Time a.k.a. Shutter Speed

So if aperture is nothing but hole size, shutter speed is simply time:  how long the hole remains open.  We did a demonstration on the relationship between aperture and shutter speed in which we poured rice through two hole sizes:  small (a funnel) and large (a paper towel tube).

The rice represents light:  we need "x" amount of light to create an exposure.  So, we can use a small hole but it took a really long time to get all the rice through.  Or we can use a really large hole, and then we'll move the rice through more quickly.  So why not use really large holes, all the time, to cut down on time and therefore blur?  Good question, but the easiest answer is this:  sometimes we WANT blur, for example to emphasize movement in an image. 

In this photograph by W., we know that little Perry is on the *move* ... which he usually is!  We are communicating more about Perry by allowing his movement to become part of the image in a meaningful way.

So using *blur* is another way that photography communicates in a unique way, like restricting focus with depth of field.  In fact, when you think about it, this means that photography can communicate time passing in a still image!  Fascinating!
 

 ps.  this blog entry is getting too long, so I'll talk about the these two *time* exposures next time... but as a sneak, one is fixed and one is panned.

p.p.s  on my desktop this morning:  "I awoke this morning with devout thanksgiving for my friends, the old and the new."  - Ralph Waldo Emerson

Thank you, Mrs. DiMella and Perry, for modeling for us!  Nice portrait, W.!