Hands-on sync-speed mini-review

NikolaiNikolai Registered Users Posts: 19,035 Major grins
edited March 5, 2006 in Accessories
For a number of reasons I *really* had to know synchronization capabilities of my camera (Canon 20D) and my external flash ("potato-masher" Sunpak Auto 555EX, max guide number 150).
To test it I used the following setup/test matrix:
  • Flash on a light stand, connected
    a) via PocketWizard
    b) via pc cable (to the pc slot on a side)
  • White backdrop about 6 ft away.
  • Camera with 50mm f/1.8, in full manual mode, full open, ISO 800, mid-size normal jpegs
  • Curtain sync (custom function):
    a) front
    b) rear
  • 9 pm, room with lights off (i.e. *dark*:-)
  • Shutter speed changed through all the intervals from 1/100s to 1/8000s.
  • At first I used continuos drive, 3 shots per test case. However, after first couple of full series I realized that all frames in each test case are identical, so I switched to single-shots to save the shutter:-)
Results:
  1. 20D can sync up with 555EX up to:
    a) 1/320s via PocketWizard
    b) 1/400s via PC cable
    After the maximum speed is reached, the frames become partially exposed (consistently over 3-4 bursts at 5 fps), at first losing about 10% of the frame (lost happens at the bottom of the frame) at 1/400s (data for PW), then ~30% at 1/500s, ~55% at 1/640s, ~66% at 1/800s, ~80% at 1/1000s, and so forth, until totally losing it at 1/1600s. Data for PC are similar with one "click" better.
  2. It does not matter what curtain mode is used.
HTH
"May the f/stop be with you!"

Comments

  • Shay StephensShay Stephens Registered Users Posts: 3,165 Major grins
    edited March 5, 2006
    Cool test!
    Creator of Dgrin's "Last Photographer Standing" contest
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  • NikolaiNikolai Registered Users Posts: 19,035 Major grins
    edited March 5, 2006
    Thanks, Shay!
    Shay Stephens wrote:
    Cool test!
    I would be really interested to see similar data for 5D and 1D*Mk* bodies...
    "May the f/stop be with you!"
  • trihokietrihokie Registered Users Posts: 78 Big grins
    edited March 5, 2006
    Nikola,
    Thanks for the very interesting info. I have been shooting road race finish lines with my 20D. When the runners finish with their back to the sun, I bring along my Alienbees 800w strobe with Vagabond power pack. Problem is that even set at ISO 100 (lowest setting on the 20D) the background was still about 1-1/2 to 2 stops overexposed at the 1/250 sec advertised flash sync speed. I even thought about using a neutral density filter. I just blindly thought the Canon rated sync speed was "The Gospel". I will run a test of my own with my lighting setup.
    Thanks for making me go... "Hmmmm"
    Barry
    http://trihokie.smugmug.com
    Hokies Rule!
    www.trihokie.com
  • ian408ian408 Administrators Posts: 21,938 moderator
    edited March 5, 2006
    trihokie wrote:
    Nikola,
    Thanks for the very interesting info. I have been shooting road race finish lines with my 20D. When the runners finish with their back to the sun, I bring along my Alienbees 800w strobe with Vagabond power pack. Problem is that even set at ISO 100 (lowest setting on the 20D) the background was still about 1-1/2 to 2 stops overexposed at the 1/250 sec advertised flash sync speed. I even thought about using a neutral density filter. I just blindly thought the Canon rated sync speed was "The Gospel". I will run a test of my own with my lighting setup.
    Thanks for making me go... "Hmmmm"
    Barry
    http://trihokie.smugmug.com

    Sync speed and exposure are two different things.
    Moderator Journeys/Sports/Big Picture :: Need some help with dgrin?
  • NikolaiNikolai Registered Users Posts: 19,035 Major grins
    edited March 5, 2006
    Sync-speed and exposure
    ian408 wrote:
    Sync speed and exposure are two different things.

    Just to clarify this - correct - thought.
    When you do flash in the dark, as I did, you'll get the same exposure if you use the same power level no matter what the shutter speed is, as long as it does not go above the said limit. After that you have part of the diaphragm blade covering part of a frame while the flash is firing (camera and flash become out of sync).
    If you do fill-flash during the day light - it's a different story. You can still play with the shutter speed, which in this case would affect the amount of ambient (natural) light and thus affecting the total amount of light coming through the lens. In this case I'd say you can go a couple of "clicks" beyond the said limits: ambient light would give you enough light in general, and the flash would still cover the bigger part of the frame, let even letting the bottom part to underexpose. You can simply count on this and frame your shots a bit wider to account for the loss of light in the bottom part with the intention to crop it out later. In my situation that means I can easily go up to 1/500s on PW and up to 1/640s on PC cord since the lost bottom part is really narrow.. That is, of course, in horizontal mode. On a vertical you'll lose one side, so you need to decided which one.

    HTH
    "May the f/stop be with you!"
  • trihokietrihokie Registered Users Posts: 78 Big grins
    edited March 5, 2006
    I suppose I will have to experiment. I am still not sure about the difference. If I expose for the background, and fill the shadows with the flash which fires at 1/3200 second, which is well below the anticipated 1/320-1/400 second of the shutter, I should get the same diaphram blade shadow as what we are talking about in a completely dark room, right? I will just have to experiment to see how much blade shadow I can live with or work around.
    Thanks for the further information,
    Hokies Rule!
    www.trihokie.com
  • NikolaiNikolai Registered Users Posts: 19,035 Major grins
    edited March 5, 2006
    Yep...
    trihokie wrote:
    I suppose I will have to experiment. I am still not sure about the difference. If I expose for the background, and fill the shadows with the flash which fires at 1/3200 second, which is well below the anticipated 1/320-1/400 second of the shutter, I should get the same diaphram blade shadow as what we are talking about in a completely dark room, right? I will just have to experiment to see how much blade shadow I can live with or work around.
    Thanks for the further information,

    Exactly so. You just need to find out how much of a shatter blade is OK. Once again, for me going one or even two "clicks" higher means only losing a fraction of a bottom part of the frame.
    If you put it to test, please let us know your results!
    Cheers!1drink.gif
    "May the f/stop be with you!"
  • trihokietrihokie Registered Users Posts: 78 Big grins
    edited March 5, 2006
    Nikolai,
    Will do, but right now the wife has me doing stupid stuff like cutting the grass, changing the oil in the van and cleaning out the garage. I wonder if Ansel Adams had these distractions...
    Hokies Rule!
    www.trihokie.com
  • NikolaiNikolai Registered Users Posts: 19,035 Major grins
    edited March 5, 2006
    No rush...
    trihokie wrote:
    Nikolai,
    Will do, but right now the wife has me doing stupid stuff like cutting the grass, changing the oil in the van and cleaning out the garage. I wonder if Ansel Adams had these distractions...

    Chores first:-)deal.gif
    "May the f/stop be with you!"
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