Longitudinal Chromatic Aberration and focus shift
Although the Tamron 70-300mm f4.5-6.3 Di III has a focal ratio of only f6.3 at the long end I tested for longitudinal color aberrations (loCA, a.k.a. “axial color” or “bokeh CA”). These can show up as magenta coloration in the foreground and greenish hues in the background and are not easily corrected in post-processing. The Tamron shows practically no loCA or focus shift in this test.
But if you look closely at the following shot the Tamron 70-300mm f4.5-6.3 Di III produces a bit of purple fringing around high-contrast edges in the focus plane and some green outlining around background subjects:
Sharpness and contrast
Let’s have a look at the theoretical performance of the new Tamron 70-300mm f4.5-6.3 Di III and compare it to the Sigma 100-400mm f5-6.3 DG DN OS, Sony FE 100-400mm f4.5-5.6 GM OSS:
These MTF charts show the computed lens-performance of lenses wide open without influence of diffraction at 10 line-pairs/mm (yellow/red) and 30 lp/mm (gray/green). Higher values are better (more contrast) and the closer the dotted and solid lines are together the less contrast dependents on the orientation of the test-pattern (less astigmatism). The x-axis displays the distance from the optical axis (=center of the sensor) in mm.
From the charts the Tamron 70-300mm f4.5-6.3 Di III should be pretty contrasty and sharp in the APS-C/DX image-circle. But towards the full-frame corners it develops quite some astigmatism and resolution of fine details drops clearly at the short end. Both Nikkors are better behaved in this respect.
Let’s see how this theoretical performance translates into real life results in the sharpness test based on Siemens-stars shot on a 45MP Nikon Z7. Processing was done in Lightroom 12.1/CRAW 15.1 from RAW to Adobe Color profile with the built-in lens profile applied. Noise-reduction is set to 0, sharpening to 50/0.5/36/10, with no extra tone, color, or saturation adjustment. White-balance was adjusted to a neutral white and I did some exposure compensation to make the brightness of all crops match. So you will not see light fall-off in the corners.
The following are all 100% crops!
First up is an overview of the wide-open performance at different focal lengths. You can jump to the detailed results at different apertures and comparisons with other lenses by clicking on the crops of the respective focal length.
Tamron’s 70-300mm looks very sharp in the APS-C/DX image-circle with a slight softening at 300mm. The FF/FX-corner also looks pretty good up to 200mm but I had to compensate quite a bit for field curvature which is strongest at the short end and becomes stronger the closer you focus.
The following 100% crops for each focal length show the Tamron 70-300mm f4.5-6.3 Di III from wide open down to f11 compared to the Nikon AF-P 70-300mm f4.5-5.6E VR (shot on a 36MP Nikon D810), Nikon Z 24-200mm f4.0-6.3 VR, and Nikon Z 100-400mm f4.5-5-6 VR S. The Nikon D810 has 12% less linear resolution than the Nikon Z7 but this is still close enough to compare sharpness.
If you want to see all the details and comparisons read on. Or you can fast-forward to the performance at long distances.
Performance at 70mm:
At 70mm all three lenses are pretty much comparable in the DX image-circle. But the Tamron 70-300mm f4.5-6.3 Di III has the sharper FX-corner than both Nikkors.
Performance at 100mm:
At 100mm the Nikon Z 100-400mm f4.5-5.6 VR S enters the competition – and takes the lead. But both 70-300mm lenses are pretty close. The Nikon Z 24-200mm f4.0-6.3 VR is not bad but suffers from a mushy FX-corner.
Performance at 200mm:
At 200mm we see the same ranking as at 100mm focal length. Stopping the Tamron 70-300mm f4.5-6.3 Di III down to f8.0 improves performance only slightly
Performance at 300mm:
At the long end both 70-300mm lenses are still pretty close with the Tamron 70-300mm f4.5-6.3 Di III being slightly sharper in the DX image-circle. The Nikon Z 100-400mm f4.5-5.6 VR S clearly produces the sharpest FX-corner. Stopping the Tamron 70-300mm f4.5-6.3 Di III down to f8.0 does not improve its FX-corner by much and f11 softens the rendering due to diffraction.
