I have been admiring many of the pictures posted in this forum. I noticed many of the images are slightly "soft", is this due to the lens' design, hand-holding this beast, or the tripods not being up to par? Or simply due to additional cropping (on top of the other variables)?
Another possibility is atmospheric conditions. Moist air, smog, and other atmospheric "junk" can affect IQ, especially at greater distances between lens and subject.