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Canon EOS D60

Canon updates their D30 Semi Pro SLR with a 6 megapixel sensor and other improvements, and sets a new low-price point in the process!

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Page 3:Design

Review First Posted: 2/22/2002


Design
With a nearly identical body design to the previous EOS D30, the EOS D60 looks and feels very similar to the film cameras with which it shares the EOS name, and bears a particularly strong resemblance to the EOS Rebel G camera (known in Europe as the EOS 500N, and in Japan as the EOS Kiss). This similarity to the EOS line will make transition to digital much easier for photographers used to the EOS film cameras, avoiding any relearning of the camera's layout. With a weight of somee1.8 pounds (840 g) or so with the batteries and flash card, but minus the lens, the D60 is about the same weight as its nearest rival the Fuji FinePix S2 Pro (as of this writing, announced, but not yet shipping), and 30 percent lighter than Nikon's D1x (although the D1x has a portrait grip built-in, and the EOS weight does not include its optional portrait grip, which adds another 13.5 ounces (including the second battery). By comparison, Canon's ultra-rugged EOS-1D professional SLR is almost twice as heavy. While it couldn't necessarily be described as "light," the EOS D60 does tie with the Fuji S2 for the title of "lightest interchangeable-lens SLR digital camera" - and the difference in weight with other digital SLRs is very noticeable. Despite it's relatively svelte proportions though, the EOS D60 has a solid heft and displays a very high build quality. The camera measures 5.9 x 4.2 x 3.0 inches (149.5 x 106.5 x 75 mm), also without the lens, batteries or flash. This is a touch (0.2-inch) wider than the S2 Pro, but a full inch shorter and about 0.1-inch slimmer. Nikon's D1x is 0.3-inch wider and deeper than the EOS D60, and fully 1.8 inches taller - but this again does not account for the D1x's built-in portrait grip, and the D60's accessory grip adds about 1.75 inches to its height.

The front of the camera features a standard Canon EF lens mount. 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 popup button (on the upper left of the lens mount) and the redeye reduction lamp/focus illuminator light (the clear window at upper left in the view above). (As a side note, if you haven't seen one of these krypton-filled focus-assist lights, you'll likely be as amazed as I was. It's hard to imagine something that small putting out that much light!)

The top of the camera features the Shutter button, Mode dial and a small status display panel that reports most of the camera's settings. (New on the D60 relative to the D30 is a backlight feature for the top display panel. Very welcome when shooting under dim lighting!) Also on top are the Main dial and several control buttons (metering mode, flash exposure compensation, drive mode, AF mode, and white balance). 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 flashes, and hole for a locking pin to prevent rotation of the speedlight. Fixed neck strap eyelets are located on both sides of the top of the camera as well.

On the hand grip side of the camera, towards the rear of the handgrip there is a large door which opens forward, behind which the CompactFlash slot (which supports Type-I and Type-II cards including the IBM MicroDrive) is located. Underneath the CompactFlash slot is a small gray eject button for removing the CompactFlash cards.

The opposite side of the camera features a hinged rubber flap behind which are the digital (USB) and NTSC/PAL selectable video out sockets. Below this are two more sockets, likewise protected by a rubber flap. The forward of these sockets is a standard PC flash sync terminal, while the rear socket is for an N3 remote control. A design wrinkle here relative to the D30 is that the covers for all these sockets are attached to the camera body, eliminating concerns of losing the little screw-in covers used on the D30 to cover the two bottom sockets. Big kudos on this feature, little screw-in covers just beg to be lost. (Nothing comes for free though - While the large flap does a good job of sealing the digital and video sockets, I found it a little tricky to get its various projections and dimples properly seated again after having it open.) You can also see more clearly in this picture the depth of field preview button (bottom) and flash popup button (top) on the side of the lens mount.

The back panel of the EOS D60 is home to many of the camera's controls, as well as the large, bright LCD screen, and is identical in all respects to the rear panel of the D30. On the left-hand side is the main power on/off switch, as well as several buttons related to menus and playback, including the Menu, Info, Jump, Index/Enlarge, and Playback buttons. Underneath the LCD screen is the Delete button, and to the right of the screen is the Quick Control dial, in the center of which is the Set button. Above and to the left of the Quick Control dial is the Quick Control Dial switch, which enables or disables the Quick Control dial. The button in the center of the Quick Control Dial acts as a menu selection button, and also turns the top-panel backlight on and off when that feature is enabled via the appropriate menu selection. The LCD display screen itself is located near the left center of the back of the camera, directly below the optical viewfinder. 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 give grip. Finally, the AE/FE lock button and the focusing point selector button are located in the upper righthand corner of the back panel.

The very flat bottom of the camera reveals the metal tripod mount, as well as the cover for the CR2025 backup button battery, and 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.

An optional extra for the Canon EOS D60 is its portrait grip, which carries two batteries, doubling the camera's battery life. Seen above from the front, the portrait grip is connected to the camera by way of the tripod socket. With the battery chamber cover removed, the "dummy battery" protruding from the top right of the portrait grip extends into the D60's battery chamber, carrying power from the grip's own battery chambers. The Shutter button is just visible on the lower right corner of the portrait grip, and also visible is the ridged wheel used to tighten or loosen the screw on the top of the portrait grip into the D60's tripod socket.

