| Aperture | Sharpness Quality | DOF Depth | Field Use Case | | :— | :— | :— | :— | | f/5.6 – f/7.1 | Peak Sharpness | Razor Thin | Specialized portraits (eye only). | | f/8 – f/10 | The “Sweet Spot” | Thin | General Nudibranch / Bobtail work. | | f/11 – f/13 | Practical Limit | Moderate | Trying to get the “whole subject” sharp. | | f/16 – f/18 | Softening Begins | Deep | High surge / “Safety net” shots. | | f/22+ | Muddied/Mushy | Maximum | Avoid (use Focus Stacking instead). |
Wetpixel / Scubaboard Experts: Generally agree that f/11 is the “line in the sand”.
| Aperture Setting | Depth of Field (DOF) Characteristic | Diffraction Impact | Suggested Application in West Cork | | :—- | :—- | :—- | :—- | | f/2.8 - f/5.6 | Extremely shallow; bokeh-focused. | None. | Artistic isolation; “soft” macro of large anemones. | | f/8.0 - f/11 | Moderate; optimized for M43. | Minimal to none. | Standard nudibranch portraits; peak sharpness. | | f/13 - f/18 | Deep; covers most small subjects. | Moderate softening. | High-magnification shots of tiny (1cm) subjects. | | f/22 | Maximum DOF; subject fully sharp. | Significant softening. | Super macro with wet diopters; black backgrounds. |
| Subject | Recommended Aperture | Mode | Goal | | :— | :— | :— | :— | | Moving Shrimp/Fish | f/9 - f/11 | C1 (Single) | Instant capture, max sharpness | | Small Nudibranch (Profile) | f/13 - f/16 | C1 (Single) | Balance of DOF and resolution | | Super Macro (CMC-1) | f/11 | C1 + Rocking | Managing the extreme thin DOF |
| Setting | Sharpness | DOF Buffer | Verdict | | :— | :— | :— | :— | | f/9 | Clinical / Razor | Extremely Unforgiving | Best for stationary subjects in dead calm water. | | f/14 | Professional / Crisp | Moderate / Helpful | The “Secret Handshake” for night dives and surge. | | f/20 | Soft / Muddy | Deep / Maximum | Best for identification only; avoid for “art” shots. |