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Nikon Nikkor 20mm f/4 non-ai vs Tamron 20-40mm f/2.7-3.5 SP Aspherical AF

7.8oz 52mm filters for the Nikon and 18.6oz 77mm filters on the Tamron.
Today we look at the well known beautiful little Nikon Nikkor 20mm f/4 and the more unknown yet cult followed Tamron 20-40mm f/2.7-3.5 SP Aspherical AF, which may be one of the ugliest lenses ever manufactured.

Shot on a tripod with manual white balance, self timer and electronic front curtain shutter on for no vibrations. Color hue on the Tamron shifts to green. I'm surprised that they both have an identical field of view as zooms often fudge their numbers.

At f/4 it's no surprise the Nikon 20mm f/4 is about a half stop behind the Tamron 20-40mm which is closed down a stop. On the other hand the Tamron shows some distortion. 

Exposure on the Nikon 20mm pushed .5 brighter to match the Tamron 20-40mm.

Bottom right corner at f/4

At f/5.6 their exposure is perfectly matched, although the Nikon 20mm still has some vignetting, but not enough to worry about. Contrast comes alive on the Nikon.

Corners at f/5.6, the Tamron 20-40mm is clearly superior.

Centers at f/8


At f/11 diffraction takes a toll on both lenses.

Neither reach the extreme corner, but the Tamron sharpness extends closer to the edge, especially if you look at the porch railing.

An interesting look at the Tamron 20-40mm corners at f/5.6 and f/8. Unless you need the furthest corner I'd consider f/5.6 the overall ideal aperture for this lens. Impressive for an old zoom.

The Nikon 20mm f/4 has a deserved reputation for flare resistance while the Tamron 20-40mm f/2.7-3.5 has a reputation for the opposite. Out of the frame sun that was dispersed by the clouds.

Of course there is more to a lens than resolution. The lack of flare and seven bladed aperture of the Nikon 20mm f/4 make it a nice lens to use with point sources of light, while the Tamron looks terrible in this regard.

Then of course there is distorion. Note how the Tamron shifts to green, distorts, flares and loses contrast even on an overcast day.

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