Camera Video Lens Breathing Compensation and Movements Rules for Powered Zoom (PZ) Lenses

1. The optical physical nature of lens breathing effect (Focus Breathing)

Why does the background suddenly get bigger and smaller like a zoom when I change the focus while shooting a video?

1. The displacement of the inner focusing lens group changes the physical effective focal length of the entire optical system:

• Modern autofocus lenses generally adopt lightweight and compact internal focusing design (Internal Focusing/IF);
• When focusing, the outside of the lens barrel does not move, and only a set of micro floating lenses moves inside;
• Although this small displacement achieves extremely fast focusing, it breaks the overall optical path balance, causing the actual focal length of the lens to undergo a slight physical drift when the focus is pushed from near to far (for example, a 50mm lens actually becomes 46mm when the focus is closest!);

2. Breathing on the screen:

• When the focus suddenly switches from the characters in front of you to the distant background, the perspective range of the picture zooms and twitches violently; in a coherent movie narrative, this kind of twitching will be extremely dazzling and make the audience stunned!

2. The black technology algorithm and cost of in-machine breathing compensation (Breathing Compensation)

Modern flagship mirrorless cameras eliminate the breathing effect in-camera in real time through processor algorithms:

1. Real-time reverse dynamic cutting compensation:

• The camera pre-reads the breathing deformation distortion coefficient matrix of the lens at each object distance from the lens firmware;
• When the lens changes the focus distance, the in-camera image processor (Bionz XR, etc.) performs dynamic micro-scale scaling and geometric stretch alignment on the edges of the screen in real time at a frequency of dozens of times per second;
• No matter how the focus of the final video jumps horizontally, the frame boundary remains motionless like a professional movie fixed-focus lens!

2. Two major physical costs of using breathing compensation:

• The image quality angle is slightly cropped (about 5%~10% Crop): The image angle is slightly narrowed, and the actual angle of view of the 24mm lens becomes about 26mm;
• Only supports specific supported lenses from the original factory: Sub-factory lenses and old lenses cannot obtain body algorithm correction.

3. The stepless constant speed film-level lens movement rules of the Power Zoom / PZ lens

When you manually twist the zoom ring to shoot videos, the zoom speed will inevitably slow down and be extremely stiff;

1. PZ internal ultra-precision stepping ultrasonic motor drive:

• Electric zoom lenses (such as Sony 16-35 PZ, E 10-20 PZ, Panasonic 14-42 PZ) have a zoom lever on the side;
• Push nudge to advance smoothly at a constant extremely slow speed, push hard to advance extremely fast; support locking the zoom speed to a fixed 8-speed constant speed in the camera menu;

2. Hitchcock Zoom (Dolly Zoom/sliding rail retreats while electrically pushing the focus) magic skill:

• The photographer holds the stabilizer and moves back slowly and at a constant speed, while at the same time lightly pressing the zoom lever with his finger to advance the focus slowly and at the same speed;
• The size of the main character remains unchanged in the picture, while the background buildings behind him undergo a thrilling and surreal compression and expansion, creating a thrilling and suspenseful atmosphere at the cinematic level!

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