Testing the Venus Optics Laowa 15mm f/2 Lens

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by Alan Dyer of amazingsky.net

I test out a fast and very wide lens designed specifically for Sony mirrorless cameras.

In a test on my blog at www.amazingsky.net published May 31, 2018 I presented results on how well the Sony a7III mirrorless camera performs for nightscape and deep-sky photography. It works very well indeed.

But what about lenses for the Sony? Here’s one ideal for astrophotography.

TL;DR Conclusions

Made for Sony e-mount cameras, the Venus Optics 15mm f/2 Laowa provides excellent on- and off-axis performance in a fast and compact lens ideal for nightscape, time-lapse, and wide-field tracked astrophotography with Sony mirrorless cameras. (Sorry, Canon and Nikon users, it is not available for other lens mounts.)

I use it a lot and highly recommend it.

Size and Weight

While I often use the a7III with my Canon lenses by way of a Metabones adapter, the Sony really comes into its own when matched to a “native” lens made for the Sony e-mount. The selection of fast, wide lenses from Sony itself is limited, with the new Sony 24mm G-Master a popular favourite (I have yet to try it).

However, for much of my nightscape shooting, and certainly for auroras, I prefer lenses even wider than 24mm, and the faster the better.

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The Laowa 15mm f/2 from Venus Optics fills the bill very nicely, providing excellent speed in a compact lens. While wide, the Laowa is a rectilinear lens providing straight horizons even when aimed up, as shown above. This is not a fish-eye lens.

Though a very wide lens, the 15mm Laowa accepts standard 72mm filters. The metal lens hood is removable. © 2019 Alan Dyer

Though a very wide lens, the 15mm Laowa accepts standard 72mm filters. The metal lens hood is removable. © 2019 Alan Dyer

The Venus Optics 15mm realizes the potential of mirrorless cameras and their short flange distance that allows the design of fast, wide lenses without massive bulk.

Sigma 14mm f/1.8 Art lens (for Nikon mount) vs. Venus Optics 15mm f/2 lens (for Sony mount). © 2019 Alan Dyer

Sigma 14mm f/1.8 Art lens (for Nikon mount) vs. Venus Optics 15mm f/2 lens (for Sony mount). © 2019 Alan Dyer

For me, the Sony-Laowa combination is my first choice for a lightweight travel camera for overseas aurora trips.

The lens mount showing no electrical contacts to transfer lens metadata to the camera. © 2019 Alan Dyer

The lens mount showing no electrical contacts to transfer lens metadata to the camera. © 2019 Alan Dyer

However, this is a no-frills manual focus lens. Nor does it even transfer aperture data to the camera, which is a pity. There are no electrical connections between the lens and camera.

However, for nightscape work where all settings are adjusted manually, the Venus Optics 15mm works just fine. The key factor is how good are the optics. I’m happy to report that they are very good indeed.

Testing Under the Stars

To test the Venus Optics lens I shot “same night” images, all tracked, with the Sigma 14mm f/1.8 Art lens, at left, and the Rokinon 14mm SP (labeled as being f/2.4, at right). Both are much larger lenses, made for DSLRs, with bulbous front elements not able to accept filters. But they are both superb lenses. See my test report on these lenses published in 2018.

The Sigma 14mm f/1.8 Art lens (left) vs. the Rokinon SP 14mm f/2.4. © 2019 Alan Dyer

The Sigma 14mm f/1.8 Art lens (left) vs. the Rokinon SP 14mm f/2.4. © 2019 Alan Dyer

The next images show blow-ups of the same scene (the nightscape shown in full below, taken at Dinosaur Provincial Park, Alberta), and all taken on a tracker.

I used the Rokinon on the Sony a7III using the Metabones adapter which, unlike some brands of lens adapters, does not compromise the optical quality of the lens by shifting its focal position. But lacking a lens adapter for Nikon-to-Sony at the time of testing, I used the Nikon-mount Sigma lens on a Nikon D750, a DSLR camera with nearly identical sensor specs to the Sony.

Vignetting

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A tracked image with the Venus Optics Laowa 15mm at f/2.

Above is a tracked image (so the stars are not trailed, which would make it hard to tell aberrations from trails), taken wide open at f/2. No lens correction has been applied so the vignetting (the darkening of the frame corners) is as the lens provides.

As shown bottom right, when used wide open at f/2 vignetting is significant, but not much more so than with competitive lenses with much larger lenses, as I compare below.

And the vignetting is correctable in processing. Adobe Camera Raw and Lightroom have this lens in their lens profile database. That’s not the case with current versions (as of April 2019) of other raw developers such as DxO PhotoLab, ON1 Photo RAW, and Raw Therapee where vignetting corrections have to be dialled in manually by eye.

A tracked image with the Venus Optics Laowa 15mm stopped down 1 stop to f/2.8.

A tracked image with the Venus Optics Laowa 15mm stopped down 1 stop to f/2.8.

When stopped down to f/2.8 the Laowa “flattens” out a lot for vignetting and uniformity of frame illumination. Corner aberrations also improve but are still present. I show those in close-up detail below.

