The Tamron 20mm f/2.8 for Sony full-frame (and APS-C) cameras is a relatively low-cost alternative to the native Sony 20mm f/1.8 lens. The Tamron is about 1/3 the cost of the Sony, but how does it stack up in terms of performance and image quality? Read on for my impression of this lens.
Tamron 20mm f/2.8 Quick Overview
Let’s run down the basic stats and then I’ll get into my overall thoughts on this lens.
- Focal Length: 20mm
- Mount: Sony E Mount (full frame coverage, but also works for APS-C)
- Max/Min Aperture: f/2.8 – f/22
- Aperture Blades: 7
- Focus Type: AF
- Magnification Ratio: 1:2
- Minimum Focusing Distance: 4.3 inches / 11 cm
- Glass: 10 Elements in 9 Groups
- Filter Thread: 67mm
Overall Impression: Tamron 20mm f/2.8
First, here’s the full name of the lens from Tamron: 20mm F/2.8 Di III OSD M1:2 (Model F050). Wow, what a mouthful! But Tamron has a tradition of long product names, so this should not come as a surprise.
Overall, I think this is a very capable lens, especially considering the price point of $299 USD. Consider the lens it was designed to compete with: the Sony 20mm f/1.8 G, which runs about $900 USD retail (and is significantly larger and heavier). For reasons outlined below, the Tamron 20mm is a no-brainer for landscape photographers on a budget or travel photographers looking for a light-weight wide prime lens.
The overall image quality is very good, in my opinion. I was actually rather impressed given some of the less-than-amazing reviews of this lens that I’d read right after it hit the market. The center of the image is exceedingly sharp and crisp, and edge/corner sharpness is respectable as well when stopped down to f/4 or higher. As far as I can tell, there isn’t a noticeable color bias with this lens. Chromatic aberration is very well controlled at all aperture settings, based on my testing. Bokeh is pleasing enough, although it likely won’t wow anyone…and for a wide angle lens, this is perfectly acceptable.
What’s in the Box?
The Tamron 20mm comes with a plastic petal hood, as well as the expected front and rear lens caps. There’s nothing extra (bag, cleaning cloth, etc), but also nothing missing that should be in there.
Here are some sample images taken with the Tamron 20mm and shot with a Sony A7III body. Keep in mind these are not meant to be artistic, but rather highlight the strengths and weaknesses of the lens.
A shot of my neighbor’s hideous fence to show the amount of barrel distortion (as well as vignetting) exhibited by the lens. First image is minimally processed. Second is the same image, but with the lens correction profile applied in Adobe Camera RAW. I used the default amount of distortion correction, which straightens the fence but noticeably distorts the edges of the image.
Exposure: f/2.8, 1/1600, ISO 200
Focus point is a bud on a rhododendron bush in my back yard. This displays center sharpness, as well as highlights the quality of the bokeh. First image is full frame. Second is a 100% crop of the center.
Exposure: f/2.8, 1/200, ISO 200
A shot of deck railing to, again, show distortion and how it can be corrected in post processing. First is minimally processed. Second is the same image, but with the lens correction profile applied in Adobe Camera RAW. For this one, I only used 85% of the standard correction amount, as 100% looked over-corrected.
Exposure: f/2.8, 1/4000, ISO 200
Simple shot of a seltzer can. First without lens profile corrections applied; second with corrections. Based on the default distortion correction in the profile, I’d recommend going with something less than 100%.
Exposure: f/4, 1/250, ISO 200
Overall Image Quality
As I already stated, this is a very sharp lens. Surprisingly so, in fact, and even at the widest aperture settings. Based on my testing, peak center sharpness is somewhere between f/4 and f/5.6, while corner sharpness climaxes around f/8.
I think the color rendition, contrast, and overall clarity are very good. Perhaps not G Master good, but it’s also a small fraction of the price.
Surprisingly, there is almost no chromatic aberration to be found, even with high glare elements in an image. This is very unusual for sub-$1000 lenses, and even uncommon for higher priced glass.
Size / Weight / Build
This is a compact lens, weighing just under 8 ounces (~220g), a length of 2.5 inches (64mm), and a maximum diameter of 2.9 inches (73mm). It’s the perfect size and weight for travel photography and is easy to fit in a small bag. It’s also a nice option for street photographers, as it’s small size won’t draw a lot of attention. Street photogs usually like a more mid-range focal length (35mm – 50mm), but the Tamron 20mm is a nice option for wider shots, or the images could be cropped to tighten up the field of view.
Build quality is quite nice. It’s mostly a metal-plastic composite, with a metal mount. The weight, while light, is heavy enough for the size to give it a nice heft/feel. The focus ring is smooth, easy to grip, and well damped.
All around, I really believe the performance for value trade off on this lens is exceptional. It won’t be right for everyone, but value-minded shutterbugs would do well to consider the Tamron 20mm as a serious contender for the “very wide” prime spot in their bag. It’s perhaps best for stills rather than video (see notes of AF performance below).
The Tamron 20mm isn’t going to blow anyone’s mind with it’s AF performance. In my testing, AF-S mode is quite accurate, albeit a bit slow. Also, it does a full rack to find focus in this mode, which is sort of a primitive way of doing things and does take a lot longer. I hope Tamron addresses this in a future firmware update.
In AF-C mode, things are both better and worse. In ideal lighting conditions, AF-C performs fairly well, but there is the occasional missed focus that loops forever and never finds itself. Eye AF works nicely. However, in lower-light conditions, continuous focus mode regularly misses focus and can’t recover. Again, I hope this is resolved in a Tamron firmware update.
Front Focusing Up Close
It might just be my copy of this lens, but I’ve noticed that almost all images I’ve shot at distances less than about 10 inches display noticeable front focusing. To overcome this requires stopping down to f/5.6 or smaller. Again, this could just be my copy, and probably I could also make micro-adjustments in the camera body, but it’s something to consider. Anyone doing macro work is going to manually focus anyway.
A lot of reviews call out the Tamron 20mm for having a very loud focus motor. I personally don’t think it’s loud, but it’s definitely not silent like a Canon USM lens…or even other Tamron lenses in this same series. If you are doing video projects and using the in-camera microphone or an omni mic mounted on the camera hotshoe, it might be a bit loud for your uses.
Distortion and Vignetting
As to be expected on lens with this wide of a field of view (94 degrees, according to Tamron), there is noticeable barrel distortion and light falloff (vignetting) at the edges of the images. Both are correctable in post processing (and without much effort at that), but distortion correction comes at a cost of stretched edges of the images. For some applications, this will be fine, and for others (people near the edges of the image) it will be problematic. The Tamron 20mm lags behind more expensive options in this regard.
Weather Sealing…Sort Of
While it’s not weather sealed, per se, Tamron does claim this lens is “moisture resistant” and “dust resistant”. I’ve shot this lens twice in light drizzle with no issues. I can’t speak to the dust resistant claim, but it does seem to handle light precipitation well. Still, this doesn’t quite measure up to a proper weather sealed lens.
Honestly, I can’t find anything really “bad” about this lens. The AF isn’t amazing, but it’s $300 and you can’t have everything for that price. It holds up very well to at least a 24MP sensor, such as found in the A7II and A7III bodies.
If you are looking for a wide prime for street vlogging that needs super-quiet and very accurate continuous autofocus, this is NOT your lens. For the other 95% of us, the Tamron 20mm is a really good inexpensive option to put a wide prime lens in your arsenal. It’s sharp with very good IQ, has okay AF, is small and light, and won’t break the bank. Also, it can almost take the place of a macro lens with it’s super-short minimum focusing distance. Hard to beat it as a value lens, in my view.