Olympus E-3 Optics

The Olympus E-3 is a Four-Thirds camera, so is compatible with the full range of lenses made for the Four-Thirds mount by Olympus and several other manufacturers. (Notably Panasonic and major lens manufacturer Sigma.) As this report on the E-3 is being written, we're in the process of testing a number of Olympus' Zuiko lenses for the Four Thirds mount over on SLRgear, our camera lens test site (the reports of our testing should appear within a week or two of the E-3's announcement). I mention this here because we're being quite impressed with the optical quality we're seeing in the Olympus Zuiko glass.

One always tends to take manufacturers' claims with a grain of salt, and I have to confess that we did so to some extent with Olympus' claims about the superiority of their "digital specific" Zuiko lenses. The claim is that, being designed for use with digital sensors from the ground up, the Zuiko optics will perform better, with less distortion and better edge-to-edge sharpness than conventional designs. In fact, we're finding that even the inexpensive "kit" lenses are testing quite well, delivering performance better than we're accustomed to seeing in bargain optics.

This is a review of the E-3 rather than its lenses, but lenses are in fact a critically important part of any SLR system, and those from Olympus test out as among the best. (As noted, look for some test results for Olympus lenses soon, over on SLRgear.com.)


Olympus E-3 Autofocus

Autofocus is one of the more challenging technologies in modern cameras, as witness the fact that even industry leaders have difficulty with it from time to time. While the AF systems in past Olympus SLRs have worked well enough, they've lacked the sophistication found in some models from competing manufacturers.

The Olympus E3 aims to change all that, with an AF system that represents not only a quantum leap in sophistication, but that Olympus claims is the fastest of any camera currently on the market. We don't have any way to really evaluate AF speed (and we've only seen a prototype E-3 at this point, not yet in final trim for performance testing), but Olympus appears pretty confident that the E-3, combined with one of their new ultrasonic-motor lenses can more than hold its own with anything else out there. (They obviously haven't had a chance to test the Nikon D3 and D300 or Canon EOS-1DS Mark III yet, as those cameras haven't yet reached retail shelves, but they claim that the E-3's AF is faster than that of any DSLR that's currently shipping.)

Beyond its claimed speed though, the E-3 AF system increases both the number and capability of AF points over its predecessors, and also challenges the AF systems of the industry giants with all eleven of its AF points being full cross-type sensors (that is, sensitive to both horizontal and vertical detail), and a unique biaxial sensor layout, designed to improve focus accuracy.

In moving up to 11 AF points from their previous 3, Olympus engineers first analyzed thousands of photographs and interviewed many pro photographers, to find the optimum AF point positions. The illustration above (courtesy Olympus) is a plot showing the most frequent locations of subjects within the frame, overlaid by the E-3's AF sensor array. (It's fascinating to note the bias most photographers have for placing the subject in the upper left-hand quadrant of the "rule of thirds" grid -- We were surprised to see this, would have imagined that subjects would have been more evenly distributed over the frame.)

The illustration above highlights the fact that all 11 AF points are cross-type. There's more to the story though: Each AF sensor is actually doubled, with a slight offset between the pixels of the two "halves" of each point.

The dual, "biaxial" nature of the AF points is shown more clearly in the illustration above. At upper right, you see the "hounds tooth" pattern of the pixels that make up the individual lines of the sensor array. (To be clear, each cross-type AF sensor has two of these biaxial arrays, arranged at 90 degrees to each other.)

The drawing on the left side shows how the half-pixel offset between the two sides of the sensor improves discrimination of the precise focus point. The illustration shows a "subject" as a small, pixel-sized object that's straddling two pixels of the sensor array. In actuality, what will be imaged on the AF sensor pixels will be the pattern of light and dark from the subject. Think of the "Subject image" in the illustration as being an eyelash or a light/dark edge in a piece of clothing, etc. (Still a simplification, but perhaps one more connected to reality.) What's being shown is that, for any given size of sensor pixel, the biaxial sensor array can find the point of precise focus more accurately than could a single line of pixels.

