What's Up With This

As the title says, What's Up With This. That is the question and one of the following is the answer.

1. New body blackening gradient tool in Photoshop
2. Miss-aligned flag on a studio light
3. Too high of a shutter speed
4. Asymmetric vignetting

I was able to get Tom to do some QG posing for me the other day while I worked with my new lighting gear. While my intension was to get this image for the blog, images such as this are the cause of only one thing. That is too high of a shutter speed for the flash. This is referred to as flash sync speed. A DSLR camera with a Focal-plane shutter has the capability to expose the sensor in less time than the flash unit can remain at full illumination.

In the diagram above the flash duration and the shutter speed are the same. The sensor is exposed for the full 200th of a second. Now look at the diagram below. To get the higher shutter speeds the first and second curtain will be in motion at the same time thus limiting the amount photon pummeling the sensor receives.

If you look at the third frame being exposed you will also notice the amount, brightness, or amplitude the flash unit is producing. With the faster shutter speed, a portion of the sensor is not being exposed with enough photon energy and simply results in a tell tail black bar across the bottom of the image.

There is a solution to this phenomena. That of high speed sync functionality of the latest speedlites. I will hit on this at a later date. In the studio we have greater control over the ambient light where as out of doors we often want to overpower the light to gain control of exposure. The only way to do that is with a higher shutter speed which results in the need for high speed sync flash.

Hey, that will wrap it up for today. Cya tomorrow... Doug