What is the ultimate Canon astrophotography lens?
Do you own a Canon mirrorless camera? Our Best Canon Mirrorless Camera Astrophotography Lens page has your recommendations.
First, I need to clarify that I'm referring to nightscape, Milky Way, and general night sky photography that typically includes a foreground in the frame. If photographing deep-sky galaxies, nebulas, and other similar subjects, select a sharp telephoto lens and a quality equatorial tracking mount.
With that clarification out of the way — have you seen the Milky Way? Few subjects are as spectacular as this one.
I live under a moderately dark sky and get to see this incredible sight regularly. Still, I never grow tired of seeing it and will schedule photo trips to see it at other locations. I asked the question because most people (about 80% of Americans) cannot see the milky way from their homes, and a surprisingly high percentage have never seen this phenomenal sight. If you are among that percentage, you have an unchecked line item on the bucket list (add one of my photography workshops to your schedule?).
Here is a selection of nightscape pictures to inspire your interest.
Back to the lens selection. These are the characteristics of the ultimate astrophotography lens:
That is not an easy set of requirements to fill. Let's take a closer look at these requirements.
Selecting the optimal focal length is usually the first step in choosing a lens for any purpose, and it is for this one.
While nearly any wide angle of view can be used for nightscapes, I seldom use a focal length longer than 24mm and rarely go longer than 35mm (full-frame angle of view reference). The widest focal lengths available are great for this pursuit. The image immediately above is a 12mm capture.
Here is an illustration showing what the full-frame 14-35mm focal length range looks like with the Milky Way in the frame:
We see that the longer the focal length, the less Milky Way length fits in the frame. However, a longer focal length expands the width of the Milky Way in the frame, resulting in a higher percentage of the frame filled with Milky Way.
What is my favorite Milky Way lens focal length from an angle of view consideration? If I had to pick one, it would be 24mm. However, lenses covering 14mm, 20mm, and 24mm are usually in my Milky Way pack, and long exposures provide time to operate two camera setups simultaneously.
Other aspects must be factored into the focal length choice. For example, the longer the focal length, the shorter the exposure required not to exceed the minimum acceptable star trails. I'll talk more about this issue in the next section.
Another factor is that longer focal lengths provide shallower depth of field. Keeping a foreground and the stars sharp (without focus bracketing) is easier with a wider-angle focal length.
Related to focal length is the availability of front filter threads. Some of the widest-angle lenses have bulbous front elements that preclude front filter use. Primarily, we are referring to light pollution filters as blocking any other light is detrimental to night sky photography.
When stars and the Milky Way are visible, the night sky is extremely dark, and that darkness sets the stage for the next night sky lens selection criteria.
If it is dark, simply use a longer exposure, right? Partially right. While the stars appear to be motionless, the required exposures are so long that the earth's rotation promotes night sky photography into a form of action photography.
The amount of action in the night sky is dependent on the distance of the subject stars from the north star, which doesn't move. Since wide-angle focal lengths take in a wide area of the sky, the stars appearing to move the fastest generally need to be accounted for.
The amount of action in the night sky is also dependent on the focal length selected. The longer the focal length, the more the stars are magnified, the faster the camera's movement causes them to cross over pixel wells (the source of motion blur), and the shorter the tolerable exposure durations become. For example, 14mm is half of 28mm, and the 2x longer exposure available at 14mm equates to a full stop of aperture or noise within the tolerable exposure duration.
Also factoring into the exposure consideration is the pixel density of the imaging sensor. Higher density means motion is going to cross pixels more rapidly.
The final output size must be considered. Viewing the entire image on a mobile phone will hide star trails far better than a 100% resolution view on a large monitor.
While various tools are available to calculate the acceptable star trail-less shutter speed, I prefer to learn directly from my camera's results in the field. When photographing nightscapes, the manual focus setting must be confirmed, and assessing the star trails is easily accomplished simultaneously. My images usually show a slight star trail at 100% view.
Even with the widest apertures available, the necessary ISO settings for Milky Way photography are very high, and noise is a significant nightscape image quality factor.
The bottom line is that the ideal astrophotography lens will have an extremely wide max aperture. A wider aperture allows more light to reach the imaging sensor, permitting a shorter exposure or lower ISO setting.
While an ultra-wide-angle f/4 lens can work, f/2.8 is a better minimum max aperture. Wide-angle f/2.8 lenses are abundant, including zoom lens options, and multiple f/2.8 lenses made this recommendation list.
However, the fastest lenses suited for this purpose open to f/1.4, letting in 4x as much light as the f/2.8 options.
Getting into specifics — the image below was captured at 24mm, f/1.4, 13 sec., ISO 6400, and 50 MP (learn more about Low-Level Lighting).
