Casio Exilim EX-F1

It may look like an SLR, but at heart the EX-F1 is a rocket-powered point-and-shoot. The 1/1.8-inch CMOS image sensor, while tweaked for speedy performance, is much smaller than the sensor in an SLR, which led us to expect lower performance in lab testing. And while we did find color accuracy was sub-par even when compared to other point-and-shoots, we were pleased to find scores for resolution, noise and dynamic range that surpassed typical performance for other ultra-zoom cameras we've tested.


Color (5.71)
When you look at a photo and it just doesn't seem to capture the moment you remember, very often it's the color accuracy (or lack of it) that's putting you off. You were inspired by a particular blue sky, or green fields, or glowing cheeks, but when you look at the photo after the fact, the emotional impact suffers because the hues are off. Accurately assessing how color reproduction varies from camera to camera requires more than a good set of eyes – it takes a trip to the lab, with a consistent testing regimen. We photograph an industry-standard Gregtag Macbeth color chart at a wide range of exposure settings under studio lighting. The resulting images are tested using the sophisticated Imatest image analysis software to determine the difference between the known color values from the chart and the colors the camera recorded. The image shown below was produced by Imatest during testing of the EX-F1. It shows the original chart color (the small rectangle on the right in each box), the color captured by the camera (the outer rectangle) and the captured color corrected for luminance (the inner square).

Accurate color reproduction isn't the strong suit of the EX-F1. While not terrible, the problem remains consistent throughout the range of ISO settings. We also found the images were significantly undersaturated, which gives colors a dull appearance.

The following chart shows how a range of colors vary between ideal values (represented by the squares) and the colors found in photos taken with the EX-F1 (shown in the circles). The shorter the line, the more accurate the color.

Shorter lines in this Imatest chart
indicate more accurate color reproduction.

The color performance score for the EX-F1 is compared here with the results for a similarly priced SLR, the Canon EOS Rebel XSi, and three long-lens point-and-shoots we've put through our lab testing. It's interesting that in this test, the point-and-shoots aren't necessarily at a disadvantage when compared to a pricier SLR. Still, the Casio is unimpressive, though on a par with the compact Olympus SP-560 UZ.

Resolution (8.04)
Image resolution and megapixel count don't necessarily go hand in glove. A camera boasting lots of megapixels on its sensor may still disappoint when it comes to the actual sharpness of the images it captures due to differences in optical performance, signal processing and other variables. That's why we shoot literally hundreds of photos of an industry-standard test chart (shown below) at several focal lengths, analyze them using Imatest and review the results in detail.

This resolution testing produces results measured in line widths per picture height (lw/ph), indicating how many progressively thinner, alternating horizontal and vertical lines on the chart the camera can reproduce before it all starts looking like a grey blob. The higher the number, the sharper the image.

The industry-standard resolution chart we use for testing

The best-case result for the EX-F1 was 1857 horizontal and 1734 vertical, shot near the wide end of the zoom lens range. Imatest indicated that rather than artificially boosting the perceived resolution through digital sharpening algorithms, the camera took a conservative approach, slightly undersharpening the image. The figures for the middle of the camera's extensive zoom range indicate continued strong lw/ph figures, though cranking the lens to its full telephoto setting did seriously impact results. Still, looking at enlarged photos taken even at maximum range, handheld in bright sunlight, the images deliver perfectly acceptable sharpness.

As seen in this comparison chart, the EX-F1 surpasses the long-zoom competition handily in most cases, though as expected it falls short when compared to the Canon XSi SLR, with its larger image sensor.

 

Noise – Manual ISO (8.93)
Take a photo without flash in low light and look closely at the results. See the clumps and imperfections in solid-color areas? That's noise, an inevitable imperfection caused by the mass of circuitry required to take the light streaming through a lens and turn it into digital ones and zeros. While it's most noticeable in low-light photography and when making extreme enlargements, noise is a factor in every digital photo you take, to a greater or lesser extent. Manufacturers try to tame the beast by minimizing noise production on the front end, and digitally processing the sensor's initial signal to identify and remove noise before saving the file on the back end. Many cameras give you the option of turning that back-end noise reduction processing on or off. For the EX-F1 Casio decided to automatically use noise reduction for any shot taken at an exposure setting of 1 second or longer (time is one factor in increased noise production), and not to filter for noise at high ISO settings, which is another frequently employed technique. This automatically triggered noise reduction for long exposures can't be turned off by the user.

Our noise testing procedure calls for shooting color images at a range of ISO settings and having Imatest examine the results to determine how much noise each setting produces. These results are then graphed to reveal both the noise level and the rate of increase as light sensitivity ramps up. In the chart below, the percentage of noise in the captured images is shown on the left axis, the increasing ISO at the bottom.

 

Despite its small sensor size, the EX-F1 produced exceptionally low-noise images at low ISO settings, though the graph does rise steeply as ISO increases. Overall we're impressed with this level of performance, particularly when compared to other cameras we reviewed. As seen in the chart below, the Casio surpassed the other ultra-zoom models in this benchmark test.

