Understanding the 35mm Equivalent:Why Sony Says a 35mm Lens is '35mm Equivalent' on an APS-C Camera
Introduction
When shopping for lenses for cameras with smaller sensors like APS-C, you may come across the term '35mm equivalent.' This phrase is particularly common in the context of Sony cameras, where a 35mm lens on an APS-C camera is often described as having a '35mm equivalent' focal length. This article aims to clarify what this term means and why it's important for photographers to understand it.
The Concept of 35mm Equivalent
Most photographers are accustomed to thinking in terms of focal lengths' look and effect in a 35mm camera. The 35mm format, with its full frame, provides a standard reference point for lens properties. To make it easier for users of different camera systems to understand how their lenses will perform, manufacturers use the term '35mm equivalent.'
The Basics of Crop Factor
The crop factor is the ratio of the size of one sensor to another. In the case of an APS-C sensor, which is 24mm x 16mm, the crop factor compared to a full-frame 35mm sensor is approximately 1.5. This means that the APS-C sensor can capture a smaller portion of the image that the full-frame lens would normally capture.
Calculating 35mm Equivalent on an APS-C Camera
To determine the 35mm equivalent focal length, you need to multiply the focal length of the lens by the crop factor of the camera. For a Sony APS-C camera, this crop factor is 1.5. Therefore, a 35mm lens on a Sony APS-C camera would have a 35mm equivalent focal length of 52.5mm (35mm x 1.5).
Practical Implications
The use of 35mm equivalent focal lengths helps photographers intend the correct angle of view, depth of field, and general look of their images. For example, if you have a 50mm lens on a full-frame camera, it will provide a moderate telephoto effect. However, the same lens on an APS-C camera will actually provide a 75mm equivalent focal length, resulting in a much more pronounced telephoto effect, as the crop factor magnifies the field of view.
Understanding the Impact on Image Quality
The 35mm equivalent focal lengths are not just about field of view; they also affect the depth of field. At the same focal length, a smaller sensor will often result in less depth of field due to the magnification, making it easier to blur the background. This is something photographers need to consider when choosing the right lens and camera combination for their specific shooting needs.
Conclusion
Understanding the 35mm equivalent is crucial when working with APS-C cameras. By knowing and utilizing this information, photographers can make more informed decisions about lens choice and composition, ensuring they get the best results from their equipment.