Thursday, November 11, 2010

Fill Flash - cheatin' the sync

There are two basic ways to shoot with flash above the sync speed: cheat the sync speed, and program the camera for FP mode (AKA continuous flash).   Let’s look at the first option (FP is coming in a later post).  You must be able to manually set the shutter above (faster than) the sync speed or you can’t cheat the sync.

Cheating the sync means manipulating the view angle and shutter in a DSLR to take advantage of fill flash.  These cameras have curtain shutters that travel across the sensor chip from top to bottom (or vice-versa).  If you shoot a flash 1-3 f stops above the sync speed the result will display a more or less dark area along the edge of the frame.  This is where the curtain blocked the flash output.  If you shoot faster the result is a dark bar near the middle of the frame.

However, if you compose the frame with the blocked area in bright ambient light (such as the sky in a horizontal or side light in a vertical) the result is a more controlled gradient of changing brightness.  You may have to hold the camera up-side-down to get the blocked area “in the right place”. 

Another alternative is to shoot wide and crop the blocked area.  This will take some experimentation, and a handy reference is the MAGIC LANTERN GUIDE for your camera.   

This video shows you how to do it without much explanation, quick and dirty. 

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