Zion National Park, Utah
Sun block #1.
If I used the rock formations to block the sun, I could see the iridescent diffraction halo around the sun caused by the scattering of the light from small particles of nearly uniform size, such as water droplets. You can also see the halo effect when light scatters from fine dust or pollen grains in the air.
The original shot had hundreds of distracting bright specks in the sky area. They seemed to have been caused by small objects in the air catching the sunlight...insects, dust motes, pollen grains? I couldn't find any evidence in other photos taken on that same morning of significant dirt on the camera lens or filter. Because they were distracting to me, I chose to clone out the most obvious ones.
2008UtahZionZion NPparknational parkZion National ParkSpringdalesunsun halooptical effectoptical phenomenonoptical phenomenalight scatteringdispersionrainbowatmosphereatmospheric effectbacklitbacklightbacklightingcontre jourcontré jourarctangent, from