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shutter speeds not changing in Aperature Priority for HDR shooting

Lance007Lance007 Member
edited August 2014 in general photography
I have a Nikon D3 that I use with a SB800 Speedlight. I shoot HDR once in awhile for real estate shoots.I Usually shoot in Manual for this, but thought I'd try shooting in Aperature Priority which seems to be a popular technique. I set up 5 frame bracket at 1 stop each with all custom setting e5 e6 and e7 in bracketing/flash set to their defaults. I noticed that two of the shutter speeds did not change, they both stayed at 1/60th, but the other frames the shutter speed did change. Arent all the shutter speeds supposed to change when shooting in Ap priority? I also was reminded of this when loading the bracketed shots in Photomatix with the waring that two or more exposures were the same. When I take the strobe off, the shutter speeds do change around the f stop like they are supposed too. I have tried setting the strobe to manual and TTL with the same problem. Any ideas? Lance

Comments

  • Neil vNNeil vN Administrator
    Clearly the flash is holding your shutter speed where it thinks you need to be.

    No other work-around than shooting in manual mode on your camera.
  • I felt that may have been it, that's what I get for straying off the manual mode. A big thank you for clearing this up for me. Lance
  • What you are describing sounds normal to me. So with no flash it behaves as expected: It's the equivalent of taking 5 shots in aperture priority mode with -2, -1, +1, +2, 0 exposure compensation which will therefore change the shutter speed for each shot.

    Set aside bracketing for a second: If you turn on the flash in aperture priority mode, if the ambient light requires slower than the flash shutter speed setting (e2 which defaults to 1/60), it will use 1/60. (An aside is this is one of the reasons M mode is best for flash. But I digress...) If the ambient is brighter than that, where 1/60 would be an overexposure, then the shutter speed will get faster as needed. So 1/60 acts like a minimum for the shutter speed. That's how aperture priority works with the flash on. If you mess with exposure compensation in this mode with flash on, it will attempt to do the same thing but note that if the required shutter speeds are still less than 1/60 it will use that.

    The same thing holds when you use bracketing. So I think what happened is perhaps your -2 and -1 pushed the shutter speed over 1/60, but 0, +1, and +2 required shutter speeds of 1/60 or slower, so 1/60 was held. So you ended up with two shots faster than 1/60 and the rest at 1/60.

    A workaround would be to put the flash into SLOW or REAR sync mode. These modes don't use the e2 setting, so 1/60 will no longer be a minimum. The watchout is that shutter speeds might get rather slow, particularly for hand holding.

    Good luck.
  • Awesome Nikonguy, thank you so much for sharing this info, it makes perfect sense. I always use a tripod when doing my brackets, so I am looking forward to testing out your workaround. Never would have thought of that. Again, thanks Mucho. Lance
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