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Canon announces 16.06 million image pixel EOS-1D Mark IV
Monday, October 19, 2009 | by Rob Galbraith
Canon has revealed the details of its next 1-series digital SLR, the EOS-1D Mark IV. The new model is an evolution of the EOS-1D Mark III and features a 16.06 million image pixel, 1.3x crop sensor, an ISO range that tops out at a heady 102,400, 1080p video with external stereo mic jack, a revamped 45-point AF system and a wider-gamut, 920,000-dot rear LCD. All of this is inside a body that's essentially identical in appearance and control layout to the camera it replaces.

The EOS-1D Mark IV

The transition from the EOS-1D Mark II N to the EOS-1D Mark III was big. Photographers who bought the 10.01 million image pixel, 10fps digital SLR starting in late-May 2007 were getting a camera that bore little resemblance to the camera that came before. Inside and out, almost every component of the EOS-1D Mark III was new.

This time around, Canon has been more selective in what it has changed and what has remained the same.

First, they've kept the EOS-1D Mark III body intact, except for minor tweaks. Side by side, the two models are nearly indistinguishable. Outwardly visible changes include a new nameplate and mic on the front, several subtly reshaped buttons and a speaker on the back, a reworked arrangement of ports and port covers on the side (including a flap rather than a screw cap for the wireless transmitter mount) and minor tweaks to the information displayed inside the viewfinder, on the top panel LCD and the lower rear LCD.

The photos below of the EOS-1D Mark III and EOS-1D Mark IV tell the story.

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Mirror Mirror: Views of the EOS-1D Mark III, left, and EOS-1D Mark IV, right. Click photos to enlarge (Photos courtesy Canon)

Second, they've left either untouched or only mildly tweaked many of the EOS-1D Mark III's core components in the move to the EOS-1D Mark IV. This includes its viewfinder, 63-zone meter, 300,000-cycle shutter mechanism, twin CompactFlash and SD card slots (though CompactFlash write speed is promised to be dramatically quicker), LP-E4 battery and support for Canon's side-riding wireless transmitter, the WFT-E2/E2A (plus the WFT-E2 II/WFT-E2 II A, announced today). Basic performance specifications, such as its 10fps maximum burst rate, 1/8000 top shutter speed, 1/300 standard flash sync, 55ms shutter lag and 80ms mirror blackout time - these also carry over to the EOS-1D Mark IV from the 2.5-year-old camera it replaces.

That leaves what Canon has added or changed:

Sensitive: The Canon EOS-1D Mark IV's 16.06 million image pixel CMOS sensor. Click photo to enlarge (Photo courtesy Canon)
Image sensor and ISO range Canon gave themselves a difficult task with the EOS-1D Mark IV: add over six million image pixels to the sensor while simultaneously increasing the extended ISO range by four stops.

Bumping up the image pixel count from 10.01 to 16.06 million, in a sensor that's about the same 1.3x crop size as before (at 27.9mm x 18.6mm, the Mark IV sensor is fractionally smaller than that of the EOS-1D Mark III), meant dropping the pixel pitch from 7.2m to 5.7m.

All other things being equal, larger pixels lead to better high ISO pictures than smaller pixels, so Canon's self-assigned mission to significantly boost image resolution and high ISO could well be viewed as an impossible one.

The Canon-supplied graphic below illustrates the ISO range and pixel size differences between the EOS-1D Mark III and EOS-1D Mark IV.

canon_markiv_iso_range.jpg

In tackling this challenge, Canon employed every new trick they've learned about sensor design in the last couple of years, the goal being to noticeably improve the light gathering efficiency of each tiny pixel. This includes, says Canon USA Technical Information Advisor Chuck Westfall, making the colour filter array over the sensor more transmissive, eliminating the gap between each pixel's light-boosting microlens and redesigning both the internal structure of each pixel as well as the circuitry that reads each pixel's signal before pumping it through eight channels to the analog-to-digital converter.

All of this technical mumbo-jumbo, says Canon USA's Westfall, means that high ISO image quality from the EOS-1D Mark IV is promised to handily surpass the EOS-1D Mark III, despite the older model's pixel size advantage. This is true both in the JPEGs rolling out of the camera, as well its RAW CR2 files, he says. In other words, Westfall is emphasizing that the camera's better high ISO image quality doesn't stem from the EOS-1D Mark IV's twin DIGIC 4 processors massaging the heck out of noisy RAW data and turning it into clean camera JPEGs. Rather, it's the fact the RAW data emerging from the sensor is noticeably less noisy in the first place.

As a result, Canon is pitching the EOS-1D Mark IV as their best-performing digital SLR ever in low light, one that can produce usable files right up to ISO 102,400. Whether this is true remains to be seen, and it's hard not to be skeptical, so enormous is the challenge Canon has set out for itself.

