What is crop factor?
Crop factor is a number that describes how much smaller (or larger) a camera sensor is compared to a standard 35mm full-frame sensor. A full-frame sensor measures 36 mm by 24 mm, which gives it a diagonal of approximately 43.3 mm. When a sensor is smaller than this reference size, it captures a narrower portion of the image projected by the lens, effectively "cropping" the scene and producing a tighter field of view.
For example, an APS-C sensor on a Canon camera has a crop factor of 1.6x. This means a 50 mm lens mounted on that camera produces a field of view equivalent to an 80 mm lens on a full-frame body. The lens itself does not change, but the smaller sensor sees less of the image circle, creating the illusion of a longer focal length.
Medium format cameras work in the opposite direction. With a crop factor below 1.0 (such as 0.79x on the Fuji GFX system), the larger sensor captures more of the scene, resulting in a wider field of view than the same lens would produce on full frame.
How the calculator works
This calculator uses several straightforward formulas based on sensor geometry and optics:
**Equivalent Focal Length:** \`\`\` Equivalent Focal Length = Actual Focal Length x Crop Factor \`\`\`
**Equivalent Aperture (for depth of field comparison):** \`\`\` Equivalent Aperture = Actual Aperture x Crop Factor \`\`\` This tells you what aperture you would need on a full-frame camera to achieve the same depth of field. A 50mm f/1.8 lens on an APS-C 1.5x body produces depth of field comparable to a 75mm f/2.7 lens on full frame.
**Equivalent ISO (for noise comparison):** \`\`\` Equivalent ISO = Actual ISO x Crop Factor^2 \`\`\` Smaller sensors collect less total light, so the same ISO setting on a crop sensor produces more noise than on full frame. This formula estimates the comparable noise level.
**Field of View:** \`\`\` FOV = 2 x arctan(Sensor Diagonal / (2 x Focal Length)) \`\`\` The diagonal field of view is determined by the physical size of the sensor and the focal length of the lens.
Common sensor formats
Different camera systems use different sensor sizes. Here are the most common formats and their crop factors:
- **Full Frame (35mm)** -- 36.0 x 24.0 mm, crop factor 1.0x. The reference standard used by Canon EOS R, Nikon Z, and Sony A7 series cameras. - **APS-C (Canon)** -- 22.2 x 14.8 mm, crop factor 1.6x. Used in Canon EOS R7, R10, and older Rebel/EOS xxD series. - **APS-C (Nikon/Sony/Fuji)** -- 23.6 x 15.6 mm, crop factor 1.5x. Found in Nikon Z50, Sony A6000 series, and Fujifilm X-series cameras. - **Micro Four Thirds** -- 17.3 x 13.0 mm, crop factor 2.0x. Used by Olympus (OM System) and Panasonic Lumix cameras. - **Medium Format (Fuji GFX)** -- 43.8 x 32.9 mm, crop factor 0.79x. Found in Fujifilm GFX 100S and Hasselblad X series. - **1" Sensor** -- 13.2 x 8.8 mm, crop factor 2.7x. Common in premium compact cameras like the Sony RX100 series. - **Super 35mm (Cinema)** -- 24.89 x 18.66 mm, crop factor 1.39x. The standard for cinema cameras such as the RED Komodo and Sony FX6.
How to use this calculator
1. Enter your lens focal length in millimeters (for example, 35, 50, or 200). 2. Select your camera's sensor format from the dropdown menu. If your sensor is not listed, choose "Custom Crop Factor" and enter the value manually. 3. Optionally enter your lens aperture (f-stop number like 1.4, 2.8, or 5.6) to see the equivalent depth of field on full frame. 4. Optionally enter your ISO setting to see the equivalent noise comparison. 5. Review the results: the hero card shows your full-frame equivalent focal length, the grid shows additional metrics, and the visual bar chart compares your sensor's field of view to full frame.
Practical examples
**Street photography on Fuji X-T5 (APS-C 1.5x):** A 23mm f/2 lens becomes a 34.5mm equivalent with depth of field similar to f/3 on full frame. This is close to the classic 35mm street photography focal length.
**Wildlife on Canon R7 (APS-C 1.6x):** A 100-400mm zoom becomes 160-640mm equivalent, giving you significant extra reach without carrying a heavier lens. This is one of the biggest advantages of crop sensors for telephoto work.
**Portraiture on Micro Four Thirds (2.0x):** A 42.5mm f/1.2 lens gives an 85mm equivalent field of view with depth of field similar to f/2.4 on full frame, which is an excellent portrait combination.
**Cinematic shooting on Super 35mm (1.39x):** Filmmakers have used Super 35mm for decades. A 35mm cinema lens gives roughly a 49mm equivalent field of view, which is close to the natural perspective of the human eye.
FAQs
Q: Does crop factor actually change the focal length of my lens? A: No. Crop factor does not physically alter your lens. A 50mm lens is always a 50mm lens regardless of what camera it is mounted on. What changes is the field of view because the smaller sensor captures a narrower portion of the image projected by the lens. The "equivalent focal length" is simply a convenient way to describe what focal length you would need on a full-frame camera to see the same field of view.
Q: Why do photographers care about equivalent aperture? A: Equivalent aperture helps compare depth of field across different sensor sizes. A smaller sensor with a fast lens (like f/1.4) will produce less background blur than the same aperture on full frame because the physical entrance pupil is smaller relative to the framing. Knowing the equivalent aperture lets you set realistic expectations when comparing images from different systems.
Q: Is a higher crop factor better or worse? A: Neither. It depends on what you shoot. A higher crop factor gives you extra reach for wildlife and sports photography because it narrows the field of view. A lower crop factor (like medium format) gives a wider field of view and shallower depth of field, which is preferred for landscape and portrait work. Each sensor size has tradeoffs in terms of reach, depth of field, low-light performance, and camera body size.
Q: Does crop factor affect image quality? A: Crop factor itself does not determine image quality, but sensor size does influence it. Larger sensors typically have larger photosites, which capture more light and produce less noise at high ISO settings. However, modern APS-C and Micro Four Thirds sensors have excellent image quality for most uses, and factors like lens quality, lighting, and technique matter far more than sensor size alone.
Q: Can I use this calculator for smartphone cameras? A: Yes. Many smartphones have very small sensors with crop factors ranging from about 5x to 8x. If you know your phone's sensor dimensions or crop factor, select "Custom Crop Factor" and enter the value. This will show you why phone cameras need such short focal lengths (like 4-7mm) to achieve a normal field of view.
Q: What is the crop factor for medium format cameras? A: Medium format sensors are larger than full frame, so they have a crop factor below 1.0. The Fuji GFX system uses a 43.8 x 32.9mm sensor with a crop factor of approximately 0.79x. This means a 63mm lens on medium format gives roughly the same field of view as a 50mm lens on full frame.
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