Tamron 70-180 mm f/2.8 Di III VC VXD G2 review - Distortion and field of view

Have you rated your lenses yet?

Tamron 70-180 mm f/2.8 Di III VC VXD G2

8 February 2024

Maciej Latałło

6. Distortion and field of view

Field of view

A full frame rectilinear 70-180 mm lens should offer you a range of angles of view changing from 34.3 to 13.7 deg. Of course some exceptions are always possible – after all, as we are going to show in a moment, the lens doesn't correct distortion in a perfect way so is not perfectly rectilinear. What's more, its real focal length might be a tad different than the one officially declared. The producers always round such values to whole numbers so several percent of difference is nothing strange.

Fortunately, when it comes to fields of view of the tested Tamron, we don't have to guess. We measured them precisely as it should be done, for rays of light coming from infinity. Our measurements were based on photos of starry sky; 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.

In case of the 70 mm focal length we used 100 stars positioned evenly across the frame. The transformation error amounted to 4 minutes of arc. The field, measured this way, amounted to 32.6 deg with measurement error not exceeding 0.1 of a degree. The field is significantly narrower than the one stated in official specifications and it corresponds more to the 74 mm focal length, than to the 70 mm one.

Please Support Us

If you enjoy our reviews and articles, and you want us to continue our work please, support our website by donating through PayPal. The funds are going to be used for paying our editorial team, renting servers, and equipping our testing studio; only that way we will be able to continue providing you interesting content for free.

- - - - - - - - - - - - - - - - - advertisement - - - - - - - - - - - - - - - - -

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

In case of the 180 mm focal length the transformation was based on 57 stars and the transformation error amounted to 4 seconds of the arc as well. The field, measured by us this way, amounted to 13.45 degrees, with the measurement error not exceeding 0.05 of a degree. Here the field is also a tad narrower than the declared one but this time the difference is not big; with such a value of the focal length it seems completely negligible.

Finally you should remember that, when it comes to fields of view, you deal here with a 74-183 mm device, not the 70-180 mm lens.

Distortion

When you employ the smaller APS-C/DX sensor distortion won't be especially bothersome. At the widest angle of view you deal with low pincushion variant of this aberration, amounting to +0.66%, which then increase with the increase of the focal length. At 100 mm its level is +1.27%, at 135 you get +1.44%, and at 180 mm the result is +1.50%.

Sony A7R IIIa, APS-C, 70 mm

Sony A7R IIIa, APS-C, 100 mm

Sony A7R IIIa, APS-C, 135 mm

Sony A7R IIIa, APS-C, 180 mm

In case of full frame at the 70 mm you deal with a moderate level of +1.48%; still at longer focal lengths distortion becomes visible, reaching +2.24% at 100 mm, +2.49% at 135 mm and 2.82% at 180 mm.

It's a pity the optics constructors didn't try to correct distortion a bit more efficiently. After all you don't deal here with wide angles of view, and the zoom magnification reaches just 2.57x. It isn't such a big challenge and I think distortion could have been properly corrected in this lens with a satisfactory result.