Konica Minolta DiMAGE Z5By: Dave Etchells & Mike Tomkins
Konica Minolta existing Z3 model gets an updated sensor, larger LCD and slightly updated control layout.
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Z5 Imatest ResultsReview First Posted: 03/28/2005
Detailed analysis of the Konica Minolta Z5 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.
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 Konica Minolta Z5:
For the most part, the Konica Minolta Z5 has better than fairly good color accuracy, avoiding the oversaturation that's so common among consumer digicams. That said, most consumers prefer slightly oversaturated color, so some people may find the Z5's technically more accurate color a little flat-looking. In the chart above oversaturation is shown by the extent to which the circles (camera color) are displaced outward (higher saturation) relative to the ideal values (squares), while undersaturation is shown by circles that are displaced inward. On average, color saturation of swatches on the MacBeth ColorChecker(tm) chart are 99.18% of their ideal values. (An average undersaturation of 0.82%.) Where the Z5 does err a little is in its hue accuracy, tending to shift purples and deep blues towards blue/cyan. Also, the extent of the undersaturation in the green-to-yellow range is greater than that of most consumer digital cameras I've tested. Foliage colors will tend to appear a little muted with the Z5.
These images show the color behavior of the DiMAGE Z5 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 space.
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 Z5's noise levels are pretty low across the board, and
the noise spectrum is such that the noise is fairly fine-grained.
This chart compares the Konica Minolta DiMAGE Z5's noise performance over a range of ISOs against that of other cameras. As you can see, the Z5 comes in at the low end of the scale, across the full ISO range. What isn't shown here though, is the extent to which the camera trades away subject detail to achieve such low noise levels, particularly at ISO 320. Even at ISO 200, there's quite a bit of subject detail traded away in the pursuit of low image noise. (I'd personally be happy to see a bit more image noise at ISO 200 and 320, if it meant hanging on to more subject detail.)
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 1416 line widths
per picture height in the horizontal direction (corresponding to the vertically-oriented
edge), and 1385 along the vertical axis (corresponding to the horizontally-oriented
edge), for a combined average of 1401 LW/PH. Correcting to a "standardized"
sharpening with a one-pixel radius decreases this number a fair bit, to an average
of 1310 LW/PH. A reasonable if not spectacular number for a five-megapixel camera.
For the real techno-geeks, the two plots below show the actual edge response of the Z5, for horizontal and vertical edges. (Here, you can see the fairly significant overshoot caused by the sharpening algorithm, and the extent to which it is reduced by Imatest's correction to a "standard" 1-pixel edge sharpening.
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