All-in-all the new Tamron 70-300mm f4.5-6.3 Di III zoom lens seems right up there or even better than the Nikon AF-P 70-300mm f4.5-5.6E VR and clearly better than the Nikon Z 24-200mm f4-6.3 VR in the overlapping zoom range. Just remember that field curvature might get in the way of rendering the sharpest FX-corner on (near) flat subjects. The Nikon Z 100-400mm f4.5-5.6 VR S shows the best performance in this comparison – but then it’s four times as expensive as the Tamron.
Performance at long distances
The Siemens-star test-targets are shot at a distance of 45x focal length (i.e. at around 14m for 300mm focal length). But performance of lenses also depends on the shooting distance. Therefore, I present another series of images shot on a 45MP Nikon Z 7 of a city around 1 km away. Processing was done in Lightroom 12.1/CRAW 15.1 from RAW to Adobe Color profile with the built-in lens profile applied. Noise-reduction is set to 0, sharpening to 50/0.5/36/10, with no extra tone, color, or saturation adjustment. All shots were made from a heavy tripod with image stabilization switched off at ISO 64. As usual I have selected the diagonal that provided the better corner results although the 70-300 was only slightly decentered.
The following images show the complete scene wide open plus 100% crops from the center, APS-C/DX-corner, and FF/FX-corner. You can access the large originals but please respect our copyright and only use those images for personal use.
At the short end sharpness is good to very good in the DX image-circle but the FX-corner is soft. Even stopping down to f8.0 does not lift the FX-corner to good acuity.
At 100mm focal length the FX-corner improves significantly and the image is very sharp all across the full-frame.
200mm and 300mm (see below) sees a slight softening of the DX- and FX-corner.
In this long-distance test the Tamron 70-300mm f4.5-6.3 Di III performed best at around 100mm focal length. At longer focal lengths the lens became slightly softer outside the center but still delivers good to very good sharpness across the full frame. At 70mm the lens produces the softest FX-corners due to field curvature – even when stopped down.
Vignetting and distortions
To make it easier to see light fall-off in the corners of a full-frame sensor I’ve arranged a series of three shots each with the Tamron 70-300mm f4.5-6.3 Di III at 70mm and 300mm focal length and different apertures. All images were developed from RAW with Adobe Color profile to the same brightness in the center and are shown with vignette control Off (1st row) or Normal (2nd row):
At 70mm vignetting is pretty strong at f4.5 and only lifted by about 0.6 EV with vignette control set to Normal. Same at 300mm – only that light fall-off is not as abrupt as at 70mm. Adobe’s RAW converter automatically applies vignette control as it was set in camera – but you cannot alter the setting in postprocessing.
Distortions are very low at 70mm but become clearly visible pincushion type from 100mm focal length onwards. The setting for distortion compensation in camera is currently ignored by Adobe’s RAW converter and treated as On. The following composite images show the upper border of the full-frame image first with auto distortion control Off and then On (all out-of-camera JPGs):
Distortion compensation through the built-in lens profile works well when applied in camera to JPGs or through Adobe’s RAW converter.
Rendering of point-light sources at night-shots
Night-shots pose a different challenge for lenses as the contrast is even higher than under bright sun and point-light sources can reveal some weaknesses such as coma, haloing and colour-aberrations that do not show up as prominently in other test-shots. The 100% crops below the main image show the effect of coma in the FF-corner of the Tamron 70-300mm f4.5-6.3 Di III at different apertures:
The Tamron 70-300mm f4.5-6.3 Di III produces very little coma even wide open. The test also shows no color artifacts around bright streetlights.
This test is for the rendering of point-light sources in an out-of-focus background. The circle of confusion that is produced by the test is pretty indicative of Bokeh performance (in the background) and light fall-off. Ideally the out-of-focus image of the point-light is evenly lit and perfectly circular, with no “onion-rings”, and without coloration. Lenses normally produce an effect known as “cat’s eye” the further away from the optical axis the point-light is projected. This is due to optical vignetting in the lens barrel when light enters the lens from an angle.
