Olympus E-P1 Optics

Olympus M.Zuiko Lenses

The Olympus E-P1 is compatible with any Micro Four Thirds lens, as well as standard Four Thirds lenses via an optional adapter. Olympus has dubbed their Micro Four Thirds lenses "M.Zuiko," and at the time of writing (June 2009), only two M.Zuiko lenses have been released. The Olympus 14-42mm f/3.5-5.6 ED M.Zuiko Digital zoom lens offers a fairly typical 3x zoom ratio, with a 35mm equivalent focal range of 28-82mm. When bundled with the E-P1 body, the kit lists for US$800. The test shots shown on this page were taken with that lens, unless otherwise noted. One interesting feature of this lens is it "collapses" for a smaller footprint when not in use. Shown unmounted to the right of the E-P1, it's in its collapsed position in this photograph.

Also offered is the Olympus 17mm f/2.8 M.Zuiko Digital, a sharp, fairly fast (f/2.8), and compact prime lens with an equivalent focal length of 34mm. The 17mm E-P1 bundle lists for US$900, and includes an optical viewfinder which mounts in the flash hot-shoe (see image above right). Because the E-P1 features in-body image stabilization, these lenses do not themselves incorporate optical image stabilization. (Note that Panasonic Micro Four Thirds lenses work with the Olympus E-P1, but you have to disable their built-in O.I.S. systems.)

Olympus E-P1 Autofocus

11-Area AF. Focus areas are bit large and their size is fixed, making it difficult to focus on small objects without resorting to manual focus.

The Olympus E-P1 has an 11-area contrast-detect autofocus system, using the main imaging-sensor to determine focus, similar to how most Point & Shoot cameras work. There are two AF Area options: "All Target" mode, where the camera automatically selects the active area(s) for you, or "Single Target" mode, where you specify the active area by selecting it with the 4-way controller or either of the dials. When Face Detection is enabled, 25 areas are available for automatic selection.

You can register a "Home" position for the active AF by pressing the Function (Fn) and EV Compensation buttons simultaneously. This is useful for quickly retrieving your favorite AF area position, simply by pressing the Fn button. There is no option to change the size of the active area, a feature we think would be a useful enhancement, as we had difficulties focusing on the small AF target in our Indoor Portrait series.

Of course, the Olympus E-P1 also offers a manual focus mode. In MF mode, an option called MF assist causes the camera to optionally magnify the preview image by 7x or 10x whenever the focus ring is adjusted, to help determine critical focus. The focus area can also be freely moved around the entire screen, to a total of 225 positions once in magnified view mode, and we found that this could be done in autofocus mode as well, a nice feature that seems to be undocumented. For use with old manual-focus lenses (which lack the communication that would tell the body when the focus ring was being adjusted), or perhaps to simply check the focus that the AF system has achieved, you can also enable the 7x/10x magnification manually by using the Info button to select the screen with the green AF square in the middle; then just press the OK button to activate the zoomed view. Use the vertical control wheel to switch between 7x and 10x.

As we note elsewhere, the LCD on the E-P1 isn't one of the newer-generation high-resolution designs, as it has only 230K dots. For precise manual focusing, we'd really have preferred to have a higher-resolution LCD, even with the 10x magnification mode. That said, we found that we could still produce sharp images when focusing manually, at least under ideal conditions. Ideal conditions mean the camera mounted on a solid tripod, and a subject with strongly contrasting fine detail to examine while focusing. Under such conditions, we could consistently produce results as sharp as those delivered by the AF system, but we always felt like we were guessing somewhat as to where optimum focus really was. The results showed we perhaps should have had more confidence in our ability to focus the E-P1 manually, but we really would have been happier if the E-P1's LCD screen had more resolution.

