Have you ever taken an image in a studio and found a black line down one side of it?
Flash synchronisation is probably the answer…
A (brief) word on camera shutters
There are two types of shutters, leaf and focal-plane. Leaf shutters are found in the lens, while focal-plane shutters are in the camera just in front of the camera sensor. You probably have the focal-plane variety (especially if you use a digital SLR camera). Focal-plane shutters are like two sliding doors, when you press the button to take a photo, the shutter in front of the sensor will slide away to let the light in, then a second shutter will slide into its place to again block the light hitting the sensor.
The shutters control the length of time that light will hit the camera sensor. A longer shutter speed (e.g. 1/10 of a second will mean the camera shutter will be open longer than one of say 1/200 of a second).
Flash synchronisation & the black line
So what is causing the black line?
If you are in the studio using a flash or strobe light, the burst of light from the flash needs to occur at the same time the camera shutter is open.
Due to mechanical limitations of the equipment, if your shutter speed is to fast, it will open then close out of synch with the light. When this occurs, your image will contain what is actually one of your shutters starting to close, thereby causing a black line down one side of your image.
The wrong shutter speed could result in a black line in your image
Remedy
To fix this problem, you must use a shutter speed no faster than what your equipment can handle. For a lot of cameras it is a shutter speed no quicker than 1/200 of a second. Some cameras can handle faster e.g. 1/250 second.
If you cant find the flash sync of your camera, try taking a shot with a shutter speed of 1/160, 1/200 and 1/250 second to see which speed will work, and which will produce the black line.
Happy shooting
Michael..
