Should a photobook list actual focal length or 35mm-equivalent focal length?
Asked 7/3/2017
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I'm preparing a personal photobook and want to include exposure details for selected images: aperture, ISO, shutter speed, and focal length. All photos were taken on a Canon EOS M3 with an APS-C sensor (1.6x crop factor). For the focal length, is it better to list the lens's actual focal length as recorded by the camera, perhaps noting the camera's crop factor, or to convert it to a 35mm-equivalent focal length for readers?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
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The "equivalent" focal length draws from history, namely how it relates to a 35mm film camera, and there should come a time (and I think it is past) when we move on.
The focal length IS the focal length. Having a smaller sensor may crop a portion of the field of view, but the focal length is a real and meaningful number. Anyone who is interested in the technical aspect of the photo will also want to know the camera (and thus sensor size), and will know how these relate. Anyone who does not understand that really will not gain anything from focal length regardless whether equivalent or real.
Frankly I wish manufacturers would get away from trying to "spin" their products by such machinations as "35mm equivalents". Stating the crop factor is frankly all one needs to know in that regard, and you need to know that anyway.
Originally by user28109. Source · Licensed CC BY-SA 4.0
user28109
9y ago
0
Generated from our catalog & community — verify before relying on it.
Use the actual focal length if you want to present technically correct shooting data. Focal length is a real property of the lens, while “35mm equivalent” is only a reference to angle of view on a full-frame/35mm camera.
A good compromise is to list the real focal length and identify the camera or sensor format once, for example: “Canon EOS M3 (APS-C, 1.6x crop).” Readers who understand the technical side can interpret it easily.
If your audience is less technical, 35mm-equivalent focal length may be more immediately meaningful, especially for people familiar with 35mm cameras. An even simpler option is to describe the lens view in plain language such as “wide-angle,” “normal,” or “telephoto.”
So the best choice depends on your readers:
- technical audience: actual focal length + camera/sensor info
- general audience: 35mm equivalent or plain-language lens description
Also keep in mind that focal length alone doesn’t fully describe the final image view, since sensor size, subject distance, and any later cropping also affect what the viewer sees.
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