Does an FX lens change focal length or aperture on a Nikon DX camera?
Asked 1/2/2011
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If I mount a full-frame Nikon FX lens, such as a Nikkor 35mm f/2, on a Nikon DX body, does the lens still remain 35mm f/2? Or does the smaller DX sensor change the effective focal length or the maximum/minimum aperture?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
15y ago
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Aperture is unaffected.
The field of view becomes 35mm x (the crop factor of your sensor), which is 1.5 in the case of Nikon DX cameras (It's also 1.5 for Pentax and Sony, 1.6 for Canon and 2 for Panasonic & Olympus).
So your 35mm Nikon lens has a 35mm x 1.5 = 52.5mm "35mm equivalent" field of view.
Note that the perspective doesn't change, just the amount of 'stuff' you can fit in the frame. The image will still look like a 35mm image as shot on a full-frame sensor, but with the sides cropped in to give you the field of view of a 52.5mm lens on a full-frame sensor.
(Most people round that to 50mm "35mm equivalent" field of view, regardless of 1.5 or 1.6 crop factor)
Originally by user1615. Source · Licensed CC BY-SA 4.0
user1615
15y ago
0
Generated from our catalog & community — verify before relying on it.
The lens itself does not change: a 35mm f/2 lens is still 35mm f/2 on a DX body. The aperture value is unaffected.
What changes is the field of view because the DX sensor captures a smaller central portion of the image circle. On Nikon DX, the crop factor is 1.5×, so a 35mm lens gives a field of view similar to about a 52.5mm lens on full frame.
So:
- focal length: still 35mm
- aperture: still f/2
- field of view: equivalent to roughly 52.5mm on full frame
A useful way to think of it is that the image looks like a crop from what the same lens would show on an FX camera. That means you fit less of the scene into the frame, but the lens’s actual optical specs do not change.
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