On Martian Day 33 (September 8, 2012, or the 33rd day of the mission), the reclosable dust cover was removed from the Mars Hand Lens Imager (MAHLI) aboard the Curiosity rover.
The NASA article "First Image From Curiosity's Arm Camera With Dust Cover Open" shows the enlarged picture of the surface of Mars taken by the MAHLI camera, which is much larger than the image shown above.
And, according to a series of three images within the NASA article "Martian Ground Seen by Arm Camera With and Without Dust Cover (Thumbnails)", the center picture is the image with the dust cover removed (the clearest picture of the Mars surface to date).
The three-picture image, as seen above, is credited to: NASA/JPL-Caltech/Malin Space Science Systems.
NASA states, "The other two images presented here for comparison were taken before the cover was opened (left) and after the cover was closed again (right)."
And, "All three images were taken from the same position: about 5 feet (1.5 meters) above the ground, facing down. The patch of ground shown in each image is about 34 inches (86 centimeters) across."
NASA made the following statements about the image: "The level of detail apparent in the image shows that haziness in earlier MAHLI images since landing was due to dust that had settled on the dust cover during the landing."
And, "The patch of ground shown is about 34 inches (86 centimeters) across. The size of the largest pebble, near the bottom of the image, is about 3 inches (8 centimeters)."
Further, "Notice that the ground immediately around that pebble has less dust visible (more gravel exposed) than in other parts of the image. The presence of the pebble may have affected the wind in a way that preferentially removes dust from the surface around it."