Autofocus servo modes consist of S-AF (single shot autofocus), C-AF (continuous autofocus), MF (manual focus), and S-AF+MF (single shot autofocus with manual focus tweaking). In S-AF or S-AF+MF mode, focus is locked when the shutter button is half-pressed. In C-AF mode, the camera continuously cycles its AF system, which helps it track moving objects, keeping the current lens focal distance setting closer to the current subject distance than it might otherwise be. This can reduce AF "hunting" when it comes time to snap the actual shot.

Because contrast-detect AF systems have to perturb the focus in order to tell whether the image is actually in focus or not, the E-P1's Continuous-AF mode disturbs the viewfinder display on the LCD while it's operating. That is, the viewfinder image continuously shifts in and out of focus when C-AF is active, as the camera constantly re-checks its focus setting. This is a necessity for any contrast-detect AF system, but the amount of defocusing required by the E-P1 to check focus is greater than we've seen in some other systems.

While the recent G-series Micro Four Thirds cameras from Panasonic feature surprisingly fast contrast-detect autofocus, we found the AF performance on the Olympus E-P1 more in line with that of the contrast-detect systems in Live View-capable SLRs, its shutter lag with the 14-42mm kit lens ranging from 1.2 to 1.3 seconds.

AF in Movie mode

In Movie mode, you have the same focusing options available as when shooting stills, but the C-AF option operates a bit differently, and you may want to choose either S-AF, S-AF+MF or MF modes to minimize the impact of the focus motor noises on your audio track. With the 14-42mm kit lens attached, we found the focus motor noise to be very prominent in the audio track, especially during quiet passages. Even with a sound level corresponding to normal conversation, the focus motor noise was clearly audible in the sound track. With C-AF mode selected, the lens would cycle fairly rapidly whenever it made a change, creating more focus motor noise. If we carefully "pulled focus" manually, moving the focus ring slowly to track a moving subject, the focus motor noise was greatly reduced, but still audible unless the ambient sound level was fairly high. Also, we're not sure just what triggered AF cycles in C-AF mode while recording video. As best we could tell, the camera kept track of the overall scene brightness each time it cycled the AF, and then refocused whenever the brightness changed by more than some predetermined amount. The AF cycles thus tended to be somewhat unpredictable, and they didn't always correspond to there having been changes in the subject distance. (It seemed that the subject could move closer or further away without necessarily causing the camera to refocus, but nothing more than a relatively abrupt change in light level could trigger it at other times. Even under best-case conditions, the C-AF option didn't appear to be very useful for tracking moving subjects when recording videos.

Olympus E-P1 Sensor Cleaning

The Olympus E-P1 features an ultrasonic dust-reduction system, especially important since the E-P1's shutter is normally open for full-time Live View. The system automatically runs at power-up, and unfortunately, there is no option to disable it or run it manually, as it does contribute to startup time. The SSWF ("Super Sonic Wave Filter") LED on the top of the camera blinks when self-cleaning is performed.


Olympus E-P1 Kit Lens Test Results

Although we ended up preferring the 17mm f/2.8 lens, we did the majority of our optical performance testing with the 14-42mm f/3.5-5.6.


Kit Lens Test Results

Excellent performance with the 14-42mm kit lens.

14mm 42mm

The Olympus E-P1 is available bundled with a Olympus14-42mm f/3.5-5.6 ED M.Zuiko Digital Micro Four Thirds lens, the first Olympus M.Zuiko zoom. The kit lens possesses a very typical optical zoom range of 3x, and the 35mm equivalent focal range is about 28-82mm, because of the E-P1's 2x "crop factor." Results were quite good at 14mm, with only slightly soft corners and strong detail throughout the frame. Coma distortion in the trees was low; however, chromatic aberration in the corners was moderate. Results were excellent at the 42mm setting, with sharp corners and just a a hint of chromatic aberration. Overall, an excellent result for a kit lens. The Olympus E-P1 does not offer a digital zoom mode.

A smaller than average area (for an SLD* kit lens), with excellent detail.

