Clean Sensor + Clean Lens = Clean Photo.
I already learned about the clean sensor part from an earlier trip. Nothing more aggravating than coming home to discover that all the photos were marred by spots in the same exact location. These spots are really evident when photographing a large expanse of blue sky. So, before I head out, I always take some test photos to make sure my sensor is clean.
Evidently, I didn’t pay attention to the clean lens lesson. A lens hood is not enough to protect the lens from light rain. I did not wipe the lens right away and ended up having to do some retouching to clean up the image. Lesson learned.
Nikon D800, AF-S Zoom-Nikkor 24-70mm f/2.8G ED, ISO 100, 29mm, 1.7 EV, f/16, 15.0s
The 1.7 EV was because this was one of a series of bracketed photos that I had intended to use for an HDR composite. Did not like how the sky was rendered though.
4 Feb 2014: The first time I encountered a dirty sensor problem was while I was in Arizona. Because of that episode, I always take a few test photos before I head out on a trip. Any issues with dirt on the sensor is readily apparent in a photo with a wide expanse of sky. Moreover, it is particularly noticeable at smaller apertures. I thought I had a dirty lens issue, but a few photos at f/22 revealed all.