Rudy Winston
Rudy Winston

Rudy Winston has over 14 years experience with Canon USA's Pro Products team, and has been responsible during that time for training Canon's staff on new products, creating presentations for customers and dealers, numerous writing projects, and providing technical assistance to professional and amateur photographers.

The EOS-1D X's 100,000-pixel RGB Metering

October 17, 2011

"The EOS-1D X uses an actual RGB sensor, with approximately 100,000 pixels on it"

Canon EOS cameras have had multi-zone metering systems since the very first EOS 650 and EOS 620 cameras of 1987. Any form of multi-zone exposure metering tries to read different areas of the frame, and compare readings – ultimately, to be able to identify unusual lighting conditions, and apply some sort of corrections automatically.

But until now, every EOS camera used a light-sensitive metering sensor that essentially could only measure how much light there was. Some of the latest models, like the EOS 7D and 60D, used a multi-layer system with the ability to detect excessive red or green tones, and apply a slight correction. But they couldn't detect other colors, or perform any type of subject recognition. Even so, the 63-zone Evaluative metering in these cameras has been well-received by critical users, and is useable in a broad range of situations.

The EOS-1D X, however, offers much more. Befitting its standing as the top-of-the line camera in the EOS line-up, its metering system truly breaks new ground, and offers features and capabilities never seen before in an EOS camera. Instead of a segmented light-sensitive metering sensor, the EOS-1D X uses an actual RGB sensor, with approximately 100,000 pixels on it. You can think of it as a miniature version of the imaging sensor in a digital camera. Covered with Red, Green or Blue filtration over each pixel, it can read that elusive combination of brightness and color. And, because it has over 100,000 pixels, it can also read enough detail at the subject to be able to recognize many types of subjects and scenes – without resorting to Live View, and before a picture is taken.

We'll explore some of the features and potential of this new 100,000-pixel RGB Metering Sensor, and give photographers some ideas of how it can be used in real-life scenarios.

The metering sensor:

The new RGB sensor for light metering is located up in the prism area of the camera, above the eyepiece optics. It reads most of the image area, looking down on the focus screen. This is typical of nearly all current digital SLRs. But extremely atypical is this sensor's ability to read color information. Because it uses the combined results from Red, Green and Blue pixels, it can ascertain subject colors, distribution of color over the frame, and therefore do a good job of recognizing many types of scenes.

Armed with this information, the metering system can apply subtle corrections when colors such as yellow or green are detected in a scene. (Green subjects, for instance, normally tend to cause slight over-exposure in an image, if they dominate a scene.) Because the RGB metering system can account for color throughout the frame, exposure is less likely to be influenced by the color of background objects, or the color of parts of a scene like a subject's clothes. The result of reading not only brightness but color information provides great exposure stability, an important consideration for pros and serious enthusiasts who are using automatic exposure along with Evaluative metering.

Face Detection technology – an industry first

Face Detection during exposure metering is another landmark EOS-1D X capability. Canon's 100,000-pixel RGB Metering Sensor introduces what Canon calls " EOS iSA (Intelligent Subject Analysis) System". And a key aspect of this Intelligent Subject Analysis is the meter’s ability to identify and correct for a human face in a scene.

The camera's RGB metering system has sufficiently fine resolution to detect human faces, as well as insuring during Evaluative metering that exposure is based on the detected primary face in the scene. This makes it the first digital SLR in the world (as of September 1, 2011) to offer face detection technology when using the eye-level optical viewfinder. All previous SLRs with face detection capability to date required users to switch to Live View, so that the camera's high-resolution imaging sensor could be used for face detection.

The Intelligent Subject Analysis system may be a terrific metering option for any shots of human subjects. Evaluative metering is immediately based around the detected face, with (of course) consideration for the remainder of the scene factored in to some degree as well. For anything from wedding pictures to basketball under available light, this impressive new technology raises the bar in what's possible from in-camera metering – especially for those who like to rely on automatic exposure control.

The EOS-1D X's face detection metering technology also teams up with the Auto Lighting Optimizer (a separate imaging feature that's been seen in previous EOS models). Auto Lighting Optimizer, sometimes abbreviated ALO, is designed to alter image processing in-camera if large areas of dark shadow are detected. It will adjust the contrast to bring out additional shadow details, without significantly affecting highlight areas – and this is performed on a shot-by-shot basis, so any correction is done on an as-needed basis. With the EOS-1D X's intelligent Subject Analysis system, if a face is detected and it's detected to be back-lit, exposure and processing are adjusted to bring out details in the face. (With RAW images, exposure is adjusted in-camera by the RGB metering system, and the images are "tagged" for the camera-defined level of Auto Lighting Optimizer correction if they're subsequently processed in Canon's supplied Digital Photo Professional RAW processing software.)

While Intelligent Subject Analysis metering with the 100,000 pixel RGB sensor is always available whenever it's set for Evaluative metering, Auto Lighting Optimizer can be independently set to Low, Standard or High settings, or turned completely off. There's a new menu option that automatically shuts off the ALO whenever the camera is put into Manual exposure mode (preventing any subtle contrast/exposure shifts in successive manual images), too.

