Canon F1.4 Prime L Lens Developers Interview

Mayu Okumura : As you can tell from the name, the “F1.4 prime L lens series” is a series that falls under the “L” category, with an aperture of F1.4.

Within the RF lenses are the “L lenses”, “standard RF lenses”, and “RF-S lenses”, each of which includes “zoom lenses” and “prime lenses”. Since this is an L lens series, the L lenses are positioned as part of the RF lenses, and below them is an F1.4 prime lens.

In the EF lens era, there were F1.4 lenses with several focal lengths, but there were no such products in the RF lens category. Therefore, although it is not that such products have never existed before at Canon, this will be the first product for the RF mount.

Ms. Okumura : The main differences between the “F1.4 prime L lens” and the EF lens era are the uniform size of the entire series and the inclusion of an iris ring. In response to the growing demand due to the recent expansion of the video shooting market, we are developing this series as a hybrid lens.

In order to meet customer needs as the market expands, such as single-operator video shooters and small production companies, we have made some changes to our concept from the EF lens era.

Our cameras are designed to be used by customers for both still images and videos, and although the proportions vary, the number of video-compatible products is increasing.

The lenses are based on the same concept, and of course, video shooting is not impossible with any lens released so far. However, the reason we are calling them hybrids and emphasizing their video performance is because of the ease of operation with the iris ring, the excellent focus breathing suppression across the entire series, and the uniform size.

Still image users may not place much importance on the lens sizes being completely standardized, but we have taken into consideration ease of use when incorporated into a rig and the wide range of methods of expression, and have launched this product with a particular emphasis on these points in order to meet the needs of users who shoot video by using a variety of prime lenses in the series on location.

Mr. Saito: This is the first time that the VCM has been installed in this series. This series uses a VCM that is suitable for driving heavy, large-diameter lenses.

At first glance, you might think that a VCM is unnecessary because it is so small and lightweight. We also use actuators such as STM and nano USM in our other lenses, but the VCM has the advantage of being able to obtain a greater thrust force than these.

In the “maximum aperture value F1.4 prime L lens series,” the mass of the focus lens as a whole is approximately 80g, which is heavy compared to other large-diameter lenses, so a high-thrust VCM was essential.

Mr. Saito: To give an idea, take the super telephoto zoom lens “RF100-300mm F2.8 L IS USM.” Many people may think this lens is heavy from its appearance, but it moves a focus lens group with a mass of about 20g. In the “maximum aperture Canon F1.4 Prime L lens series,” it is necessary to move a lens group with a mass of about 80g inside this relatively small lens, which is why a VCM was needed.

In other words, the advantage of VCM is that it can move heavy objects and still operate quietly as a video compatible lens.

　 　　

Mr. Ino: In terms of optical design, in addition to suppressing the “breathing phenomenon” to accommodate video shooting, we also had to meet the requirements of “ensuring shooting performance at close range” and “maintaining high optical performance at all shooting distances, from close range to infinity.”

Taking these requirements into consideration, it became necessary to drive a heavy lens group and also to incorporate a floating focus mechanism, which I will explain later. Without adding these mechanisms, it would have been difficult to achieve both performances, so the weight of the focus lens group ended up being heavy.

Mr. Saito: It’s true that there were heavy lenses in the past. However, during the EF lens era, ring USMs were used to drive those heavy lenses. Ring USMs were also used during the EF lens era, and in RF lenses before the advent of VCM.

The main difference between Ring USM and VCM is in their structure. Ring USM has an arc-shaped ring, which restricts its size. This means that there is an issue with limiting the degree of freedom of the internal structure. On the other hand, by adopting VCM, it is possible to fit the internal structure of the lens more compactly, which is a major feature that allows for miniaturization.

Also, from the perspective of video compatibility, there is a big difference in drive noise. VCM is overwhelmingly quieter.

Mr. Omori: From the perspective of mechanical design, I would like to answer your question in comparison to the “PRIME Lens” series of the “CINEMA EOS SYSTEM”. The “PRIME Lens” series is a lens for cinema production, and is designed with an emphasis on manual operability. Therefore, the price and size are based on the assumption of team operation, so the user base is limited.

On the other hand, RF lenses are basically developed with a “by-wire structure” that converts movement into electronic signals to control the motor inside the lens, and are designed for operation by a small number of people using AF. Therefore, from the perspective of mechanical design, they are significantly lighter than the “PRIME Lens” series. In terms of optical design, electronic correction is used in wide-angle lenses to reduce their size.

Mr. Ino: One of the elements that contributed greatly to the miniaturization of the RF35mm F1.4 L VCM and RF24mm F1.4 L VCM in particular was distortion correction. The biggest factor in miniaturization was the adoption of a lens design that takes distortion correction into account.

