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Canon EOS 300D Digital Rebel

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Page 6:Exposure & Flash

Review First Posted: 09/04/2003

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Like the EOS 10D, the Digital Rebel 300D provides as little or as much exposure control as you could want. Standard exposure modes include the usual Program, Aperture-Priority, Shutter-Priority, and full Manual modes, as well as some "Image Zone" (scene-based preset) modes, and one of the most unique (and useful) modes I've yet seen, an Automatic Depth-of-Field mode. The "Image Zone" exposure modes include Portrait, Landscape, Close-up (macro), Sports, Night Portrait, and Flash Off modes. These modes preset a variety of camera parameters to make it easier for non-expert photographers to achieve good exposures in a variety of standard shooting situations. The Flash Off mode simply disables the flash and external Speedlite (if attached), and puts the camera under automatic exposure control. The full Auto mode takes over all camera functions, turning the 300D into a very easy to use point and shoot camera, albeit a very capable one.

The Aperture Priority and Shutter Priority modes work much the same as on any other camera, allowing you to adjust one exposure variable while the camera selects the other for the best exposure. Program mode keeps both variables under automatic control, while Manual mode gives you full control over everything. The Automatic Depth-of-Field mode (A-DEP) uses all seven autofocus zones to determine the depth of field in the active subject area. Once it has determined the range of focusing distances present across the seven zones, it automatically computes the combination of aperture and shutter speed needed to render the nearest and furthest points in sharp focus. This is a remarkably useful feature, even for professional photographers. In many situations, you want to keep several subjects in focus, while at the same time trying for the highest shutter speed (largest aperture) that will permit that. In practice, faced with such situations, I've usually resorted to just picking the smallest aperture feasible and hoping for the best. With the 300D's A-DEP mode, the camera takes the guesswork out of this process and gives you the fastest shutter speed it can manage while still keeping things in focus. (In playing with this, I was often surprised by how large an aperture in fact would work. I frequently would have chosen a much smaller aperture to stay on the safe side.)

Exposure metering options are similar to the 10D, as the 300D offers Evaluative, Partial, and Center-Weighted options. However, the 300D offers somewhat less flexibility in choosing the metering mode. In Shutter Priority, Aperture Priority, or Program AE modes, the camera defaults to the Evaluative mode. Pressing the AE Lock button momentarily switches to Partial metering, which reads from approximately nine percent of the frame, in the very center of the image area. In Manual mode, Center-Weighted metering is the default mode, but pressing the AE Lock button again switches to Partial mode. (Evaluative is unavailable in Manual mode.) The EOS 300D offers variable light sensitivity, with ISO equivalents of 100, 200, 400, 800, and 1,600. For adjusting the exposure, the 300D's Exposure Compensation setting increases or decreases overall exposure from +/-2 EV in one-third EV increments. An automatic exposure bracketing feature lets you set the total exposure variation (across three shots) at anywhere from +/- 1/3 EV all the way up to +/- 2 EV. The nice part is that 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 0.7EV, and then have the camera give you a variation of +/- 2/3 EV around that point.

I really like the amount of information the 300D gives you about its exposure, not only in terms of the settings it's using, but in the form of feedback on how pictures you've captured turned out. You can select an "Info" display mode when viewing captured images on the rear-panel LCD screen, which produces the display shown at right. Notable here is that you not only can see all the exposure parameters, but you get excellent feedback on the tonal range of the image itself. One form of feedback is the histogram display at upper right, which shows how the tonal values are distributed within the image. Histogram displays are useful for directly seeing how the overall exposure turned out in an image, but I've found them to be of limited usefulness for making critical judgments about highlight exposure.

