Longitudinal Chromatic Aberration and focus shift
Lenses with focal ratios of f2.8 or larger are often prone to longitudinal color aberrations (loCA, a.k.a. “axial color” or “bokeh CA”). These normally show up as magenta coloration in the foreground and greenish hues in the background and are not easily corrected in post-processing. The new Tamron has practically no loCA or focus-shift at the long end. But at 50mm focal length the lens shows a bit of loCA and a clear focus shift to the background when the lens is stopped down to f2.8.
The following 100% crop from a real life shot shows that the Tamron 35-150mm f2-2.8 Di III produces a bit of glare and purple fringing around high-contrast edges in the focal plane plus some green outlining around background subjects:
Sharpness and contrast
Let’s have a look at the theoretical performance of the new Tamron 35-150mm f2-2.8 Di III and compare it to some other lenses:
These MTF charts show the computed lens-performance of lenses wide open without influence of diffraction at 10 line-pairs/mm (red) and 30 lp/mm (gray). 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.
Overall contrast of the Tamron 35-150mm f2-2.8 Di III (red line) looks very high in these charts – both on the long end and the short end. Resolution of small details (gray line) starts very good in the center with a soft roll-off towards the corners and some astigmatism developing early on. Compared to the other two Tamron lenses I’d expect similar performance at the short end but the Tamron 70-180 looks superior to the Tamron 35-150 at the long end.
Let’s see how this theoretical performance translates into real life results in the sharpness test based on Siemens-stars. Processing was done in Lightroom 11.0/CRAW 14.0 from RAW to Adobe Color profile with the built-in lens profile for CA and shading compensation 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 by clicking on the crops of the respective focal length.
Tamron’s new zoom lens performs very well at the short end – especially considering its bright focal ratio of f2.0. Towards the long end the lens becomes progressively softer outside the center. Field curvature is relatively low except at 35mm focal length.
The following 100% crops for each focal length show the Tamron 35-150mm f2-2.8 Di III from wide open down to f8/f11 compared to the Tamron 28-75mm f2.8 Di III G2 and Tamron 70-180mm f2.8 Di III. It shows that the 35-150 is clearly sharper than the 28-75 G2 especially at 50mm and 70mm focal length. But Tamron’s 70-180 is even sharper than their 35-150mm lens at the long end. Find all the detail below or fast-forward to the performance at long distances.
Performance at 35mm:
Performance at 50mm:
Performance at 70mm:
Performance at 105mm:
Performance at 150mm:
Performance at long distances
The Siemens-star test-targets are shot at a distance of 45x focal length (i.e. at around 4.5m for 100mm focal length). But performance of lenses also depends on the shooting distance. Therefore I present another series of test-shots of a city around 1 km away. Processing was done in Lightroom 11.0/CRAW 14.0 from RAW to Adobe Color profile with the built-in lens profile compensating CA and vignetting. 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. ISO was set to 200 to keep shutter speeds on the safe side. As usual I have selected the diagonal that provided the better corner results as the lens was a bit decentered.
The following images show the complete scene wide open to give you an impression of the angle of view. Following each main image are 100% crops from the center, APS-C-corner, and FF-corner. You can access the large originals but please respect our copyright and only use those images for personal use.
Wide open the Tamron 35-150mm f2-2.8 Di III produces a very sharp center over the complete zoom-range. The APS-C-corner is a bit soft at 35mm and f2.0 probably due to field curvature but shows good resolution from 50mm onwards. The FF-corner trails the APS-C-corner a bit and is strongest at 50mm and 70mm. Overall the lens shows good to very good sharpness over its complete zoom-range with a slight softening towards the corners. Stopping down to f4.0 at 35mm helps with the field curvature and produces very high and even sharpness across the sensor. And the FF-corner at 100mm and 150mm gets a nice boost in acuity from stopping down to f5.6.
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 35-150mm f2-2.8 Di III from f2.0 to f4.0 at 35mm and f2.8-f5.6 at 150mm focal length. All images were developed to the same brightness in the center and with the built-in lens profile compensating vignetting:
The sample images above show that even with the lens profile applied vignetting is clearly visible especially at 35mm f2.0 although automatic shading compensation lifts the extreme corners by 1 EV. Adobe’s RAW converter automatically applies shading compensation as it was set in camera – but you cannot alter the setting in postprocessing.
