The Tamron 20mm f/2.8 Di III OSD M1:2 is a good wide angle for the Sony system.

The Tamron 20 mm f/2.8 Di III OSD M1:2 is part of a series of three new wide-angle lenses for Sony: the Tamron 20 mm f/2.8 Di III OSD M1:2, the Tamron 24 mm f/2.8 Di III OSD M1:2 and the Tamron 35 mm f/2.8 Di III OSD M1:2. The lenses have a fixed focal length and are not very bright at f/2.8. Certainly for the 35mm, you might expect a little more. The brightness is not too bad for the 20mm. You buy a 20mm wide angle more for wide landscapes than for the ultimate bokeh. And you will probably use a lens like this more at f/5.6 or f/8 than at full aperture. The same applies to the dimensions. The 35 mm f/2.8 is a bit on the big side considering the low brightness, but it is not bad for a 20 mm.

Tamron has chosen to give the three wide-angle lenses the same dimensions. They also have the same design and 67 mm filter size as the f/2.8 zooms for Sony, the Tamron 28-75 mm f/2.8 Di III RXD and the Tamron 17-28 mm f/2.8 Di III RXD.  Of course they are a lot shorter than those zooms and also considerably lighter and cheaper. This makes the Tamron 20 mm f/2.8 Di III OSD M1:2 a good alternative to the previously released Tamron 17-28 mm f/2.8 Di III RXD wide-angle zoom.  It only weighs half as much as the zoom and takes up less space. The Tamron 20 mm f/2.8 Di III OSD M1:2 is therefore, for example, a nice addition to the Tamron 28-75 mm f/2.8 Di III RXD and a good alternative to the wide-angle zoom for photographers who like to travel light.

Macro

The three new wide-angle lenses have a great feature that you will not find on the zooms, and that’s the ability to focus to a magnification of 1:2. Because of this, you can get almost-macro photos with a lot of background in view. That creates different images than you can make with a longer macro lens.

BUILD AND OPERATION

The Tamron 20 mm f/2.8 Di III OSD M1:2 has the same plastic housing as the 24 mm and 35 mm. The use of plastic makes it feel less high-quality than, for example, a Zeiss Batis lens. But that’s a purely emotional argument. High-quality plastic does not have to be less good than metal. The advantage is that the housing feels better in cold weather and that the whole lens is a bit lighter. At 220 grams, the 20 mm is really a lightweight. At the same time it is sealed against dust and moisture and the Tamron 20 mm f/2.8 Di III OSD M1:2 has a gasket on the back.

The lens is also fairly simple. The only control element is the wide focus ring. The lens has no AF/MF switch, image stabilization or Focus Lock button. This makes it easier to seal this lens, of course. The front lens has a fluorine coating which makes it less easy to attach moisture, grease and dirt to the glass and makes it easier to clean the front lens.

IMAGE QUALITY

The Tamron 20 mm f/2.8 Di III OSD M1:2 performs exceptionally well. The sharpness is excellent at full aperture, with only a very small gradient from the center to the corners. If you use the corrections in the camera or – in the near future – the corrections for the RAW files in software, then that image remains the same for all apertures. For a 20mm wide angle, that’s very good, especially on the 60-megapixel A7R IV.  Cameras with so many pixels are very critical and reveal every down side of a lens. That the gradient is so even says a lot about the quality of this 20 mm. You can find some purple-colored edges when you shoot fine, dark subjects against a gray sky. On the other hand, the 20mm hardly suffers from flare at all due to that good coating.

The vignetting is very low, both in RAW and in the jpegs. In RAW, it is only a fraction more than in the corrected jpegs, and with the corrections on, it’s just a bit more than one stop at full aperture. At f/4, that’s almost half, and with further stopping down, it decreases a little more. Certainly for a 20mm wide angle, these are nice values.

The values for the distortion look very different from those for vignetting. In RAW, the distortion is a substantial 8%.  A few years ago, we would have found that a significant minus. But modern lenses for mirrorless cameras are designed to be used with the corrections in the camera. With the Tamron 20 mm f/2.8 Di III OSD M1:2, you therefore see no excessive loss of sharpness in the corners as a result of the elimination of the distortion. With the corrections on, the distortion is around 0.8%, and that’s a value that you will not be bothered by in practice.

This is what 8% distortion looks like if you do not use the corrections. But why would you want to do that:

With the corrections in the camera on, this is what you can expect in the viewfinder and in the end result:

Autofocus

The Tamron 20mm f/2.8 Di III OSD M1:2 focuses reasonably quickly and quietly. It uses the OSD (Optimized Silent Drive), not the RXD motor that we find in the zoom lenses. A difference between the 20 mm and, for example, the 17-28 mm f/2.8 zoom is that with the 20 mm there is no internal autofocus, but the entire lens group moves for focusing. Partly because of this, the autofocus is a fraction slower. You will also see a significant change in the image ratio during focusing. That’s not great for video, because it creates a lot of focus breathing. Also, the autofocus sometimes has to search a little more for the right focus in low light than Sony’s own wide angles. The focus is very accurate.

SPECIAL FUNCTIONS

What’s great about the Tamron 20 mm f/2.8 Di III OSD M1:2, and that also applies to the 24 mm and 35 mm, is that it can focus very close. In the case of the 20 mm, that is up to 11 cm. This produces a magnification scale of 1:2. A subject of about 6 centimeters in size is almost full screen. Because the Tamron 20 mm f/2.8 Di III OSD M1:2 is a wide-angle lens, you can get more background in frame than with macro lenses with a longer focal length, even more than with the 24 mm and 35 mm. You can use that beautifully by photographing flowers or insects in their environment. Of course, your depth of field with very short shooting distances is very small. And then the quality of the bokeh is important. And that’s perfectly fine on the Tamron 20mm f/2.8 Di III OSD M1:2. 

The Tamron 20 mm f/2.8 Di III OSD M1:2 has a nine-blade diaphram that ensures beautiful round bokeh balls at full aperture. The bokeh is very nice, with hardly any hard edges and little restlessness in the soft areas. With a 20 mm, you will normally not see much blur in the background, but because it can focus very close to 20 mm, it is reassuring to know that the background looks good with such close-up shots.

COMPARED TO THE COMPETITION

While you have more choice for the 35 mm and 24 mm, the Tamron 20 mm f/2.8 Di III OSD M1:2 has fewer direct competitors. Samyang has released the Samyang AF 18 mm f/2.8 FE. That lens is a bit lighter and a lot smaller, but it lacks the weather resistance and close-focus capability of the Tamron. Another option is the Zeiss Batis 18 mm f/2.8. We found that lens to be one of the best wide angles for the Sony cameras. Just like the Tamron, it is weatherproof, but it lacks the unique macro capability of the Tamron. The Zeiss does have a metal housing and a nice OLED screen. You pay for that, because it costs double the Tamron.

TAMRON 20MM F/2.8 DI III OSD M1:2 (MODEL F050) FOR SONY FE

Curious about the performance of the Tamron 20 mm f/2.8 Di III OSD M1:2 in practice? Click on the button below and visit our renewed web gallery with sample images. The images can be downloaded in full resolution to be viewed at 100%.

ConclusiON: REVIEW TAMRON 20MM F/2.8 DI III OSD M1:2 (MODEL F050) @ SONY A7R mk4