15mm Laowa vs. Rokinon 14mm SP vs. Sigma Art 14mm – Comparing the left side of the image for vignetting (light fall-off), wide open and stopped down. ©2018 Alan Dyer

15mm Laowa vs. Rokinon 14mm SP vs. Sigma Art 14mm – Comparing the left side of the image for vignetting (light fall-off), wide open and stopped down. ©2018 Alan Dyer

Opposite page bottom right, , I compare the vignetting of the three lenses, both wide open and when stopped down. Wide open, all the lenses, even the Sigma and Rokinon despite their large front elements, show quite a bit of drop off in illumination at the corners.

The Rokinon SP actually seems to be the worst of the trio, showing some residual vignetting even at f/2.8, while it is reduced significantly in the Laowa and Sigma lenses. Oddly, the Rokinon SP, even though it is labeled as f/2.4, seemed to open to f/2.2, at least as indicated by the aperture metadata.

On-Axis Performance

15mm Laowa vs. Rokinon 14mm SP vs. Sigma Art 14mm – Comparing the centre of the image for sharpness, wide open and stopped down. Click or tap on an image to download a full-resolution JPG for closer inspection © 2018 Alan Dyer

15mm Laowa vs. Rokinon 14mm SP vs. Sigma Art 14mm – Comparing the centre of the image for sharpness, wide open and stopped down. Click or tap on an image to download a full-resolution JPG for closer inspection © 2018 Alan Dyer

Above I show lens sharpness on-axis, both wide open and stopped down, to check for spherical and chromatic aberrations with the bright blue star Vega centered. The red box in the Navigator window at top right indicates what portion of the frame I am showing, at 200% magnification in Photoshop.

On-axis, the Venus Optics 15mm shows stars just as sharply as the premium Sigma and Rokinon lenses, with no sign of blurring spherical aberration nor coloured haloes from chromatic aberration.

This is where this lens reaches sharpest focus on stars, just shy of the Infinity mark. © 2019 Alan Dyer

This is where this lens reaches sharpest focus on stars, just shy of the Infinity mark. © 2019 Alan Dyer

Focusing is precise and easy to achieve with the Sony on Live View. My unit reaches sharpest focus on stars with the lens set just shy of the middle of the infinity symbol. This is consistent and allows me to preset focus just by dialing the focus ring, handy for shooting auroras at -35° C, when I prefer to minimize fussing with camera settings, thank you very much!

Off-Axis Performance

15mm Laowa vs. Rokinon 14mm SP vs. Sigma Art 14mm – Comparing

15mm Laowa vs. Rokinon 14mm SP vs. Sigma Art 14mm – Comparing

The Laowa and Sigma lenses show similar levels of off-axis coma and astigmatism, with the Laowa exhibiting slightly more lateral chromatic aberration than the Sigma. Both improve a lot when stopped down one stop, but aberrations are still present though to a lesser degree.

However, I find that the Laowa 15mm performs as well as the Sigma 14mm Art for star quality on- and off-axis. And that’s a high standard to match.

The Rokinon SP is the worst of the trio, showing significant elongation of off-axis star images (they look like lines aimed at the frame centre), likely due to astigmatism. With the 14mm SP, this aberration was still present at f/2.8, and was worse at the upper right corner than at the upper left corner, an indication to me that even the premium Rokinon SP lens exhibits slight lens de-centering, an issue users have often found with other Rokinon lenses.

Real-World Examples – The Milky Way

The fast speed of the Laowa 15mm is ideal for shooting tracked wide-field images of the Milky Way, and untracked camera-on-tripod nightscapes and time-lapses of the Milky Way.

Image aberrations are very acceptable at f/2, a speed that allows shutter speed and ISO to be kept lower for minimal star trailing and noise while ensuring a well-exposed frame.

This is a stack of 8 x 2-minute exposures with the Venus Optics Laowa 15mm lens at f/2 and Sony a7III at ISO 800, on the Sky-Watcher Star Adventurer tracker. A single exposure taken through the Kenko Softon A filter layered in with Lighten mode adds the star glows, though exaggerates the lens distortion on the bright stars.

This is a stack of 8 x 2-minute exposures with the Venus Optics Laowa 15mm lens at f/2 and Sony a7III at ISO 800, on the Sky-Watcher Star Adventurer tracker. A single exposure taken through the Kenko Softon A filter layered in with Lighten mode adds the star glows, though exaggerates the lens distortion on the bright stars.

This is a stack of 12 exposures for the ground, mean combined to smooth noise, and one exposure for the sky, all 30 seconds at f/2 with the Laowa 15mm lens on the Sony a7III camera at ISO 6400. These were the last frames in a 340-frame time-lapse sequence.

This is a stack of 12 exposures for the ground, mean combined to smooth noise, and one exposure for the sky, all 30 seconds at f/2 with the Laowa 15mm lens on the Sony a7III camera at ISO 6400. These were the last frames in a 340-frame time-lapse sequence.

The fast speed of the Laowa 15mm is ideal for shooting tracked wide-field images of the Milky Way, and untracked camera-on-tripod nightscapes and time-lapses of the Milky Way.

Image aberrations are very acceptable at f/2, a speed that allows shutter speed and ISO to be kept lower for minimal star trailing and noise while ensuring a well-exposed frame.