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When matching real-world camera shots/footage, I need to know whether the Focal Length in Blender represents the focal length set on the lens or the "true" focal length, taking into account a cropped sensor, e.g. Nikon DX.

For example, using my 50mm lens on my DX sensor bodies, the effective or "real" focal length of the images is actually 75mm because of the 1.5x factor.

Thanks.

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Yes, I if you set the sensor size to the Nikon DX preset, the field of view should be the same as a real camera. The field of view is computed from the dimensions of the sensor and the length of the lens, as is in the real world.

A 75mm lens on a full sensor camera (24x36mm sensor size) would cover a field of view of 26.9 degrees.

A 50mm lens on an APS size sensor (23.6x15.8mm) would cover afield of view of 26.6 degrees.

Remember that the 1.5 factor in real life is "approximate". The exact match for a 75mm lens would be a 49.34mm lens.

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  • $\begingroup$ So, to clarify, if I select the DX preset and then enter the lens focal length as shot (50mm in my example) then the FOV should be correct? $\endgroup$ – D. Waschow Jun 4 '14 at 20:43
  • $\begingroup$ Yes, just use the preset and you're good to go. $\endgroup$ – cegaton Jun 4 '14 at 20:55
  • $\begingroup$ Andrew Price has a really good video tutorial on camera tracking. He specifically talks about your question at 24:30 in the video. youtube.com/watch?v=CVPcT0dJmoY $\endgroup$ – Justin Jun 5 '14 at 14:35
  • $\begingroup$ So @cegaton, just for further clarification. If the preset is used, the focal length should not be manually adjusted based on the crop factor of the camer I.e. I have a Canon 550D using a 17mm. I should just select the Canon APS-C preset and then enter 17mm for focal length. I should NOT select Canon APS-C and input a manually adjusted focal length of 27.2 based on the crop factor. Is that right? $\endgroup$ – Jeffrey Jul 11 '17 at 11:05
  • $\begingroup$ @Jeffrey if you know the lens and the sensor for the camera used, then use that information, that will give you a solid start point. If your lens is a17mm use that number. Just keep in mind that when you refine your camera solution, blender might find a better match by changing the lens focal length. Maybe your 17mm is a 16.8mm or a 19.6 for example. $\endgroup$ – cegaton Jul 11 '17 at 20:50

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