Distortions show a slight mustachio at 35mm and evolve to a strong pin-cushion type at 150mm focal length. The setting for distortion compensation in camera is currently ignored by Adobe’s RAW converter and treated as OFF but there is a lens profile for the lens in Lightroom 11.0 / CRAW 14.0. If you activate Adobe’s lens profile just dial vignetting compensation back if you already had shading compensation in camera set to Auto. This is all pretty frustrating and I can only hope that one day Adobe and the lens/camera makers can agree upon which part of the lens profile is automatically applied in RAW development and which part has to be activated manually in post-processing. But Adobe’s lens profile at least does a pretty good job to correct for distortions – as does the distortion compensation in camera when you shoot JPGs:
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 35-150mm f2-2.8 Di III:
The lens shows very little coma and no disturbing colored haloes around bright lights.
This test is for the rendering of point-light sources in an out-of-focus background. The circle of confusion that is produced by this 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. There’s also 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 images were shot at the longest focal length. Crops are from the center, APS-C-corner, and FF-corner resized to make them comparable across all my reviews.
The diameter of the Bokeh balls in the center is determined by the entrance pupil of the lens which is 54mm for the Tamron 35-150, 64mm for the Tamron 70-180, 71mm for a 70-200mm f2.8 lens (at their respective longest focal length and largest aperture). So the longer lenses have a slight advantage here. The Bokeh balls from Tamron’s 35-150mm f2-2.8 Di III are free of onion-rings but show a “bubbly” texture inside and a bit of outlining with no coloration from loCA. They stay pretty circular in the center up to f5.6. But the cat’s eye effect in the corners is very strong wide open and could lead to “swirly Bokeh”.
Now let’s see how this analysis of out-of-focus point-light sources translates into Bokeh-performance shooting a book-shelf. Crops are from the foreground, middle-ground, and background resized to make them comparable across all my reviews.
Compared to Tamron’s 70-180mm f2.8 Di III at 165mm Bokeh of the 35-150mm f2-2.8 Di III is clearly softer especially in the transition zone and the background. The transition zone is free of color artifacts or double contours (see 100% crop below).
The Tamron 35-150mm f2-2.8 Di III achieves a maximum magnification of around 1:5 (depending on focal length) in close-up shooting. The following images were shot at 35mm focal length and 1:4.7 magnification where the area of sharp focus is just 169 x 113mm. The 100% crops shown below are from 0mm, 12mm, and 17mm off the center of the sensor respectively. For the following crops I focused once on the center wide open and did not change focus: Each row of crops is from the same shot, focused optimally for the center. So this is the best results you can get from a single shot of a flat subject as any issues with field curvature show up here.
The lens is pretty sharp in the center even at f2.0. But outside the center quality deteriorates very quickly. Even stopped down to f11 the outmost crop (17mm image height) stays mushy. This is only in part due to field curvature which the following crops show where I focused specifically for each crop: The results are still not very satisfying:
Using the lens at 150mm focal length produces better results outside the center with less field-curvature. The following images were shot at 150mm focal length and 1:5.3 magnification where the area of sharp focus is just 191 x 127mm. Crops are from 0mm, 13mm, and 18mm off the center of the sensor respectively:
Focusing each crop separately yields slightly better results:
Flare, ghosting, and sun-stars
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 the new Tamron 35-150mm f2-2.8 Di III for these artifacts I went through a series of well calculated shots against a strong light source to provoke glare and ghosting. The lens hood was mounted in all shots. Following are just two examples at different focal lengths. 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 35-150mm f2-2.8 Di III behaves pretty well at the short end with very little veiling glare even when the light source is near the center. But at the long end it can produce quite some ghosting artifacts and overall contrast is considerably reduced through veiling glare.
Sunstars start to form at f5.6 but become clearly more prominent at f8 and f11:
Next check out my sample images!Check prices on the Tamron 35-150mm f2-2.8 Di III at B&H, Adorama, WEX UK or Calumet.de. Alternatively get yourself a copy of my In Camera book or treat me to a coffee! Thanks!