The Canon 1D Mark IV also gains a significantly upgraded autofocus system, a higher-resolution LCD display with improved reflection / glare resistance, and this year's must-have feature: high definition video capability. Other changes of note include support for UDMA CompactFlash cards, Peripheral Illumination Correction, a new generation of Canon's Auto Lighting Optimizer technology, and quite a bit more besides.
Pricing for the new Canon 1D Mark IV is set at US$4,999.00, with a ship date of late December 2009.
The Canon EOS-1D Mark IV features a rugged professional grade magnesium alloy body with 76 gaskets and seals for weather and dust resistance, over a magnesium alloy inner body. Weight of the body without a lens attached has increased just slightly by one ounce, to around 42.6 ounces (1,180 grams), with the weight gain being attributed to the new LCD display. The camera weighs in at 49 ounces or 1,390 grams with battery and CompactFlash card.
Progression. The Canon 1D series has established quite a legacy. The following table sets out the progression of the series, and sets out the salient changes in the new Mark IV model. The 1D series has always used the APS-H format -- an imaging sensor that's 28.1mm wide by 18.7mm tall. The Mark II saw the conversion from a CCD sensor to a CMOS sensor, and while the Mark III version offered Live View functionality, the Mark IV is the first 1D with a movie recording mode. Except for the model number badge, the only real change that differentiates the 1D Mark IV from its predecessor externally is the presence of a new microphone grill on the front panel, used to record audio.
Backstory. Theories abound concerning the release of the EOS 1D Mark IV. For sports shooters, the autofocus performance of the 1D Mark III proved to be unreliable. Four months after the release of the 1D Mark III, Nikon released its game-changing D3, with Canon trying to salvage its position by offering numerous firmware and hardware upgrades (including a servicing program to replace a faulty focusing sub-mirror). Despite these updates, the camera was said to be inferior in performance to that of the previous 1D Mark II N. (One of the most definitive reporting sources of the entire 1D Mark III focusing saga can be found at Rob Galbraith's website.) The Internet came to life with stories far and wide of Canon shooters switching over to other systems. If you pore over Canon's historical release dates in the 1D series, a new model comes out in the first quarter every three years; the 1D Mark IV came out six months "ahead of schedule."
Sensor. Inside the 1D Mark IV's body, Canon has coupled a newly designed image sensor and dual DIGIC 4 image processors that together bring improvements in a number of areas. Approximately equivalent in size to a frame of APS-H film, the Mark IV's RGB-filtered Canon CMOS image sensor has an effective resolution of 16.1 megapixels, and a total resolution of 17.0 megapixels.
The imager has a native 3:2 aspect ratio, and yields images to a maximum resolution of 4,896 x 3,264 pixels in both JPEG and 14-bit CR2 Raw formats. Lower-resolution options include 4,320 x 2,880 pixels (JPEG only), 3,672 x 2,448 pixels (M-Raw only), 3,552 x 2,368 pixels (JPEG only), and 2,448 x 1,632 pixels (JPEG or S-Raw).
Perhaps indicating the company's confidence, Canon is stating that noise levels in Raw data from the Canon EOS-1D Mark IV should show a noticeable improvement over those of the previous model, at equivalent sensitivity. Canon says they achieved this through of a number of design changes to the new CMOS imager.
For one, the ratio of light sensitive to non-light sensitive area for each pixel has been increased, although the boost in resolution means that each pixel is now 5.7 microns, down from the 7.2-micron photodiodes in the Mark III sensor. Other changes include a new amplifier design that improves the signal to noise ratio, deeper photodiode wells that improve dynamic range, the use of gapless microlenses that are also closer to the photodiode surface to improve light gathering efficiency, and the selection of more efficient materials for the color filter array.
Sensitivity. By default, the Canon 1D Mark IV offers sensitivity ranging from ISO 100 to 12,800 equivalents. A custom function expands this range to include ISO 50 at the low end, to ISO 102,400 at the high end, matching the highest ISO of Nikon D3s. The lower limits are unchanged from those of the Mark III, but the maximum sensitivities are vastly higher than the standard ISO 3,200 and expanded ISO 6,400 of the 1D Mark III. Indeed, the Mark IV offers the widest ISO range of any Canon EOS digital SLR to date, which is an especially impressive step forward when one considers the simultaneous increase in sensor resolution from the 10.1-megapixel 1D Mark III.
DIGIC 4. In addition, JPEG shooters will gain the benefits of Canon's current-generation DIGIC 4 image processing, instead of the DIGIC III processing of the 1D Mark III.
Frame rate and buffer. Like its predecessor, the Canon 1D Mark IV is capable of burst shooting at up to ten frames per second. Despite the increase in resolution, large/fine JPEG burst depth has actually increased slightly to 121 frames, from the 110 frames achievable with the Mark III. Raw shooters will find burst depth has decreased by a couple of frames, with 28-frame Raw or 20-frame Raw+JPEG bursts possible. (These are Canon's figures.)
