Flash Sync Speeds… No Experience Necessary

Bar caused by too high a shutter speed

First, a disclaimer.  This is a very complex and scientific subject, and I’m going to do my best to explain this topic in very simple terms because this is an oft-misunderstood subject.  So if you’re an advanced super-photographer, just feel free to tell me what I missed in the comments below, but know that I probably skipped it on purpose.

The path to understanding flash sync speeds begins with understanding the shutter in your DSLR camera.  The shutter is made up of two curtains that quickly slide from the bottom of the frame to the top of the frame, thus revealing a slit of light.  The two curtains move very quickly.  In fact, on most cameras, if the shutter speed is under 1/200th of a second, then the entire sensor will be revealed before the second curtain begins to slide across the sensor.

Like shutters, the light coming from a flash is extremely fast.  One burst of light from a flash begins and ends in 1/500th of a second or faster.  The trouble with flash is that, if a shutter speed of over (or faster than) 1/200th of a second is used, the flash can only illuminate the portion of the image that is not covered by the sliding shutter.  That leaves part of the image correctly exposed, and part of the image dark and untouched by flash.  Woops!  In case you are wondering what that looks like, check out the disastrous piece of photography to the left.

So what can you do to fix this short-coming of flash photography?  Two answers.

First, if you are using the flash made by the manufacturer of your camera, you can often bump it up a little higher–often to 1/250th or 1/320th.  There is a setting in your camera menu that will allow you to enable this function.  This is convenient for shooting a wedding or other event where you’ll often have the flash on the camera and bounce the light off walls or the ceiling.

Second, if you buy one of the new fancy flashes from either Canon or Nikon, you can use what is called high-speed sync.  This turns your flash into a machine gun, but with less destruction.  It makes the flash fire several low-power extremely quick bursts of light.  The multiple bursts will occur at planned times during the exposure so that the whole frame will be illuminated.  With high speed flash sync, photographers can use shutter speeds of over (or faster than) 1/1000th of a second.  If you turn on high-speed flash sync and you only detect one burst of light, it is because the bursts occur so quickly and in such rapid a succession that it is impossible to detect the multiple bursts.

There you have it… flash sync speed.   Have a question about something that wasn’t quite clear?  Leave a comment below!

Comments from the I.P. Community

  1. says

    Please don’t mind me, but fractions always given me a hard time : ) What do you mean when you refer to “over” and “under” with regard to the shutter speed fraction? For example, would 1/100 be considered over, or under 1/200?


  2. says

    Ditto, Emily. Fractions are never fun. 1/200th of a second is faster than 1/100th of a second. When I say “over”, I mean it in the traditional photography sense of a faster shutter speed. “Under” means slower than that shutter speed. Good question. I can see why that is confusing.

  3. Kim Coulter says

    After reading the first paragraph I thought for sure I wasn’t going to be able to comprehend your explaination. VERY well put, I understood every word :o). Now I’m off to shoot some pictures with that high-speed sync thing you speak of.

  4. mahdi says

    Hi jim, and thank you so much.
    How can I use my nikon D7100 ‘s built in flash as a filling flash in bright sunny days?.
    With my nikon D70 it was possible to use a higher shutter speeds but with new camera it is not.
    Any way to inactivate the shutter syn.speed in certain circumstances or not?
    Warm regards.

  5. Jawad says

    Hi Jim,
    that was really helpful. Since I do bird photography where I need to go as fast as 1/4000s of shutter speed at times or often 1/2000s. Now i had the same limitation since i was using a Manual flash and any shutter above 1/250s would give me one side of frame to be darkened just like your example shown above. Now I plan to buy Nikon SB-910, just to be able to get rid of this curtain effect in high speed photography. Please confirm whether using sb-910 on hot shoe with the settings on FP mode can rid me of this problem? and will i then be able to illuminate my subject at, say 1/1600s or 1/2000s ? Your kind response is awaited, pls.


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