Sharpness is perceived. Of course some lenses are sharper then others. The camera your using can have an effect. But sharpness is perceived! I get asked about sharpness as much as any other aspect of photography. “What lenses do you use?” “What amount of sharpening do you do in Photoshop?”“What is your sharpening process for enlarging images?” Etc. The answer is……… ask a different question. Yes sharpening on the computer and shooting with great equipment has an effect on the sharpness of your image. But the circumstances in which you take a picture are actually much much more important. “How do you take a better image?” is the right question.
If you want sharper pictures, the key is good light, clear air, color, and making the subject stand out with either light or an out of focus background. Red and orange seem much sharper to the eye. When a scene has warmer tones or red or orange colors it will appear sharper then a scene with cooler blue tones. If you shoot in great morning light (which happens to be very warm) in clear atmospheric conditions your already half way there. Then keep in mind that drawing the the eye to a main subject in the picture, and making sure that subject is in perfect focus will also help greatly. The main subject of an image really sets the stage for how the sharpness of the entire image is perceived. Although there are many technical elements to making a sharp landscape image (using a tripod, understanding depth of field and aperture, using a cable release or timer, etc.) that are extremely important, shooting in the right conditions really determines what makes the image appear sharp (especially when viewed small in places like flickr)
Compare the image above to the image below. The above image was taken with a small Canon point & shoot with a six inch mini tripod, while the image below was taken with my Nikon D700, super sharp 70-300mm lens and Really Right Stuff tripod and ball head. Although my Nikon is a much much better camera, the RRS tripod is 1000 times better then my mini travel tripod, and the optical quality of the lenses are in a different world, the image above appears sharper. Of course there is no comparison between the two setups, and I can’t even enlarge the images made with the Canon P&S over 16X20 or sell the images for serious stock, yet it appears sharper!!! It has warm tones and red and orange colors, as well as a strong focal point that is in perfect focus. The image below has cool blue tones, no strong focal point and the air was very hazy. I love image below, but I really don’t think anyone would call it sharp.
(If you really want to know how I normally sharpen images in post: I have found that for normal sized prints Lightroom 3 does a great job, and if I want to go really really big I spend about 5 minutes with Genuine Fractals)