As a landscape photographer, sooner or later you're going to have to either a) pull your wide angle lens out of your bag in a hurry while the light is fading fast and throw it on your body in time to catch the magnificence, or b) focus on stars in the dark. What is the key ingredient to knowing how to do both? Knowing the infinty focus point of your lens - and I mean knowing it just by looking at it - so you can set it in your hand before you even put it on your camera.
Let's go back to "Photography 101" for a minute to review a crucially important fundamental concept - depth of field (DOF). This is a principle of optical physics whereby a lens will produce sharpness over distance away from the camera propoertional to the size of the aperture within itself. If you just said "huh?" then you need to go back to school!
Let's boil it down with a rule of thumb: big hole means more light, small number, and shallow depth of field. Small hole means bigger number, and deep depth of field.
Landscape photogaphers as a general rule like to show crisp sharpness from edge to edge in the bulk of our images. How do we do that? By using depth of field. We shoot at f/10 and up most of the time. Set lens to infinty, and far away mountains all the way back to the rocks at our tripod legs are crisp and sharp, just like our eyes perceive them.
Take a close look at this image of Mt. Yotei volcano in Japan. See how the volcano, the stars, and the trees are all crisp and sharp? That's due to my setting my Canon 16-35mm f/2.8 L II lens at f/2.8, and setting the infinty focus point correctly on my lens.
Always always always check your focus on your LCD screen right after shooting to make sure you have the sharpeness where you want it to be in your images.
In another post, I'[ll cover an additional tactic that you need to have in your bag - how to determine the distance from your lens objects are in focus when your lens is set to infinty.