Just how this will play out in the Olympus E3 will depend on a number of factors. If Olympus uses pixels in its AF sensor similar in size to those of competing AF systems, the E-3's AF would be more accurate. Alternatively, they could use AF pixels that are twice the size of those in competing systems, and achieve the same AF accuracy with better light sensitivity and therefore better low-light performance.

It's interesting to see how technology advancements pace each other between camera manufacturers: Until recently, we weren't aware of any camera that used a "biaxial" sensor layout of this sort. Just a couple of months ago though, Canon describes what they call a "zigzag" AF sensor on their new EOS-40D model, and similar designs have apparently been used on other recent cameras of theirs, including the Rebel XTi. Sound familiar? We can't be sure based on the limited data we have on both cameras, but it certainly sounds like the horizontal-line-sensitive sensors in the middle of the 40D's AF array (top center, center, and bottom center) use this same sort of sensor design for improved accuracy. Where Canon uses these dual sensors only up the middle of their array, and only for the horizontal-sensitive points though, Olympus uses biaxial AF sensors for all AF points, and in both horizontal and vertical directions. As noted though, it remains to be seen what difference this technology might make in the E-3's actual AF operation.

Olympus E-3 AF Assist

An AF illuminator option can be turned on through the camera's Custom menu, to help the camera's AF system determine focus in dark shooting conditions. The camera actually uses light from the flash as the AF illuminator, so the flash must be upright for this option to be available. The flash can however be disabled, so that natural light images can be captured with AF assist enabled, however this is not as convenient as a dedicated AF assist lamp.

Olympus E-3 Image Stabilization

The Olympus E-3 is equipped with sensor-shift image stabilization. Olympus claims it can provide up to 4-stops of compensation. That is, images taken hand-held at 1/25s can be as sharp as ones taken at 1/400s without IS (your mileage may vary). This is very handy in low-light conditions when you're forced to use a slower shutter speed, or when shooting with a long telephoto lens, where even slight camera movement can cause image blur. Having IS built into the body has the advantage that all your lenses are stabilized, and you don't incur the expense of an IS system for each lens. The disadvantage is that you don't see the effects of stabilization in the optical viewfinder, though you can see it when using Live View. The Olympus E-3 even lets you enable IS for non Four-Thirds lenses mounted via an adapter. You'll need to manually enter the focal length for those lenses. The Olympus E-3 offers two image stabilization modes to handle different shooting occasions: Mode 1 works to stabilize images in both vertical and horizontal axis and Mode 2 in the vertical axis only. Newer Olympus models equipped with IS offer a third mode that works in the horizontal axis only. This enables you to use IS in a range of situations. As is usually the case, it is recommended to turn IS off when using a tripod.

"Supersonic Wave Filter (tm)" Automatic Sensor Cleaning

The built-in Supersonic Wave Filter was first introduced on the E-1 SLR, and has been carried forward to newer models including the E-3. This is a feature that's hard to evaluate in any sort of a rigorous, quantitative way, but that appears to work fairly well, based on subjective observation. However, it's important to remember that no dust removal system is completely effective, so you're going to have to clean your sensor at some point, or have it cleaned professionally, regardless of the type of dust-removal system your SLR might have built into it.

Dust has proven to be a bane for digital SLR users from the beginning. In film cameras, the imaging surface (the film) is constantly refreshed as each new frame is advanced. Any dust that might accumulate on one frame will thus not affect subsequent ones. In digital SLRs though, the sensor surface is fixed, so any dust falling on it tends to stay there, the surface becoming increasingly dirty over time. Various accessories are available to clean CCD surfaces, but their use presents an ongoing risk of accident. (That is, while the cleaning gadgets themselves may be perfectly safe, every time you open your SLR and start sticking things inside the camera body, there's a finite risk that you'll do something to damage the sensor chip.)

In the E-3, every time the camera is turned on, an ultrasonic system activates, vibrating the protective cover glass over the sensor at a frequency of 35,000 cycles/second, thereby dislodging dust particles that may have settled on the sensor's surface. (Dislodged dust is collected and trapped in an internal receptacle, so it won't float around the mirror compartment to cause more problems down the line.) A full cleaning cycle takes only 200 milliseconds (0.2 seconds).

