Re: [photo-3d] Re: Flash photography

[Bill Costa - Network Info Srvs <Bill.Costa@xxxxxxxxxxxxxx>]

From: Bill Costa - Network Info Srvs <Bill.Costa@xxxxxxxxxxxxxx>


    David Motz <david.motz@xxxxxxx> recently posted...

> What bothers me though is when I have the Vivitar on the hotshoe and the
> Cullmann in slave mode I get f4 again, so apparently the slave flash is
> not going off when the shutter is open?  

    This would be an easy thing to test.  See below...

> Is it common for the flash timing to be off this way?  Can this be fixed?

    There are two basic types of flash sync: flash bulb (M) and 
    electronic flash (X).  With bulb sync the flash has to be triggered
    some time before the shutter is fully open since there is a delay
    before the bulb comes up to full illumination.  Given the age of
    the Realist, I would say it must be using M sync.  Now I didn't
    think this was an issue with leaf shutters, but it might be, at 
    least in this particular case.

    There are lots of people on this list I am sure that are using
    electronic flash on a Realist, so it would be good to hear from
    them.

    But what you *can* do is actually test what's going on.  It should
    be fairly easy, you just need an empty camera.

    If you can take the main flash off the camera but still trip it, i.e.
    by using a cord, then do so.  Otherwise you'll need a mirror or 
    large light colored reflective surface.
    
    1. Open the back of the camera, put it on Bulb so that the shutter
       stays open for as long as you hold down the release.  Fire
       the flash manually, either with it off the camera and pointing
       directly at the lens, or by using a mirror or very reflective
       surface to catch the light and direct it back at the camera.

    2. Each time you fire the flash, you should be able to see a nice
       large round circle of light through the lens.  Remember we're 
       holding the shutter wide open, and the aperture is wide open,
       so there should be no obstruction of the light passing through
       the lens.  It should be easy to observe this.

    3. Now that you know what that looks like, try the same experiment
       only using the camera to trip the flash.  Start at the slowest
       speeds and work your way up.  What you should see, is a perfect
       circle at every speed and it should look just as bright as the
       when you were holding the lens open.  If not, then there is 
       indeed a problem with the flash sync.

    4. Of course we're expecting the above test to work, it's the
       slave that has been called into question.  You should now place
       the slave right in front of the lens, use paper and tape if you
       have to, so that the lens sees only the slave.  Use the
       on-camera flash to trigger the slave.  You should only need to
       point the main flash at the ceiling to get it to trip the
       slave, and thus you'll be sure that what you're seeing in the
       lens is only the slave's light.

    5. Again, try holding the lens open manually first so you can see
       what the flash looks like under a known good situation.  Then
       start trying different shutter speeds to see if you can see any
       difference.

    I believe these tests should reveal without any doubt if you are
    having any flash sync problems.  If you are, you will see either a
    smaller circle, or a partially blocked circle.  Either indicates
    that some of the light is being blocked, thus effectively changing
    your effective aperture with regards to the flash.  You might find
    that the solution will be to simply shoot at a slower shutter
    speed.  If that's the case, just be careful when doing so that the
    resulting ambient light exposure will not be too close to the
    flash exposure.  This will be a particular problem when shooting
    at a 1/30th of a second or slower since you may get a ghost-like
    blurred ambient light exposure with the sharp flash exposure
    superimposed on it.  This rarely is what you want unless you are
    going for an 'arty' look.  ^_^

                                                       Later....BC

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| Bill Costa                                          |
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