Why the Myth Persists:
* Depth of Field (DoF): The primary reason for recommending f/16 is to maximize depth of field. Landscape photographers typically want everything in the scene, from the foreground rocks to the distant mountains, to appear sharp. Smaller apertures (higher f-numbers like f/16) achieve greater DoF.
* "Tradition" and "Old Habits": In the film photography days, the slow ISOs and lack of instant feedback encouraged wider use of smaller apertures to ensure maximum sharpness and depth of field. This habit carried over into the digital world.
* Simplicity: Telling a beginner to "shoot at f/16" is a simple rule to remember. It provides a starting point, but it's crucial to understand *why* and *when* to deviate from it.
Why f/16 Isn't Always Best:
* Diffraction: This is the BIGGEST reason to avoid shooting at excessively small apertures. Diffraction is a physical phenomenon that occurs when light waves pass through a small opening (the aperture). It causes light to bend and spread, resulting in a noticeable *softening* of the image. At f/16, and especially at even smaller apertures like f/22, diffraction often becomes significant, effectively canceling out any gains in DoF with a loss of overall sharpness.
* Lens Performance (Sweet Spot): Most lenses have a "sweet spot" – an aperture at which they perform optimally in terms of sharpness, distortion, and vignetting. This sweet spot is often somewhere between f/5.6 and f/11. Shooting at these apertures generally yields sharper images than shooting at f/16, *especially when diffraction is taken into account*.
* Subject Distance and Focusing: Depth of field depends on the distance to your subject. If your closest element is far enough away, you might not need f/16 to get everything in focus. Precise focusing is also critical. Using focus stacking techniques (taking multiple images with different focus points and blending them together) can achieve sharpness from front to back without relying on very small apertures.
* ISO and Shutter Speed: Shooting at f/16 often requires a longer shutter speed, especially in lower light conditions. This can lead to motion blur, either from camera shake (requiring a tripod) or from moving subjects (e.g., windblown grass, flowing water). Higher ISOs might be needed to compensate, introducing noise into the image.
* Dust Spots: Small apertures make any dust on your camera sensor much more visible in your photos.
Better Approaches to Landscape Aperture Selection:
1. Understand Depth of Field: Learn how aperture, focal length, and subject distance affect DoF. Use a DoF calculator app to visualize the range of sharpness at different settings.
2. Find Your Lens's Sweet Spot: Test your lenses at different apertures to determine their optimal performance. Online reviews often provide sharpness tests for different apertures.
3. Focus Carefully: Precise focusing is essential. Use Live View, magnification, and focus peaking to nail the focus on your desired subject.
4. Consider Focus Stacking: If you need extreme depth of field and want to avoid diffraction, focus stacking is the superior technique.
5. Evaluate the Scene: Assess the scene and determine how much DoF you *actually* need. Is the closest element very close? Is the background extremely far away?
6. Choose the Best Aperture Based on Priorities: Balance sharpness, depth of field, and other considerations (e.g., motion blur) to select the optimal aperture for the specific situation.
In summary:
Instead of blindly adhering to the f/16 rule, landscape photographers should develop a deeper understanding of depth of field, lens performance, and the effects of diffraction. The goal is to choose the aperture that delivers the desired combination of sharpness and depth of field while minimizing unwanted artifacts. Sometimes that *might* be f/16, but more often it will be something wider, perhaps f/8 or f/11, particularly when combined with careful focusing or focus stacking techniques. Think critically and make informed decisions, not just following outdated advice.