To set appropriate expectations for Olympus' Supersonic Wave Filter system, it's important to note that it certainly isn't effective against grease smudges caused by fingerprints. -- So continue to be careful about putting your fingers inside the mirror compartment when the sensor is exposed.

Zuiko 12-60mm f/2.8-4 ED SWD Lens Optical Tests

Excellent performance from the newly-announced 12-60mm lens.

12mm 60mm

The Olympus Zuiko Digital 12-60mm f/2.8-4 ED SWD lens was announced at the same time as the Olympus E-3 digital SLR was , equivalent to a 24-120mm lens on a 35mm camera. It doesn't appear that this will technically be a "kit" lens for the E-3, but it's a lens that's clearly intended for use with the camera, so we thought it would be an appropriate optic to use to test the E-3 with. (The 12-60mm's fast SWD focus motor is essential to getting the most out of the E-3's fast AF system.) This focal length range is both wider and longer than the typical 18-55mm kit lenses often bundled with SLRs with 1.5x crop factor sensors. With a maximum aperture of f/2.8 - 4, it's also faster than most kit lenses. Results were very good at 12mm, with minimal corner softness and strong detail throughout the frame. Coma distortion in the trees is very low, though minor chromatic aberration is visible in the corners and edges. Results are very good at the 60mm setting as well, with no signs of visible coma distortion and only minor chromatic aberration. All in all, a great performance, a very nice-looking lens.

An better than average-sized macro area with the 12-60mm lens, though good detail and high resolution. Flash exposure was uneven up close.

Standard Macro Macro with Flash

The Olympus E-3's macro setting performed well, though macro performance will obviously depend entirely on the lens in use. With the 12-60mm SWD lens, the E-3 captured a minimum area of 2.30 x 1.72 inches (58 x 44 millimeters), somewhat better than most moderate-ratio zoom lenses that we've tested. Detail and resolution were both very good, though details are a bit soft overall, with minor softening in the corners. The built-in flash produced a very uneven exposure here, partially blocked by the lens barrel, so plan on using external lighting for macro shots with this lens.

An average amount of barrel distortion at wide angle, and average pincushion distortion at telephoto as well.

Barrel distortion at 12mm is 0.7%
Pincushion at 60mm is less than 0.2%

This is the tendency for the lens to bend straight lines outward (like a barrel -- usually at wide angle) or inward (like a pincushion -- usually at telephoto). The Olympus E-3's 12-60mm lens produced about 0.7% barrel distortion at full wide angle, and was noticeable in some images. This is about average performance, and not at all unexpected at such a wide angle. At the 60mm telephoto end, barrel distortion was about 0.2%; also average, but not as noticeable.

Chromatic aberration
Moderately low, though bright.

Wide: Moderately low but bright,
bottom left @ 200%
Wide: Moderately low but bright,
bottom right @ 200%
Tele: Moderately low,
bottom left @200%
Tele: Moderately low,
bottom right @200%

Chromatic aberration is moderately low, showing about 3-4 pixels of fairly bright coloration on either side of the target lines at both wide angle and telephoto focal lengths. The effect is only slightly visible in some shots. (This distortion is visible as a very slight colored fringe around the objects at the edges of the field of view on the resolution target.) The CA extends a fair ways into the frame, but diminished as it went, and we found it to be quite unobtrusive. A good performance here.

Corner Sharpness
Low to moderate softening in the corners of the frame with the 12-60mm SWD lens.

Wide: Moderately soft in
the corners (lower left)
Wide: Sharp at center.
Tele: Slightly soft in
the corners (lower right)
Tele: Fairly sharp at center.

The Zuiko 12-60mm SWD lens produced moderately soft corners at wide angle, with the lower left corner being the softest, but the softening didn't extend very far into the frame at all, so the net effect was really quite minimal. At full telephoto, the corners were only slightly softer than the center of the frame. Again, very good performance.


The images above were taken from our standardized test shots. For a collection of more pictorial photos, see our Olympus E-3 Photo Gallery .

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