Stars are tiny and sharp. Rendering them true to life in a photograph requires a corner-to-corner sharp lens.
While many lenses are sharp when stopped down a couple of stops, requiring that attribute from an ultra-wide aperture raises the bar significantly. Don't expect absolute perfection from any of them — the perfect lens does not exist.
While many lenses, including some inexpensive ones, can produce sharp wide-open image quality in the center of the frame, a select few can produce even close to perfect corner image quality. Coma, astigmatism, and lateral CA (more easily corrected) combine to stretch stars into undesired, sometimes wild-looking shapes.
I mentioned that I am not referring to deep sky photography using a tracking mount. Still, a mount such as the Sky-Watcher Star Adventurer Pro can be extremely advantageous for general nightscape photography.
A mount with 1/2 speed rotation up to doubles the acceptable exposure duration by splitting the motion between the foreground and the sky. The up to 1-stop difference in aperture or ISO setting is considerable.
The amount of a lens's peripheral shading directly offsets the advantage of its widest apertures.
Unfortunately, wide apertures and wide angles usually result in strong peripheral shading. I saved this requirement for last because my strategy is usually to deal with whatever the lens delivers.
Stopping down the aperture decreases peripheral shading, but a higher ISO setting is required to offset that change. The higher ISO setting results in increased noise throughout the entire image. So, consider a balanced approach if stopping down for this reason.
Because night sky post-processing generally involves increasing contrast, uncorrected peripheral shading results in very dark corners. Therefore, correcting most or all of the vignetting during RAW image processing is recommended, and increased noise in the image periphery is the end result.
A good northern lights show is considerably brighter than the Milky Way. However, dancing northern lights can move fast, meaning a substantially shorter exposure is required to avoid smearing of the light. Thus, the same attributes needed by a Milky Way lens are needed for photographing the aurora borealis.
During a Canon event a couple of years ago, an engineer asked which lens I wanted to see next. I requested an astrophotography lens as described above. That optimal lens still seems missing in the Canon lineup. Here are my recommendations.
Ultra-Wide Aperture, Ultra-Wide Focal Length, Art Series Build Quality, Solid Overall Performer
No one will accuse the Sigma 14mm f/1.8 DG HSM Art Lens of being small or light, but the f/1.8 aperture and 14mm focal length combine to create a great nightscapes lens. This lens's optical performance makes the grade for this challenging pursuit.
Canon's Best Ultra-Wide Zoom Lens
The EF 16-35mm f/2.8L III USM Lens is the Canon wide-angle zoom lens you want. This professional-grade lens is the perfect choice for a wide variety of uses, and the image quality it creates is impressive. The lens is well built and includes weather sealing. If weddings and other indoor events are on your to-do list, this lens should be in your kit. Those photographing the night sky will also find the f/2.8 aperture advantageous.
Ultra-wide Angle, Impressive Image Quality, Wide f/2.8 Aperture, Modest Price
Sometimes, the Sigma 14-24mm Art's wide f/2.8 constant max aperture can save the day. The lens' AF consistency did not prove to be great, and like many other ultra-wide-angle lenses, it will not accept front filters, but most photographers will find the Sigma 14-24mm Art's benefits outweigh its downsides.
Incredible Image Quality, Ultra-wide f/1.4 Aperture, Very Useful Focal Length, Fast Ring USM AF, Pro-Grade Weather-Sealed Build Quality
The 35mm focal length is a staple for photojournalism, and the wide f/1.4 aperture is ready for the darkest venues. When image quality is paramount, this lens will surpass the requirement. The 35 f/1.4L II is the complete package, including a great AF system and ready-for-daily-professional-use build quality.
Extremely Wide Aperture, Great Nightscapes Focal Length, Art Series Build Quality
This is a large and heavy lens, but it delivers good center and mid-frame image quality at its extremely wide maximum aperture. From a nightscapes perspective, the primary downside to this lens choice is the mediocre peripheral image quality performance.
Extremely Wide Aperture, Great Nightscapes Focal Length, Art Series Build Quality
While this lens is otherwise an ideal nightscapes lens choice, it delivers only mediocre image quality at f/1.4.
Affordable, Great Nightscapes Focal Length
My experience with this lens is that it must be stopped down about 2 stops to f/2.8 for decent image sharpness. The f/2.8 aperture is not especially wide for 24mm night sky photography, but at f/2.8, this lens is sharp from corner to corner and has a very low amount of peripheral shading, taking back some of the loss from stopping down.
This is a manual focus, manual aperture lens. While neither of those issues are concerns for nightscapes, they reduce the versatility of this lens.
Visit the Canon Lens Recommendations page for more lens advice.