using Olympus cameras to achieve a key-shift effect with flash
introduction
key shift is a photographic term used when the photographer chooses to under-expose the ambient light (eg sunlit scenes) and light the subject with artificial lighting such as a flash (although this needs either a very fast flash sync or very powerful flash units or close flash-to-subject distances if ambient is sunlight)
the photographer may also choose to alter the color rending of the ambient light to create an even more dramatic effect
An example of key shifting with color shift using an Olympus E-M5 - note the deep blue trees in the background at midday while the subject has perfect white balance from the custom WB set to match the gel:
more from this zombies series and further details on how I achieved this effect here: http://www.ayton.id.au/wp02/?p=6606
technique
preferably have the subject in the shade - particularly if your flash is not powerful enough to overcome sunlit scenes
attach flash and set to Manual
start with maximum output or 1/2 power
if you want to try pushing shutter speed faster than flash sync to try to overpower sun, you must connect flash to camera only via PC sync cable or via the central hotshoe pin
if you use a compliant flash attaching via the TTL pins, the camera will not allow you to increase shutter faster than the x-sync for that flash-camera combination!
thus can use a Canon flash directly, but if using an Olympus flash, must use a simple one-pin hotshoe adapter so the camera does not detect it is a compliant flash unit
of course, the flash cannot use TTL exposure, and you must resort to Auto or, preferably, just Manual flash exposure
with the OM-D's, a shutter of 1/400th sec will result in a small area at the TOP of the image not being lit by flash - this is fine if you have no subject there, at 1/500th sec, you have almost half the top not being lit by flash - this may still be manageable depending upon your subject
if you have a camera such as the Panasonic LX-100 which has a shutter inside the lens, it will sync all the way up to 1/4000th sec with full flash output and with full frame coverage (not Super FP or HSS mode which is useless for key shifting)
set camera exposure mode to Manual
set
flash mode to Fill-In (even though it will be your main light)
set aperture to your desired aperture
if you want a wide aperture for shallow
depth of field (DOF), you will need to also use a polarising filter or ND filter in bright scenes
set ISO to base ISO (eg 200) for best quality - may need to change this later
set shutter speed to the fastest shutter speed possible
now assess the ambient exposure - you are generally aiming to underexpose by 1-2 stops:
now assess the flash exposure
adding color shift
set Menu:Cogs G:flash+WB item to OFF otherwise camera may default to autoWB even tjough you have set a custom WB
choose a colored gel and place on your flash unit
use a full CTO (Color Temperature Orange) gel if you want daylight ambience to appear blue (can also use this to match incandescent lighting)
use a blue gel if you want daylight ambience to appear orange like a sunset
perform a
custom WB with the flash and gel aimed at a neutral target
if using manual flash exposure be aware that gels will DECREASE the amount of light coming from your flash
Here, a blue filter was used on the flash with custom WB to simulate a lovely warm sunset in the background: