Hypersync – Constant ISO, Aperture, Flash Power and Distance, yet varying the Shutterspeed
From my previous tests I wanted to confirm my previous observation of the effect of shutterspeed on the flash exposure, something that does not happen in traditional flash photography using shutterspeeds at or below the camera’s advertised sync speed.
So with a constant ISO of 100, aperture constant at F2.8, flashes at constant power and flash to model distance kept constant, I shot my model at shutterspeeds ranging from 1/1,000th to 1/8,000th of a second in one stop increments. As you can see from the image below the relationship with flash exposure is inverse and linear. Double the shutterspeed, and all other variables kept constant, the flash exposure, as well as the ambient exposure (obviously) drops by one stop.
As a sidebar, the reason for adding the palm leaves in the foreground was to have something at the edge of the frame that would be hit by the flash so I could see how far the dreaded shutter curtain banding was intruding into the image. And you can see the flash banding start to intrude onto the palm leaves on the right hand side of each image, especially noticeable at 1/4,000th and 1/8,000th shutterspeeds.
Hypersync – Constant ISO and Aperture, increasing Flash Power with increase in Shutterspeed
So I did another experiment to confirm it, but this time, each time I increased the shutterspeed, I increased the flash power by one stop. And as you can see in the image below, while the ambient exposure decreased linearly at 1 stop increments, the flash exposure remained constant.
So this further confirms that the flash exposure is affected in exactly the same manner as the ambient exposure …. An increase in shutterspeed above the advertised sync speed will affect the flash exposure at the same rate as it affects the ambient exposure.
And of course the banding is now way more visible with the extra flash illumination. For my use, the banding is not negatively affecting the image at shutterspeeds up to 1/2,000th but as I get above that I will need to pay attention to how I frame the image if I have any objects that will receive flash illumination in the foreground. As long as I frame the image to allow for the banding I will be able to shoot with flash all the way up to 1/8,000th of a second.
Cool – now I understand it better and kind of know what I want to do next!