Tuesday, June 12, 2012

Shutter Speed and Motion

Having put together a small write-up to answer a friend's question, I thought she was probably not the only one  who could benefit from this explanation. The result with illustrations is below  - hope it will help you control the way you show the motion in your images.

As you take your camera off Auto or Program mode (which can do an admirable job in many aspects but one, we will get back to it later), you stumble onto three modes: A, S and M. This short articles is about S - Shutter Priority mode (Canon calls it Tv mode) and how it controls the way you display your object's motion. Let's start with an image (what is the better way to talk about photography techniques than to look at, umm, photographs, right?)

This is nice and cozy corner of the Minter Gardens, shot at f/2.8 and 1/130 sec. From technical point of view it looks fine, and this is what your camera would have produced in Program mode. It would do a fine job balancing the exposure... but here is the aspect at which P mode fails: it can't read your mind. This epic failure leaves it with no way to produce an image matching your intent. Let's see how this design flaw (really, those engineers still haven't found the way to built in "Read Owner's Mind" function?) manifests itself in this particular case. Have a closer look at the wheel:

See the problem? It's frozen. It's not moving. We can see the water stream coming on and off the wheel, and we know it should rotate - and lack of the rotation makes image counter-intuitively static. How do we correct this flaw (short of calling Japan and giving those engineers piece of our mind)? Let's try and slow down our shutter. Next shot is made at f/6.3 and 1/6 sec (normally at these shutter speeds you better have tripod or your shots will be blurry).

See how the wheel came alive? Looking at this shot you know it rotates in a typical slow fashion. Let's see if we can make it turbo. Here is what f/10 and 1/2 sec buys us, wheel on steroids:

Feels a bit too much to me, especially in enlarged view:

Since we are not looking for a space shuttle replacement, I'd stick with second set of parameters - there is slow motion there, matching our perception well. Trial and errors get you there although with little practice you start getting a sense for the appropriate shutter speed for your intent.

Let's look at some of the frequent examples where changing shutter speed allows you to control how your image looks. This one below, taken at f/5.6 and 1/500 sec, froze the water so the jet broke down to separate droplets:

I may very well be your intention to show the water like this but in case you want it to look like a stream, try to drop the shutter speed to 1/30 and then to 1/15 sec and see if you like these better:

Another often seen object in the photographs taken in parks and gardens is a fountain. Look at this two below - by now no doubt your eye is trained to see the difference right away. Make your pick:

 1/250 sec

and 1/15

Let us not forget about waterfalls. Remember those stunning photos of the falls where water looks so silky, you can almost feel it pouring down? So many budding photographers look at their own shots of those same waterfalls, see frozen streams looking unnaturally immobile and ask themselves "how come my photos look nothing like that?" Well, two things. First, it's a great question to ask, because that's when you start digging into HOW part of this wonderful craft. Second - drop that shutter speed and get that smooth silky water:

Want to freeze the duck flapping its wings in the water, or want to show the swinging motion of the wingtips? Stop the moving car or reflect its speed? Freeze the basketball player in the air entirely or let his hands blur in motion as he dunks the ball in the basket? You've got a tool to control all that now. Enjoy the practice!

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