By comparison, Nikon has also just announced a camera - the D3S - that sports a top ISO of 102,400. But with a pixel pitch of 8.45m, Nikon's job of achieving this ISO from its 12.05 million image pixel full-frame sensor, not to mention decent performance in the ISO 6400-12,800 range, seems like a walk in the park by comparison. And speaking of the D3S, it's perhaps surprising that the EOS-1D Mark IV's sensor isn't full frame, since Nikon has demonstrated that to be a viable sensor size for the news and sports shooter using a mix of wide angle though long telephoto glass.

With the EOS-1D Mark IV the proof will be in the pictures, and if you're a Canon low light shooter, you'll want to cross your fingers and hope that Canon has gotten the job done.

Other things to note:
  • Full resolution pixel dimensions for the EOS-1D Mark IV are 4912 x 3270.

  • canon_markiv_iso_menu.jpg
    Electric Range: Canon EOS-1D Mark IV ISO settings (Screenshot courtesy Canon)
    The standard ISO range of the EOS-1D Mark IV is 100-12,800 in 1/3-step increments (the camera can be configured for 1/2-step and full step increments too).

    Switching on ISO expansion enables the selection of L (ISO 50), H1 (ISO 25,600), H2 (51,200) and H3 (102,400), in full step increments above and below the standard ISO settings.

    All ISO settings are available when shooting stills; with the camera set to record video, only ISO 50 is not selectable.

  • The EOS-1D Mark IV offers one full resolution plus two reduced resolution RAW settings, MRAW and SRAW. The EOS-1D Mark III has a single reduced resolution sRAW setting.

  • Auto Lighting Optimizer, Canon's automatic image adjustment feature for in-camera JPEGs, works in Manual exposure mode, a first for a Canon digital SLR. The toning adjustments it applies are also somewhat different than Auto Lighting Optimizer in other models. They've been tweaked to better match the contrast needs of news shooters.

  • Like the EOS-1D Mark III, the EOS-1D Mark IV's sensor is the self-cleaning variety. The newer camera, however, incorporates an anti-dust fluorine coating on the outer surface of the sensor package.

  • Burst depth is specified by Canon to be 121 Large JPEG, 28 RAW or 20 RAW+JPEG.
AF system Troubled since its inception, numerous aspects of the 45-point AF system in the EOS-1D Mark III have been reworked for the EOS-1D Mark IV. Canon has made changes to both the hardware components responsible for AF as well as the algorithms that govern the AF system's behaviour. There are feature changes too, such as the ability to manually select from all 45 points individually (the EOS-1D Mark III limits manual selection to a maximum of 19 points).

canon_markiv_af_points_2.jpg
Power Point: The 45 point AF ellipse in the EOS-1D Mark IV. The six points marked with a blue line only are single-line sensitive, while the remaining 39 are cross-type (Graphic courtesy Canon)
To improve AF detection, Canon has evolved the AF sensor in the EOS-1D Mark IV from that of the EOS-1D Mark III. While the AF sensor module in each model is largely the same, covers the same proportion of the picture area and has the same 45 AF points, the version in the newer camera has 39 cross-type points (up from 19 in the EOS-1D Mark III), a higher signal-to-noise ratio, improved performance when the lens is defocused and generally a superior ability to detect focus in low light, bright light and with low contrast subjects.

The sum of these changes, says Westfall, is an AF sensor capable of delivering better AF information than before.

To improve AF calculation, particularly when tracking moving subjects, Canon has developed a new AF algorithm to process the information coming from the sensor. The new algorithm has been dubbed AI Servo II by Canon. It is, says Westfall, "all about making better decisions." AI Servo II is promised to be better at handling situations like a referee passing in front of the player being tracked or a swimmer bobbing in and out of the water as they progress towards the photographer. Overall, the EOS-1D Mark IV is meant to deliver a greater percentage of properly focused or usably focused frames in a tracking sequence than the EOS-1D Mark III.

A Canon UK document further describes the changes in AI Servo II:

Stable lens drive: In normal operation, the AI Servo algorithm makes calculations, and based on these results, instructs the lens to change focus position. Now, if the algorithm gets two results one after the other that are very different - for example, the subject changed direction rapidly and was not where the system expected it to be - this calculation is ignored and the system waits to instruct the lens until two results match. This means that errors generated no longer cause the lens to jump unexpectedly out of focus.

Secure focus tracking of a subject: If an obstacle is detected or if the AF point is not kept over the subject, tracking continues based on the last known trajectory result immediately before the interruption.

Moderate lens drive: If there is a radical change in focus distance, the lens is not driven straight to that value. It is slowly taken there based on past prediction results. This means that if a photographer drifts off the subject to the background for an extended period of time, the lens will not snap focus straight to the background. This in turn means that if the photographer gets the AF point back onto the subject that the lens is able to achieve sharp focus much more quickly.