Auto Noise (6.24)
In addition to testing by manually setting the ISO, we shoot using the Auto ISO setting, letting the camera pick its own level and scoring the result. In this case the EX-F1 shot at a reasonable ISO 200 and produced a good, if not outstanding, result. As seen below, the EX-F1 bested the point-and-shoot competition here and fell only slightly short of the Canon SLR. In practical terms, this test is less important than our manual noise testing, since it's a simple matter to set an appropriate ISO level while shooting and maximize the effect of the camera's low-noise capabilities.

White Balance (5.08)
The actual color of light varies widely depending on the source. While our sophisticated brains do a wonderful job adjusting for this, perceiving essentially white light in all but the most extreme conditions, our cameras have a much harder time. They need to both accurately meter the color of incoming light and digitally adjust that value so that, in the final image, the scene looks the way we remember after mentally compensating for off-hues in the lighting. Not easy, and important to test. That's why we shoot under a variety of lighting conditions, including fluorescents, tungsten (i.e., light bulbs), photo flash and shaded daylight. In addition to automatically adjusting white to lighting conditions, most cameras offer preset white balance settings for a variety of sources, so the photographer can manually adjust when the automatic system doesn't seem to be producing accurate results. In the case of the EX-F1, the number of white balance presets is limited to six, and doesn't include a setting for flash (though it does accommodate two types of fluorescent bulbs). As a result, we tested manual white balance on three instead of our usual four parameters.

Auto White Balance (4.21)
We shot the Gregtag Macbeth color test chart under four types of illumination with the EX-F1 set to automatic white balance and ran the results through Imatest, which produced the chart below. It's important to note that the images shown here display intentionally exaggerated differences in white balance, to demonstrate the type of color shift you'd experience rather than the degree of color shift in real-world images.

Exaggerated White Balance Errors

Auto WB - Flash Illumination

Auto WB - Fluorescent Illumination

Auto WB - Daylight illumination

Auto WB - Tungsten illumination

The results here are a mixed bag. Under shaded daylight the automatic white balance delivers very good results (nearly identical to those using the manual preset, in fact). While fluorescent lighting proved difficult for the camera overall, the auto setting actually produced better results than either of the preset options. The auto white balance system didn't respond well to tungsten lighting, though, which represents a problem when shooting indoors with the EX-F1 under common household illumination.

Preset (5.96)
Shooting the same color chart under the same lighting conditions, but using the camera's preset white balance values produced varied results. Using the preset dramatically improved performance under tungsten illumination – indoor shots will look noticeably better if you take the time to make this manual adjustment. Daylight shade results were virtually unchanged, which means they're pretty good with either auto of manual settings. And, as mentioned above, fluorescent lighting baffles both the manual and automatic white balance systems.

Exaggerated White Balance Errors (Presets)

Florescent Preset WB - Fluorescent Illumination

Cloudy Daylight preset WB - Daylight illumination

Tungsten preset WB - Tungsten illumination

Still Life
To provide a side-by-side comparison of image quality, we shoot the same two still life scenes for each camera review. These photos are taken under standard fluorescent lighting with all camera adjustments set to automatic, at a range of ISO settings. The images of our happy (if somewhat stiff) married couple and a colorful still life below are clickable to open the full-resolution originals. These are multi-megabyte files, though, so they can take a while to download.

Low Light (5.60)
Flash photography is a great advance over no photography at all in the dark, but it has its antisocial aspects – aggravated party guests, crying babies – and the harsh illumination produced by on-camera flash often leads to the undesirable deer-in-the-headlights motif. That's why available-light photography is so important, and why we test a camera's low-light capabilities extensively. Low-light performance is also an important differentiating factor when comparing competing cameras head-to-head in today's market. Everybody has gotten better at shooting in low light, but some manufacturers have succeeded far more than others.

We perform two different types of low-light testing, one where the level of lighting is the variable, the other where exposure time starts at one second and stretches out to 30 seconds. The EX-F1 wasn't entirely accommodating on this last one, since the shutter speeds topped out at a modest 8 seconds with the camera set to ISO 400. While the shutter speed range actually stretches out to 60 seconds, the EX-F1 limits the exposure length based on ISO, throttling down the time as you boost the ISO – presumably because noise levels in long-exposure high-ISO shots would be unacceptable, though that’s only an assumption.

In our first test we set the camera to ISO 1600 (the highest available speed for the EX-F1) and varied light levels in our lab from a high of 60 lux (about what you'd find in a normal household environment) down to 5 lux (roughly the illumination from a single candle).

As shown in the chart above, the EX-F1 did well in our low-light testing considering its small sensor size, maintaining consistent exposure throughout the range of lighting condtions without gross color errors. Noise did climb as the lights dimmed, as expected, but the EX-F1 performance was in line with other point-and-shoot cameras we've tested.

To assess the camera's performance during long exposures we set the ISO to 400 and increase the shutter speed in increments till we reach 30 seconds, then analyze the camera's noise performance across this range. As mentioned above, the EX-F1 shutter speed range stopped at 8 seconds at ISO 400, so we shot three groups of test shots, at 1 second, 5 seconds and 8 seconds. This produced a flat response at an average noise value just over .835 percent, which is a good result, as might be expected given the camera's noteworthy performance in our other image noise testing.

Casio EX-F1 Long-Exposure Noise

The EX-F1 tested well versus other ultra-zooms, posting a significantly higher score, though it doesn't measure up to the performance of the Rebel XSi SLR.

 

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