Macro with
14-42mm kit lens

As with zoom performance, the Olympus E-P1's macro performance will depend entirely on the lens in use. However, with the 14-42mm kit lens set to 42mm, the Olympus E-P1 captured an smaller than average minimum area measuring 1.96 x 1.47 inches (50 x 37 millimeters). Resolution and detail were excellent, with very little if any softening in the corners. (Most lenses have some softening in the corners at macro distances, the Olympus E-P1's kit lens has much less than most.) Excellent performance for a kit lens here as well.

*SLD = Single Lens Direct-view

Geometric Distortion
Low geometric distortion with the 14-42mm kit lens in JPEGs, higher than average distortion in uncorrected RAW files.

In-Camera JPEG: Barrel distortion at 14mm is 0.6 percent
In-Camera JPEG: Pincushion distortion at 42mm is practically nonexistent
Uncorrected RAW: Barrel distortion at 14mm is 1.6 percent
Uncorrected RAW: Pincushion distortion at 42mm is 0.8 percent

When shooting JPEGs, the Olympus E-P1's 14-42mm kit lens produced about 0.6 percent barrel distortion at wide-angle, somewhat less than that produced by most cameras we've tested, and hardly noticeable in most of its images. At the telephoto end, there's almost no distortion, practically imperceptible. 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).

We suspected the camera was correcting distortion in JPEGs (similar to the Panasonic G1/GH1), so we converted RAW files from the above shots with dcraw, which does not correct for distortion. As you can see, at wide angle, the barrel distortion is high at 1.6 percent, and pincushion distortion at telephoto is also fairly high at 0.8%. We've started to expect this for smaller interchangeable lenses though, so it's nothing to be concerned about unless you are using a RAW converter which does not understand the embedded "opcodes" to perform distortion corrections automatically. Most RAW converters these days are capable of applying distortion correction automatically, as specified by the manufacturer. (There's going to be some loss of resolution as a result of such correction, because pixels in the corners of the frame are being "stretched" to correct for the distortion. Obviously, a lens that doesn't require such correction, and is also sharp in the corners to begin with would be preferable, but relaxing constraints on barrel and pincushion distortion could bring other benefits in the lens design.)

Chromatic Aberration
Moderate at wide angle with the 14-42mm kit lens, low at telephoto.

In-Camera JPEGs
Wide: Moderate,
top left
Wide: Moderate,
top right
Tele: Low,
top left
Tele: Low,
top right

When shooting JPEGs, chromatic aberration in the corners with the Olympus E-P1's 14-42mm kit lens is moderate at the 14mm setting, with 4-5 pixels of fairly bright fringing. At 42mm telephoto, this distortion is much lower and hardly noticeable. (This distortion is visible as a slight colored fringe around the objects at the edges of the field of view on the resolution target.) Unlike some other manufacturers (notably Panasonic and Nikon, on their pro SLRs), the Olympus E-P1 does not appear to correct for lateral chromatic aberration in its JPEGs, as uncorrected RAW files do not show any significant increase in chromatic aberration.

Corner Sharpness
Slight blurring in the corners of the frame at wide angle, very little softening at telephoto with the 14-42mm kit lens. Some slight shading (vignetting) in the corners at maximum aperture.

Wide: Slightly soft in the
corners (upper right).
Wide: Sharp at center.
Tele: Just a touch soft in the
corners (upper right).
Tele: Sharp at center.

At wide angle with the 14-42mm kit lens, the extreme corners of our test targets were a little soft compared to the center. At telephoto, corners showed hardly any softening, There was also some minor shading (vignetting) at both wide angle and telephoto, as you can see in the two pairs of crops: Note how it's darker in the corner than in the center. Despite the slightly soft corners at wide angle, this is well above average performance for a kit lens, especially considering these shots were taken with the lens wide open. (Corner sharpness and vignetting typically improve when stopping down to a smaller aperture.) Again, an excellent performance.


The images above were taken from our standardized test shots. For a collection of more pictorial photos, see our Olympus PEN E-P1 Photo Gallery .

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