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Olympus C-7000 Wide Zoom

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C-7000 Imatest Results

Review First Posted: 11/26/04

Detailed analysis of the Olympus C-7000 Zoom images, from Imatest(tm)

I've recently begun using Norman Koren's excellent "Imatest" analysis program for quantitative, thoroughly objective analysis of digicam test images. I highly commend it to our technically-oriented readers, as it's far and away the best, most comprehensive analysis program I've found to date. (And with an introductory price of only $59, it's hard to beat.)

My comments below are just brief observations of what I see in the Imatest results. A full discussion of all the data Imatest produces is really beyond the scope of this review: Visit the Imatest web site for a full discussion of what the program measures, how it performs its computations, and how to interpret its output.

Here's some of the results produced by Imatest for the Olympus C-7000:

Color Accuracy

The Olympus C-7000 doesn't oversaturate its colors as much as most consumer/prosumer cameras I test. This has led some reviewers to mark it down for more dull-looking color, but its color is in fact more accurate than most cameras on the market. (It does produce rather dull-looking bright yellows though.) Being accurate doesn't do you any good though, if what everyone wants is bright, snappy-looking color. Fortunately, the C-7000's color saturation control lets you tweak the color up exactly the amount you want. The saturation control has nice, fine adjustment steps that cover a broad range. If you want the C-7000's color to look more like that of other cameras on the market, try just leaving the saturation control boosted one or two notches. On average, color saturation of swatches on the MacBeth ColorChecker(tm) chart are 102.9% of their ideal values. (An average oversaturation of 2.9%.)

Color Analysis

These images show the color behavior of the C-7000 directly. In each color swatch, the outer perimeter shows the color as actually captured by the camera, the inner square shows the color after correcting for the luminance of the photographed chart (as determined by a 2nd-order curve fit to the values of the gray swatches), and the small rectangle inside the inner square shows what the color should actually be, based on perfect rendering to the sRGB color spacer. From this plot, we can see how close the C-7000's color is to the ideal values across much of the spectrum. The major deviation is the rather dark yellow it produces here.

Gray Patch Tone and Noise Analysis

There's a lot in this particular graph, a lot more than I have room to go into here. Bottom line, the Olympus C-7000's noise levels are right in line with those of the best competing 7-megapixel cameras, with a nice, fine-grained character.

This chart compares the C-7000's noise performance over a range of ISOs against that of competing cameras. As you can see, the C-7000 and Sony DSC-V3 have very similar performance, the Sony DSC-P150 coming in just a hair lower. Despite the low noise levels in its final images, the C-7000 does a good job of maintaining subject detail in areas of subtle contrast. An excellent performance overall.

Resolution Chart Test Results

The chart above shows consolidated results from spatial frequency response measurements in both the horizontal and vertical axes. The "MTF 50" numbers tend to correlate best with visual perceptions of sharpness, so those are what I focus on here. The uncorrected resolution figures are 1285 line widths per picture height in the horizontal direction (corresponding to the vertically-oriented edge), and 1301 along the vertical axis (corresponding to the horizontally-oriented edge), for a combined average of 1293 LW/PH. Correcting to a "standardized" sharpening with a one-pixel radius increases this number slightly, to an average of 1583 LW/PH, an excellent number that's better than some 8-megapixel cameras manage.

For the real techno-geeks, the two plots below show the actual edge response of the C-7000, for horizontal and vertical edge. What's interesting in these plots is how restrained the C-7000's default sharpening is, and how little it disturbs the underlying image detail. There's really no over-sharpening at all. This has led some to mark its images off for being soft, but here again, the camera's image-adjustment controls work very well. - Just dial up the sharpness setting a couple of notches.

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