Alongside the new FE 28mm f/2, Sony released two conversion lenses that attach to the 28mm and turn the combination into a 21mm ultra-wide lens and a 16mm fisheye lens. Today, I’m reviewing the 21mm ultra-wide conversion lens, otherwise known as the SEL075UWC. The 21mm conversion lens attaches to the front of the FE 28mm and creates a 21mm f/2.8 lens combination with full autofocus and autoaperture. EXIF data is passed along as well, so the in-body image stabilization of the A7 II and new A7R II will automatically work at the correct focal length. The 21mm conversion lensretails for $249, so it’s an inexpensive way to gain an autofocus ultra-wide for your full-frame E-Mount camera. Sometimes these add-on lenses are more hype than real imaging solution, so I was very interested to see which of these things is true of the 21mm lens. One thing before we start: If you haven’t seen my review of the FE 28mm f/2, make sure you check that out as well.
Construction and Handling
Ok, to get one thing out of the way, writing “21mm Ultra-Wide Conversion Lens” is something that I don’t feel the need to do throughout this article. Likewise, I’ve never been fond of referring to Sony lenses by their stock number. So, at many points throughout the review, I’ll refer to the 28mm f/2 + 21mm UWA conversion lens as the “FE 21mm f/2.8.” There are two reasons for this. First, it’s a lot easier. Second, it’s the nomenclature that Sony uses in the EXIF data when the conversion lens is mounted. If it’s good enough for Sony, it’s good enough for this review.
The conversion lens is a simply plastic and glass lens with no moving parts and no electronics. The lens attaches to the FE 28mm f/2 via the hood bayonet mount, and it locks securely into place. A magnet sensor in the conversion lens tells the FE 28mm that it is mounted, and all camera information then views the lens as the FE 21mm f/2.8. The conversion lens is simple and sturdily built, but the connection feels a bit too flimsy to me. This doesn’t mean it wobbles excessively or anything, but rather I don’t know how much I would trust the lens to a solid knock near the front, and I don’t know how well that slim connector will hold up to repeated use. I would have preferred the bayonet on both pieces to be metal and a bit larger and more robust.
The FE 21mm f/2.8 combo turns the compact FE 28mm f/2 into a rather long and moderately heavy lens. I found the lens to handle well when shooting, though the process of detaching the UWA converter from the 28mm and putting it away, especially with the more difficult to attach rear cap, was less convenient than switching between two dedicated lenses, though the space saved in the bag vs. two different lenses is a nice bonus.
The FE 21mm has a unique lens cap that fits inside the fixed lens hood to seal the whole front of the lens. The cap is well designed and clicks securely in place. The reason for the oddly designed cap, is that the FE 21mm lacks any filter threads, so using a polarizer or neutral density filter is impossible without rigging up some ad-hoc square filter holder.
The FE 21mm f/2.8 focuses effectively as fast as the bare FE 28mm f/2 lens, which was a nice surprise. Despite the one stop slower aperture, there was no apparent difference to me in how the lens focused, both in speed and in accuracy. As the FE 28mm can struggle somewhat in dimmer light or backlit scenarios, so too can the combination with the UWA converter.
As I mentioned earlier, most add-on conversion lenses tend to do a number on image quality vs. the native bare lens. While there is some loss of definition to the files, I was very pleased to see that overall image quality of the FE 21mm f/2.8 combination was actually quite good.
Sharpness is the thing that suffers most with these conversion lenses, but overall, the FE 21mm conversion lens bucks this trend fairly well. While distortion correction does cause a notable reduction in corner sharpness, which I’ll talk more about in a bit, I was generally quite happy with the sharpness the FE 21mm produced. Starting from wide open, the lens starts with good central resolution, though rather poor edges and corners. However, upon stopping down to f/5.6 or smaller, the edges sharpen up considerably. While it’s not going to achieve critical edge-to-edge sharpness, as you might expect, the central 80% of the frame becomes very sharp, while the edges and corners do sharpen to a good level. While it’s not the sharpest ultra-wide lens in the world, it’s definitely good enough for most shooting, especially if you don’t shoot ultra-wide-angle a tremendous amount. Click on the image below and click the green arrow at the bottom of the screen to view the image at full size to get an idea of what you can expect.
Bokeh, Color and Contrast
I’m combining a few categories here, as in many cases there are close similarities to the FE 28mm f/2 that makes up over half the optical path when using the UWA converter. The UWA converter doesn’t appreciably alter the color, contrast or bokeh characteristics of the FE 28mm. The bokeh remains quite creamy when shot close up, and still fairly nice further away, though a bit more nervous. Color is natural and contrast is good without being overly punchy.
Distortion, Chromatic Aberration, Vignetting and Flare
If you’ve read my FE 28mm review, you’ll know that lens suffers from rather strong barrel distortion, and the UWA conversion lens simply adds to that distortion. In the major weakness of the FE 21mm, heavy barrel distortion will require digital correction for almost all shots. Simply consider it part of the workflow. Thankfully, JPEGs are automatically corrected and Lightroom has a profile as well that eliminates most of the distortion, though I found I often needed to add an additional few steps of correction beyond the profile.
While the FE 28mm performed quite well with regards to chromatic aberration, this is another area where the conversion lens adds a bit of fault. While lateral CA is still negligible, some purple fringing can be induced with the FE 21mm, especially at wide apertures. Vignetting, however, is actually slightly reduced with the 21mm converter attached.
Flare resistance, thankfully, continues to be excellent, with the FE 21mm turning in a performance with minimal ghosting and virtually no loss of contrast when shooting into bright light.
- Inexpensive way to add an ultra-wide lens to your kit
- Well constructed
- Good central sharpness and acceptable edges at smaller apertures
- Pleasing bokeh
- Excellent flare control
- Good color and contrast
- Edge sharpness is poor wide open
- Heavy barrel distortion without digital correction
- Some purple fringing possible at wide apertures
- Bayonet mount seems like it may not hold up over years of use
- Can’t use filters
I have to say, I didn’t really hold out very high hopes for the Sony 21mm Ultra-Wide Conversion lens. These sorts of lenses are often sub-par optically, but I’m glad to say that this lens is actually pretty good. While shooters who use ultra-wide-angle lenses often should probably look to the Zeiss FE 16-35mm f/4, the FE 21mm conversion lens allows you to get a nice ultra-wide lens for minimal additional cost. Overall sharpness is good, though not great, and the excellent flare control and solid color and contrast make this a very viable option for those seeking to go wider.
On the down side, there is heavy barrel distortion that effectively requires correction in post-processing, and the inability to use filters will limit some of its use as a landscape lens. If you really aren’t sure about buying the FE 28mm on its own, I’m not sure it’s worth it to purchase 28mm and this lens just for the 21mm capabilities. In many cases you may be better off saving up for the 16-35, or using a manual focus lens such as the Canon FD 20mm f/2.8, which should provide a bit better image quality.
However, for those who already own or are planning to buy the Sony FE 28mm f/2, I think the 21mm UWA conversion lens is almost a no-brainer add-on, unless you already have the FE 16-35mm. It’s inexpensive and definitely good enough to produce high-quality images.