Since its release in 2014, the EF16-35mm f/4L IS USM has been a popular choice among landscape photographers, offering a slightly more accessibly-priced option for those who did not need a fast lens. What does it take to improve an ultra-wide-angle lens? Just how groundbreaking was the EF16-35mm f/4L IS USM when it was released? Here’s what we learnt from Junichi Date’s interview with the developers of the EF16-35mm f/4L IS USM.
The full interview can be found here.

 

1. It was released in May 2014 in response to growing camera pixel counts

Before that, its closest ultra-wide-angle zoom counterparts were the much-older EF17-40mm f/4L USM (released 2004) and the EF16-35mm f/2.8L II USM (released 2007). In between, there had been a jump in the number of megapixels offered by DSLR cameras. For example, the EOS 5D (released 2005) had 12.8 megapixels, whereas the EOS 5D Mark III (released 2012) provided 22.3 megapixels— almost twice the resolution.

Optical performance had to keep up with these advancements, and the peripheral image quality was particularly an issue on the wide-angle lenses. This was what the Canon lens developers focused on improving when they developed the EF16-35mm f/4L IS USM.

 

2. Its unprecedented corner-to-corner image quality was a huge achievement

Improving image quality in the corners has been a longstanding challenge in wide-angle lens design. The developers have to do two things:

1. Keep the focal plane flat (reduce field curvature), and
2. Reduce distortions. 

These two goals are in direct opposition to each other, and achieving both requires a design breakthrough. 

On the EF16-35mm f/4L IS USM, this was done by using two glass-moulded double-sided aspherical lens elements in the frontmost lens group.

Lens construction

A: Aspherical lens 
B: UD lens 
C: IS unit 

This optical design ensured vastly-improved image quality compared to the EF16-35mm f/2.8L II USM, as you can see from the MTF charts below.  Generally, the higher the lines, the better the lens performance. See the full interview for more details.

EF16-35mm f/4L IS USM

EF16-35mm f/2.8L II USM

Horizontal axis: Distance from centre of image frame
Vertical axis: Contrast/Resolution

Spatial Frequency	Max. Aperture		f/8
	S	M	S	M
10 Lines/mm
30 Lines/mm

Note: In 2016, Canon released the EF16-35mm f/2.8L III USM, which has similar optical performance as the EF16-35mm f/4L IS USM.

 

3. It spurred advancements in production technology that influenced future Canon ultra-wide-angle zoom lenses

If you look at the lens diagram above, you will notice that the first lens element is very large. The EF16-35mm f/4L IS USM was not the first lens to use double-sided aspherical lens elements, but it is the first to use one with such a large diameter. This requires extremely high precision to produce.

Developing the production technology to make this lens a reality was a significant breakthrough. As one of the lens developers mentions, “If we had come up with this design a few years earlier, we wouldn't have been able to produce a lens with the same level of performance."

- The EF-S10-18mm f/4.5-5.6 IS STM also benefited from these technological advancements. (See what the developers have to say about this lens here)

- The design paved the way for the EF16-35mm f/2.8L III USM, which uses two large-diameter double-sided aspherical lenses.

 

4. It is the first and only ultra-wide angle zoom EF lens with image stabilisation (IS)

This lens provides IS equivalent to up to 4 shutter speed stops, which means that you can shoot as slow as 1/8 second and obtain an image as sharp as though it were shot at around 1/125 second. This is an advantage for taking handheld shots in low light, such as in a dark forest, at sunrise, or after sunset—great for when you don’t want to carry a tripod around. 

EOS 5D Mark III/ EF16-35mm f/4L IS USM/ FL: 16mm/ Aperture-priority AE (f/11, 1.6 sec, EV±0)/ ISO 100/ WB: Manual  

IS makes it possible to obtain sharp handheld captures of breath-taking but dim scenes without increasing the ISO speed even when shooting as slow as 1.6 seconds.

 

5. Notice that the lens barrel stays the same length when you zoom?

The lens elements are designed to move within the barrel when you zoom in and out, instead of the barrel itself extending like on most other zoom lenses. This non-extending design not only prevents zoom creep, but also has mechanical benefits:

i) It helps to maintain the precise alignment of the lens elements, especially those in the first lens group. This is crucial for maximising image quality.

ii) Keeping movement within the lens barrel protects the lens elements, especially the larger, heavier frontmost elements, from external shock, resulting in better durability.

For more information about the lens design, optical qualities and some maintenance tips, read the full interview here.

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What do professional photographers have to say about this lens? Find out in:
A Close Look at the Features of the Wide-angle Zoom Lens
Lens Review: EF16-35mm f/4L IS USM in Landscape Photography
EF16-35mm f/4L IS USM: Breath-taking Landscape Photography Even With Handheld Shooting 

If you are using an APS-C camera, consider the EF-S10-18mm f/4.5-5.6 IS STM, which offers a similar full-frame equivalent focal range on APS-C cameras.

Find out more about Canon’s f/4L EF zoom lenses in:
How Well Do You Know Your f/4L Zoom Lenses?

 

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