D80 - FP sync exposure problem

Discussion in 'General flash photography, lighting, and technique' started by DougD50, Jul 6, 2007.

  1. DougD50

    DougD50

    97
    Aug 29, 2006
    I posted this thread in the D80 section, but thought I might be able to get some more input from this section as well.
    In preparation for strobism, I played with my SB-600 in manual power mode and got under exposed pictures when shooting at shutter speed faster than the camera's normal sync speed. I have my AUTO FP setting turned on on my D80. I took the following 4 pictures in M mode (f/5.6. varying only shutter speed each time: 1/100, 1/200, 1/400, 1/800), with my SB-600 set on manual at 1/64. I expected my exposure to be about the same for the 4 pictures because the flash should happen much faster than 1/800 S. I tried the same test on my friend's D200 and got 4 shots (varying only shutter speed) to have the same exposure . Is something wrong with my D80?
    Uncle Frank, thanks in advance because I know you will have some comments on this.

    #1: iso 200, f/5.6, 1/100, SB-600 set to 1/64
    723834790_b11a29051e.

    #2: iso 200, f/5.6, 1/200, SB-600 set to 1/64
    View attachment 104345

    #3: iso 200, f/5.6, 1/400, SB-600 set to 1/64
    View attachment 104346

    #4: iso 200, f/5.6, 1/800, SB-600 set to 1/64
    View attachment 104347
     
  2. Occam's Razor: All things being equal, the simplest solution tends to be the best one.

    Try fresh batteries.
     
  3. See my post in the D-80 section. I don't think there is anything wrong with the equipment, batteries or otherwise. I have a D-80 and SB-800, and although I don't use FP sync and manual flash very often, I ran a test by dialing in a fractional manual power setting, using FP sync and high shutter speeds, and sure enough I got the same results. This is what I would expect to happen.

    In other words, as the shutter speed gets shorter (all other settings remaining the same) the exposure is reduced. This is what I would expect when I set a MANUAL fractional power with FP sync.

    I see that you have a D-200 and SB-800. Would you do a quick test with your camera and see if it works the same? I strongly suspect it does.:wink:
     
  4. photoshooter

    photoshooter Guest

    I just did the same test, same results.
    Think about it, the light from the flash has at 1/800 has substanially less time to enter the camera, 1/400. 1/200 etc.

    Look at the histogram.

    If you want to see what happens, the variable is the power output, of your flash.
    Every time you changethe shutter speed, you need to change the power output in manual.

    This is why you use TTL
     
  5. I dont see the problem

    If everything is set to manual, why on earth should the flash/camera compensate for your variation in shutter speed ?

    Just as without flash the faster shutter speed you use, the less time for the light to hit the sensor. With ttl the flash compensate by adjusting the power, in manual its up to you.
     
  6. Doug, one other thing to consider. The shutter speed shouldn't effect the number of photons that the flash will contribute to the illumination, but reducing the shutter speed will effect the contribution made by the ambient light.
     
    Last edited by a moderator: Jul 6, 2007
  7. Is this due to the reduced power from the flash you get when it pulses to light the whole of the frame? Remember that the whole frame is not exposed at once when you get above the max sync speed.

    Ronnie
     
    Last edited by a moderator: Jul 6, 2007
  8. Its correct what both UF and Ronnie says.

    But since you where shooting inside i guess the ambient light didnt contribute all that much to the exposure.

    But as you can see in your image the exposure differ not all that much between the two shots when you are within the sync speed.

    What im actually curious about is why/how this would be a problem? The reasons you will use FP is often because the ambient light is quite strong and/or you want to control the dof.
     
  9. DougD50

    DougD50

    97
    Aug 29, 2006
    Thanks to all of you for your help. I do understand that in manual mode I have the ability to crank up my power so that exposure would not be a problem.

    I also tried to rule out the effect of ambient by shooting at 1/100 withtout flash, my I got a completely dark frame (obviously because I shoot at night indoor with very dim light).

    The thing that bugs me is that I borrowed my friend D200 and took 4 shots with the same exact settings and the 4 shots taken with his D200 have the same exposure (unlike the shots from D80 having different exposure once the shutter speed is faster than 200). I also took a shot with shutter speed at 1/250 with the D80, and it is way underexposed as compared to shot with 1/200. I just spoke with a Nikon service guy on the phone and he said that 1/200 and 1/250 exposure should not be much difference espcially if the flash dominates exposure. He asked me to send the camera in, so we'll see.

    Doug
     
    Last edited by a moderator: Jul 7, 2007
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