Focus Breathing Compensation Calculator

Enter your lens focal length, aperture, subject distance, circle of confusion and focus breathing factor to calculate effective focal length, depth of field, field-of-view shift and frame coverage after breathing compensation.

Created by Luis GonzalezLast updated: May 9, 2026

How to Use This Calculator

1
Enter Nominal Focal Length
Input the focal length of your lens in millimeters (e.g., 50mm). This is the stated length.
2
Specify Aperture (f-number)
Enter the aperture f-number you are using (e.g., f/2.8). This impacts depth of field.
3
Input Subject Distance
Provide the distance from your camera to the subject in meters. Focus breathing is more pronounced at closer distances.
4
Set Circle of Confusion (CoC)
Enter the acceptable blur diameter in millimeters. Use 0.030mm for full-frame or 0.020mm for APS-C.
5
Define Focus Breathing Factor
Input your lens's focus breathing percentage. Cinema lenses typically have 1-2%; photo lenses 5-15%.
6
Review Compensation Metrics
The calculator will display the effective focal length, depth of field, field-of-view shift, and other critical data.

Example Calculation

A videographer is shooting with a 50mm f/2.8 lens at a subject distance of 3 meters, using a full-frame camera (CoC 0.030mm), and estimates their lens has a 5% focus breathing factor.

Focal Length

50 mm

Aperture (f-number)

2.8 f/

Subject Distance

3 m

Circle of Confusion

0.030 mm

Focus Breathing Factor

Results

48.3 mm

Tips

Test Your Lens's Breathing Factor

To accurately determine your lens's breathing, set it on a tripod, focus at infinity, then at its minimum focus distance, and observe the field of view shift. Estimate the percentage change for the 'breathing factor' input.

Compensate for Breathing in Video

During a 'focus pull' (changing focus from one subject to another) in video, focus breathing can cause the image to subtly zoom in or out. Compensate by slightly adjusting the camera's position or using a lens with minimal breathing for critical shots.

Choose Lenses with Minimal Breathing for Cinema

For professional video and cinema work, lenses with extremely low focus breathing (typically 1-2%) are highly prized. Investing in such lenses, often purpose-built cinema lenses, ensures consistent framing during focus transitions.

Achieving Cinematic Precision with Lens Selection

The Focus Breathing Compensation Calculator is an invaluable tool for videographers and cinematographers, offering precise insights into how focus breathing affects their shots. By calculating the effective focal length, depth of field limits, and the crucial field-of-view shift, it empowers creators to make informed decisions about lens selection and focus pull techniques. Understanding that a 50mm f/2.8 lens with 5% breathing can effectively become a 48.3mm lens at close focus, causing a noticeable framing change, is vital for maintaining consistent composition in video sequences.

Achieving Cinematic Precision with Lens Selection

Understanding focus breathing is not just a technicality; it's a crucial aspect of professional videography and cinematography. In film and video production, smooth focus pulls (racks) are fundamental to storytelling, guiding the viewer's eye. Focus breathing, the subtle change in focal length as a lens focuses, can cause the image to appear to zoom in or out during these pulls, creating an distracting and unprofessional effect. This phenomenon is why high-end cinema lenses are meticulously engineered to minimize breathing to 1-2%, ensuring consistent framing and a seamless visual experience, a critical factor for productions where visual fidelity and narrative flow are paramount.

The Optics of Focus Breathing and Depth of Field

This calculator employs optical principles to determine how focus breathing impacts a lens's effective focal length and, consequently, the depth of field and field of view. It models the change in effective focal length based on a specified breathing factor and subject distance, as breathing is most pronounced at closer focus. Using this adjusted focal length, it then calculates the hyperfocal distance, near and far focus limits, and the total depth of field. Finally, it quantifies the field-of-view shift, revealing the degree of "zoom" that occurs.

effective focal length = nominal focal length × (1 - breathing factor % × distance factor)
hyperfocal distance (H) = (effective focal length² / (aperture × circle of confusion)) + effective focal length
near focus limit = (H × subject distance) / (H + (subject distance - effective focal length))
far focus limit = (H × subject distance) / (H - (subject distance - effective focal length))

These calculations provide a comprehensive analysis of a lens's performance during focus adjustments.

