In this interview series, developers of the EOS-1D X describes superb shooting performances of this new flagship model of the EOS series including high-precision AF and low-light shooting ability that enables even ISO 12800 at clear image quality. Dive into behind the scenes of EOS-1D X, how it combined the two professional lines of EOS series, one with a high pixel count, and the other with a high continuous shooting speed. (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

High Tracking Capability of "EOS iTR AF"

― The phase-difference AF unit uses a 61-point High-density Reticular AF system. Is it the same as that employed on the EOS 5D Mark III?

Yoshida The secondary image-registration lens of the phase-difference AF unit on the EOS 5D Mark III uses a plastic mold. In contrast, a glass mold that is resistant to changes in humidity and temperature has been adopted for the EOS-1D X in consideration of the fact that this professional model will be used for shooting in harsher environments. Besides the difference in the optical components used, the AF unit of the EOS-1D X basically has the same level of performance as that of the EOS 5D Mark III.

Also, the EOS-1D X comes with an "EOS iSA System," which employs a 10-megapixel RGB metering sensor and a DIGIC 4 image processor used exclusively by the metering sensor to detect the color, face, and brightness of the subject for enhanced automated AE or AF control. When the AF area selection mode is set to 61-point automatic selection AF or Zone AF, the EOS iSA System utilizes the face and color information detected to operate the EOS iTR AF for selecting an AF point or switching the AF point according to the movement of the subject. The most straightforward example is when a large part of the composition is occupied by the face of a subject. In this case, even when an object comes between the camera and the subject, the EOS iTR AF is capable of selecting the AF point at the eye accurately by activating face detection. This is a feature that is available only on the EOS-1D X and not on the EOS 5D Mark III.

― I was told that as compared to the EOS 5D Mark III, the power for driving the focusing mechanism is stronger when the body of the EOS-1D series is combined with lenses such as a large-diameter telephoto lens. Is this true?

Oshima The EOS 5D and others in the lower series of the EOS lineup do not have the same battery capacity as the flagship EOS-1D series, so the power that can be supplied to the lens is also different. During significant movement of the focusing mechanism, such as when the image is completely out of focus, the EOS-1D series is able to drive the focusing lens elements more powerfully. While such a difference may show up between the EOS 5D Mark III and the EOS-1D X under extreme conditions, they basically share the same level of AF sensor performance and microcomputer processing ability.

― The cross-type sensors are capable of offering stable AF without being affected by the patterns on the subject. Do they also enhance the AF accuracy at the same time?

Yoshida For subjects with lines that intersect with the line sensors, their accuracy is the same as that of the cross-type sensors. However, if the lines are almost parallel or at a slight angle to the line sensors, error is likely to occur even if focusing could be performed, and the level of AF accuracy obtained may be inadequate even though the focus confirmation light is illuminated. In this case, the cross-type sensors, which are capable of detecting both vertical and horizontal lines, not only provide the necessary support to boost the capturing performance, but they can also be expected to offer a high level of precision.

― On the EOS-1D X, there are now more cross-type AF points at the peripheral areas to support focusing by lenses with a maximum aperture of f/4 or f/5.6. This allows for cross-type focusing by a wider range of lenses. However, the number of AF points that can be used varies even for lenses with the same maximum aperture. Why is this so?

Yoshida If you look through a lens from the side to be attached to the lens mount, and move the lens in the left and right directions, you can tell that light coming from the front of the lens becomes invisible due to vignetting in the lens tube. The amount of lens movement that causes vignetting differs depending on the optical system of the lens and the structure of the lens tube. If we were to fix the number of AF points to be used based on each maximum aperture value, we would need to choose a number according to the lens with the strongest vignetting effect. However, it would be too wasteful to do so, hence our decision to fully utilize the AF points usable for each lens. This explains why the number of usable AF points now comes in a few different patterns.

― Is there a possibility of expanding the AF area further even for a full-frame sensor?

Yoshida To widen the AF area, it is necessary to upsize the sub-mirror to prevent vignetting from occurring while light entering the lens is directed to the AF sensor. Doing so will give rise to many issues, such as the lack of space to build in the shutter unit, and the need to compromise the continuous shooting performance due to the inability to move the mirror at a high speed.

Considerable enhancement in the high ISO image quality

― After trying out the EOS-1D X, I was amazed by the little noise even at a high ISO speed of ISO 6400. With ISO speeds up to ISO 12800 usable as the standard range, I feel that the EOS-1D X excels a little more than the EOS 5D Mark III in terms of high ISO speed performance. Although the difference in the pixel count between the EOS-1D X (approx. 18.1 megapixels) and the EOS 5D Mark III (approx. 22.3 megapixels) is not substantial, since they both employ the same DIGIC 5+ image processor, can I say that the difference in the high-sensitivity performance is attributable to the difference in the pixel count, or is it because new technologies have been adopted for the CMOS sensor of the EOS-1D X?

Sugimori Indeed, there may be some difference in the high ISO performance compared to the EOS 5D Mark III. Although there is no substantial difference in the pixel pitch between 18.1 megapixels and 22.3 megapixels, this slight difference is nonetheless reflected in the image quality of the EOS-1D X.

― What are the specific differences between DIGIC 5 and DIGIC 5+?

Oshima We have increased the width of the bus, or the route of data flow inside the circuit. Doing so allows a large amount of data to be transmitted at the same time. Compared to the 32 bits of the DIGIC 5 for processing voluminous data at a high speed, DIGIC 5+, which handles data with 128 bits, is about three times higher in capacity. While the EOS 5D Mark III is equipped with one DIGIC 5+ processor, the EOS-1D X has two.

― Despite the lower pixel count of the EOS-1D X compared to the EOS-1Ds Mark III, it is said that the same level of apparent resolution can be obtained in terms of image quality. Was image processing performed or were there any other efforts made to improve the apparent resolution?

Sugimori We did not perform any form of image processing, such as reducing the effect of the low-pass filter, to improve the apparent resolution. What we did was basically tuning in the same way as with all past models. As to how detailed an image can be resolved, it goes without saying that the EOS-1Ds Mark III and EOS 5D Mark III, which have a higher pixel count, have a greater advantage. However, this is limited to shooting at low ISO speeds, and the situation is reversed at a higher ISO speed. This is because the EOS-1D X boasts an extremely high level of sensitivity at the sensor level, and so there is no need to apply a strong noise-reduction effect at a high ISO speed. Therefore, there is little deterioration in the resolving power as a result of noise reduction.

― I see. In sum, the aim and also the charm of the EOS-1D X lie in the ability to capture scenes not possible before. This is realized by allowing continuous shooting at an overwhelmingly high speed with little deterioration in the image quality even at a high ISO speed. Thank you for sharing your time with us today.