The crops below the main image are from the center, APS-C/DX-corner, and FF/FX-corner of the 4k version.
The diameter of the Bokeh balls in the center is determined by the entrance pupil of the lens. This is 48mm for the new Tamron at 300mm focal length which is only slightly smaller than the 54mm of a 300mm lens with a focal ratio of f5.6. Compression of the circle towards the corners is relatively strong wide open. The circle of confusion in the center is round wide open – but only at focal lengths of 170mm and longer. At shorter focal lengths the aperture blades protrude a bit into the path of light even when the aperture is wide open. This leads to less than perfectly rounded Bokeh balls in the center and can also produce diffraction spikes (a.k.a. sunstars). The inside of the Bokeh balls is pretty smooth without onion-rings but there is a bit of outlining – albeit without coloration from loCA.
Let’s see how this analysis of out-of-focus point-light sources translates into Bokeh-performance shooting a bookshelf. Crops are from the foreground, middle-ground, and background resized to make them comparable across all my reviews. I used the longest focal length that I could to produce a comparable shot to my other reviews which was 162mm in the case of the Tamron 70-300mm f4.5-6.3 Di III.
The Tamron 70-300mm f4.5-6.3 Di III shows a softer transition zone and background than the Nikon AF-P 70-300mm f4.5-5.6E VR and in that respect is closer to the Nikon Z 100-400mm f4.5-5.6 VR S. In the (less important) foreground the F-Nikkor looks smoothest, the Tamron is so-so, and the Z-Nikkor 100-400 is blurry but plagued by double contours. See also the following crops (now at 100%) from the same images showing the ruler in the transition zone.
All-in-all the Tamron 70-300mm f4.5-6.3 Di III produces a relatively nice Bokeh considering its meagre focal ratio.
The Tamron 70-300mm f4.5-6.3 Di III achieves a maximum magnification of only 1:7.4 in close-up shooting at 70mm focal length and a more useful 1:4.6 at 300mm focal length where the area of sharp focus is just 110 x 166mm. First up are the shots at 70mm with crops from 0mm, 8mm, and 16mm off the center of the sensor respectively.
The Tamron 70-300mm f4.5-6.3 Di III is sharp in the center even wide open but gets soft pretty soon and outright mushy when you look into the DX-corner. Even stopping down to f16 does not bring the DX-corner into good sharpness but at least 8mm image height become very usable. This is only partly due to the strong field curvature of the lens as the following crops show which are from three different shots at f8.0 each focused specifically for each crop to eliminate field curvature:
The results are better now but still soft and fuzzy once you look towards the DX-corner (or beyond). It’s clearly better to use the lens at its longest focal length for close-up work as the following shots at 300mm with crops from 0mm, 14mm, 20mm image height show:
Flare, ghosting, and sunstars
Catching a strong light-source shining directly into the lens is always a risky business: it could produce strange colorful ghost-images or reduce contrast considerably through flare and glare. The appearance of flare and ghosting depends on factors like the aperture and the angle of the light hitting the lens. So to judge the proclivity of Tamron’s 70-300mm f4.5-6.3 Di III for these artifacts I went through a series of well calculated shots at the short end against a strong light source to provoke glare and ghosting. The lens hood was mounted in all shots. Following are two of the more extreme example results. The little bright square inset in the upper left shows the respective area with an exposure compensation of +3 EV to make it easier to see which levels of black the lens renders at that point:
The Tamron 70-300mm f4.5-6.3 Di III shows some ghosting artifacts when the light-source is inside the frame. Veiling glare is relatively well controlled unless the light-source is closer to the center.
At 70mm focal length the lens produces sunstars even wide open. They look best at f5.6 and become fuzzier when the lens is stopped further down to f8 or f11:
Next check out my sample images!Check prices on the Tamron 70-300mm f4.5-6.3 Di III at B&H, Adorama, WEX UK or Calumet.de. Alternatively get yourself a copy of my In Camera book, an official Cameralabs T-shirt or mug, or treat me to a coffee! Thanks!