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Aug 2006

Conventional and Fill-Flash TTL mode in close-up photography

Sometimes we have to decide how to set our TTL flah. The Nikon SB-800 autofocus flash has two options you can set on your Nikon DSLR (and on several SLR cameras as well):

Using "conventional" TTL (top panel above), the camera & flash combination doesn't try to balance your flash to the ambient levels. The flash output is considered and measured on its own. Therefore, conventional (or standard) TTL is perfect for when your speedlight dominates as a light source, i.e. when you want to take pictures with the flashgun as the main light source. In Fill-Flash TTL mode (TTL BL), the camera & flash combination will try to keep your flash output as a fill-flash only. This mode is useful for daylight fill-flash, where the ambient light level dominates. The two grasshopper pictures below should help explaining the difference between TTL and fill-TTL flash. In the first picture the light from the flash is almost equal to the light level of the ambient light (counterlight sunshine). In the second image I set my SB-800 on TTL BL. Fill flash did allow to fill in the shadows found in ambient light. Differently from the first image, the second picture can be still considered a counterlight shot, but without underexposed shadow areas.

links to related topics:

• Moose Peterson explains TTL flash systems
• Planet Neil photography

Images © 2006 Riccardo Polini