Canon 60D Exposure
Canon 60D Exposure
The Canon 60D adopts the same exposure system which debuted in the company's flagship APS-C format digital SLR, the EOS 7D. Dubbed IFCL -- which stands for Intelligent Focus, Color, Luminance -- the new metering system takes into not only account subject luminance, but also both color information and focus distance. Because silicon light sensors are significantly more sensitive to longer-wavelength light, unless an exposure sensor's response is substantially tweaked via a filter system of some sort (which naturally decreases sensitivity), it will tend to underexpose red-colored objects or scenes, and overexpose ones dominated by blue or green hues. To prevent this issue, the 60D takes advantage of color information provided by its dual-layer autoexposure sensor, with the upper layer being sensitive to Blue/Green light, and the lower layer to Green/Red light. The Canon 60D should hence be able to markedly improve exposure accuracy in situations where the subject is dominated by colors at one end or the other of the color spectrum.
The Canon 60D's autoexposure sensor divides the frame into 63 separate zones, the data from which can be evaluated in a variety of ways, depending on the AE mode you're operating in. AE and AF zones are aligned, allowing exposure information to be associated with specific AF sensors and the area around them.
The 60D's AE system also integrates distance information from the autofocus system into the exposure metering process, thanks to a rather clever assumption: If you've identified the subject as being located a certain distance away from the camera, nearby objects that are close to the same distance are most likely part of the subject, too. Thus, rather than simply relying on a spot AE reading centered on the primary AF point, or blindly combining exposure information from a cluster of AE points in some arbitrary geometric grouping around the active AF point, the Canon 60D instead gives stronger weighting to exposure sensor segments that lie beneath adjacent AF points showing a similar distance reading.
Although we've not had confirmation of this from Canon, we suspect that the color-sensitive capability of the new AE sensor plays a role here too: It seems highly likely that the 60D's exposure system takes color into account and considers contiguous areas of similar color to be an indication of the extent of the subject as well.
The Canon 60D's exposure metering options include 63-zone Evaluative, Center-weighted Average, Partial (6.5% of viewfinder at center), and Spot (2.8% of viewfinder) options. Metering sensitivity range is specified at 1-20 EV (at 23°C/73°F, with EF 50mm f/1.4 USM lens, ISO 100).
The Canon 60D's Exposure Compensation setting allows the user to increase or decrease the metered exposure by up to five stops positively or negatively, in one-third or one-half EV increments -- a much more useful range than the two stops either side of nominal exposure offered in the previous 50D model. Although Evaluative metering is linked to the active AF point (whether automatically or manually selected), Spot metering is fixed to the center of the viewfinder (unlike Nikon SLRs, which can spot meter at any selected AF point).
Here you can see the coverage of the 60D's four metering modes, accompanied by the positions of the nine autofocus points. From left to right: 63-zone Evaluative, Center-weighted Average, 6.5% Partial, and 2.8% Spot metering.
In Live View mode, evaluative metering is always used, however Canon does not specify how many zones. The sensitivity range for Live View metering is specified at 0-20 EV (again, at 23°C/73°F, with EF 50mm f/1.4 USM lens, ISO 100).When Face Detection AF is enabled in Live View mode, the Canon 60D biases the exposure in an attempt to properly expose for a detected face.
ISO Sensitivity Options
The Canon 60D offers regular ISO equivalents of 100, 200, 400, 800, 1,600, 3,200 and 6,400, with the option to use fractional settings in 1/3-EV increments (100, 125, 160...). The EOS 60D also offers a high-range ISO setting enabled when ISO Expansion is turned on, which is equivalent to ISO 12,800. An Auto ISO mode adjusts the ISO as the camera deems necessary, from 100 to 6,400 in Creative Zone modes, or 100 to 3,200 in Basic Zone modes. When shooting in Creative Zone modes, it's possible to set an upper limit on the Auto ISO range. This upper limit can be set to any sensitivity between ISO 400 and ISO 6,400, but you can't specify the minimum shutter speed the camera should use before raising the ISO. The limit is ignored for flash photography, unless using bounce flash with an external Speedlite flash strobe. Auto ISO when using a flash defaults to ISO 400, but will throttle down as low as ISO 100 to prevent overexposure, and will range as high as ISO 1,600 for bounce flash, if allowed by the Auto ISO limit.
Automatic Exposure Bracketing
An automatic exposure bracketing feature lets you set the Canon 60D's total exposure variation (across three shots) at anywhere from +/- one-third or one-half EV, up to +/- 3 EV, a rather wider range than was available in the 50D. Exposure bracketing and exposure compensation are additive, in other words the automatic variation is centered around whatever level of manual exposure compensation you have dialed in. Thus, you could manually set a positive exposure compensation of 1 EV, and then have the camera give you a variation of +/- 2/3 EV around that point. (This also means that the bracketed exposures can go outside of the standard exposure compensation range, allowing one shot as far as 8 EV from the metered exposure.) The number of shots in a sequence is fixed to three, and the sequence order can be changed to either 0, -, + (metered, under, over), or -, 0, + (under, metered, over).