Lens mount. Like its predecessor, the Canon 1D Mark IV accepts Canon EF, TS-E, or MP-E lenses -- but not the EF-S lenses designed for the smaller APS-C sensor format.
Vignetting. The EOS-1D Mark IV includes Canon's Peripheral Illumination Correction function, which aims to correct for vignetting or light fall-off with certain Canon lenses.
Dust control. To combat the adverse effects of dust on image quality, Canon's EOS Integrated Cleaning System is retained from the Mark III design. Dust adhering to the low-pass filter over the image sensor is shaken free using ultrasonic vibrations, and is captured by an absorbent material around the filter's perimeter. The locations of any stubborn particles that remain can then be mapped and tagged in the headers of both JPEG and Raw images for automatic or manual removal using Canon's bundled Digital Photo Professional software.
By default, the ultrasonic dust removal process is triggered for several seconds whenever the camera is first powered on, although this can be disabled, and the process triggered manually at the user's discretion. In either case, a touch of the shutter button immediately stops the dust removal process and returns the camera to normal operation should an unanticipated photo opportunity present itself.
Autofocus improvements. Canon has given its autofocusing system a significant overhaul for the EOS-1D Mark IV. While the total number of focusing points is unchanged at 45, the number of cross-type points has more than doubled. Where the Mark III offered 19 cross-type points, no less than 39 of the Mark IV's 45 points are high-precision (f/2.8 compatible) cross-type points. In addition, where the Mark III's 26 remaining line-sensitive AF points were available as assist points only and hence weren't user selectable, the 1D Mark IV provides for user selection of all 45 points.
An interesting side note concerns those cross-type sensors. In the EOS 1D Mark III, the center point functioned as a cross-type sensor not only at f/2.8, but also at f/4. This is still true in the Mark IV, but with certain lenses or combinations of lens plus teleconverter, the same is true of all the other cross-type points. The precise list of lenses and combinations for which all 39 points can function in high-precision mode is as follows:

EF 17-40mm f/4L EF 24-105mm f/4L IS EF 70-200mm f/2.8L IS w/ Extender EF 1.4x II EF 200mm f/2L IS + Extender EF 2x II EF 300mm f/2.8L IS + Extender EF 1.4x II EF 400mm f/2.8L IS + Extender EF 1.4x II

AF working range is unchanged from the Mark III, being rated at -1EV to 18EV at ISO 100 (73F / 23C). Interestingly, though, Canon is describing AF performance in both low-light / low-contrast and bright light as being improved, although without detailing precisely how.
The Canon EOS-1D Mark IV's AF modes include both one-shot and servo, with the latter earning the new designation AI Servo II AF, thanks to several changes to the underlying algorithms. There's no longer a delay between the subject beginning to move and AI Servo AF beginning to track and predict the focus position. Should an obstacle pass between subject and camera, or the AF point slip off the subject, then the camera will initially continue tracking based on the last calculated subject trajectory. Should the photographer leave the AF point off the subject for a longer period, the camera will begin to drive the focus point towards the new position, but will do so more gradually than was previously the case, rather than suddenly snapping focus to the background. If the subject suddenly changes its trajectory, the AI Servo II AF system now ignores the initial result and waits until it has two matching results before the focus point changes, reducing the likelihood that an error will suddenly throw the lens off focus.
Canon has also added a second claw-like mirror stopper mechanism to the AF submirror, supplementing the mirror stopper on the main mirror as featured in the 1D Mark III design. This should help to provide a steadier image that will allow the AI Servo II AF mode to make better focusing decisions during high-speed burst shooting.
Viewfinder. Images are framed on the Canon EOS-1D Mark IV's fixed eye-level pentaprism viewfinder, whose design is unchanged since the Mark III. As you'd expect in a camera aimed at professional use, the viewfinder offers 100% coverage both horizontally and vertically. The active AF point is indicated in the viewfinder, which also includes a display that provides a wide range of variables including ISO sensitivity, shutter speed, aperture, and more.
Magnification is 0.76x (-1 diopters with a 50mm lens at infinity), and -3.0 to +1.0 diopters of adjustment is available with an eyepoint of 20mm. A built-in eyepiece shutter is a nice touch, preventing ingress of light when your eye isn't against the viewfinder (which could potentially cause metering issues), without the need for a fiddly and easily lost external viewfinder cover.
Perhaps one of the smallest changes most welcomed by shooters both pro and amateur alike is the modification of the viewfinder eyecup. On previous models (the "Eb" model), the eyepiece was fairly easy to remove, so easy in fact that it tended to fall off during casual transport. The eyecup has now been modified with a catch added on each side, so that it must be "squeezed" to be removed. The new "Eg" eyecup is apparently compatible with the Mark III, as well as the 7D camera.
