Why the Myth of f/16 Persists:
* Historical Context: In the days of film, smaller apertures like f/16 were often necessary to achieve acceptable sharpness across the image, especially with older lens designs. Film cameras also often had less sophisticated focusing systems, making a greater depth of field more forgiving.
* Depth of Field (DOF) Understanding: f/16 gives a large depth of field, meaning more of the scene from near to far will appear in focus. This is crucial for landscapes where you often want everything from the foreground to the distant mountains to be sharp.
* Easy Rule of Thumb: It's a simple and easy-to-remember guideline, especially for beginners who are just learning about aperture. It offers a starting point for achieving overall sharpness.
Why f/16 is NOT Always Best:
* Diffraction: This is the *most important* reason. As you stop down your aperture (increase the f-number), light waves bend around the edges of the aperture blades. This bending interferes with the sharpness of the image, causing a softening effect. Diffraction becomes more pronounced at smaller apertures (like f/16 and smaller) and can actually *reduce* overall sharpness. Modern lenses, especially on high-resolution sensors, are particularly susceptible to diffraction.
* Lens Performance: Different lenses have different "sweet spots" in terms of sharpness. The sharpest aperture is rarely the widest (e.g., f/2.8) or the smallest (e.g., f/22). Often, lenses are sharpest around f/5.6 to f/8. Knowing your lens's performance is crucial. You can test this by taking test shots at different apertures and comparing the sharpness.
* Creative Control: Aperture affects more than just depth of field. It also influences:
* Light Gathering: Smaller apertures require longer shutter speeds (or higher ISO), which can lead to motion blur in moving elements like water or clouds. Sometimes you want a faster shutter speed for creative effect.
* Sunstars: Aperture size affects the appearance of sunstars (the starburst effect around bright light sources). Smaller apertures generally produce more defined and longer sunstars.
* Subject Distance: The closer your subject is to the lens, the narrower your depth of field becomes. You might not need f/16 to get everything sharp if your closest subject is a reasonable distance away. Using online depth of field calculators can help determine what aperture is truly needed.
So, What Aperture *Should* You Use for Landscapes?
The best aperture depends entirely on the specific scene, your lens, and your creative goals. Here's a more nuanced approach:
1. Determine the Necessary Depth of Field: Use the hyperfocal distance technique, focusing about 1/3rd of the way into the scene. This optimizes sharpness from near to infinity.
2. Start with Your Lens's Sweet Spot: Begin with an aperture in the range of f/5.6 to f/8 (or whatever you know to be the sharpest for *your* lens).
3. Evaluate: Take a test shot and carefully review the sharpness at different points in the image, especially the near and far points.
4. Adjust as Needed:
* If foreground is blurry: Stop down to a smaller aperture (e.g., f/11).
* If distant objects are blurry: Re-focus, or consider slightly stopping down (e.g. f/11).
* If you need a faster shutter speed: Open up the aperture to a wider setting (e.g., f/4 or wider) and accept a shallower depth of field. Alternatively, increase ISO (with the understanding that it can introduce noise) or use a neutral density filter.
5. Be Mindful of Diffraction: Avoid going beyond f/16 unless absolutely necessary. Most cameras will exhibit noticeable softening due to diffraction at f/16 and beyond, so only use this if the situation requires it, and be aware of the compromise.
6. Consider Focus Stacking: For scenes with extreme depth requirements and close foreground subjects, focus stacking can be a better option than stopping down to very small apertures. This involves taking multiple shots with different focus points and then combining them in post-processing to create an image that is sharp from front to back.
In summary:
* Forget the "f/16 is always best" rule.
* Prioritize understanding depth of field, your lens's performance, and the effects of diffraction.
* Start with a sharp aperture (f/5.6 - f/8) and adjust based on your specific needs.
* Consider focus stacking for challenging scenes.
By understanding these principles, you'll be able to make informed decisions about aperture and create sharper, more compelling landscape photos.