Using the AD600 UNIT/ALT menu for masking
The AD600 menu includes a UNIT/ALT feature. In the unit window the light can be configured for 2Mask, 3alt, or 4 alt. Then in the ALT window the light is assigned which fire signal to obey. Thus, if group A light(s) is set to 1 and group B light(s) is set to 2 they will alternate firing as the shutter is tripped.
With the Sony A7RII that I use, the easiest way to fire multiple frames is to use the burst mode setting. It has hi and lo options. The lo is slow enough so that I can fire two frames and release the shutter button before a third frame is triggered. One thing I discovered is that the sequence is repetitive. So if I did hold down too long and a third frame was exposed it would be Group A, then when I started a second sequence, Group B would be the first to fire.
Because the two shot sequence means a bit of a time lag, even with Hi option selected, the masking technique will require the subject be still during the exposure sequence.
These three images illustrate the capabilities for creating masks. The first two are the images make using 2 AD600s setup with the feature. The third an example of how the two images are used to mask the main subject out of the background.
The benefit for this capability is production product or green screen work. Manually creating the mask from the second image took about 3 minutes in Photoshop. There is software available that will automate the process. The manual process I used could be make into an acton to help automate it as well. The most time, about 30 seconds, was spent using the dodge and burn tool to make the mask truly black and white.
The key to optimum results is taking care that the background, although nearly white, does not wrap the subject creating highlights or halos that complicate the masking.
Personally, I’d like to see either the UNIT/ALT menu items added to all the other Godox X system lights. Or, have the feature implemented in an X1T trigger. Even a special version of the trigger.