Tuesday, December 20, 2011

P20: sun stars and diffraction

Heading deeply into photographic cliche, this project asks for a study of sun stars and the affect of differing aperture on the sun stars.  Sun stars have there place in the photographic lexicon, just not quite sure where in mine.  Unlike other projects I did not set out specifically one day to study sun stars, but did have this in mind as I worked on the images for the Transient Light project.  As my goal was to shoot early in the morning and study the way in which the sun slowly changes the lighting as it rises above the horizon and then above the tree/building line, there were plenty of occasions when sun stars could be captured.

On the whole I try to avoid sun stars, not simply for aesthetic reasons, but also because they are generally accompanied by a lot of artifacts created by the bright light of the sun reflecting within the elements of the lens.  Even the highest quality properly coated elements will generate some flare when directly imaging the sun.  The first pair of photographs illustrates this issue quite well:

The first image is f/4, the second f/22, the limits of the 24-105mm zoom I am currently using.  The Sun is almost central to the frame and generating a strong halo as well as all sorts of other artifacts.  The second shot shows much greater "light noise" probably a reminder that I need to clean this lens.  When I started on the early morning shots I removed the UV filter from the lens as I knew this would create problems with flare.  However, what these two shots also clearly show is the affect of aperture on the sun star.  The very much narrower f/22 has generated a much more precisely defined star and one that fills a good proportion of the frame.

The next sequence takes a slightly different view, with the sun shining through some trees rather then being imaged directly.  Here I have taken the aperture through 4 stops, f/8, f/11, f/16, and f/22.

With each shot the star progressively expands in size and tightens in shape.  I presume the sun star is an artifact of light diffraction as it passes the sharp blades of the aperture, the smaller the hole subtended the larger the effect.

The brief asked for comparison between a wide and normal lens, I did not do that, but did look at the effect generated by a different camera, this time an APS-C mirrorless compact.  Focal length is pretty much the same as the 24mm above (16mm on a 1.5x crop).  Shot directly into the sun on a clear blue sky at f/8, the sun star is distinctly different in shape and form, no where near as satisfying a shape as the Canon lens used earlier.  Executing an effective sun star is more than simply framing, focal length, and exposure, the very nature of the construction of the lens will impact the quality of the photograph.

OK, so I can do sun stars, big deal - it is how they are used for effect that interests me, and counter to the suggestion that these need to be created on a clear day, a hint of fog dramatically improves the effect.  The shot below was captured just after dawn at f/11, an attempt to combine the explosion of morning with the mist and reflection in the water.  Here the sun star is very evident, but muted, softened by the mist.  I very much prefer this softer approach to the harsh crisp sun stars of the earlier photos. This shot is a strong candidate for my Transient Light Assignment 3.

Taking it a step further, the following shot goes to a further abstraction of the sun burst effect, with the suns rays illuminating the shadow around a tree.  In this case I think we are looking at the actual effect of the sun, not an artifact of lens design.

The last word, though, needs to go to the sun, and the fact that a sun star is an artifact used for dramatic effect, I find the orb of the sun far more satisfying than the star burst.  Here the sinking sun is diffusing through low cloud into an almost perfect sphere, radiating a fiery red warmth.  Another candidate for my transient light set and one that uses no trickery (well it will one Photoshop removes the cranes).

Strange exercise and difficult to place the learning into the context of the own practice.  Next stop silhouettes, hang on a minute, just done that.  These projects are weird.

Key Learning:

  1. Do not use sun stars in my photography, unless very subtly applied
  2. Clean my bloody lenses once in a while

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