Viltrox AF 50 mm f/1.4 Pro
7. Distortion and field of view
Field of view
A rectilinear 50 mm lens should give you, on full frame, an angle of view of 46.8 degrees. In their official specification the producer of the Viltrox AF 85 mm f/1.4 Pro states that the offered angle of view is a bit lower, amounting to 46.6 degrees. We decided to take a reality check. To do so, we took photos of a starry sky and saved them as uncorrected JPEG files. Then we transformed the pixel layout (X,Y) from the photo into the equatorial coordinate system (right ascension and declination), which locates a star on a celestial sphere. That way we were able to measure the field very precisely, and exactly as it should be done, for rays of light coming from infinity. Our transformation was based on positions of 150 stars spread evenly across the frame. An average mesh-fitting error amounted to just 12 seconds of arc.Our final result amounted to 46.21 deg with a measurement error on a level of 0.04 of a degree. It's even a tad lower than stated by official specifications and suggested by the focal length itself. Still, differences are slight and mean that the resulting angle of view is an equivalent of distortion-free 50.7 mm focal length.
Distortion
A contemporary 50 mm lens with a complex optical system should correct distortion properly. Fortunately, the Viltrox AF 50 mm f/1.4 Pro performs as it should in this category; it's obvious its constructors didn't count on the help of software of a camera. On the smaller APS-C/DX sensor, you deal with practically invisible barrel deformations of -0.36%. On full frame they increase to -0.96% but any result lower than 1% in absolute numbers we consider to be slight. As you see, there are practically no problems here.
In this category, the Viltrox with a price tag of $466 can put to shame the Panasonic S Pro 50 mm f/1.4, a lens almost four times more expensive, that gave up on correction of this aberration. The Viltrox also fares much better than the more expensive Sigma A 50 mm f/1.4 DG DN, but it is a tad weaker than the Nikkor Z 50 mm f/1.4, the Sony FE 50 mm f/1.4 GM, and the Samyang AF 50 mm f/1.4 FE II.
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| Nikon Z8, 50 mm, APS-C/DX | |||
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| Nikon Z8, 50 mm, FF | |||
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