Image Resolution explained
Image Resolution Explained Resolution refers to the amount of detail an image holds, and it’s typically measured in pixels (short for “picture elements”). Higher resolution
How does sensor size affect focal length
Sensor size plays a significant role in how focal length affects the field of view (FoV) and overall perspective of your photos. It doesn’t change the focal length of the lens itself, but it changes the way the image is captured. Here’s how it affects focal length:
1. Field of View (Crop Factor)
The most important effect sensor size has on focal length is the crop factor, which alters the field of view of a lens when used on a smaller sensor. The crop factor is a multiplier that compares the sensor size to a full-frame sensor (35mm format).
- Full-frame sensors: These are the largest common sensors (36mm x 24mm) and have a 1x crop factor.
- APS-C sensors: These are smaller sensors (typically around 22mm x 15mm) and have a crop factor between 1.5x and 1.6x, depending on the brand.
- Micro Four Thirds (MFT): Even smaller sensors (typically 17.3mm x 13mm) with a crop factor of 2x.
Example: If you put a 50mm lens on a camera with an APS-C sensor that has a 1.5x crop factor, the effective focal length becomes 50mm * 1.5 = 75mm. This means you’ll get a narrower field of view than if you were using the same lens on a full-frame camera.
2. Impact on Composition
When you use a lens on a crop-sensor camera, it effectively “zooms in” on the scene due to the crop factor. This can make long focal lengths seem even longer (useful for wildlife or sports photography), while wide-angle lenses might feel less wide. For instance:
- Wide-angle lens on a crop sensor: A 24mm lens on a crop-sensor camera might act like a 36mm lens (24mm * 1.5 crop factor), which is not as wide as it would be on a full-frame camera.
- Telephoto lens on a crop sensor: A 200mm lens on a crop-sensor camera might act like a 300mm lens (200mm * 1.5 crop factor), which is beneficial for telephoto work like wildlife or sports.
3. Depth of Field (DOF)
A smaller sensor (like APS-C or MFT) has greater depth of field for the same aperture and focal length compared to a larger sensor (like full-frame). This means that a full-frame camera can achieve more pronounced background blur (bokeh) at the same aperture and focal length.
Example: With the same 50mm f/1.8 lens:
- On a full-frame sensor, the background will blur more due to the larger sensor’s shallower depth of field.
- On an APS-C sensor, you’ll get a deeper depth of field, meaning more of the image will appear in focus at the same aperture.
4. Effective Focal Length (EFL)
The effective focal length is the focal length of the lens, adjusted for the crop factor of the sensor. This affects your choice of lenses depending on your subject and framing needs.
- Wide-angle lenses (e.g., 16mm on a full-frame) may only give you a 24mm equivalent on an APS-C sensor, which is more suitable for landscapes or architecture.
- Telephoto lenses (e.g., 200mm on a full-frame) give you a 300mm equivalent on an APS-C sensor, useful for wildlife or sports.
5. Example Comparisons:
- 50mm lens on Full-frame: Gives a field of view of 50mm.
- 50mm lens on APS-C sensor with 1.5x crop factor: Gives a field of view equivalent to 75mm.
- 50mm lens on Micro Four Thirds: Gives a field of view equivalent to 100mm (due to 2x crop factor).
Summary
- Smaller sensor = Narrower field of view (more “zoomed in”) for a given focal length.
- Larger sensor = Wider field of view for the same focal length.
- Smaller sensors have greater depth of field, meaning you’ll need a larger aperture to achieve similar background blur.
- The effective focal length depends on the sensor size: a 50mm lens on a full-frame sensor gives a 50mm field of view, but the same lens on a crop sensor (e.g., APS-C) gives a narrower view, effectively behaving like a 75mm lens.
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Hi I'm Monique
Personal and business brand image expert. Photographer and educator who is super passionate about empowering business women and men to have a positive self perception, with the right tools and guidance so they can share their gifts with the world.
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How does sensor size affect focal length
Grab the PDF version here
How does sensor size affect focal length
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