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[Part 4] Pursuing a High Level of Durability & Dust- and Drip-Resistance

In this final part of our interview with the developers of the EF11-24mm f/4L USM, we hear more background stories about the durability as well as dust- and drip-resistance of the lens. Various efforts have been made to enable users to enjoy the performance of this super wide-angle zoom lens to the fullest. (Reported by: Ryosuke Takahashi)

(From left to right)

ICP Group 1: Shota Shimada

ICP Development Centre1: Hideki Sakai

ICP Development Centre 1: Tadanori Okada

Widening the flocking sheets for thorough protection against dust and moisture

- Is the dust- and drip-resistance of this lens equivalent to that of other L lenses?

Okada Yes, the EF11-24mm f/4L USM maintains the same level of performance as other L lenses in terms of durability as well as dust- and drip-resistance. For this lens, we focused on movement of the first lens group during the zooming operation, and implemented measures to prevent moisture or dust from entering the lens.

The switch panel as well as the mount, zoom ring and focusing ring (all marked in blue) of the EF11-24mm f/4L USM have all been constructed to be dust- and drip- resistant. Additionally, the first and last lens elements have also been coated with a layer of fluorine for enhanced stain resistance

- So the first lens group moves each time you zoom the lens.

Okada For lens elements that are movable, we placed a flocking sheet in the space between them to prevent foreign objects from entering. We widened the sheet to more than twice the standard size to ensure thorough protection against dust and moisture.

- How wide is the flocking sheet?

Okada A standard flocking sheet has a width of about 2mm. For this lens, we widened it to about 5mm to 6mm. The sheet is attached to the interior of the lens barrel, which is where the first lens group will move. On the EF11-24mm f/4L USM, it is the first lens group, made up of large-diameter lens elements, that moves during the zooming operation. Even the slightest amount of tilt in the lens body when the lens barrel extends out would compromise the optical performance. We therefore introduced a three-point mounting roller to ensure accurate and smooth extension of the lens barrel.

If we observe the front surface of the lens, we will notice the black flocking sheet inserted between the lens and the lens barrel. The fine fibres of the flocking sheet form a wall that prevents moisture and dust from entering the lens.

- Can you tell us what other efforts you have made?

Okada This is a minor detail, but we included a shock-absorbing rubber material inside the hood to prevent any shock impact to it from damaging the optical unit.

- Where is the rubber material placed?

Okada You would notice it if you look from the front. It is located in the space just inside the hood. In addition to this, there is also the spring-like mechanism of the hood, which functions as a cushion to absorb any shock impact from the front. The hood retracts slightly when it is subjected to shock. We have further enhanced the shock-resistance structure of the lens in consideration of its large front surface.

Shot taken using the EF11-24mm f/4L USM (photo by Canon). This lens is equipped with a level of dust- and drip-resistance that is able to meet the needs of professionals shooting under harsh conditions.
Top: EOS 5D Mark III/ EF11-24mm f/4L USM/ FL: 11mm/ Aperture-priority AE (f/8, 1/640 sec.)/ ISO 100/ WB: Auto
Bottom: EOS 5D Mark III/ EF11-24mm f/4L USM/ FL: 11mm/ Manual (f/4, 30 sec.)/ ISO 800/ WB: White fluorescent light

- This is a rather costly lens. Can you explain the basis for determining the recommended selling price of this lens?

Shimada As this lens has a focal length that starts from 11mm, even from a technical point of view it is very different from the conventional series that starts from 16mm. To achieve the design requirements for the EF11-24mm f/4L USM, we made use of one large-diameter ground and polished glass aspherical lens element, three high-precision glass-moulded aspherical lens elements, as well as one UD and one super UD lens element. Additionally, we also mobilised all of Canon's optical technologies, including the application of SWC and ASC coatings to multiple surfaces. Mechanically, the lens also offers a design that achieves both high image quality and reliability that can meet the needs of professionals. All these factors collectively contributed to the high price of this lens compared to other lenses. Of course, it would be possible to manufacture the lens at a lower price if we were to strike a compromise somewhere, but we did not want any trade-off on the image quality when designing the EF11-24mm f/4L USM. This is the reason for the current price setting, and we hope our users will understand.

- Lastly, to summarise, can you briefly express your views toward the development of this lens?

Sakai The specs of the EF11-24mm f/4L USM was an unprecedented challenge, and we needed to utilise all of Canon's technologies, from those related to aspherical lenses to anti-reflection, lens barrel, and assembly. To us, it was a major advantage that all our divisions related to lens technology are located in Utsunomiya. We were able to maintain consistent correspondence with the different technical divisions, which allowed us to produce the best lens.

- Thank you for sharing such intriguing information.

EF11-24mm f/4L USM

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Ryosuke Takahashi

Born in Aichi in 1960, Takahashi started his freelance career in 1987 after working with an advertising photo studio and a publishing house. Photographing for major magazines, he has travelled to many parts of the world from his bases in Japan and China. Takahashi is a member of the Japan Professional Photographers Society (JPS).

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