This is the second part of my experience review of the Sigma 105mm f/1.4, the craziest lens I’ve ever had the pleasure of owning. Over the last several years, I used the Sigma 105mm f/1.4 almost exclusively for my astrophotography work and it completely changed the way that I photograph the night sky.
This is the second part of my review of the Sigma 105mm f/1.4 DG HSM Art lens. You can read the landscape-centric first part of my review of the Sigma 105mm f/1.4 Art Lens here. Although the primary marketing for this lens is centered around portrait photography, it was actually designed with astrophotography in mind. Sigma’s lens information page says that the lens is “ideal for portrait and astro photographies”. After a few years of use, I would have to agree.
In the first post of this review series, I talked about how I used the Sigma 105mm f/1.4 Art lens almost exclusively for landscape photography in Iceland. In that post, I shared some of my favorite large format panoramas shot with the Sigma 105mm f/1.4 Art and talked about the experience of how different it feels to shoot landscape astrophotography exclusively with a medium telephoto lens. But my original goals for how I would use this lens centered around its performance for astrophotography and how well it would work for making large format astrophotography panoramas. Let’s jump right into why this is the best lens that I’ve ever used for astrophotography.
Sharpness and Aberration
One of the most important quality traits I desire out of any lens is sharpness. I was most excited with the Sigma 105mm f/1.4 Art lens’s aberration performance at low f/numbers when shooting stars and, secondarily, its vignetting performance at low f/numbers.
With coma and astigmatism performance of the 105mm Art being nearly flawless, the Sigma 105mm f/1.4 Art lens is the best I have ever used in this regard.
Wide-open at f/1.4, straight out to the extreme corners, the Sigma 105mm f/1.4 Art has almost no tangible aberrations. Maybe there’s a very slight drop in sagittal sharpness (sagittal astigmatism), but relative to the overall image size, any apparent aberration is minuscule and is only present in the very extreme corners. Stop it down to f/2 or f/2.8 and it’s basically sharper than razor sharp. There is absolutely no chromatic aberration or color separation visible either.
On this long of a lens, you’re pretty limited in terms of untracked night sky shots, but since it has such a bright f/1.4 aperture, it’s possible to just dial in f/1.4, and 5 seconds for the exposure and the result will be a very nice exposure of the night sky with nearly perfect pinpoint stars. The Sigma 105mm Art may have been designed as the perfect portrait lens, but it’s also a perfect astrophotography lens. Seriously, I’ve never used an f/1.4 lens with this level of perfection wide open. The large aperture makes it possible to shoot very low-noise untracked astrophotos.
When you buy a lens like this, you buy it to use it wide open at f/1.4. Luckily, there are almost no reasons not to use it at f/1.4. Combine this lens with a stacking or tracking method, and you’ve got a full-fledged wide-field astrophotography telescope.
One of the most helpful traits of a lens for my uses with panorama creation is its vignetting performance. In order to improve the processing workflow and results of panorama stitching, I wanted a lens that had as little light falloff (vignetting) in the corners as possible when shooting wide open. The less vignetting, the easier it is to correct in post-processing without detrimentally increasing noise in the corners of each frame. The Sigma 105mm f/1.4 Art excels in this regard when compared to most other f/1.4 lenses.
In the case of the Sigma 105mm f/1.4, there’s certainly some very mild vignetting when set to f/1.4. Upon stopping down, vignetting diminishes quickly and is insignificant by f/2.5 and higher f/numbers.
But shooting at f/1.4 is completely viable, even for panorama stitching. At f/1.4, corners are only about 1.5 stops darker than the center of the image when shooting wide open. Overall, this level of light falloff is minor for an f/1.4 lens and is exceptionally easy to correct in Adobe Lightroom with automatic profile corrections enabled. Along with the overall brightness increase that comes along with the f/1.4 aperture, corrected f/1.4 corners remain nearly noise free.
After some practice with panorama stitching software, PTGui Pro, and by combining the auto lens corrections in Lightroom with those in the PTGui Pro software, I actually became quite comfortable shooting astrophotography panoramas with the 105mm wide-open at f/1.4. This allowed me to take full advantage of the massive aperture of the lens for making extremely low noise images in otherwise difficult, dark conditions.
The advantage of the Sigma 105’s huge aperture size becomes immediately apparent in the resulting panoramas. Foregrounds that would have otherwise been pitch black, or exceptionally noisy with a less than 5 second exposure are revealed in full color with minimal noise levels. Colors that are completely invisible to the naked eye, like the celeste blue-green of the Menorcan shoreline, are easily revealed by the massive light gathering power of this lens.
One of the more obvious challenges I encountered while using this lens at night when creating these large panoramas is the exceptionally narrow depth of field. When focusing to infinity for the stars, the foreground quickly blurs out of focus, creating a look more akin to a large format photograph from a view camera, shot wide open.
Sharp stars with SharpStar2
The short depth of field also means that accurate focusing is significantly more critical to the success of the image. Using a focusing tool like my SharpStar2 focusing filter is highly recommended when using a longer lens like this. Even the slightest bump of the focusing ring can throw the stars out of focus, so the precision gained by using the SharpStar2 helps dramatically and the visual confirmation of focus adds a lot of confidence in assuring proper focus.
