Focus and Sharpness

Key takeaways

• Use AF-S/One Shot for stationary subjects
• Use AF-C/AI Servo for subjects changing distance
• Pair Manual Focus with magnification or focus peaking
• Back-button focus can separate focus activation from shutter release
• Autofocus needs contrast or recognizable structure and may hunt on smooth, dark surfaces
• Focus peaking is an edge-contrast guide; magnification is more dependable for critical work
• To configure back-button focus, assign AF On to a rear button, disable AF w/ shutter, and verify that a half-press no longer activates AF. In AF-C, hold the rear button to follow and release it to stop updating focus; disable Pre-AF too when you need a fixed distance.
• On the A7C, the default AF-ON assignment is Tracking On + AF On, which behaves differently from ordinary AF On. Inspect the current assignment before changing it rather than assuming every camera is configured alike.
• For focus peaking, choose a visible color and a low/moderate level, turn the focus ring toward the intended detail, then confirm with Focus Magnifier. Peaking marks contrast, so a colored edge does not guarantee the intended focus plane.

Practical example

For a person walking toward the camera, begin with AF-C, subject detection, a moderate tracking area, low burst, and around 1/500 sec. Acquire the subject before movement begins and keep focus active through the sequence. If tracking jumps to the background, use a smaller initial area or reduce subject-switching sensitivity when the camera offers that control. Photograph a person standing, then walking toward you. With configured AF-C back-button focus, hold the rear button while they move, release it when they stop on the mark, and make a short sequence. Hold it again if they move closer. Use MF with magnification for a difficult stationary detail rather than treating MF as a cure for all tracking failures.

Key takeaways

• Single point is precise for still subjects and cluttered backgrounds
• Zone AF balances control with the ability to follow predictable action
• Tracking is useful for subjects moving unpredictably across the frame
• Wide areas may favor the nearest, brightest, or highest-contrast object
• The ideal area size depends on subject size and your ability to keep it covered
• Moving the AF point onto the subject avoids the errors of large focus-and-recompose movements
• Tracking AF needs an explicit starting target: place a small area over the subject, initiate tracking, and maintain AF-C as it moves. If the frame jumps to another person, reacquire instead of continuing a missed sequence. Eye detection refines focus placement but does not choose your main character for you.

Practical example

A bird isolated against the sky works well with a wide area. The same bird among branches may require a small zone or a carefully initialized tracker. For a player among other athletes, begin tracking on the correct face or body before peak action. If tracking keeps switching to foreground players, reduce the area and hold it over the predicted action zone.

Key takeaways

• Focus on the eye nearest the camera when depth of field is shallow
• Choose the intended person explicitly in a crowded frame
• Eye AF cannot replace an aperture deep enough for groups on different planes
• Tracking sensitivity and subject-switching behavior must be tested on your camera
• A soft eye can result from motion blur or shallow depth of field, not only AF failure
• Be ready to fall back to zone or point AF in low light or when the face is hidden

Practical example

At f/1.8, the near eye may be sharp while the far eye is soft. Select the near eye instead of allowing the camera to alternate. With two people, initialize tracking on the primary face and align them at similar distances or stop down enough to cover both. Eye AF cannot make two different focus planes simultaneously sharp.

Key takeaways

• Lock focus before changing the composition
• Do not lean forward or backward after focus is locked
• Larger rotations increase focus-plane error
• AF-S is easier for this technique because AF-C may keep updating
• Direct AF-point placement is safer at close distances and wide apertures
• High-resolution output makes small focus errors more visible

Practical example

At 1 m with an 85 mm lens at f/1.8, focusing with the center point and rotating the eye toward a rule-of-thirds position can move the eye outside the sharp plane. At f/8 from 4 m, the larger depth of field may hide the same geometric error. The skill is knowing the safe conditions, not banning the method entirely.

Key takeaways

• Acceptable sharpness depends on output size and viewing distance
• Depth of field usually extends farther behind the focus plane, but not by a fixed one-third rule
• Focusing one-third into a landscape is only an estimate, not a universal law
• Hyperfocal focus trades maximum infinity sharpness for a broader acceptable range
• Very near foreground plus infinity may require focus stacking
• Excessively small apertures can lose detail through diffraction and force slow shutter speeds
• Automatic focus bracketing only moves the focus point; frames still need adequate overlap plus fixed composition and exposure

Practical example

With a 24 mm lens at f/8, focusing into the scene often covers more foreground than focusing at infinity. If a foreground rock is 0.5 m away and mountains are at infinity, one frame may still be insufficient for a large detailed print. Move the foreground farther away or make near, middle, and infinity focus frames for stacking.

Key takeaways

• A common blur direction across the frame usually points to camera shake
• A blurred subject against a sharp background usually needs a faster shutter
• Sharp detail in front of or behind the subject indicates a focus-placement problem
• Uniform softness at high shutter speed can involve haze, a poor filter, noise reduction, or diffraction
• One frame is not enough to diagnose lens calibration; use controlled repeated tests
• EXIF, AF-point data, and adjacent frames narrow the cause before editing begins
• IBIS moves the sensor to counter camera movement; optical stabilization moves lens elements. Neither stops subject movement. Compare enabled/disabled at the same focal length and shutter speed to find your own limits; follow the camera/lens guidance for tripod use rather than applying one rule to every system.

Practical example

If a background sign is sharp but a moving hand is blurred, autofocus is not the problem. If both show the same diagonal trail, camera movement is likely. If the sign behind the face is crisp with no trail, AF selected the background or lagged behind. Those three appearances need three different corrections: stabilize the camera, increase shutter speed, or improve AF placement/tracking.