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Photo Tip: #2

So what does fast mean?

Fast, when talking about a lens, actually refers to the greatest amount of light the lens will let in.

Think of it this way…

If your camera needs more light to hit the digital sensor in order to make a correctly exposed image, then it has three choices:

1) It can open up your aperture and let more light in through the lens…

2) It can slow down your shutter speed and let the light that’s coming in from your lens sit on the digital sensor for a longer amount of time…

3) It can speed up the “film speed” or ISO on digital cameras.

So if your camera measures the light in the room and thinks it needs an aperture reading of 1.4 but your lens only opens to 5.6, it’ll slow your shutter speed to get the shot. And a slow shutter speed — if you’re hand holding your camera — will give you a blurry image.

Most photographers consider a fast lens to be one that will open up to at least f-2.8.

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