💡 The Depth of Field is a key output here. To explore how different subject distances impact this crucial photographic element, our Subject Distance to Depth of Field Calculator offers more insights.

Analyzing Focus Breathing for a 50mm Lens

Consider a videographer using a 50 mm Focal Length lens at f/2.8, with a Subject Distance of 3 m. They are shooting on a full-frame camera (with a 0.030 mm Circle of Confusion) and estimate their lens has a 5% Focus Breathing Factor.

Focal Length: Enter 50 mm.
Aperture (f-number): Enter 2.8 f/.
Subject Distance: Enter 3 m.
Circle of Confusion: Enter 0.030 mm.
Focus Breathing Factor: Enter 5%.

The calculator determines:

Effective Focal Length: 48.3 mm. This shows a noticeable shortening from the nominal 50mm.
Depth of Field: 0.236 m. This is a shallow depth of field.
Horizontal Field of View: 37.9°.
DOF Shift from Breathing: 0.006 m (or 6mm). This small but measurable shift can impact focus pulls.

The Effective Focal Length is Reduced from 50mm by breathing, resulting in a Slight narrowing: 1.2° lost in the field of view. This data is crucial for the videographer to anticipate and potentially compensate for the subtle "zoom out" effect during a focus pull.

💡 For more advanced control over light in video production, especially when shooting outdoors, our Stacked ND Filter Exposure Calculator can help manage bright scenes.

Achieving Cinematic Precision with Lens Selection

Industry Standards for Lens Performance and Breathing

While there aren't formal "regulations" in the traditional sense for focus breathing in photography lenses, the professional film and video industry adheres to rigorous performance standards that effectively serve as benchmarks. High-end cinema lens manufacturers (e.g., Cooke, Zeiss, Arri) specifically design and market their lenses as "parfocal" (maintaining focus during zooming) and "zero breathing" (maintaining focal length during focusing). These characteristics are considered essential for professional production, where consistent framing during a focus pull is paramount. Organizations like the American Society of Cinematographers (ASC) and various industry publications regularly review and test lenses, setting de facto standards by highlighting which lenses meet these demanding criteria. For instance, a lens with a focus breathing factor above 2-3% is generally deemed unsuitable for professional cinematic work, pushing manufacturers to innovate for minimal optical shifts.

Frequently Asked Questions

What is focus breathing in photography/videography?

Focus breathing is an optical phenomenon where a lens's focal length subtly changes as you adjust focus from near to far, causing the field of view to slightly expand or contract. This effect is most noticeable in video production during 'focus pulls' (racks), where the image appears to zoom in or out, rather than just shifting focus. High-quality cinema lenses are specifically designed to minimize this effect.

Why is focus breathing a problem for videographers?

Focus breathing is a significant problem for videographers because it creates an distracting 'zoom' effect during focus pulls, making the footage look unprofessional. When a cinematographer racks focus from a foreground subject to a background subject, the audience expects only the focal plane to shift, not the framing to change. Lenses with strong breathing can ruin the seamlessness of a shot.

How does aperture affect depth of field?

Aperture, represented by the f-number (e.g., f/2.8), directly controls the depth of field (DoF). A wider aperture (smaller f-number like f/1.4) creates a shallower DoF, blurring the background and isolating the subject. A narrower aperture (larger f-number like f/16) results in a deeper DoF, keeping more of the scene in focus. This is a fundamental creative control in photography and videography.

What is the 'Circle of Confusion'?

The Circle of Confusion (CoC) is the maximum acceptable diameter of a blurred point of light that will still be perceived as sharp by the human eye in a final image. It's a critical factor in depth of field calculations. For full-frame cameras, a common CoC value is 0.030mm, while for APS-C sensors, it's typically around 0.020mm. A larger CoC results in a deeper perceived depth of field.