Up till the appearance of the EOS-1D X, the professional models of the EOS lineup were divided into two separate lines, one with a high pixel count, and the other with a high continuous shooting speed. Below is an article on an interview with Canons developers on the background that led to the development of the EOS-1D X, the new flagship model of the EOS series. Here in [Part 1], developers share the story of the incredible approx. 12fps maximum burst speed of the EOS-1D X. (Based on the interview held in October 2012)(Interviewer: Junichi Date/ Photos of Interviewees and Edited by: Masahiko Taira)

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(From left)
Tomokazu Yoshida, Camera Development Center/ Masami Sugimori, Camera Development Center/ Shintaro Oshima, Photo Products Group/ Shunji Yoshikai, Photo Products Group/ Tomoya Masamura, Photo Products Group

Design that places priority on the continuous shooting speed

― The EOS-1D X is said to be an attempt to integrate the two existing flagship lines, "1D" that excels in speed and "1Ds" with a high resolution. However, the new EOS-1D X has a lower pixel count when compared to the EOS-1Ds Mark III. Are the users of the 1Ds series really satisfied with the pixel count of the EOS-1D X, which is about 18.1 megapixels? Also, wouldn't the users of the 1D series have reservations about the shift from the use of an APS-H format sensor to a full-frame sensor?

Yoshikai Continuous shooting speed and resolution are basically in an opposing relationship to each other. Pursuing a higher speed lowers the pixel count, while placing priority on the resolving power results in a lower continuous shooting speed. As it was difficult to achieve both a "high speed" and a "high resolution" in the past, the only option was to establish two different lines, 1D and 1Ds. However, with technological advancements, this is no longer an impossible task. That is why we decided to integrate the 1D and 1Ds into the EOS-1D X, which aims to achieve a versatile performance that covers both speed and image quality.

But if you were to ask me if all the existing 1Ds users were completely satisfied with this change, the fact is some of them still prefer the pixel count to be higher instead of the drop. As for the users of the 1D series, we have received feedback that with the switch from the use of an APS-H format sensor to a full-frame sensor, they are no longer able to enjoy the advantage of the sensor size, which converts to about 1.3 times the focal length in the 35mm format. For example, I have heard that at the 2012 London Olympics, many press and sports photographers carried along with them both the EOS-1D Mark IV and EOS-1D X, and used them for different situations. In this sense, while a single model does not cover all the scenes, the combination of the resolving power by the full-frame-sensor with about 18.1 megapixels with the high-speed continuous shooting performance is nonetheless very much well-received by our users, so we believe we have successfully achieved the initial goal.

― If we do a simple calculation based on the assumption that the data of the 18.1 megapixels is read out at about 12fps, and that the EOS-1D X possesses the necessary image processing capacity, we could get 21.6 megapixels if the speed is reduced to 10fps, or 27 megapixels at 8fps, so why the decision to adopt the speed of 12fps?

Yoshikai Based on the aim to achieve both a "high speed" and a "high resolution" in the development of the EOS-1D X, one of the most important propositions was to realize the highest level of continuous shooting performance as an SLR camera with a speed of about 12fps during AF/AE tracking, and a speed of about 14fps with the mirror locked up. To us, compromising the continuous shooting performance to increase the pixel count was not an option, which was why we decided to adopt a pixel count of about 18.1 megapixels. In fact, some sports photographers who have used the EOS-1D X mentioned that at a speed of about 12fps, the photos that can be captured as well as the sensation during the shooting process are different from before. Having received voices that the EOS-1D X has opened the door to a whole new world of expression, we are convinced that our initial aim was a correct one.

The super high-speed drive and accurate control of the mirror system

― Technically speaking, to what extent is a speed of 12fps more difficult to realize than 10fps?

Oshima We did not increase the continuous shooting speed from 10fps to 12fps in a single leap. Based on simple calculation, the operation time allowed for each frame is 0.1 second at a speed of 10fps, and 0.083 second at 12fps. In other words, we needed to reduce the duration of each operation by 0.017 second. Within each operation, a series of control, such as flipping the mirror up and down, AE and AF calculation, lens aperture control and focus drive, need to be performed speedily and accurately. To do so, we strived to shorten the focusing time by increasing the speed of mirror drive and that of AF-related microcomputers.
Also, with the higher continuous shooting speed, it is necessary to process a vast amount of image data instantly and write them to the recording media at the same time. We have made every possible effort to enhance the speed, including the use of two DIGIC 5+ image processors and optimization of the control software.

The biggest hurdle in realizing a speed of 12fps, in particular, is mirror control. For SLR cameras, it is not as simple as moving the mirror up and down quickly. Bounce of the mirror when it flips up causes it to be captured in the resulting image, while the viewfinder image may appear blurry if the mirror is not locked in place when it is flipped down. Not only so, if the sub-mirror behind the main mirror is not locked in place, focusing cannot be performed correctly as light cannot be directed stably to the phase-difference AF sensor. The most crucial point in realizing a high continuous shooting speed, therefore, is to ensure that the mirror can move quickly and stop instantly and accurately. The EOS-1D X is equipped with a "Quad Active mirror stopper" mechanism, which helps to ensure speedy, accurate, and stable mirror drive.

― Compared to the EOS-1D Mark IV, which is designed for high-speed continuous shooting, what are the differences specifically?

Oshima On the EOS-1D Mark IV, a balancer for absorbing mirror shock and a lock mechanism to suppress mirror bounce are found respectively on one side of the main mirror and the sub-mirror. With the EOS-1D X, these are built into a total of four different locations on the two sides of the main mirror and sub-mirror.

― With the mirror locked up, the "Super high speed continuous shooting" mode, which fixes the focus and exposure based on the first shot, realizes a speed of about 14fps. Am I right to say that this is the highest speed limit for mirror drive?

Oshima Yes. Not only is it difficult to flip the mirror up and down beyond this speed, there wouldn't be enough time to perform AE and AF, and the control operation of the lens aperture blades would not be able to catch up with the higher speed too. Canon's EF lenses make use of an electromagnetic aperture, but some of the lenses released in the past may not be able to attain the speed of about 12fps until the aperture is almost fully open. This is due to the slower speed at which the aperture blades are being driven. For our latest lenses, such as the EF300mm f/2.8L IS II USM, efforts have been made to enhance the drive speed of the electromagnetic aperture, thus enabling high-speed continuous shooting at about 12fps up to three stops from the maximum aperture. However, there would not be sufficient time allowance to move the aperture blades at a continuous shooting speed of about 14fps. This is why the aperture blades and aperture value are fixed in the Super high speed continuous shooting mode.