The f-stop or number on your camera tells you how much light your lens is letting in or the size of the lens opening. The numbers for the f-stop are usually imprinted on the lens barrel. The f- stop numbers let you know the size of the aperture in relation to the lens' focal length. A smaller f-stop number actually means the lens is open wider, so an f-stop of 2.8 means the lens is letting in more light than an f-stop of 5.6.
Fast Lens
A lens that has a wider aperture opening (meaning a lower f-stop number) means it can let in more light than a lens with a higher minimum f-stop number. Therefore a 2.8 lens is faster than a 5.6 lens.
Fill Flash
This means to use a flash to fill in an object's shadow area with the flash's light. This will in effect reduce the contrast. This method is often used outside and is also known as flash fill and fill-in flash.
Firewire
A firewire is computer connector that enables you to download high-speed data from your digital camera.
Flare
Flare is unwanted light that shouldn't be on your image. You often get glare in your photos if your camera is facing a source of light. Flare may show up in the photo as a reflection from camera's insides or from its lens. To cut down on flare, you should use a lens hood or filter.
Flash Synchronization
This means to trigger the flash so it goes off only when the camera's shutter is completely open. This will give you a complete exposure of the whole film frame.
Focal Length
This is the distance between the lens's focal point and the film plane when the lens is focused at infinity. Focal length is used to tell you the relative size and angle of view of the lens. It is expressed in millimeters. Your lens's focal length is usually printed or engraved on the front of the lens.
Front Lighting
This refers to a light that is illuminating the front of an object.
Full Aperture
This is the maximum opening of your lens diaphragm. The lowest f-stop number is actually the maximum opening.