On the back of the portrait grip, you can see the dual battery chambers, and the other side of the wheel for locking/unlocking the portrait grip to the camera. There's also a sliding latch which opens the battery compartment. At bottom right are duplicate controls for the AE/AF and focus zone selector buttons.

Finally, on the bottom of the portrait grip we see a metal tripod thread, allowing the camera to be tripod-mounted even when the portrait grip is being used. There's also another metal strap eyelet recessed into the base of the portrait grip, intended for use ith Canon's Handstrap E1. This is a large, padded leather strap that wraps around the back of your hand, providing added security when hand-holding with long lenses. The Shutter button and a duplicated Main dial are to be found on the bottom right corner of the portrait grip, and just above and to the right of these, tucked safely away on the inside of the bulge below the dummy battery, is a switch which can be used to disable the controls on the portrait grip (which you'll find very useful the first time you leave the grip attached to the camera and revert to landscape shooting - were it not for this switch, you'd be driving yourself nuts taking photos of people's waists every time you bumped the shutter button on something!)

 


Internal Design(!)

We're indebted to Canon USA, Inc. for the following series of photos and illustrations. They show the design of the original D30, but also apply to the D60, since the two cameras are based on the same core body design. They reveal some interesting aspects of the camera's design and operation, and hold intriguing possibilities for the future...

First and foremost, a key factor in the D30 and D60's design is that they weren't just modifications of an existing film body: The body was designed from the ground up to be a digital SLR, which is a significant part of why Canon was able to make it so compact. Not having to dedicate space to the usual film transport and focal plane mechanism, the designers were able to save considerable space. The diagram below shows a schematic illustration of the D60's body in cross-section. You can see from the way the components are stacked that it would have required much more space for the engineers to simply have tacked electronic components onto a film camera's body.

The illustration below expands on the cross-section above, showing how light passes through the D60's body to both the autofocus and flash sensors. As shown by the red lines, autofocus happens by virtue of a partially transmissive region in the middle of the main mirror. A secondary mirror reflects the light down to the base of the camera body, where it passes through a lens, reflects from yet another mirror, and thence into the AF sensor itself. Focusing can thus be continuous right up until the mirror flips up for the exposure itself.

The TTL (through the lens) flash sensor resides at the top of the camera, behind the pentaprism. Here, a small mirror and lens pick off a portion of the light passing to the viewfinder. (Note that this is before the focusing elements of the viewfinder optics, so it achieves more area coverage than you might expect.) The light reflects from a mirror, passes through a lens, and thence to the photodiode that measures returning flash energy. This design requires a pre-flash for metering, but is the same system used by other EOS cameras. This means that all EOS-compatible Canon flash units will be fully functional with the EOS D60. This approach also avoids the difficulties inherent in adapting camera designs based on Off-The-Film (OTF) flash metering. The disadvantage is that the metering occurs a small fraction of a second before the shutter opens. The strong advantage though is that it alleviates problems relating to differences between sensor and film reflectivity. (I found the flash metering of the D60 to be exceptionally accurate.)

The real "guts" of the D30/D60 is a cast plastic optical box holding the lens mount on the front, the pentaprism on top, and the CMOS image sensor on the rear. This compact arrangement is a major factor in the small profile and light weight of the D60 overall.

Here's a look at the D30/D60's optical box from the back, revealing several interesting features, as detailed in the photo's caption. (The comments we made back then now seem a bit more prophetic...)

The design of the original D30 struck us with its modularity: Canon's engineers obviously weren't designing with one camera in mind, but an entire family. In our conversations with them, Canon USA's technical folks made much of the component shown in the photo below, the "Engine" that handles the D30/D60's image processing. Again, note our comments in the photo caption below.

The shot below shows both why the D60 has a very rigid, rugged "feel", but also part of why Canon themselves don't claim it to be a "professional" model. The body is composed of heavy gauge stamped metal: Very rugged and rigid, but clearly not in the same class as the die-cast body of the EOS-1D. Still, there's no doubt that this isn't a "plastic" camera!

 


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 my mind, the D30's widely noted superb tonality can be traced directly to the CMOS sensor technology Canon used in building it. 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 read-out 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 read-out 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 read-out 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 read-out 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 the D60's CMOS sensor, Canon has tackled this by first taking the image off the CMOS 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 EOS D60 is the first high-end digital camera we've seen using CMOS technology, and it is likely that the projected price advantage the camera has in comparison with its nearest rivals (the Fuji FinePix S1 Pro and Nikon D1) is in large part due to the choice of the CMOS image sensor. The image sensor in the EOS D60 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 EOS D60. The illustration below shows the difference in sizes (to scale) of a consumer CCD, the EOS D30/60 sensor (they're both 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 thus far has been 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. We suspect we'll hear more details as Canon's patent position is solidified, but it sounds as though 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. As the digicam market continues to evolve, it will be interesting to see whether Canon's sensor technology will constitute a competitive advantage for them relative to other manufacturers. (A note, added February, 2002: Canon has continued to be fairly close-mouthed about their CMOS technology. No new details have come to us in the year or so since the D30 was first introduced...)

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