26 Apr 2010

Synchro Scan Shutter on the HVX

Filming No Comments

Have you ever dialed open the iris of your HVX200 or HPX170 and wish you had a bit more light?  The quick answer is to bump the gain setting, but then you introduce some grain to your image.  The next alternative?  Slow down the shutter speed and the camera will let in more light.  If you normally shoot at a shutter speed of 1/60, try bumping it down to 1/24.  You will notice everything gets brighter.  You will also notice that fast moving objects start to leave trails.  You see, the longer that shutter stays open, the greater the possibility of capturing more movement on each frame.  This translates to motion blur.  I suppose there can be artistic reasons for having excess motion blur on your films, but most of the time it’s probably just dang unprofessional.  So how do you let in a bit more light without all the blur?  The answer:  syncro scan.

Ok, admittedly this is a bit weird.  The HVX200 and HPX170 have two different modes of operation when setting up your scene files.  Under operation type, you can choose “video cam” or “film cam” mode.  In video cam mode, shutter speeds are expressed in fractions of a second.  In film cam mode, they are expressed in degrees.  The difference between these two camera modes is another post for another day, but just know you need to be in film cam mode for this to work.  Once you select film cam mode, go on down and choose synchro scan.  Where as video cam mode locks you into specific shutter speeds and jumps from 1/60 down to 1/24, with synchro scan in film cam mode, you can make adjustments in half degree increments.  Now, I know what you  are thinking, “That’s great, but how the heck do I translate degrees to fractions?”  Thankfully, Bary Green, the Panasonic expert has shared the magic formula, which I found in this thread:

Consider that the FILM CAM Syncro Scan shutter speeds are spelling out “degrees” in terms of 360 degrees in a circle. So get the ratio of degrees to 360, as in (360 / syncro scan shutter) and then multiply that by the Frame Rate.

exposure time = 1 / ((360 / ss) * fps)

For 180 degrees at 24 fps, that becomes:
1 / (360 / 180) * 24), which = 1/48.

If all that makes perfect sense, great.  If not, I’ve found a good place to start is around 200 degrees, which would translate to about 1/43 of a second.  It’s a good spot between 1/24 and 1/60, so you get quite a bit more light without the motion blur.  One thing to remember: setting synchro scan in the scene file menu will not actually activate it; you will still need to bump your shutter down on the side of the camera until it says “syncrho scan”.  Now go let some light in!

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