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would it ever make sense to use anything other than iso 100 when using high speed sync?

NaftoliNaftoli Member
edited January 2012 in news & discussions
would it ever make sense to use anything other than iso 100 when using high speed sync?
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  • Depends on the situation. You loose a lot of power using HSS.
  • TrevTrev Moderator
    Naftoli,

    Yes, depends on situation, but having a higher ISO does help the flash in HSS, but you need to balance that against a faster shutter speed for ambient.

    Hint: Put your flash on camera in HSS mode, then change the ISO and watch your flash LCD and see the effective distance scale move to greater distances. Just try test shots.

    I have a couple of ISO/shutter combos set in my brain [daylight scene] so I can auto go to them in HSS. Beauty of Nikon flash though, it just goes to HSS without having to actually dial it in compared to Canon where you deliberately need to. Of course you need to 'remember' this and change shutter speed to sync/below if you want more power.

    Trev.
  • Neil vNNeil vN Administrator
    edited January 2012
    Naftoli .. You're thinking of this in terms of a studio setup, where available light isn't a factor.
    Then you'd just blast a ton of light to get the 100 ISO setting.

    It usually doesn't work that way on location with available light.
    On location, you'd use a range of ISO settings, depending on the available light.

    You're more likely to use this type of algorithm then:
    - set the shutter speed you need to stop action,
    - set the aperture you need for your depth of field ...
    - then balance this with the appropriate ISO setting.
  • @Trev. I'm a Canon user and, whilst I accept that Nikon probably has the edge with its flash system, selection of HSS is probably not a good example. While you (Nikon users) have to delve into your camera's custom settings menu to activate this function, we Canon users simply have to press a single button on the back of the flash. As it's a 'sticky' setting, we're in the same position as you regarding staying below max sync speed for more power etc.

    Just thought I'd mention it :)
  • @Allen: Nikon users simply have to set the Auto FP in the custom settings only once. As long as you know the camera's sync speed, simply stay below that to prevent engaging the HSS. Canon may make accessing HSS easier, but it's not like Nikon users have to go through this repeatedly.
  • Zenon Neil, Allen,Trev, yes u lose allot of power going into hss but the only reason u r going into hss is to underexpose the ambient light but by raising the iso ud be stabbing urself in the back, Neil the the situation i was referring to was shooting portraits outdoors on a bright day, where u would need to choose a fast shutter speed to underexpose the ambient light to retain detail in the sky/background etc. (closing down fstop is not an option B/c i want small dof) so i would start off setting my camera to max sync speed f2.8, if i have to go into hss why would i use anything other than iso 100
  • AllenAllen Member
    edited January 2012
    Steven, it was suggested that this was one of Nikon's flash advantages. I was simply saying that it's not. Once you've set it, whether on the camera or the flash, it's done. No advantage to either.
  • AllenAllen Member
    edited January 2012
    Naftoli, sorry for the distraction. I tried Trev's suggestion above about checking the flash range as I increase the ISO setting in HSS and, predictably, it increases by about 1.5x per stop. Unfortunately as I increase the shutter speed it reduces the range by the same amount. So the range at 100 ISO @ 1/250th is the same as 1600 ISO @ 1/4000th. The result is you're simply trading faster shutter speed for poorer quality.

    If you're using on camera flash, you probably need a déjà vu filter :)
  • Neil vNNeil vN Administrator
    Allen .. double check this on your camera.

    100 ISO @ 1/200 (or 1/250)
    will not give you the same flash range as
    1600 ISO @ 1/4000

    You lose power in HSS
    http://neilvn.com/tangents/2010/08/02/high-speed-flash-sync/


    I just checked it again on my Canon 5D mk2
    There is a substantial drop in the flash range.
  • Hi Neil. I do lose power in HSS. The examples in my previous post were chosen to show that in HSS there was no advantage to using a higher ISO and faster shutter speed combination to get more flash power. If I'd used 1/200 I would revert to normal flash and the flash range would double.

    With hindsight, using 100 ISO and 1/250 as a starting point wasn't a good idea as a lot of cameras aren't in HSS yet, but mine is. Sorry if that caused some confusion.

    I did actually check the values earlier and I've just re-checked them, and for my camera, flash and lens they are correct.

  • another proof would be the fact that u get more power efficiency from ur flash when u put an nd filter on the lens then going into hss, so to by lowering ur iso ur getting better efficiency from ur flash then going into hss,
  • NaftoliNaftoli Member
    edited January 2012
    example; i took put an sb700 on my d7000, (flash set to M at full power) i then set my d7000 to its maximum sync speed which is 320/of a sec. and f5.6 iso 200, my flash distance scale tells me it has a range of 27 feet, now lets say at these settings i have perfect exposure for the ambient light, however our goal (for arguments sake) is to underexpose the ambient by one stop (and have flash add a stop of light to our subject), so first lets do that by adjusting shutter speed, so we turn the dial one stop above 1/320th to 1/640th of a sec, now the flash distance scale reads only 8.4 feet!
    now lets go back to our origanal settings and instead of underexposing the ambient by raising our shutter speed we will underexpose it by lowering the iso one stop from 200 to 100, now the flash distance scale reads 19 feet!

    in conclusion by going to iso 100 and staying at maximum sync i gained about 11 feet in flash power!
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