As landscape photographers, we are always desperate to achieve the greatest sharpness and depth of field; in fact, the best of both worlds. I am afraid though that sometimes we have to compromise. Stopping down the lens to a small aperture (i.e. large f/stop number), in order to achieve as much depth of field as possible, does not always produce the best results.
What is the best solution? We need small apertures to cover depth of field adequately in landscape work, so here are some suggestions.
- Check all your lenses indoors in a controlled environment to find out at what aperture diffraction is severe. Take the same picture at f/8, f/11, f/16 and f/22 and compare them at a view of 100%.
- Make sure your focusing technique is correct for best depth of field results.
- You can buy a tilt/shift lens and learn how to use it, see here for details.
- Learn how to use your live view properly, if your camera offers it; this will improve your focusing technique.
- Start with a larger aperture, say f/8, while focusing and keep checking the results; then stop down if you need to. If you are not sure, focus at different parts of the scene and experiment.
In a nutshell, I recommend using an aperture no smaller than f/11 when using a DSLR with a small (APS-C) sensor or f/16 when using a full frame sensor.