Predictive control with quick response: The system is now able to achieve predictive focus immediately as the subject starts moving and there is no delay before it can start tracking.


The camera's 39 cross-type AF points act as cross type with any lens whose maximum aperture is f/2.8 or faster, as well as with certain f/4 lenses or lens+teleconverter combinations that add up to f/4. (In all previous 1-series digital SLRs, only the centre point would retain its cross type detection capabilities when an f/4 lens was attached.)

The eligible Canon lenses are:
  • Canon EF 17-40mm f/4L
  • Canon EF 24-105mm f/4L IS
  • Canon EF 70-200mm f/2.8L IS + Extender EF 1.4x II
  • Canon EF 200mm f/2L IS + Extender EF 2x II
  • Canon EF 300mm f/2.8L IS + Extender EF 1.4x II
  • Canon EF 400mm f/2.8L IS + Extender EF 1.4x II
This is thought to be the complete list of f/4 glass that can reap the benefit of 39 cross-type points, which means other lenses, such as the EF 500mm f/4L IS or the Canon EF 70-200mm f/2.8L (non-IS) + Extender EF 1.4x II, will not have the benefit of cross-type operation from all 39 AF points. The centre point, however, will continue to provide cross-type sensitivity with any f/4 lens or combo not on the list above.

As with the EOS-1D Mark III and earlier top-end Canon digital SLRs, all 45 AF points are single-line sensitive with f/5.6 lenses. With f/8 Canon EF lenses (this really means a lens+teleconverter together, such as the EF 600mm f/4L IS mated to an Extender EF 2x II), the AF system will continue to function, but only the centre point is operational and is single-line sensitive.

Other AF system changes include:
  • Before the EOS-1D Mark III, it was possible to manually select any of the 45 points in the AF ellipse of a 1-series digital SLR, as a benefit to photographers wanting to focus at a particular spot in the frame without adjusting the composition to do so (such as when the camera is locked down on a tripod). The EOS-1D Mark III lacked this capability; manual selection was restricted to 19 points. All 45 points can once again be chosen in the EOS-1D Mark IV. This signals the return of certain EOS-1D Mark II-era options as well, as longtime Canon shooters will note in several of the changes described ahead.

  • The EOS-1D Mark IV contains all the single and multiple point AF modes and options of the EOS-1D Mark III, plus more. Additions include:

    • More AF point patterns The EOS-1D Mark III offers three selectable AF point patterns: 19 throughout the ellipse, nine throughout the ellipse and nine at the centre. The EOS-1D Mark IV adds two more: 11 throughout the ellipse and all 45 points. The graphic below shows the complete slate:
canon_markiv_af_points.jpg
    • Spot AF Similar to the feature introduced in the 7D, when set to Spot AF the detection area is restricted to just beyond the left, right, top and bottom borders of the selected AF point. By comparison, when the camera is not set to Spot AF, an AF point's detection area extends noticeably beyond its borders.

      In the 7D, Spot AF can be teamed up with any lens; in the EOS-1D Mark IV, it's restricted to lenses with an AF Stop button, which translates to Canon's range of supertelephotos only.

    • Expanded AF Expansion In the EOS-1D Mark III, it's possible to augment the manual selection of a single point with either up-to-two or up-to-six Assist AF points around the selected point. In the EOS-1D Mark IV, Canon has added an up-to-18 Assist AF point grouping, and revised the six-point grouping to use eight Assist AF points at times. The graphic below shows the available AF Expansion options in the new camera.

canon_markiv_af_expansion.jpg

    • Orientation linked AF The EOS-1D Mark IV can optionally be configured so that the active AF point automatically switches when the camera pivots from horizontal to vertical, or vice versa. The graphic below illustrates this.
canon_markiv_af_horzvert.jpg
    • AI Servo 1st/2nd Image Priority The AI Servo 1st/2nd Image Priority Custom Function, which dictates whether acquiring focus or shooting speed is the priority before the first frame in a sequence and then between subsequent frames in a sequence. Of the four total possible combinations, the EOS-1D Mark III offered three. The EOS-1D Mark IV adds the fourth for full configuration flexibility.
If you're an EOS-1D Mark III owner who has struggled with the tracking difficulties that camera presents, you're probably far less interested in the EOS-1D Mark IV's new AF system features and far more interested in whether the darned camera can keep a moving subject in focus. Because we've not been involved in beta testing the EOS-1D Mark IV, we can't give an opinion about this. Like many of you, we hope that Canon has been able to successfully address the design, manufacturing and calibration problems that have been the tale of EOS-1D Mark III autofocus since the beginning.

Canon USA has published an extensive overview of EOS-1D Mark IV AF on their Digital Learning Center website.

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