Canon EOS 300D Digital RebelCanon knocks the bottom out of the Digital SLR market, with an amazingly affordable, full-featured model!
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Page 3:DesignReview First Posted: 09/04/2003
Hitting the digicam market at a lower price point than previous Canon EOS digital SLRs, the Canon EOS 300D (marketed in the US as the Digital Rebel) offers a lot of the functionality of the EOS 10D, but with a few minor changes. The two cameras share the same size sensor and basic exposure functions, though the EOS 300D features an all-plastic body, slightly different control layout, and a few feature differences. If purchased as part of the Digital Rebel kit, the camera comes with a Canon EF-S 18-55mm f/3.5-5.6 lens, designed for use only with the Digital Rebel. Otherwise, the camera offers the same EF lens mount compatible with the full range of EOS lenses. The EOS 300D looks a lot like the film-based EOS models with which it shares its name, with just a few design tweaks here and there. Photographers already accustomed to EOS film cameras will find the transition to digital much easier with this model, as the camera's control layout is very similar. With a weight of some 19.7 ounces (560 grams) or so without the batteries, flash card, or lens, the EOS 300D is lighter than the 10D, most likely due to the much more extensive use of plastic in its body panels. The EOS 300D is also slightly smaller than the 10D, measuring 5.6 x 3.9 x 2.9 inches (142 x 99 x 73 millimeters).
The Digital Rebel is really a masterful exercise in cost reduction, with Canon paring away anything they could to drop the price under the magical $999 US, but still retaining an amazingly full range of functions and features. As mentioned, part of what they did was to make much more extensive use of plastic in its body than they did in the 10D or any previous D-SLR of theirs. The result is a tactile feel that I personally dislike, but which I've found few other reviewers or users to whom I've showed the camera seem to object to. (And I should point out that I myself would gladly put up with the feel of the case, if it meant the difference between owning a Digital Rebel (with lens) or not owning a 10D.) I don't know what the insides of the Digital Rebel look like, but can't help wondering why Canon couldn't have put just a little more plastic into the case, particularly in the rear panel area under the shooter's right thumb, and in the top and front along the left side. Likewise, perhaps a bit on the right front as well, next to the handgrip. These are the areas where I'm likely to hit the camera with my fingernails as I grab it, resulting in a tinny-sounding click whenever I do so. If that "click" could be made to sound more like a "thunk," I think it would contribute a lot to an overall feeling of solidity for the camera.
The front of the camera features a new lens mount, which accepts both standard Canon EF lenses, as well as the new EF-S lens, designed specifically for the Digital Rebel (more on this later). On the outside edge of the lens mount is the red dot for lining up standard EF lenses, as well as a white square, corresponding to the same alignment icon on the new EF-S lens. There's also the lens release button, a depth of field preview button (on the lower left of the lens mount as viewed from the rear), a flash head release button (on the upper left of the lens mount), and the redeye reduction lamp (the frosted window at upper left in the view above). On the front of the hand grip is the sensor for the IR remote, and tucked into the inside edge of the handgrip is a slot for the DC coupler cord (for the optional AC power adapter), beneath a small plastic cover. From this view, you can also see the camera's Shutter button, which angles down from the top panel.
The top of the camera features the Shutter button, Mode dial, Main dial, Power switch, and Drive Mode button. The pop-up flash compartment is just behind the lens. (The pop-up flash head projects a good distance above the lens, helping to avoid red-eye problems.) The top of the camera also contains a hot shoe for mounting an external flash unit. The hot shoe has the usual trigger terminal in the center, as well as four other contacts for interfacing to Canon EX Speedlite flash units, and a hole for a locking pin to prevent rotation of the speedlight. Fixed neck strap eyelets are located on both sides of the top panel as well.
On the hand grip side of the camera, towards the rear of the handgrip is a large door which slides back and out to reveal the CompactFlash slot (which supports Type-I and Type-II cards, including the IBM MicroDrive, as well as the latest 4GB memory cards, which use the FAT32 file system). Inside the compartment, underneath the CompactFlash slot is a small, black eject button for removing the card.
The opposite side of the camera features a hinged rubber flap covering the digital (USB), Video Out, and Wired Remote Control sockets. This picture also shows the Depth of Field Preview button (bottom) and Flash Pop-up button (top) on the side of the lens mount a little more clearly.
The rear panel of the EOS 300D is home to the bulk of the camera's controls, as well as the large, bright LCD screen and smaller LCD data readout panel. Lining the left side of the LCD monitor are several buttons related to menus and playback, including the Menu, Info, Jump, Playback, and Erase buttons. To the right of the LCD monitor is the Four-Way Arrow pad and Set button, for navigating through menus. A small LED (labeled "CF") rests below the arrow pad, and illuminates whenever the camera is accessing the CompactFlash card. Just above the Four-Way Arrow pad are the AV/Exposure Compensation and LCD Illuminator buttons. On the top right corner of the optical viewfinder is the diopter adjustment knob, recessed slightly to prevent accidental changes, and featuring a ridged surface to make it easier to turn when you want to. Finally, the top right corner of the rear panel features the AE/FE Lock / Index and AF Point / Enlarge buttons.
