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... is a freelance photographer working in Middle Georgia

Friday, June 20, 2008

High Speed Flash Technique

I have written several times about shooting flash outside in daylight and synchronizing the flash with my D70 at a really high shutter speed.(The D70 does this through a bit of a design fluke) I have had questions about how you fool the camera into synching higher than its usual top speed of 1/500th second with a flash.

This is a very useful technique, not just for including the sun in the photo.
It always makes a very dramatic image.

You normally slip the flash into the camera's hot shoe, or use an off camera cord to link it to the camera. The shoe and flash have four matching contacts to relay information from the camera to control the flash. If you look at the camera you will see the contacts, one large in the center of the shoe, and three smaller ones. The large contact fires the flash. The other three make the camera and flash work together, using the various automatic functions. If you shoot using all the links from camera to flash and shoot above 1/500th, the flash only lights part of the frame and you end up with half your picture being black.

By using the hot shoe PC adapter shown here with a regular PC cord going from camera to flash you only use the large contact, firing the flash. Since you are not using the camera/flash automatic modes, the flash dumps a constant amount of light each time. The camera has no idea what the flash is doing, so you have to set the exposure mode on manual and tell it what exposure you want to shoot.

I have a 15 foot long cord so I can put my flash on a stand and not have to be right beside it.

The aperture controls the exposure by the flash, and you use a high shutter speed to darken the sky to the density you want in your picture. I usually set the flash at
1/8 power. In this image it was close enough so it didn't light the subjects' full length. I wanted their legs darker. The sky gives separation.

It is a good idea to buy a hot shoe adapter that tightens in place so it will not move off the contact as you move around and pull on the synch cord. Lon Coleman at sells them, and also PC cords that screw into the adapter and into Nikon speedlights. They will not slip out.

1 comment:

misty said...

nice use of a graphic, Danny! Very helpful in visualizing what you're explaining!

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