Digital cameras need to be exposed more or less like slide film, in that you need to zealously protect your highlight detail. Once you've hit the limit of what the sensor can handle, the image "clips" and all detail is lost in the highlight areas. The problem is that it's quite common for critical highlights to occupy only a very small percentage of the overall image area. Because they correspond to such a small percentage of the total image pixels, the peak at 100 percent brightness can be very hard to distinguish in the histogram display. To handle such situations, the Digital Rebel blinks any pixels that are 100 percent white on its screen, alternating them between black and white. This makes localized overexposure problems leap out at you, making it very easy to control the critical highlight exposure precisely. (The sample image shown in the display above is a pathological example, chosen to show how the feature works. In practice, you'd probably never overexpose an image that badly.)

Besides the abovementioned exposure information and feedback, the 300D's playback options include a thumbnail index display, normal full-frame viewing of captured images, and a zoomed view, as shown at right. There's also a "jump" mode, activated via the Jump button on the rear panel of the camera. Jump mode lets you very quickly move through images stored on the memory card, jumping 10 shots at a time. The zoomed playback option is an area where the 300D improves greatly on the performance of the 10D. The 300D's image playback can be zoomed in very small steps anywhere from 1.5-10x. Once you've zoomed in at any level, you can scroll the zoomed window all around the image area, using the rear-panel arrow keys. The scroll frame-by-frame at the magnified view is the same on both cameras. Once you've dialed in the magnification and scrolling parameters, you can go to the next or previous image by turning the main dial next to the shutter button.

Another feature deserving comment is the 300D's separation of the autoexposure and autofocus lock functions. In consumer-level digicams, half-pressing the Shutter button locks exposure and focus simultaneously. You can use this to deal with an off-center subject by pointing the camera at the subject, locking exposure and focus, and then reframing the picture before finally snapping the shutter. The only problem is that you sometimes need to perform a more radical recomposition of the subject in order to determine the proper exposure. For instance, you may want to zoom in on the subject, grab an exposure setting, and then zoom back out before taking the picture. Situations like that require locking the exposure independently of the focusing, and the 300D provides for just such eventualities by way of a separate AE lock button on the back of the camera, right under your right thumb. A very handy feature indeed, for those times you need it.

The EOS 300D offers a full range of White Balance settings, including six presets, an Auto setting, and a Custom setting. The six presets include Daylight, Shade, Cloudy, Tungsten, Fluorescent, and Flash. 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. A White Balance bracketing option snaps only one image, then writes 3 successive files from that single image. Bracketing steps are from -/+ 3 stops in whole-stop increments. (Each stop corresponds to 5 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 5500K.) The EOS 300D also offers a Parameters option through the LCD menu, which lets you select Adobe RGB color space, select one of two default settings, or configure as many as three custom Parameters setups. Each setup lets you adjust Contrast, Sharpness, Saturation, and Color Tone (red/blue hue balance), but the defaults and custom setups are all based on the sRGB color space. The two new preset parameters are Parameter 1 and Parameter 2. Parameter 1 sets both the contrast and saturation adjustments to +1, while raising the in-camera sharpening to +2, for a brighter, sharper image. Parameter 2 sets up the camera to perform much like the 10D at its default settings, with contrast, sharpness, saturation, and color tone controls all at their neutral positions.

Metering accuracy and bias
I found that the Digital Rebel's exposure system frequently underexposed shots relative to what my personal preferences would have been for a given scene. Looking at the images I captured, it seemed that the camera reacted very strongly to high-key subjects and strong highlights in otherwise well-balanced scenes. This is technically the most correct approach to take, and is the one preferred by most professional photographers, but I think is poorly suited to the needs and desires of most amateur shooters. The idea is that it's most important to preserve detail in the highlights of the images, since once detail is lost to overexposure there, it's gone forever. Dark midtones and shadows can always be fixed on a computer after the fact, albeit at the cost of somewhat elevated image noise levels.

Given that Canon is aiming the Digital Rebel at a more consumer-oriented audience though, and particularly given that they're pitching direct-from-camera printing as a primary feature, I think they should really reconsider the Digital Rebel's exposure system settings. In my experience, the average consumer is much more concerned with how their midtones look, as opposed to detail in the highlights. Even many "enthusiast" shooters prefer images in which the overall level of brightness matches what they saw in the scene, regardless of whether that means losing some detail in the highlights. On the 300D, this problem is exacerbated by Canon's decision to boost the default contrast level relative to that of the 10D. With the resulting steep tone curve, underexposing to save highlight detail results in even darker midtones and shadows than would otherwise be the case.