The rear-panel data readout conveys a wealth of information about the current status of the camera and its settings. As with other user-interface elements on the 300D, this display shows essentially the same information as the top-panel display on the EOS-10D, with only elements corresponding to features not implemented on the 300D missing. (Flash exposure compensation, custom function indicator, and AF mode indicator.) The illustration above shows all possible segments and icons and their interpretation. (Illustration courtesy Canon USA):
The very flat bottom of the camera reveals the metal tripod mount, as well as the main BP-511 Lithium Ion battery chamber cover. The main battery compartment cover is removable, necessary when installing the optional portrait grip on the camera. A small latch lever at the outside edge of the battery chamber cover unlocks it so that it may be opened. The battery compartment cover is far enough from the tripod socket that you should be able to swap batteries without removing the camera from your tripod mount. The large surface area of the camera's bottom provides a stable mounting surface for use with a tripod, even with fairly large lenses attached.
I didn't receive a sample to play with, but the Canon-supplied shot above shows the new "BG-E1" Battery Grip that will be available for the Digital Rebel, more or less simultaneous with the camera's retail availability. The grip holds two BP-511 batteries, and also provides a secondary shutter release to facilitate vertical-format shooting. The BG-E1 will carry a suggested list price of $140.
CMOS Versus CCD & What's It All Mean?
Back when the D30 was first introduced, Canon's use of a CMOS image sensor was seen as pretty revolutionary, and it still is to some extent. To my mind, the D30 and its successors' widely noted superb tonality can be traced directly to the CMOS sensor technology Canon used in building them. Accordingly, I think it appropriate to include the following section (copied from our D30 review) here, to give a little background on CMOS vs CCD sensor technology. (Thanks to IR News Editor Mike Tomkins for his work in researching and largely writing this technology briefing.)
To understand what CMOS sensor technology can bring to a digital camera, first of all you need some understanding of how CCD and CMOS sensors work, and what they do differently. CCD, or Charge-Coupled Device image sensors, were invented at the end of the 1960s by scientists at Bell Labs, and were originally conceived not as a method of capturing photographic images, but as a way of storing computer data. Obviously this idea didn't catch on; today we instead have RAM (Random Access Memory) chips in our computers which are, ironically enough, manufactured using the CMOS process.
Where CCDs did catch on, however was recording images — by 1975 CCDs were appearing in television cameras and flatbed scanners. The mid 80s saw CCDs appearing in the first "filmless" still cameras… CCDs rapidly attained great image quality, but they weren't perfect. Perhaps most significantly, CCDs required a manufacturing process which was different to that used for manufacturing other computer chips such as processors and RAM. This means that specialized CCD fabs have to be constructed, and they cannot be used for making other components, making CCDs inherently more expensive.
Interline Transfer CCDs consist of many MOS (Metal Oxide Semiconductor) capacitors arranged in a pattern, usually in a square grid, which can capture and convert light photons to electrical charge, storing this charge before transferring it for processing by supporting chips. To record color information, colored filters are placed over each individual light receptor making it sensitive to only one light color (generally, Red, Green and Blue filters are used, but this is not always the case). This gives a value for one color at each pixel, and the surrounding pixels can provide eight more values, four each of the two remaining colors from which they may be interpolated for our original pixel.
After the exposure is complete, the charge is transferred row by row into a readout register, and from there to an output amplifier, analog/digital converters and on for processing. This row-by-row processing of the CCD's light "data" is where the sensor gets the term "Charge-Coupled" in its name. One row of information is transferred to the readout register, and the rows behind it are each shifted one row closer to the register. After being "read out", the charge is released and the register is empty again for the next charge. Repeat the process a number of times, and eventually you read out the entire contents of the CCD sensor. (Think of a bucket brigade, moving water from point A to point B by pouring it from one bucket into the next...)
A number of disadvantages to this approach to sensor design now become apparent, in addition to the already mentioned cost. For one thing, the entire contents of the CCD must be read out, even if you're only interested in a small part thereof (for example, when using the digital zooms that are all the vogue in digital cameras, you have no interest in a large part of the sensor's data, so why take the time to read it out?) There are also a number of supporting chips required for the CCD sensor, each of which adds to the complexity and size of the camera design, increasing cost and power consumption. CCDs also suffer from blooming (where charge "leaks" from one light receptor into surrounding ones), "fading" (a loss of charge as it is passed along the chain before being read out), and smearing (where the image quality can be adversely affected by light arriving during the readout process, leaving streaks behind bright scene areas).
There's also the issue of speed. The step by step process used in a CCD is not exactly conducive to very high speed, and for just this reason a second type of CCD exists. The Frame Interline Transfer CCD features a readout register as large as the light receptor area is, allowing the entire contents of the CCD to be read out in one pass. This, though, adds significantly to the area of silicon required, and hence to the cost of the CCD.
