My 18-55mm EF-S Lens (which came with Canon 400D DSLR camera) doesn't give clear shots of Landscape. Why?

Usually when shooting landscapes, you will want a larger area in focus called depth of field. To achieve this, you need a smaller lens opening or aperture. Thus, you need to stop down to f/13 or f/16 to get this depth of field, while shooting in aperture preferred mode (Av mode). Shooting wide open at f/3.5 narrows your area in focus, not a problem for an infinity shot, but that aperture gives soft images and will render objects closer to the camera as out of focus.

Because small apertures tend to mean slower shutter speeds, maintaining sharpness means you'll need to use a tripod and a self-timer or remote to minimize any vibration.

Finally, Nathan is incorrect; the Canon 18-55mm is inferior to the Nikon 18-55mm. It's just not as good a performer, although it should be adequate for basic shooting. Nikon does a better job with wider lenses than Canon.

To recap what you need to do:
1) Use a tripod to minimize camera shake and maintain sharpness.
2) Use the self-timer or remote release to minimize shake and maintain sharpness.
3) Set your camera to Av or aperture preferred.
4) Use a small aperture like f/13 or f/16. Try to keep the apertures in the range from f/11 to f/16--which should be a sweet spot for the lens.
5) Keep your ISO low to avoid noise/grain

That should get you the maximum quality from your lens.

You may also wish to adjust the contrast and sharpness settings on the camera as well; perhaps you need higher contrast in your photos.

It should, i don't see why it wouldn't. I have a nikkor 18-55mm lens, and the canon one is identical. Maybe you have the canon camera on the wrong setting, try putting rebel on the automatica landscape setting, It's the one that's directly below the portrait one, which shows a picture of a woman's face. If it doesn't work, something has to be wrong with the lens. :P

It has to do with lighting, and your exposure settings. Try using a tripod when the light is poor.. and a faster shutter speed.... shoot at 18mm with 3.5 aperture in AV mode, I think you'll find a difference.

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