Today, boys and girls, we are going to learn about shutter speed and gravity. Are you ready? Hold on to your hats! For it will be an exciting one. I've even got some photos to demonstrate.
First lets talk about shutter speed. A shutter is a little tiny door in a camera. Whenever a photo is taken the shutter opens and closes, so as to let in the desired amount of light. The longer that little shutter door is open, the more light is let in. Another side effect of the shutter speed, is the crispness or blurriness of the subject. When the camera opens the shutter, it takes in and captures everything, even the movement. If the subject is moving at all, or if the person operating the camera is moving, the subject will blur. This blur, however, can be counter-attacked by using a very quick shutter speed. Quick shutter speeds will freeze whatever is in the frame and create an image of it. (That is, if there's enough light, but we won't get into that right now.)
Shutter speeds are measured in seconds and fractions of sections. For example, if your shutter speed is set to 1s, then the little door on the camera will be open for one second -- a long time in the camera world -- and will capture all movement during that entire second. If the shutter is set to 1/1000s, then the little door on the camera will be held open for only one, one-thousandth of a second. Quick, yeah? Not a lot of movement can make it through 1/1000. You can imagine, then, what happens when you set the shutter speed for 1/4000. You could freeze-frame Superman as he flies around the world to reverse the everlasting doom of Lex Luther! You could also capture the thigh epidermis of a 38-year-old-marathon-running-female as the centripetal acceleration of her foot pounding the downhill pavement forces that thigh skin to fold over the nether region of her knee cap.
Lovely, yes? Now. Someone else took this photo, so how did I know the shutter speed was quick? It's simple, really. Just look at the crispness of my sagging 38-year-old skin! The proof is in my puddin-esque pelt, dripping like moltenous metal on the cool, frozen by a quick shutter speed for all time and infinity to admire. I also bought the photo, and since I bought the photo, I have its complete metadata: ISO 200, f/3.5, 1/4000s. (Here's another hint, the open-small-numbered fstop was revealed by the blurry guy in the background, but fstop is for another day.)
To compare and contrast, let's look at the photographer's next photo. It has the same 1/4000s shutter speed, but the absence of above thunderclap of the road, and the foot of that saggy-skinned 38-year-old lady, leaves the skin nice and supply attached to where it should be. Hence our lesson about gravity. Quick shutter speeds are a-okay, until gravity gets involved.
To sell more photos, the photographer could decrease the shutter speed so as not to freeze unwanted skin flappage. However, if you the decrease the shutter speed on a moving subject, the result could be blurry. That, and, you might let too much light in and blow the image (that's another topic for another day -- blowing your images, which sounds like a fortuitous arrangement, but it's not.)
Next up, take a look at the following photo, in the which there are two things to note. First, it's a tad blurry. Without knowing the metadata for this image, one could concluded rather quickly that the shutter speed was not a quick one. Moving subject, plenty of light, must mean the photographer used a small-large-numbered fstop, and slow shutter.
Actual metadata: ISO 640, f/18.0, 1/320s
The second noteworthy mentionable of this photo is the positioning of the photographer. Because of gravity, and gravity's stubborning refusal to be anything but gravitous (phouey on physics!), it is never all that flattering for the photographer to be low and looking up at the subject. (This picture isn't so bad, however, prolly because it's a bit blurry.) When the photographer is low and looking up, whatever is closest (usually the thighs) will appear larger. And if you don't have a double-chin, having a photo taken from below will grow you one. (The wideness of the lens, and the zoom of that lens has a great deal to do with the bigness factor, but that's yet another topic for another day.) If possible, the photographer should get a bit of height so as to look down on subject instead of up. As can be seen in this finishing photo:
Notice that the mashup of gravity and foot are in full-force. Also note that the shutter is somewhat quick at 1/500s, but the photographer being above the subject doesn't exemplify the sagging of said skin.
Okay. Now that we've covered the shutter speed and gravity basics, let me introduce you to the perfect marathon photo, the new photo for the wall, the photo that propelled me into purchasing the above over-priced images. (I had to buy one for something like 45 bucks or all 15 images for 70.) This photo was taken at at mile 24.5ish of the The George. The photographer was placed above the road somehow. I was going too fast (har har) to see just how. As I stepped onto that painted marathon red carpet, I heard a whistle, and an "up here!"
I looked up and cheesed it. As big as I could.
P.S. If you want an excellent demonstration on shutter speed, check out the waterfall photo(s) on wiki's shutter speed entry.