This is where CMOS image sensors step in. CMOS, or Complementary Metal Oxide Semiconductor, is actually a generic term for the process used to create these image sensors, along with numerous other semiconductor items such as computer RAM, processors such as those from Intel and other manufacturers, and much more. CMOS image sensors can be made in the same fabs as these other items, with the same equipment. This technology is, of necessity, very advanced with the amount of competition in processor and other markets contributing to new techniques in CMOS fabrication. Add to this that there is a very significant economy of scale, when your fab can make not only CMOS image sensors, but other devices as well, and you find that CMOS image sensors are much cheaper to make than CCDs.
This cost advantage is even more significant when you consider the way a CMOS sensor works. The Active Pixel CMOS image sensors used in digital imaging are very similar to a CCD sensor, but with one major difference — supporting circuitry is actually located alongside each light receptor, allowing noise at each pixel to be canceled out at the site. Further to this, other processes can be integrated right into the CMOS image sensor chip, eliminating the need for extra chips — things such as analog/digital conversion, white balancing, and more can be built into the CMOS sensor. This reduces cost of supporting circuitry required, as well as camera complexity, and also power consumption, as does the fact that CMOS sensors require a significantly lower voltage than CCD sensors. CMOS sensors themselves also claim lower power consumption than CCD sensors, with one manufacturer claiming their CMOS sensors draw some 10x less power than equivalent CCD sensors.
CMOS sensors have other advantages, as well. For one thing, they can be addressed randomly. If you're only interested in a certain area of the image, you can access it directly and don't need to deal with the unwanted data. Blooming and smearing are also less of a problem with CMOS sensors. CMOS sensors are capable of much higher speeds than their CCD rivals, with one CMOS chip we've heard of capable of running at over 500 frames per second at megapixel resolution.
With these advantages, you'd think CMOS would be a shoe-in to replace CCD in digital cameras, but thus far it has really only impacted the lower end of the market, with CMOS rapidly becoming dominant in the entry level digital cameras and tethered cameras. Why hasn't CMOS taken over at the high end? Well, up until now, image quality has not been on a par with CCD… CMOS sensors, with their many amplifiers at each pixel, suffer from so-called "fixed pattern noise". The amplifiers aren't all equal, and this creates a noise pattern across the image. In their CMOS sensors, Canon has tackled this by first taking the image off the sensor in 10 milliseconds, and then reading just the fixed-pattern noise from the sensor in the following 10 milliseconds. Subtract the second image from the first, and you neatly remove the noise.
There's also the fact that CMOS sensors are generally less sensitive than their CCD counterparts. High end "Full Frame" CCD image sensors have a "fill factor" of 100%, because the whole CCD sensor area is being used for light capture — but in a CMOS sensor the fill factor is lower, because the extra circuitry alongside each pixel takes up space. This space can't be used to capture light, and so you lose some of it… Two techniques exist to combat this — firstly reducing the size of this support circuitry, and secondly the microlens. Reducing the size of the support circuitry is the less ideal of the two methods — the smaller you make it, harder the sensor is to manufacture, and the more expensive it becomes. The microlens is considered to be the better answer, then. Essentially, the support circuitry is covered by an opaque metal layer, and a microscopic lens is placed over the entire area of the light receptor and support circuitry, redirecting the light that would otherwise fall on the support circuitry and focusing it on the light receptor.
Canon's new Digital Rebel 300D is now the fourth high-end digital camera we've seen using CMOS technology, and it is likely that the apparent price advantage the camera has in comparison with its nearest rivals (the Nikon D100, Fuji S2 Pro, and Sigma SD9) is in large part due to the choice of the CMOS image sensor. (Not to mention Canon's in-house semiconductor fabrication capability.) The image sensor in the 300D is only ever so slightly smaller than those used in these two cameras, and significantly bigger than the sensors used in consumer cameras, as can be seen in the comparison photo above, which shows the CCD sensor from Canon's PowerShot S20 digital camera alongside the CMOS sensor from the original D30. The illustration below shows the difference in sizes (to scale) of a consumer CCD, the EOS D30/60/10D/300D sensor (all three are the same size), the D1/D1x/Fuji S1 Pro sensors (also all the same size), an APS film frame, and a standard 35mm frame.
Canon has continued to be fairly closed-mouthed about their CMOS sensor technology, but have talked about a few details of it. As with other Active-Pixel CMOS sensors, theirs does in fact have a signal amplifier located at each pixel site. More intriguing though, is that they also claim to have an A/D (analog to digital) converter at each individual pixel site as well. If this last is true, then it must be a very different sort of A/D than is normally used with CCDs, as those circuits are quite complex and space-consuming. I keep expecting that we'll hear more details as Canon's patent position is solidified, but so far not much information has been forthcoming. It does seem though, that there's been some genuine innovation in Canon's back labs. It's unusual these days to see a company moving toward vertical integration, developing component technology in-house rather than farming it out to specialist companies. Canon has been moving strongly in the opposite direction, bringing not only sensor technology in-house, but the processing circuitry as well, with their much-vaunted DIGIC chip. Based on the pricing of the Digital Rebel 300D, it does appear that there's been some monetary advantage in this approach.
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