Regardless of aperture setting, when focus is accurate, the stars are so sharp and pinpoint-like that they can almost get lost relative to the whole image. At scale, using a long lens provides significantly more resolution over a short focal length lens and so using the Sigma 105mm f/1.4 Art to shoot landscape astrophotography creates night sky images where the dimmest stars melt away and only the very brightest, most colorful stars shine through. As a result, the structures of the Milky Way: the dark dust lanes and glowing nebulae, take more of a front seat to the constellations.
Because of this trait, shooting astrophotography with the Sigma 105mm f/1.4 Art lens may benefit from a fog filter to diffuse the light of the brightest stars to bring out more distinct constellations and augment the color of the stars. One of the problems, though, is that the lens also has a really large 105mm diameter front filter thread.
Filters in this huge size are only rarely available and only a few square filter systems have appropriate adaptor rings in the 105mm diameter. B&H has a number of 105mm fog filters listed, but they’re rarely in stock. If you have the Sigma Art and happen to see one of these exceptionally rare 105mm filters in stock, I’d recommend snatching it up.
One of the main advantages of using a lens like this is its ability to capture so much more light and as a result, more color, particularly from emission and reflection nebulae. Ultimately, it’s all about getting the most from the f/1.4 aperture. The larger aperture makes each exposure more likely to overcome noise from the camera sensor and residual heat and as a result images should have better colors straight out of the camera. A better exposure straight away makes shooting and processing easier because less total exposure will be required to mitigate noise when using a stacking method of processing. With a little bit of LRGB processing, photos from the Sigma 105mm f/1.4 are fairly easy to pull out a plethora of colors. Pointing it toward the Rho Ophiuchi region of the night sky reveals the colorful reflection nebula around the bright star Antares.
And under the right conditions, the larger aperture of the Sigma 105mm f/1.4 Art lens makes it much easier to reveal the subtle green and magenta colors of airglow in the upper atmosphere. This phenomenon is similar to aurora and is caused by the excitation of atomic oxygen and other elements in the atmosphere. It is visible at all latitudes, but is much dimmer than aurora.
At 105mm, it’s fairly easy to treat this lens like a telescope. Specification for specification, it’s basically an exceptionally well-corrected wide-field 75mm apochromatic refractor telescope with the perk of autofocus capabilities.
Shooting Experience and Thoughts
Having spent several years shooting with this lens, there is only one significant issue I have with it: its size. It’s big and heavy, long and wide. It’s just a monster. To support it on my tripod, I use a custom built DIY panorama head that’s beefy enough for such a large lens, but small enough to not add to much to my already heavy camera bag.
I’m still personally attached to the process of wide angle landscape astrophotography and attempting this type of photography with such a long lens (and the use of panorama stitching) is not particularly easy, but the satisfaction I get from this lens are unmatched.
Even with the challenges that come along with large format astrophotography panoramas, the Sigma 105mm f/1.4 Art brings so many advantages that make the process easier. The exceptionally bright f/1.4 aperture makes focusing and composition trivial, especially when paired with the SharpStar2 and the Sony Alpha camera’s “bright monitoring” feature available on most of my camera bodies like the a7III and a7C (on the a7S, I often use PP7 if I need help with composition).
One of the more subtle features that improved my experience when using this lens was the built-in Arca dovetail on the tripod collar shoe. Most lens manufacturers have only a single 1/4″-20 threaded insert in their tripod collar, which makes it necessary to install some kind of tripod plate in order to mount the lens to a tripod head.
But with the Sigma 105mm f/1.4 Art, you can just set the tripod collar shoe directly into any Arca clamp, no additional plate required. The tripod shoe also has two removable slide-stop retaining screws on either size of the dovetail so that the lens won’t slide off of a loose clamp and fall to the floor.
While the lens tripod collar is technically removable, the only reason I can think of not using it would be if you were exclusively using the lens for hand-held portraiture and felt that it got in the way.
After several years of using the Sigma 105mm f/1.4 Art, I think my standards for image quality have shifted, and it’s this lens exclusively that has raised the bar. As a tool for creating large format panoramas, its exceptional sharpness, aberration free rendering, minimal vignetting and solid build quality have all set the standard by which I will judge every lens from today forward.
I and my arms will tell you straight away that I wish so deeply that there was a more compact “DN” version of this lens designed exclusively for mirrorless cameras. The design tested here would clearly be more balanced on larger DSLR body like a Canon 5D Mark IV or Nikon D850. It’s a little awkward on my Sony mirrorless bodies. Sigma has already shown us what they can do with their Sigma 85mm f/1.4 DG DN Art lens in terms of reducing the size of a lens designed exclusively for mirrorless camera bodies. And so I’ll wait and wish for a future 105mm version: the not-yet-realized Sigma 105mm f/1.4 DG DN Art, which will hopefully one day grace my camera bag. Let’s go Sigma.
Until then, this is it, the monster, the one lens to rule them all, the very best camera lens I have ever used, ever: the Sigma 105mm f/1.4 DG HSM Art. With it, I’ve become a stronger photographer, both figuratively and literally. I’ll likely never approach astrophotography in the same way because of this lens and for that, I’m ever grateful that Sigma has made such an amazing tool available to all of us.
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This is the gear that I used to shoot most of the photos from this post
- Sony a7S
- Sigma 105mm f/1.4 Art Lens
- Leofoto LS-284C Tripod
- Wireless Shutter Remote
- Custom DIY Panorama Head
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-Ian and Diana