Venus Optics LAOWA FFII 90 mm f/2.8 CA-Dreamer Macro 2X
6. Distortion and field of view
Field of view
A rectilinear 90 mm lens on a full frame sensor should provide you an angle of view of 27 deg and the producers in their official specifications state this value exactly. Of course we decided to check how big this field really is anyway. In order to do so we took photos of 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 could determine the field of view of the lens with utter precision and in the right way, so for rays of light coming from infinity. The transformation was based on the locations of 118 stars spread evenly across the frame and the average mesh-fitting error amounted to 17 seconds of arc.
Finally we got a result of 27.62 deg with an error on a level of 0.05 deg. The real field of view of the tested instrument is a tad wider than the declared one and it means the real focal length of the Laowa is a tad closer to 88 mm than to 90 mm.
Distortion
In case of the performance on the smaller APS-C/DX sensor geometric deformations are completely imperceptible. Our official result amounts to +0.33% so, within the margin of error, almost interlocking with zero.
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On full frame distortion is a tad higher and you deal here with a value of +0.48%. Still it is not a level that should make you worry.
| Nikon Z7, 90 mm, JPEG, APS-C/DX | |||
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| Nikon Z7, 90 mm, JPEG, FF | |||
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