f/2.8 zoom lenses are bright enough to photograph stars, with the added advantage of framing flexibility.

In this 4-part series, we share some ideas for taking full advantage of what your f/2.8 constant aperture zoom lens can do, as well as tips for fine-tuning them to get a better shot. Because why do what a variable aperture zoom lens can do when your f/2.8 zoom can do more?

In Part 3, learn about the advantages of using an f/2.8 zoom lens for astrophotography, as well as some shooting tips. (Reported by: Chikako Yagi, Digital Camera Magazine)

This is Part 3 of a 4-part series. Click on the links to read the other parts!
- Part 1: Highlighting a Subject
- Part 2: Creating Depth & Dimensionality
- Part 4: Up Your Low Light Landscape Photography Game

 

Why use an f/2.8 zoom lens for star photography?

A lens with a large maximum aperture (also described as a “fast” lens or a “bright” lens) always helps when you’re photographing at night. Such lenses allow more light to enter and reach the sensor at any given time, which has two key benefits for photographing stars:

1. You can capture stars as points
Stars will trail if the shutter speed is too slow. A large aperture lens lets you set a faster shutter speed.

2. Cleaner images
You can also set a lower ISO speed to avoid image noise without compromising on exposure.

While f/1.4 or f/1.8 wide-angle prime lenses exist, it helps to have the flexibility to change the framing when you’re shooting in an unfamiliar location and don’t know what to expect.

An f/2.8 zoom lens lets you zoom out to capture the scenery on the ground along with the starry sky, or zoom in to specific stars or formations—and it’s sufficient for keeping noise at manageable, if not practically invisible levels. Don’t hesitate to bring your f/2.8 wide-angle or standard zoom lens the next time you go stargazing!

Know this: f/2.8 is sufficient for keeping noise minimal

An f/2.8 zoom lens allows sufficient light to reach the camera’s image sensor so you can, for example, use ISO 3200 instead of the ISO 6400 and above you might have to use with a lens with a maximum aperture of f/4 or higher. The difference in noise level can be huge, as the above close-up example shows!

Also see:
Camera Basics #5: ISO Speed

 

Pro technique 1: Adjust your focal length to achieve different effects

A focal length of around 24mm is sufficient for photographing starscapes (landscapes against the starry sky), but you get different results if you go wider.

24mm: Emphasises terrestrial scenery and specific stars

EOS R5 Mark II/ RF24-70mm f/2.8L IS USM/ FL: 24mm/ Manual exposure (f/2.8, 8 sec)/ ISO 800/ WB: Auto

24mm is wide enough to capture not only a huge expanse of sky, but also the scenery on the ground along with it. You’ll have lots of flexibility to adjust the framing when using a zoom lens, so feel free to experiment until you achieve your ideal land-sky balance!

15mm: A dynamic feel with lots of sky

EOS R5 Mark II/ RF15-35mm f/2.8L IS USM/ FL: 15mm/ Aperture-priority AE (f/2.8, 15 sec)/ ISO 1250/ WB: Auto

An ultra-wide-angle focal length like 15mm lets you include even more of the sky. This not only infuses the composition with greater dynamism, it also brings out a sense of scale: terrestrial objects look much smaller, which makes the sky look even vaster in comparison.

 

Pro technique 2: Use a shutter speed that avoids star trails

Locations for star photography are inherently darker than locations for most other types of night photography. You can’t avoid using longer exposures even when using a large aperture lens. And because of Earth’s rotation, such long exposures can result in blurry star trails.

Nearly all methods of calculating the longest exposure you can use before the stars start trailing depend on your focal length. The longer your focal length, the shorter the exposure has to be, whereas you get more leeway with shorter focal lengths. I recommend the Rule of 200:

200 ÷ Focal length = Max. exposure time

Focal length	Shutter speed
15mm	200 ÷ 15 = 13 sec
16mm	200 ÷ 16 = 13 sec
20mm	200 ÷ 20 = 10 sec
24mm	200 ÷ 24 = 8 sec

If you are using an APS-C camera, your calculation should account for the 1.6x crop factor, i.e.: 200 ÷ (focal length x 1.6) = Max. exposure time.

 

 

Recommended f/2.8 zoom lenses

Wide-angle f/2.8 zoom lenses

24mm is the wide-angle end of standard zoom lenses like the RF24-70mm f/2.8L IS USM and RF24-105mm f/2.8L IS USM Z, and it’s sufficient. However, as we’ve shown above, you can achieve more dynamic images with an ultra-wide-angle zoom lens like the RF15-35mm f/2.8L IS USM or RF16-28mm f/2.8 IS STM.

Left: RF15-35mm f/2.8L IS USM
Right: RF16-28mm f/2.8 IS STM

The RF15-35mm f/2.8L IS USM is a professional-grade lens designed to provide the best possible pictures under the harshest conditions. It has a dust- and drip-resistant structure that is great for outdoor shooting, and special lenses and coatings so you get clean and clear images even when shooting into backlight. It takes 82mm screw-in filters.

The RF16-28mm f/2.8 IS STM is a smaller and lighter f/2.8 wide-angle zoom lens for users who prioritise portability. Besides its excellent optical quality, it is also weather-sealed, though not to the same extent as its L-series counterpart. It takes 67mm screw-in filters.