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<blockquote data-quote="jwstl" data-source="post: 174177" data-attributes="member: 12977">They are actual. Focal length is a measurement of distance from focal point to the film/sensor and that distance doesn't change on any camera, DX or FX. So there are 2 good reasons not to include the DX equivalent focal length on DX lenses:1. Because it's wrong. A 24mm lens is 24mm to the sensor on both DX and FX. It just happens to have the field of view of a longer lens on DX because the sensor is smaller. This is why all lenses, DX and FX, have that &quot;crop factor&quot; on DX.2. Let's say they included the DX focal length equivalent on lenses. What do you do if you decide to switch to a different size DX sensor and the crop factor changes? You would need to change your manufacturing of DX lenses to include the new numbers and the numbers on the existing DX lenses would be inaccurate for the new cameras.So they did the right thing and kept the actual focal length.Sent from my iPad using Tapatalk HD</blockquote>

[QUOTE="jwstl, post: 174177, member: 12977"] They are actual. Focal length is a measurement of distance from focal point to the film/sensor and that distance doesn't change on any camera, DX or FX. So there are 2 good reasons not to include the DX equivalent focal length on DX lenses: 1. Because it's wrong. A 24mm lens is 24mm to the sensor on both DX and FX. It just happens to have the field of view of a longer lens on DX because the sensor is smaller. This is why all lenses, DX and FX, have that "crop factor" on DX. 2. Let's say they included the DX focal length equivalent on lenses. What do you do if you decide to switch to a different size DX sensor and the crop factor changes? You would need to change your manufacturing of DX lenses to include the new numbers and the numbers on the existing DX lenses would be inaccurate for the new cameras. So they did the right thing and kept the actual focal length. Sent from my iPad using Tapatalk HD [/QUOTE]

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