Any time the new 100,000 pixel RGB metering sensor is called upon to perform subject detection, it uses the entire available pixel array, with no dividing or segmenting of pixels into separate zones.

252-zone Evaluative metering

When actual Evaluative metering of light occurs, the approximately 100,000 pixels on the RGB metering sensor are divided into a 252-zone matrix of square-shaped metering areas. Covering a 21x12 grid, these square-shaped zones detect variations in brightness throughout a scene, and cover most of the picture area. With this many metering zones, backed-up by the performance of the RGB metering system, the EOS-1D X provides the finest metering segmentation ever in a Canon EOS camera.

When Evaluative metering is active, the above-mentioned EOS iSA (Intelligent Subject Analysis) System and face detection technologies are activated automatically; there's no requirement for the photographer to turn them on or off.

As with all previous EOS models, the basic concept of Evaluative metering is to read exposure over the entire picture area, knowing what and where the primary subject likely is in the scene – the EOS-1D X's color metering and scene detection technologies obviously are a huge help here. The AF system provides information to the metering system, identifying the active AF point(s), and thus pointing the Evaluative metering system to the probable location of the primary subject.

Then, armed with this info, the scene is metered, with the 100,000 pixel RGB sensor broken down to 252 separate zones. And, if variations are detected in the lighting in the scene (think of a typical back-lit scene, or a spot-lit actor on a stage), Evaluative metering takes the next step for the photographer. Subtle adjustments to exposure are performed automatically, to correct for possible problem lighting.

Historically, Canon's Evaluative metering has been the metering system of choice for users who usually rely on automatic exposure modes, such as Shutter-priority, Aperture-priority, or full Program auto exposure. Serious users who up to now may have resisted the idea of Evaluative metering in their shooting may want to re-consider, and experiment with what the EOS-1D X's new RGB metering system can deliver for them.

Other metering patterns

While many EOS users rarely venture away from the factory-default Evaluative metering, there are other metering options for EOS-1D X users. All of these continue to use the 100,000 pixel RGB metering sensor to read exposure, but without the sophisticated multi-zone comparisons that occur during Evaluative metering.

  • Center-weighted metering
    The camera reads the majority of the image area, but concentrates upon the center of the scene – regardless of which AF point(s) are being used. Unlike Evaluative metering, there's no attempt to compare brightness and color at different regions of the scene, and apply corrections for backlighting or other detected problems. Many SLR users who got started with 35mm film cameras in the 1970s and 1980s are familiar with this method, and it is often preferred by experienced SLR shooters who would rather dial-in their own exposure compensation.
  • Partial metering
    Partial metering always takes place in the center of the viewfinder. Many users think of Partial metering as a "fat spot" method, reading roughly 10% of the overall picture area. It actually is quite practical for users who want to take a selective meter reading off of a fairly broad area of a scene, such as metering the face in a typical portrait. With automatic exposure (Aperture-priority, Shutter-priority or Program AE), it's easy to apply AE Lock and/or exposure compensation once a reading is taken, re-compose, and shoot. And, like Spot metering, Partial metering can be a very practical method when users prefer to take a little more time with Manual exposure control.
  • Spot metering
    A long-time favorite of pros and experienced SLR enthusiasts who prefer to expose carefully and really lock-in a reading. Spot metering on the EOS-1D X reads a tiny portion of the overall scene, making very precise readings of small areas of a scene easy and quick. As with Partial metering, it can be combined with AE Lock (when shooting in an automatic exposure mode), or used with Manual exposure mode.

    Spot Metering linked to the active AF point(s)
    By default, Spot meter readings are taken from the dead-center of the finder, regardless of which AF point(s) are active. However, there's a Custom Function for "Spot meter linked to AF point" – activate this, and spot metering can be linked to any AF point or AF Zone that's been manually chosen by the user. Now, AF and precise Spot metering can be carried out quickly and basically with one step, avoiding the need to have to meter using the center of the focusing screen and re-compose. (When the camera is set for Automatic AF point selection, Spot metering is always performed from the center of the viewfinder.)

    Up to eight Spot readings, with Multi-Spot metering
    Multi-spot metering, a great feature on previous EOS-1D and EOS-1Ds versions, remains available with the EOS-1D X. Press a button (any of several that can be configured for FEL and Multi-spot metering), and a single Spot reading is taken. Move the Spot area to read a different part of the scene, and each additional button press registers another Spot reading. Each spot reading is added and averaged. Up to eight separate Spot readings can be taken and averaged this way. The camera's extensive analog metering scale in the viewfinder not only shows the cumulative exposure, but graphically indicates the difference between each meter reading. It's the ultimate in-camera tool for the precise and careful shooter who prefers to take exacting readings with Spot metering.

