Monday, March 25, 2013

Starbursts and the camera lens

The dynamics of how a camera lens captures light in water is amazing.  Not only does it capture the light, it diffracts and distorts what it "sees," creating a new version of reality.  A nice example of this distortion is the starbursts in the photos below.
The two water droplet pics were taken with different camera lenses and have very different numbers of rays in their starbursts.  The difference is because of the special way each lens used bends light.  Details on how this works are below the pictures, in case you're interested.

Results from a lens with odd number of ray thingies

Result from a lens with even number of ray thingies

A few details on how starburst rays are formed

Lenses have what are called "aperture blades" that close down over the lens when you snap a shot.  To understand aperture blades, think of the swirls  that close down around James Bond in this image.  Each swirl is like one aperture blade.

Lenses with an EVEN number of aperture blades create as many of the little starburst rays as they have aperture blades.  Lenses with an ODD number of aperture blades create twice as many starburst rays as they have aperture blades.  Of course, the more rays, the prettier the starbursts...and the more expensive the lens of course.

I won't go into the micro details about how the aperture bends the light.  That is physics and I hate physics ;-).

A test:  Which photo above was taken with a lens with an ODD number of aperture blades?  (Answer: The one on the left).  How many aperture blades does the lens used to shoot the photo on the right have?  (Answer: 8)

BTW, to reliably shoot starburst shots, you need the following:
  1. A DSLR camera with a decent lens.
  2. Your camera F-stop (aperture) setting at between F/18 and F/22.
  3. If you want to be "organic," you'll also need a decent rain followed by some nice bright sunshine.  Otherwise a sunny day and a squirt bottle will work as well.
  4. The sun BEHIND the water drop.
Hope this helps.

The two lenses I've owned, loved, and used to shoot these images.  The one on the left has the odd number of aperture blades.

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