Distortion correction through digital correction involves stretching the image to correct the compression of the peripheral image, which inevitably results in degradation of image quality. For this reason, some people may have a negative impression of distortion correction through digital correction. However, by optically allowing distortion, it is possible to actively correct aberrations such as field curvature that cannot be removed through digital correction optically. As a result, although there is degradation of image quality due to digital correction, it is possible to achieve image quality that is equal to or better than that of a lens design that does not assume distortion correction.

For this wide-angle lens, we have adopted an optical design that actively utilizes distortion correction. By designing it with distortion correction in mind, we have eliminated the need for a large front lens, which would be necessary if optical correction were used. This is a system that has made it possible to achieve a significant reduction in size compared to wide-angle lenses that have optically corrected distortion.

Compact size and high image quality.

Mr. Omori : I’ll answer from the perspective of mechanical design. As you pointed out, in order to create a sense of unity across the entire series, we aimed to standardize the overall length and exterior parts from the early stages of development. In terms of mechanical design, we aimed to standardize not only the exterior parts, but also the internal parts from the beginning.

In order to achieve the standardization of parts, we asked the optical design team to adhere to strict restrictions regarding lens size and weight. I imagine this was a very difficult task for the optical design team. The entire team, including the optical design team, worked closely together to come up with the design through repeated trial and error.

As a result, we believe that the RF lens is a product that combines high image quality with ease of use.

Ino: Now I’d like to answer your questions about the difficulties faced by the optical design team.

In normal lens development, the optical design is first done and then the mechanical design is adjusted accordingly. However, with this lens, the process was reversed in a sense; the mechanical design was decided first and then the optical design was incorporated into it.

Of course, in the early stages, the optical design team made proposals for common layout and optical design, but it was extremely difficult because we had to design multiple lenses at the same time. We exchanged various opinions, such as adopting VCM, and it was only because VCM was adopted that we were able to realize the project.

What was particularly difficult was that we had to design multiple lenses simultaneously with high precision. If the precision was low, there was a risk that the lenses would not be able to be incorporated later. Therefore, it was extremely difficult to find the optimal solution for all the lenses with high precision at an early stage.

Mr. Ino: I’ll talk about it from the perspective of optical design. Rather than talking about the difficulties, we had envisioned hybrid use for video and still images from the beginning, so suppressing the breathing phenomenon was an essential issue. With this lens, we knew from the beginning that we would need to move two lens groups to suppress breathing, so we asked the mechanical and electrical design team to install a floating focus mechanism for this purpose.

Ms. Toyoda : I’ll answer from the perspective of electrical design. As explained earlier, the floating focus mechanism was adopted, which required the control of two lens groups. In this case, the focus group is controlled by the VCM, and the floating group is controlled by the nano USM.

We therefore struggled to realize highly precise control at the micrometer level so that the positions of both lens groups were always synchronized. We believe that by achieving this, we were able to significantly suppress the breathing phenomenon.

Mr. Saito: This lens design is a hybrid of still and video, what is required for still images is high-speed and highly accurate AF. On the other hand, for video, we are aiming for smooth and quiet focusing. We have been developing this F1.4 series with the aim of achieving both.

By adopting the VCM this time, we were able to obtain a large thrust and achieve a compact size instead of using a ring USM. The adoption of the VCM also made it possible to achieve quiet AF. This lens series uses a VCM in the focus group and a nano USM in the floating group, and by skillfully controlling these two types of actuators, we are able to precisely control the focus in micrometer units while suppressing focus breathing, so I think we have achieved performance that will satisfy users for both video and still images. We are particularly confident about the AF performance.

In addition, the maximum aperture of F1.4 makes it very bright, with a large bokeh effect and a shallow depth of field, so you can take impressively beautiful photos. Also, our company has a focus ring setting called “MF operation sensitivity” setting on the camera, which is equivalent to the linear/non-linear settings of other companies, so you can use different settings depending on the rotation angle and rotation speed. It is possible to express what the user intended when shooting videos.

Furthermore, the common exterior design makes it easy to use the same photography accessories, and the same filter diameters can be used. When shooting with a gimbal, the weight balance may be different each time, so adjustments may be necessary, but basically it should be possible to use it in the same configuration, and I think it is a very easy-to-handle, highly mobile product.

Ms. Okumura: I sometimes go to the scene, and I feel that more and more people are taking videos in addition to still images. There are also many professional photographers who take both still images and videos, with the ratio of still images to videos being 70% and 30%.

As the need for video content is increasing, the attention to detail and use cases for video shooting are also diversifying. Recently, with the development of social media, I think that more and more people are working professionally as a side job with small equipment.

We believe that the strength of our lineup is that we have been able to create small, lightweight, high-quality products at an affordable price range for such people. We hope that customers will have the option to choose from the products that best suit their needs.