AE/FE Lock (" * " button)
The Canon 60D has the same simplified AE Lock button as the 40D, which unbundled the AF Lock feature from the old button on the older EOS cameras like the 20D and 30D. Marked with an asterisk (*) symbol, the AE Lock button simply holds the exposure at one setting while you recompose the image, at least by default. (More on that in a minute.). It's very useful when spot metering, but also when dealing with subjects where you want to draw your exposure from one place, while autofocusing on another. The exposure remains locked for as long as the metering system is active, and if you need to maintain the same exposure across multiple shots with a longer duration between each frame, then you can simply hold down the AE Lock button. Pressing the button with the pop-up flash activated or with an external flash mounted activates the FE Lock (Flash Exposure) function, which fires the flash and locks the proper exposure for the following frame.
By default, the AF-ON button allows you to set focus before depressing the shutter button. On pressing the AF-On button, the 60D's metering system will come to life, and autofocus will begin. If you release the AF-On button, then the camera will release the metering lock, and will refocus if you subsequently press the Shutter button. If you keep the AF-On button depressed, though, then the Shutter button will simply initiate the exposure, with focus and metering remaining as set when the AF-On button was pressed. This default behavior can be changed in a variety of ways, as described momentarily.
The AF-ON button also controls autofocus operations in Live View and Movie shooting. The Canon 60D now has two styles of autofocus operation in Live View mode: the standard phase detection method, which requires the reflex mirror to be briefly swung back into the optical path, thus disrupting the live view briefly, or a contrast detection method which does not. Both methods have their advantages and disadvantages, but the contrast-detect method offers an uninterrupted user experience. A third method incorporates a face detection into the contrast detection method, offering the face-detecting mode of autofocus now commonly seen on consumer point-and-shoot cameras. The same three choices are available in Movie shooting, although phase detection isn't available during movie capture. If set to use phase detection AF before recording, the 60D will seamlessly switch to using contrast detection after the recording is started.
Through Custom Function IV-1, the behavior of the Shutter, AF-On, and AE Lock buttons can be changed. By default, autofocus and metering are initiated with a half-press of the shutter button or the AF-On button, while a single press of the AE Lock button locks exposure until the 60D's metering system powers down. There are no less than eight alternatives to this behavior. The first unbundles focus functions from the shutter button, so that the AF-On button must be used to lock focus. The second option does the same, but switches the functions of the AF-On and AE Lock buttons. A third option locks exposure with either the AE Lock button or a shutter button half-press, while AF and metering are handled by the AF-On button. Option four again reverses the functionality of the AF-On and AE Lock buttons from the third option. The fifth options replicates the second one, but also triggers autofocus with a half press of the shutter button. Option six uses the shutter button to start metering and autofocus, the AF-On button to cease autofocus operation, and the AE Lock button as its name would suggest. The next option again reverses the behavior of the AF-On and AE Lock buttons. Option eight is similar to number six, but disables the AF-On button altogether. Finally, option nine instead disables the AE Lock button, and uses the AF-On button for this function instead.
Custom Function IV-2 allows functions to be assigned to the Set button, located in the center of the Multi-controller. By default, this button serves no purpose in Record mode. If desired, however, it can provide quick access to image quality, picture style, white balance, flash exposure compensation, or viewfinder electronic level functions. When set to this last, information from the single-axis roll level is used to provide a level display using the exposure level scale in the viewfinder. Finally, Custom Function IV-3 allows the direction of the Main and Quick Control dials to be reversed when adjusting the Aperture or Shutter values in Priority, Manual, or Bulb-mode shooting. Rather counterintuitively, this option is ignored when in movie mode, and doesn't affect dial rotation for exposure compensation, nor for Program Shift.
In Movie mode, there is similar functionality to Custom Function IV-1, but it is set through an option in the Movie menu, since the Custom Function menu can't be accessed in Movie mode. The option set here is separate from that for still image shooting, allowing different control mappings in each mode. A separate option allows autofocus with the shutter button to be enabled or disabled in Movie mode.
White Balance Options
As you'd expect, the Canon 60D offers a full range of White Balance settings, including an Auto setting, six presets, and a Custom setting. The six presets include Daylight (5,200K), Shade (7,000K), Cloudy (6,000K), Tungsten (3,200K), White Fluorescent (4,000K), and Flash (6,000K). The Custom setting bases color balance on a previous exposure, meaning you can snap an image of a white card and then base the color temperature on that image. There's also a direct Kelvin color temperature setting, which can be set within 100K steps, from 2,500 to 10,000K.
