BetterPhoto Q&A
Category: New Answers

How to Shoot a moving train underground?

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February 22, 2006

Now, if you want to be more specific:

I can only assume that you are attempting to freeze the motion of the aforementioned "fast moving objects", rather than have them blur. Here are some pointers:

First, shutter speed, along with other variables, dictates how fast an object can be and let you "freeze" it. The other variables are the focal length of the lens you're using, your distance from the subject, and whether the subject is moving towards/away from you or across your field of view.

Longer focal length lenses magnify, or bing in, distant subjects, and similarly magnify any motion as well. In 35MM film land, the "rule of thumb" with telephoto lenses is the slowest shutter speed to use hand held is 1 over the focal length of the lens - a 200MM lens requires at least 1/250th second shutter. With DSLRs that have crop factors, the slowest shutter speed goes up accordingly.

But that slowest hand-holdable speed assumes a relatively static subject - it's purpose is to not have your own body motion cause blur. To freeze the subject's motion, you usualy need faster shutter speeds (meaning you need enough light or fast ISO setting to get the proper exposure too).

If a car is driving towards or away from you at 30MPH, you can freeze its motion with a slower speed than if it is driving across your field of view at 30MPH.

If the car is driving left to right and is 50 feet away, you will need a fast shutter speed than you will at 500 feet away.

Finally, one technique to try is "panning" - this is when you purposefully move the camera in the direction of the subject's motion - so turning the camera left to right in the above example while you "follow" the car's motion when you snap the shot can lead to a sharply exposed car against a background of blurred out sidewalk.

I hope that helps.

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February 23, 2006