The exception may be that you get better or higher speed sync with first curtain sync.

  41. Can you adjust remotely (on the broncolor transmitter) the power of your flashes? Or every time you have to adjust the flash power do you have to physically walk over to adjust or have an assistant?

  42. Hi Karl,

    When it comes to rear sync flash, do you set your camera to expose for the ambient light with the long exposure first before you bring in your flash/strobe? So that you can have the subject properly lit while moving and then the flash comes in to stop motion and make the subject in focus? I just want to know how to properly set my camera settings when using this technique.

    Thank you,

    1. Hi Derrious, I usually underexpose my ambient exposure by about one stop and then add enough flash on my subject. You’ll see me apply this technique many times in the “Fashion” section where I’m shooting on location.

  43. HHHHOOOOO….OMGOSH!!! I totally get that about flash sync and why it’s important. Plus I never knew that the shutter changed the way it operates with a request for a fast shutter speed! No one has ever explained that to me! You just changed my whole world of understanding of my camera. I only thought I knew every mechanical thing about it! I totally get that. That changes so much.

  44. At minute 22:05 you explain 3 ways to control flash exposure: aperture, flash power, flash-subject distance; actually there’s a 4th way, which is ISO! Agree?

    1. Hi Giovanni, technically speaking yes but it is not a choice I would opt for as it would require a reduction in quality. For example as you increase ISO then the image quality deteriorates so it is better to work with the others, there is also another option and that is to add filtration over the lens or lights to reduce exposure where necessary but the process of effective teaching is to feed the right information at the right time 🙂

  45. Section 1: Sync speed
    Best explanation I’ve ever seen on the subject. Simply brilliant and easy to understand.

    Section 4: Not only are you explaining 1st and 2nd curtain synchronization, you shows it in the camera too. Very handy as I use the same camera.

    I’ve surprisingly noticed (as I wanted to follow your steps) that 2nd curtain sync was not available (in the 5D mIII camera nor the speedlite) using Canon Speedlite Transmitter ST-E3-RT and Canon Speedlite 600EX-RT. But when mounting the speedlite directly on the body it was available both places.

    Does it mean that it’s depending on what kind of transmitter/trigger you have if you want to use 2nd curtain sync?

    1. Hi Tom, yes the ability to perform certain tasks on dedicated flashes may be compromised when used off camera with triggers.

  46. very nice explanation , but i am confusing with my canon 5 d mark iv when i work with this first curtain sync its work but when shoot with second curtain sync my camera body not select the second curtain i want to know why its happen because of my canon flash i use older version canon 600ex rt and wireless trigger st ex3rt but when i put flash on my camera the second curtain sync option works, why its not work with wireless trigger

    1. Hi Jaspreet, I’m afraid these sort of technical issues with various camera brands and flash combinations is not something we can help with, you will need to speak to Canon support for something like this.

  47. always been an area to stay away from BCuz its never been explained as well as you just did fir me Karl. THANK YOU My husband is getting jealous Bcuz I spend all my spare time watching you right now hahahaha! “Sorry, I am busy with Karl right now” giggle

  48. I was under the impression that my strobes pulse repeatedly in high speed sync mode to expose the image. Is that incorrect or do Broncolor lights employ a different system to handle it? Thanks!

    1. Hi Anthony, some strobes do use a repeating pulse but others now use just one extremely long pulse that lasts for the whole duration of the ‘slit’ passing across the sensor.

      1. Okay, so there’s new more efficient technology. With my strobes there is a reduction of max power when you’re in high sync mode due to the pulsing. Is there a max power output reduction with the Broncolor series due to the extended flash time? Thanks.

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