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Leaving High Speed Sync on all the times even when not needed?

PompoPompo Member
edited October 2011 in flash & lighting
Since when shooting at high speed sync we lose a lot of flash power, what happens if I shoot at the camera's max sync speed but yet leaving High-Speed Sync selected? The Canon 580 EXII says the High Speed icon will not be displayed. Does the flash keep its original full power as if High speed sync was not selected? It would make send to keep High Speed sync selected all the times and try not to exceed that...in other words let it go the high speed way only when needed but yet keeping High speed selected all the times.


  • ZenonZenon Member
    edited September 2011
    No you are fine. There is a loss of power using HSS because the flash fires in rapid succession. When you hit sync speed or lower it operates normally. This is a Pocket Wizard ad but it has some great animations. Really helped me understand HSS. You don't need the PW to make HSS work but probably already knew that.

  • thanks for the very useful link, maybe my question was a bit unclear.

    Will my Canon 580EXII flash lose power when set at High Sync speed, BUT used at speed enough low enough to be within the camera's maximum speed sync?
  • No it will not lose power if it is set to HSS and used within the cameras max sync speed.
  • Hi Pompo
    I concur with Zenon
    Also I find it very useful to have HSS on all the time.
    Some times if I follow a couple out side a Dark Church into Bright Sunlight , I'll use Aperture Priority Mode. indoors Might be F4 @ 1/60 , Out doors F4@ 1/500 If I have HSS on the camera will sync and you will still be able to get a shot when they emerge.
    Or Some times in the heat of the moment Forget to change the Sutter Speed.
    Having HSS on saved my Kiester on more then one occasion.

  • sounds great thanks for the replies :)
  • Neil vNNeil vN Administrator
    Pompo .. it depends entirely on the Canon camera you have.

    Which body do you have?
  • @Neil I have a 5d Mark II and 1d Mark IV
  • Now I an curious as well. I have a 5D2 and 7D. Both do not rapid fire at or below sync speed as far as I know.
  • Neil vNNeil vN Administrator
    With the Canon 5D (the classic, not the 5D2), if you are at max sync speed (1/200), then keeping HSS enabled, pushes your camera and flash into HSS mode. If you don't have HSS enabled (via the H button), then it stays out of HSS mode, (as you'd expect).

    So with the 5D and (I think) the 1D mk3, there is a distinct difference whether you keep your flash with HSS enabled or not, at max sync speed.
  • AllenAllen Member
    edited October 2011
    Don't all recent Canon cameras have a similar viewfinder display?:

    Lightning bolt - flash ready
    Flashing lightning bolt - subject out of range
    No lightning bolt - flash not ready (or switched off)
    Asterisk - Flash Exposure Lock
    'H' - High Speed Sync in use
    No 'H' - High Speed Sync not in use (whether activated or not)
  • I wonder if there would be a power drop even if it was on at 1/200 on the 5Dc. The shutter is fully opened so it only has to fire once, not repeatedly like at faster shutter speeds.
  • Neil vNNeil vN Administrator
    Zenon .. you can observe the drop in power easily.
    And if you don't want to check yourself, here's an easy link:

  • ZenonZenon Member
    edited October 2011
    Thanks. I'll check the out the link. I don't have the 5D classic to test it.
  • yes I tried with the 5d m2 and AS I set it to HSS the distance on the flash display automatically drops big time....even if I go with a slower shutter speed, if I dont set it to HSS the shutter speed cannot be set faster than the max sync speed...thanks :0
  • I didn't see any difference on my flash display using my 5D2 with the HSS on or off. At both 1/200 and 1/160 and flash on manual there is slight variation between exposures between HSS on and off. Then at 1/160 I tried 5 in a row with HSS engaged and then 5 in a row with it disengaged and there was the same slight variation between the first 5 and second 5 set of shots. All 10 were pretty close.

    Niel's link explains there is a quirk at maximum sync speed. One exposure looked fine while the next one looked underexposed. However it states that this happens when the HSS is on or off. So there is this quirk at 1/200 with Canon bodies. That I believe as it has been tested.

    I'm not an engineer but I'm still trying to figure this out from engineering standpoint. If I leave HSS on and shoot at 1/160 why there would be a power drop. The sensor is completely revealed as both curtains are fully opened so the flash only has to fire once.

    Well I'm probably getting myself into trouble here. I read the link a few times and I must have missed something and will read it again and do some more searching. I'm just finding this very interesting and I need to understand these things.
  • Neil vNNeil vN Administrator
    Zenon .. where you at full manual output?
  • No. I was quite a bit below that. I will try this again at full output.
  • Neil vNNeil vN Administrator
    OK ... since you were "quite a bit below" full output, your flash had the leeway in power to make up for the drop in output capability. Try it at full power and see what happens.
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