While you can certainly adjust the exposure compensation setting to correct for this tendency, that's tedious, and I often found it difficult to predict how the camera would respond to a given scene. Also, the amount of underexposure was so drastic with some high-key images that even a full +2EV of compensation was barely enough to produce a properly-exposed image.

At this late date, it's probably too much to hope for that Canon will fix the 300D's exposure system before production models hit the streets, but I hope nonetheless. - This strikes me as a fairly serious product bobble, relative to the needs and desires of its target market.

Low Light Capability
When operating the camera in full-manual exposure mode, the EOS 300D offers a Bulb exposure setting for very long exposures. Normally, exposure times are limited to a maximum of 30 seconds in Aperture- or Shutter-Priority modes, but in Manual mode, you can expose for as long as 2.5 hours by selecting Bulb mode and holding down the Shutter button for as long as you want the shutter to remain open. Obviously, 2.5-hour exposures aren't a practical reality, as sensor noise will totally swamp the signal long before that point is reached. Still though, the 300D seems quite able to take very long exposures with very little image noise resulting. Like the D60 and 10D, the 300D employs noise reduction algorithms that automatically reduce excess image noise from long exposures.

A full discussion of image sensor noise is beyond the scope of this review, but the simple story is that the most obvious and objectionable noise you'll see in long digicam exposures is so-called "fixed pattern" noise, caused by variations in "dark current" between sensor pixels. "Dark current" is just what it sounds like. Current (a signal) appears even when the sensor isn't being exposed to light. When you look at a long time exposure shot with a digital camera, you'll often see very bright pixels, where minor manufacturing defects have resulted in unusually high "dark current" levels. Often called "hot pixels," these flecks of color are very distracting visually.

The normal way to deal with hot pixels is to take an exposure with the camera's shutter closed, immediately after shooting the subject. If this "dark frame" is exposed for the same time as the subject was, you can largely eliminate the hot pixel problem by subtracting the dark frame information from the actual exposure. In practice, this works fairly well, but has the disadvantage that you have to wait for the dark frame exposure to be taken, requiring an appreciable amount of time in the case of long time exposures. (If you shot a one-minute exposure for the photo itself, you'll have to wait another minute for the dark frame exposure to be made.)

While most other high-end digicams on the market use a dark frame subtraction method to deal with image noise, the 300D (like the D60 and 10D before it) appears to be doing something very different, as there's very little delay between the end of the primary exposure and the writing of the image file to the memory card. There's clearly no "dark frame" exposure involved. I suspect that this advanced noise reduction processing in the 300D is another consequence of the "active pixel" CMOS technology Canon developed internally. Having active circuitry associated with each pixel in the sensor array allows lots of fancy processing that would be impossible otherwise, and it looks like Canon's noise reduction system takes advantage of this. However it's done, the 300D's noise reduction approach appears to be very effective.

As noted earlier in the "Optics" section of this review, the 300D uses its flash head as an autofocus-assist illuminator. This works very well, but has the drawback that there's no way to get an AF assist without also firing the flash. Using the 550EX accessory flash unit or the ST-E2 wireless sync transmitter avoids this problem, as both units have bright infrared illuminators built into them.

What's up with RAW?

Like many high-end digicams, the Canon EOS 300D Digital Rebel has a "RAW" file format as an option. If you're new to the world of high-end digital cameras, you may not be familiar with the concept of the "RAW" file format. Basically, a RAW file just captures the "raw" image data, exactly as it comes from the camera's CCD or CMOS image sensor. So why would you care about that? - RAW files let you manipulate your images post-exposure without nearly as much loss of image quality as you'd get with JPEG files. A full discussion of RAW file formats is way beyond the scope of this article, but Charlotte Lowrie of MSN Photo has written an excellent article describing the benefits of the RAW format, titled A Second Chance to Get It Right. Check it out, it's one of the clearest tutorials on RAW formats I've seen yet.


