Bright light??

Discussion in 'Nikon' started by michael_foster|6, Mar 2, 2009.

  1. OK, I really feel like a novice here. I shoot a LOT of photos, but they are mostly stage/theatre/dance events with no flash. I also do quite a bit of studio work with strobes. I am using a D2x, SB800 and usually the f2.8 17-55.
    My question is shooting outdoors or maybe a wedding with 3 SB800's firing, where there is a lot of light. I took some headshots in bright sunshine with a flash to fill in the shadows. Ideally I would like to shoot at f2.8 to keep the background out of focus. When I do, the highlights always seem to be blown out. I try to use Aperture Priority Mode, f2.8, ISO 100. I have tried dialing the exposure compensation to -3.0 which seems to work a bit. To get a decent picture, I have to got to f5.6 or f8 or higher.
    Any suggestions out there? This is a new area for me!
  2. If you really need (for creative purposes) to have that lens wide open in brighter light - and I do understand the urge! - then what you want is an ND (neutral density) filter. Essentially, sunglasses for your lense. You can get them several stops dark, if need be. Of course, it's another layer of glass over your fine lens... so don't scrimp. Get a good one from B+W or Hoya.
  3. Why aren't you just setting the flash to manual and dialing down the power? When you say exposure compensation, do you mean composation on the whole exposure or just the flash? You can set flash compensation separately, you know.
    Kent in SD
  4. I imagine, Kent, that the strobes simply have to be what they have to be in order to fill shadows in the light he's in. If we stipulate that he needs that lens wide open for the desired DoF control, the whole issue is being driven by the ambient light, and having to balance with it, strobe-wise. At some point, in that much light, there's nothing for it but to make the strobes hot enough to compete with the strong daylight (for the right look on his subjects' faces), and then to use an NDF in order to get the whole thing to settle down a bit. It might be less of an issue if he goes with high speed FP synch, and can cut back on the ambient light by using a much higher shutter speed. But that can get tricky.

    Not really an issue with nocturnal locomotive shots, of course. (not to worry, Michael - that's a little side joke that Kent will get!).
  5. Michael, if you tried to take this shot WITHOUT flash, what would the shutter speed be? I'm guessing that if you're shooting wide open at f/2.8 in bright sunlight, you'd need a very fast shutter speed to give you a proper exposure.
    Let's calculate your shutter speed using the "sunny f/16" rule:
    ISO 100 = 1/100s @ f/16 = 1/200s @ f/11 = 1/400s @ f/8
    = 1/800s @ f/5.6 = 1/1600s @ f/4 = 1/3200s @ f/2.8
    So your shutter speed might have to be in the realm of 1/3000th of a second in order to capture your highlights properly. (NOTE: If your subject(s) is/are in the shade and if you're willing to let the hightlights burn out, your shutter speed will be somewhat shower, perhaps 1/250s.)
    The camera probably can't synchronize the flash to the shutter at 1/3000 s. If you forced it to make an exposure at this speed you'd see part of the shutter in your image. Typical shutter speeds for flash are in the neighborhood of 1/60th of a second. Try setting the D2x (without flash) to S mode and dial in a shutter speed of 1/60th of a second. The camera will suggest an aperture setting. Go back to A mode and try this aperture with your flash sync time set to 1/60th of a second and now try exposing with your flash units. Your deal exposure is probably somewhere in this shutter/aperture range. You can always add some Gaussian blur to your background in PS.
    NOTE: There is a "High FP" flash mode that will let you shoot as a faster shutter speed, but probably not as high as 1/3000th of a second. You can look it up in your D2x manual and give it a try. It's meant to solve this "flash in bright settings" problem.
  6. I don't know about the D2X, but on the later cameras 1/250 is the fastest shutter that allows you to do a single flash. For the faster shutter speeds, the shutter is not open all the way (it starts to close before it's fully open) so the flash has to put out several bursts of light to get the whole frame exposed. For example at 1/2500 second you need at least 10 flashes to cover the frame (and probably more since the flash profile isn't square). In order to give you bursts like that, the flash can't put out full power.
    I think the ND filter is the easiest solution. Possibly you could use reflectors for fill light instead of flash.
  7. Yes, the problem is indeed the flash-sync. If left to its own devices it will force the shutter-speed to be far too slow for the ambient light at f/2.8. I bet it says HI in your viewfinder where the shutter-speed reading should be, indicating over-exposure. But fear not, with a D2X and an SB800, FP-high-speed sync works beautifully. It does consume more battery, though, since the strobe needs to flicker for the duration of the exposure. ND-filter would work too, but you already have all it takes. The decision between the two is one between high or slow shutter-speed, really. (Also, the ND-filter cuts the light from the flash as well, so you'll get shorter reach and high battery consumption as the flash tries to compensate. But that may or may not be equal to the FP solution.)

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