The Best Lenses for Night Photography
April 17, 2019
Two broad categories of lenses work well for night photography: ultra-wide, moderately fast lenses like a 14mm or 16mm f/2.8; and ultra-fast, moderate wide-angles like a 24mm or 35mm f/1.4.
Ultra-wide, moderately fast lenses, particularly wide-angle zooms like Nikon’s 14-24mm f/2.8 or Canon’s and Sony’s 16-35mm f/2.8s, are versatile lenses that work well both day and night. The Milky Way, one of the most common subjects for night photographers, is large in an angular sense. An ultra-wide-angle lens can usually encompass everything you want in your composition in a single frame. Ultra-wide-angle lenses also have good depth of field, even wide open. A 16mm f/2.8 lens, shot wide open and focused at infinity, offers depth of field from15 feet to infinity. (Depth of field geeks will note that I’m using a circle of confusion (CoC) of .02mm, which is a bit tighter standard for sharpness than most depth-of-field tables use.) Ultra-wide-angles are easier to focus at night and more forgiving of minor focus errors than ultra-fast moderate-wide angles. If you’re just starting out in night photography, an ultra-wide-angle, moderately fast zoom is your best bet.
If you want to dive deeply into night photography, however, ultra-fast, moderate wide-angle lenses have a major advantage over the ultra-wides: light-gathering power. In engineering terms, such lenses give you a better signal-to-noise ratio. In this case, the light is the signal. The signal-to-noise ratio is equal to the square root of the signal, so the more light that you can gather, the better the signal-to-noise ratio and the lower the noise in the final image.
Only two factors control how much light reaches your sensor: the length of the exposure, and the area of the aperture. Changing the ISO merely changes how much the signal coming off the sensor is amplified. It has no effect on the amount of light reaching the sensor. Unless you’re using a star-tracking device, the length of the exposure you can use is constrained by the rotation of the Earth. Too long an exposure, and stars are recorded as streaks. To gather more light per second of exposure, you need a bigger hole through your lens – in other words, a larger aperture.
The area of the aperture of a 35mm f/1.4 lens wide open is 19 times the area of a 16mm f/2.8 lens wide open. That means that for every second of exposure, your sensor is gathering 19 times as much light. True, the exposure will need to be shorter (about 14 seconds versus 31 seconds to keep the stars reasonably round), but the gain in light-gathering power is still huge. That translates into more stars, a brighter, more contrasty Milky Way, and lower noise.
A 35mm f/1.4 lens does have disadvantages. For starters, the angle of view is much narrower, which means that a single frame may not include everything you want in the composition. That means you may need to shoot a multi-row panorama to include the entire subject, which certainly adds complexity to both the shoot and the processing of the final image. On the flip side, sometimes an ultra-wide lens is too wide. By using a 35mm lens, you can fill the frame with the galactic center, the glowing heart of the Milky Way.
A second disadvantage is shallow depth of field. A 35mm f/1.4 lens shot wide open and focused at infinity has a depth of field from 142 feet to infinity (CoC .02mm). If you need depth of field, reach for an ultra-wide lens.
A third disadvantage is that ultra-fast lenses are highly specialized and rather expensive. If you’re intent on producing the best possible images, however, they may be worth the investment.
A final consideration when choosing a lens for night photography is stellar aberrations. Lenses vary widely in their ability to control the degree to which stars in the corners of the image grow little bat-wings. This aberration is frequently and erroneously referred to as coma, which is actually a different aberration. These aberrations are perhaps acceptable, although annoying, in a single-frame image. However, a panorama shot with such a lens will show an obvious pattern of multiple arch-like structures stretched across the sky which is nearly impossible to adequately retouch.
I know from personal experience that Canon’s EF 35mm f/1.4L II and EF 16-35mm f/2.8L III are superb lenses for night photography. I’ve seen many student images taken with Nikon’s AF-S 14-24mm f/2.8G ED lens, which also controls stellar aberrations very well. There are certainly other lenses out there that also control aberrations well. If you’re not a Canon or Nikon shooter, you should search the internet for reputable lens reviews before making a major purchase.
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