The EOS 300D's built-in flash has a guide number rating of 43 feet (13 meters) at ISO 100, translating to a range of about 15 feet at ISO 100 with a f/2.8 lens. (Reasonably powerful, but not dramatically so.) The flash features a Red-Eye Reduction option, for eliminating the occurrence of the Red-Eye effect. The pop-up flash is released via a small button on the side of the lens mount, and a Flash Off exposure mode disables it and any external flash attached.

Several of the more impressive features of the Canon flash system depend on the dedicated 550 EX speedlight. (While a number of Canon speedlights will work just fine with the 300D, their previous top-end 540EX unit apparently does not, so you'll need the new 550EX to fully tap the 300D's flash potential.) Among these are true FP (focal plane) flash sync, flash exposure bracketing with external flash units, and flash modeling. FP sync requires a flash unit to provide uniform light output for a relatively long period of time, long enough for the focal plane shutter curtain to fully traverse the "film" plane (sensor plane in the case of the 300D). On the 300D, this requires a flash duration of 1/200-second. Uniform, long-duration flash pulses like this permit use of shutter speeds as high as the 1/4,000-second maximum that the 300D is capable of. This can be invaluable when you want to exclude ambient light from the exposure.

Here's the rundown on Canon Speedlights and their compatibility with the 300D:

Speedlight Model On-Camera Capability E-TTL Wireless
550EX All Master or Slave
480EG External auto plus manual operation None
540EZ Manual operation only None
430EZ Manual operation only None
420EX All Slave Only
420EZ Manual operation only None
380EX All None
220EX All None
200E Not Compatible None
160E Not Compatible None
MR-14EX Macro Ring All Master Only
MT-24EX All Master Only
ST-E2 transmitter E-TTL, attach to camera Master Only
Non-dedicated shoe-mount units Manual operation only n/a
Studio strobe packs Manual operation only, connect via threaded PC sync socket on camera body n/a


You'll note the references to "E-TTL remote" capabilities in the table above. Canon's Speedlight system permits TTL flash metering with multiple remote units, and even allows you to set differential power ratios between the slaved units, over a six-stop flash exposure range.

The "Flash Modeling" feature of the 550EX speedlight is quite useful. With a F550EX connected to the 300D, pressing the camera's Depth of Field Preview button causes the speedlight to fire at 70 flashes per second for about one second. This creates the illusion of a constant light source for your eyes, letting you preview the lighting on your subject when the flash fires. VERY handy, and likely to save lots of shoot/check/reshoot time!

As alluded to above, the "X-sync" speed of the 300D is 1/200-second. (This is the maximum shutter speed that can be used on the 300D when working with a non-dedicated, FP-capable speedlight.) When used with higher-powered studio strobe systems, Canon recommends a maximum shutter speed of 1/60-second or slower, to accommodate the time/intensity profile of such units.

A final benefit of the dedicated Canon speedlights is that they carry powerful autofocus assist illuminators that can extend the range of the built-in AF assist light of the 300D. The AF assist beam on the 550EX is rated as good to about 50 feet, versus the roughly 13 feet of the lamp on the 300D itself. (As mentioned above though, note that the ST-E2 wireless sync transmitter can also be used for AF assist during non-flash photography, a handy trick.)

Continuous Shooting Mode and Self-Timer
The EOS 300D's Continuous Shooting mode is rated by Canon at 2.5 frames per second, for a maximum of four frames. This matched very well with the results of my own performance tests. Do note though, that the number of consecutive shots could be limited by Compact Flash space, if your memory card is nearly full.

The camera's Drive setting also accesses a Self-Timer mode, which opens the shutter 10 seconds after the Shutter button is pressed, giving you time to dash around in front of the camera. A Remote Control mode works with the dedicated and wireless remote units as well.


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