DT Copal Shutter Workaround for Phase One IQ4 150mp

DT has developed this as a temporary workaround to use until Phase One ships the new IQ4 multiport-to-sync cable and firmware that supports it. For most kinds of imaging the sensor-based electronic shutter (ES) can be used instead of the Copal shutter. Exceptions include working with strobe on a tech camera, where the flash sync speed of the copal shutter is often required for the correct exposure. Phase One knows this new cable and the firmware are important; we expect both in the next few weeks – DT has already received a prototype to begin testing; they just weren’t ready in time for the first wave of shipments. 


  • No cable is used to connect the copal shutter and back.
  • The strobe is connected to the flash sync port of the copal shutter.
  • The ES is set to a long shutter speed (must mathematically be greater than 1.3″ but in practice ~3″ is recommended).


Trigger the ES (either by pushing the button on the LCD, or using the XF Cable release, or via C1), then wait 0.6″ or longer (for the first curtain of the ES sweep to clear the bottom of the sensor), then fire the copal shutter (the flash will fire with it).


If you fire faster than 0.6″ from the the start then you’ll get a partial dark frame. If you fire closer than 0.6″ from the end you’ll get a partial dark frame. Therefore having a longer shutter speed (e.g. 3″ instead of 1.3″) gives you a longer “sweet spot” in which this technique works as intended. For example at 2″ the sweet spot is limited to the middle 0.8 seconds while at 3″ the sweet spot is anytime in the middle 3.8 seconds.


  • You have to do two things rather than one
  • The shutter speed in the metadata will say 3″ (or whatever you used) rather than 1/500th (or whatever the Copal was set to)
    Image quality at shutter speeds like 3″ are fantastic, so there is no issue there. The dark frame can be optionally set to pre-recorded to avoid a 3″ delay after capture; some sporadic hot-pixels may appear at defaults, but setting Single-Pixel Noise Reduction (in C1) to a value of 5 or 10 will remove these, without meaningful loss elsewhere.

Other Notes

  • This workaround should work with any external shutter, not just Copal shutters, as long as the user is able to trigger the mechanical shutter manually, without it being plugged into the back.