A fairly sophisticated White Balance Shift tool lets you shift the color balance toward more or less green, amber, magenta, or blue, using a +/-9 step grid format. You move a highlighted square through the grid to adjust the color balance. Also available is a White Balance bracketing option, which snaps only one image, then writes three successive files from that single exposure. Bracketing steps are from +/- 3 stops in whole-stop increments. (Each stop corresponds to five mireds of a color conversion filter, for a total range of +/- 15 mireds. This corresponds to about a +/- 500K shift at a normal daylight color temperature of 5,500K.) WB Bracketing is set on the same grid as the White Balance correction grid.
As with other recent Canon DSLRs, the Canon 60D offers a Picture Style option through the LCD menu, which lets you select from Standard, Portrait, Landscape, Neutral, Faithful, Monochrome, or three User Defined settings. In each of the preset modes, the Contrast, Saturation, Sharpness, and Color Tone are set for specific conditions. For Monochrome, Saturation is replaced with Filter effect (options are: None, Yellow, Orange, Red or Green), and Color Tone is replaced with Toning Effect (None, Sepia, Blue, Purple or Green). The three User Defined options let you manually adjust each variable, then save it as a custom parameter. Of course, you can also set the camera's color space to sRGB or Adobe RGB.
Auto Lighting Optimizer (ALO)
First seen on the Rebel XSi, Canon's Auto Lighting Optimizer (ALO) function lets you expose for the highlights, preserving detail there, while the camera adjusts the image to open up the shadows. This happens on the fly, as the files are being written to the memory card, so there's no post-capture intervention by the user required to take advantage of this function. We weren't terribly impressed with ALO on the XSi, however newer Canon models including the 60D offer four different settings for it, and the control on the 60D seems quite effective. The ALO setting is made via Record Menu 2, where you can select options of Disable, Low, Standard (the default), or Strong.
Highlight Tone Priority (HTP)
Also included on the Canon 60D is Highlight Tone Priority (HTP for short), a feature that's been on Canon SLRs for some time now, and one that works quite well when dealing with subjects with important detail in strong highlights. (Think of the standard wedding dress shot, and you'll get the idea.) Digital cameras normally expose more like slide film: Once you hit a certain exposure level, detail just vanishes. This really becomes an issue when you're dealing with contrasty lighting and a subject with lots of highlights in it.
HTP's action is pretty subtle, but the results are very evident when dealing with strong highlights under harsh lighting. The way it works is to set the camera's base ISO up one notch, to 200, so it's only half-filling the sensor's pixels with charge during the exposure. The Canon 60D then alters its tone curve, basically compressing the top half (that would normally be blown out) into a smaller range, thereby preserving the highlight detail. You can do this yourself when working from RAW files, you just need to significantly underexpose most of the scene, and then fiddle with the tone curve to drastically reduce the contrast, but only in the extreme highlights. If that sounds difficult, it is; it can be a real time-sink, and very difficult to make the end result look natural. Canon's HTP does this for you automatically, though, and the results look just great: You have no sense that the camera has been making radical adjustments to its tone curve; you just see all the detail in the highlights that otherwise would be missing. HTP is controlled via Custom Function setting II-3, giving you options to Disable (the default) or Enable it.
Noise Reduction Options
The Canon 60D offers two types of adjustable noise reduction. Long Exposure noise reduction can be performed for exposures one second or longer, and works by taking a second "dark frame" of equal duration with the shutter closed, and then subtracting it from the first frame. This reduces or eliminates most noise generated by the sensor during long exposures at low ISOs, but can make noise worse at higher ISOs (at ISO 1,600 and above). Available settings are Off, Auto and On, and are accessed from Custom Function II-1. The Off setting is the default. The 60D also offers the user four levels of high ISO sensitivity noise reduction. Options are Standard, Low, Strong, and Disable, with Standard being the default. Though the name implies this noise reduction is only applied at high ISOs, the Canon 60D applies it to all ISOs. This explains why the 60D's chroma noise in shadows and darker tones is lower than most DSLRs at low ISOs, when using the default Standard setting. These settings are accessed in Custom Function II-2. High ISO noise reduction is not applied to RAW files.
Continuous Shooting Mode and Self-Timer
The Canon 60D's Continuous Shooting mode is rated by Canon at 5.3 frames per second in high speed mode, for a total of 58 Large/Fine JPEG shots or 16 RAW before the buffer fills, or 3 frames per second in low speed mode. When shooting JPEGs of a very complex scene with a lot of sharp, fine detail may also compress less and result in lower buffer capacities, as was seen in our testing.
The camera's Drive setting also accesses two Self-Timer modes, which open the shutter 10 or 2 seconds after the Shutter button is pressed, giving you time to dash around in front of the camera. Either Self-Timer mode can also be used with an optional RC-6, RC-5, or RC-1 infra-red remote control unit, allowing an image to be captured immediately or with a two-second delay after pressing the remote's shutter release button.
The images above were taken from our standardized test shots. For a collection of more pictorial photos, see our Canon EOS 60D Photo Gallery .
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