DIFFERENT POINT OF VIEW
All the images above are unaltered jpgs directly ooc. Only the text and histogramm was added.
To get comparable results, i always tried to expose to the point where the highlights were just before starting to blow out. In this case the correct exposure for the face would have caused an overexposed bottom of the image. Since blown out highlights are more difficult to recover than too dark mids and shadows, this would be a good approach in real life as well.
There are always two images with the same shutter-speed and strobe-power-setting. The only things that differ are the “hypersync only-function” (on/off) and the resulting luminance, which is represented by f-stop and iso.
“Hypersync only = off ” gives less gradient but also less strobe-power.
“Hypersync only = on” gives more gradient but also more strobe-power.
So if you are in a situation where less strobe-power is needed you could always check “hypersync only = off” first and get away with a lighter gradient.
You often find hypersync-tests on white walls where the first examples just above standard-sync are completely white. At some point you are starting to see a light gradient, which gets darker and darker the higher the shutter speed goes.
Although these tests are technical correct, this is somehow misleading. I first thought that this indicates that the first “white frames” are exposures with no gradient at all. But this is not true … they are overexposed. If you would dial in the “correct” exposure you´ll see a light gradient.
My conclusion after a lot of testing (always aimed at “Reduced Clipping”) is this: You always get a gradient. It is typical for your special camera-strobe-combination. Some team up better than other. The gradient is less or more pronounced. The higher the shutter-speed, the more you will see the gradient.
If you are not in a “clinical white wall test-setting” but in ambient light outside, the gradient will often not be visible very much, because the ambient light is counteracting the gradient. If you start to underexpose the ambient light, you will see the gradient more. Also because of this the gradient is less pronounced in landscape than in portrait orientation, because normally in a natural lighting condition the most brighntness is at the upper part of the image.
Most of the gradients are easy to correct in post. If you want to help out a little bit before post, use a gradient-nd-filter.