    Like previous EOS-1D and EOS-1Ds models, Multi-Spot metering works in any auto exposure mode, but will not function in Manual exposure. However, with the EOS-1D X's new "AE Lock – Hold" option, it's easy to lock-in that reading for extensive shooting sessions. When the new Hold option is active, metering remains locked until Auto Power Off kicks-in.
E-TTL flash, with RGB metering

The same RGB color metering sensor used for metering ambient light is used for E-TTL flash metering as well – whether a single Speedlite is being used, or multiple Speedlites with wireless E-TTL. The EOS-1D X is fully compatible with any EX-series EOS Speedlite, current or previous, so no special "new" flash is required for full E-TTL control on this new camera.

Basic E-TTL operation has not changed. However, since the sensor that's measuring the E-TTL pre-flash now can read color and carry out intelligent Subject Analysis and even face detection, it has far more information to work with. Users can expect more consistent flash results, and less tendency for under-exposure when photographing light-colored subjects. When a human face is detected by the EOS iSA System, E-TTL instantly revises its output calculations to provide exposure that's appropriate for the face, with less chance of being influenced by the subject's clothing or backgrounds. Canon expects users to find that the EOS-1D X provides even greater levels of flash exposure consistency and reliability, opening opportunities for quicker shooting with less corrective input required from the photographer. The approximately 100,000-pixel RGB Metering Sensor is a big part of the reason why.

Subject Recognition AF: EOS Intelligent Tracking and Recognition

This is discussed in detail in a separate article here on Canon's Digital Learning Center. Simply stated, the new RGB metering sensor can be combined with Automatic AF point selection when a user is shooting moving subjects in AI Servo AF.  The technology is sufficiently noteworthy to have its own name: EOS iTR (Intelligent Tracking and Recognition) AF.  It's activated via a setting in the EOS-1D X's fourth AF menu (Auto AF pt select: EOS iTR AF > On/Off)

With this outstanding feature, the approximately 100,000-pixel RGB Metering Sensor registers the subject by its brightness and color when initial focus acquisition takes place. Now, with all AF points active, as that subject begins to move, the metering system continually updates the subject's location in the viewfinder. And, this info is instantly provided to the AF system, which now has a continually updated stream of info on where the subject is, allowing the Automatic AF point select system to much more reliably switch points to keep the subject within the AF system's view. Wildlife and action shooters in particular, when photographing subjects that move erratically, now will find that Automatic AF point selection has been truly reinforced by a new technology that may make it the go-to option for truly challenging subjects.

This is arguably the most significant AF difference between the EOS-1D X and Canon’s EOS 5D Mark III, which also uses the 61-point AF system. The 5D Mark III doesn’t have the 100,000 pixel RGB metering system, and thus lacks the ability to perform EOS iTR AF when using automatic AF point selection and follow-focusing moving subjects in AI Servo AF.

Again, a more complete discussion of how the AF system teams up with the new RGB metering system using color information to assist with AF point selection will be available here on Canon USA's Digital Learning Center.

Separate DIGIC 4 processor, exclusively for exposure system control

The vast amount of data provided by the new RGB metering system on the EOS-1D X dwarfs that which was supplied in previous 35 or 63-zone metering systems. Subject recognition AF, in particular, places unprecedented processing demands upon the metering system to provide detail to the AF system. Because of this, Canon's engineers have provided a totally separate DIGIC 4 processor in the EOS-1D X, which is exclusively dedicated to RGB metering tasks. In other words, the metering system – alone – has the same processing power available that certain entire Canon EOS cameras have had available to them previously. Of course, this RGB metering-dedicated DIGIC 4 processor is in addition to the dual DIGIC 5+ processors which are the central processing units within the EOS-1D X.


With a new metering sensor that can be thought of as similar to a small digital camera imaging sensor, the EOS-1D X has more information to work with than any previous EOS camera. Using a sensor with approximately 100,000 pixels, the camera is able to not only very precisely measure light values, but provide an advanced level of scene and subject detection, as well as face detection, and make a host of subtle corrections for accurate and stable exposure metering. The same benefits come to play for E-TTL flash metering, with any current or previous Canon EX-series Speedlite.

On top of that, this powerful metering system now can be teamed-up with the AF system to really boost its ability to automatically select AF points – elevating this ability to a point where Canon's engineers expect it to be a prime feature for pros working with fast- and erratically-moving subjects. Photographers who shoot subjects such as birds in flight, motorsports and others are among those who should experiment with Automatic AF point selection and Canon's new Intelligent Tracking and Recognition technology, to see how effectively it works in different situations.

While the EOS-1D X's tremendous shooting speed, AF performance and other highlights will no doubt capture the bulk of attention from interested SLR enthusiasts and pros, its stellar new metering system is arguably one of its most innovative features. Its potential to improve exposure quality, consistency and even contribute to the camera's AF performance should be an inspiring appeal point to critical users, and further answer the question about what does the customer get when he or she invests in a truly top-of-the-line, professional digital SLR.

The CDLC contributors are compensated spokespersons and actual users of the Canon products that they promote.

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