Display. Beneath the viewfinder eyepiece, the Canon 1D Mark IV provides a 3.0-inch LCD with approximately 920,000 dots of resolution, equivalent to a VGA (640 x 480) pixel array with three dots per color. That's a significant step up in resolution from the 230,000 dot (~320 x 240 x 3 dots per color) display on the Mark III, making the screen much better for judging focus accuracy.
The panel is what Canon refers to as a Clear View II LCD type, and is the same model that first appeared in the EOS 7D digital SLR. Coverage is 100%, and in addition to the increased resolution, the panel also offers improved resistance to glare and reflections thanks to an optical acrylic resin layer between the cover glass and LCD surface. The cover glass has also been upgraded, and is now made from scratch-resistant tempered glass rather than the acrylic plate used in the Mark III.
Live View. Like the 1D Mark III before it, the Canon 1D Mark IV also offers a Live View mode, although the higher resolution LCD and a change to the focusing capabilities should make the function rather more useful. Where the 1D Mark III's earlier generation of Live View required the use of manual focusing, the Canon 1D Mark IV allows three autofocusing options in Live View mode, as per other recent Canon digital SLRs.
The first of these is what Canon refers to as Live Mode AF, whereby the camera applies contrast detection algorithms to the data streaming from the image sensor. This allows focusing without interrupting the live view, but has the disadvantage that it is significantly slower to achieve a focus lock, which makes it less useful for handheld photography, or when shooting moving subjects. The second mode is Face Detection Live Mode. As you may expect, this mode detects and focuses on human faces. If more than one face is detected, the multi-controller can be used to select a different face. Alternatively, in what Canon refers to as Quick Mode AF, the mirror is briefly dropped to allow an autofocus operation using the camera's phase detection autofocus sensor. This mode offers quick autofocusing, but with the disadvantage that there is an interruption of the live view stream during the AF operation.
As with the Mark III, the 1D Mark IV's Live View mode also offers a selectable 5x / 10x magnified view of the selected focusing point when the photographer elects to focus manually. The Canon 1D Mark IV can also overlay grid lines on the live display to help with framing, and depth-of-field preview is possible both in Live View or with the optical viewfinder.
Metering. As you'd expect on a digital SLR aimed at professionals, operating modes on the Canon EOS-1D Mark IV include Program AE (with Program Shift), Aperture-priority AE, Shutter-priority AE, and Manual. Metering is performed with a 63-zone sensor, and modes include AF-linked evaluative, 13.5% partial, or 3.8% spot metering. The spot-metering point can either be locked at the center of the image frame, or linked to the AF point. In addition, the 1D Mark IV supports multi-spot metering, with up to eight spot meter readings in a row being combined to determine a single exposure that best captures the various metered subjects.
The metering range for the Canon 1D Mark IV is from 0 to 20EV (ISO 100, 73F / 23C, with the EF 50mm f/1.4 USM lens). Up to three stops of positive or negative exposure compensation are available, in one-third or one-half EV steps, and the Canon 1D Mark IV can also automatically shoot 2, 3, 5, or 7 bracketed exposures within the same range.
Shutter. The Canon 1D Mark IV's vertical travel focal plane shutter is controlled electronically, and allows for shutter speeds from 1/8,000 to 30 seconds in 1/3-stop increments, plus bulb. The Canon 1D Mark IV offers a two- or ten-second self timer, and includes a Canon N3-type remote terminal connection.
ALO. The Canon 1D Mark IV includes a new generation of Canon's Auto Lighting Optimizer technology, which offers the same preset positions (Disable, Low, Standard, or Strong) as in past cameras. The effectiveness of the function is said to have been improved, though, and it is also now available for the first time in manual exposure mode.
White balance. The Canon EOS-1D Mark IV offers ten white balance modes which include Auto (as determined by the image sensor), five presets, five Custom white balance settings (set in-camera), five Personal white balance settings (set from an attached computer), and finally the ability to specify the color temperature directly in the range of 2,500 to 10,000 Kelvin. It's also possible to fine-tune white balance with +/- nine steps of blue/amber or magenta/green bias, or to bracket white balance with three consecutive shots (but not both together).
Flash. There's also both a hot shoe and PC sync terminal for external flash connection, with X-sync at 1/300 second when using EOS Speedlite flash strobes. With other shoe-mount flashes, X-sync is at 1/250 second maximum, and with studio strobes at 1/60th second. Flash metering choices are E-TTL II, evaluative, or averaged. Three stops of positive or negative flash exposure compensation is available in 1/3 or 1/2EV steps.
Canon says that the algorithms for E-TTL II in the 1D Mark IV have been refined, so as to take greater account of distance information from the attached lens and hence reduce the influence of the background, improving exposure accuracy when shooting a small subject with a wide-angle lens.
HD Movie mode. Another area of significant change in the Canon EOS-1D Mark IV is its new high-definition video capture mode. The functionality is largely similar to that from the EOS 7D digital SLR, providing for recording of movie clips up to four gigabytes in size, which are saved using AVC / H.264 compression in a .MOV container.
Resolution and frame rate options include 1,920 x 1088 pixels (23.976, 25, or 29.97 frames per second), 1,280 x 720 pixels (59.94 or 50 fps), or 640 x 480 pixels (59.94 or 50 fps). The numerous different frame rates match various broadcast television formats etc., removing the need to transcode to the intended output frame rate after capture, and the available frame rates will depend on whether the camera is set to NTSC or PAL mode.
The Canon 1D Mark IV's movies include 48KHz audio, recorded either with a newly added monaural microphone on the camera's front panel, or via an external microphone attached to the camera's standard 3.5mm stereo jack. No control is offered over audio levels when recording, however. In addition to the new microphone on the front of the camera body, the 1D Mark IV also retains a rear-panel microphone used for the camera's voice memo function, as well as a rear-panel speaker that caters to both video and voice memo modes. The Canon 1D Mark IV's HD video mode would not be complete without an HDMI-out port, so that was included as well.
It is possible to perform a contrast-detect autofocus operation during movie recording; however Canon recommends against doing so on the basis that the AF operation will be noticeable in both the video and audio portions of the recording. Exposure can be controlled either automatically or manually, with all of the camera's extremely wide range of ISO sensitivities available, except for the expanded ISO 50 setting. When recording using manual exposure, it is possible to set the ISO sensitivity directly, or to leave this under the camera's control while manually specifying the aperture and shutter speed.
Limited in-camera video editing is possible, with the ability to trim the start or end of a video clip in one-second increments, and save the result as either a new file, or overwriting the original.
Much like the previous EOS 5D Mark II, the EOS-1D Mark IV provides the ability to capture a still image during movie capture by pressing the shutter button, with the still frame being recorded both as a separate image, and also placed into the video stream at the point of capture rather than leaving blank frames. Video capture itself is triggered by first placing the camera in Live View mode, then pressing the FEL button to start or stop video recording.
Custom Functions. Several custom functions have been added to the EOS-1D Mark IV which bear mentioning. The first relates to video recording, altering the previously described behavior in one detail. Through a custom function, it is possible to set the camera to remove the two-step process that requires the photographer to first enter Live View mode before the FEL button can be used to start movie recording. With this custom function set, the FEL button can instead simultaneously start live view mode and begin movie recording all in one step.
There are also several new custom functions relating to the EOS-1D Mark IV's autofocus system, which should make the camera rather more versatile. A new addition to the AF Point Expansion function allows the user to select any AF point as a starting point, and have the camera automatically track the subject beginning from that point, across any other AF point. The currently active point is indicated in the viewfinder, and also shown in Canon's Digital Photo Professional software.
The 1D Mark IV also offers a spot AF custom function like that in the EOS 7D, which acts similarly to single-point AF, except that it reduces the size of the AF point. This can be useful when shooting overlapping subjects -- for example, an animal in a cage -- but can also make it harder to obtain a focus lock, especially when hand-holding the camera or shooting moving subjects.
Finally, a EOS-1D Mark IV custom function relating to AI-Servo AF allows separate selection of focus-lock or shutter-release priority for the first shot in a burst, and subsequent shots. This allows the photographer to decide, for example, that the timing of the first shot is more important than whether the camera has determined a focus lock, but that for subsequent shots precise focus is more critical than burst speed.
Storage. The Canon EOS-1D Mark IV can store still images as Adobe RGB or sRGB compressed JPEG files, 14-bit .CR2 Raw files, or both file types simultaneously. Images are stored on either CompactFlash or Secure Digital cards, with one card slot available for each type. For CF, both Type-I and Type-II cards are supported, as are UDMA Mode 6 cards. SD support includes the faster and higher-capacity SDHC types.
It is possible to copy files between cards in-camera, and several options are available that allow the EOS-1D Mark IV to duplicate images on both cards simultaneously, to separate file types by flash card slot, or to select one card as an overflow for use when the other card is filled to capacity.
Connectivity options include USB 2.0 High-Speed data transfer, and NTSC / PAL standard definition video output.
Battery. The EOS-1D Mark IV's power comes courtesy of an LP-E4 lithium-ion rechargeable battery, the same type as that used in the EOS-1D Mark III. Battery life is rather lower, though, due to the increased sensor resolution, and the attendant increase in processing that this brings. Where the Mark III was rated to yield 2,200 shots on a charge (73F / 23C), the EOS-1D Mark IV is rated for 1,500 shots on a charge in the same conditions.