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Using the Pentax Optio W30 we snapped images of a GretagMacbeth color chart and uploaded them to Imatest software. The program used the most accurate picture from the W30 and compared its colors to those of the original color chart. The chart below is modified by the software to show the ideal colors in the vertical rectangle of each tile, the Pentax W30’s colors in the outer frame, and the luminance-corrected ideal in the inner square.
Each of the 24 color tiles are plotted on the graph below. The ideal colors are depicted as squares and the W30’s colors as circles. The center of the image is unsaturated and the outer edges are more saturated – so if a circle is bending outward from where it should be, it is oversaturated.
Many of the colors aren’t where they should be. Many of them are undersaturated too; it is surprising to see the reds undersaturated as that is one end of the spectrum that most digital cameras oversaturate specifically to enhance Caucasian skin tones. The W30’s colors were undersaturated at 97.11 percent. The mean color error came out to an awful 11.4, giving the camera an overall poor color score of 5.26. This is even lower than the Pentax W10’s awful 5.56 mark.
We secured the Pentax Optio W30 to a tripod and snapped pictures of an industry standard resolution chart for this test. We used different apertures and focal lengths to be sure that any bias from the lens was eliminated. We uploaded the images to Imatest software, which sorted through all the pictures and selected the sharpest one. That image was taken using a 14mm focal length, an aperture of f/3.9, and the lowest ISO 64 setting.
The 7.1-megapixel digital camera didn’t do a very good job of keeping the resolution chart sharp. Even in the center, some of the smaller lines blur together into an almost colorful soup. There is a lot of barrel distortion evident from the bowed black line on the bottom of the picture, accompanied by heavy purple fringing. Add to that the overall washed out look that only fades worse in the corners and the blurriness too. The entire right edge is blurrier than the rest of the image especially in the upper corner.
Imatest output numerical results in units of line widths per picture height (lw/ph) to describe the sharpness. More specifically, that unit of measurement describes the theoretical number of alternating black and white lines of equal thickness that could fit across the frame without blurring. The Pentax W30 resolved 1473 lw/ph horizontally with 6.5 percent oversharpening and 1327 lw/ph vertically with 0.6 percent undersharpening. By way of comparison, the 7.1-megapixel Canon A570 read 1794 lw/ph horizontally and 1656 lw/ph vertically. The numbers back up what the eyes can see: the Pentax W30’s resolution isn’t very good.
Noise – Auto ISO*(1.38) *
When set to the Auto ISO setting and positioned in a studio with 3000 lux on the chart, the W30 automatically selected an ISO much too high. It selected an ISO 250 setting and produced more noise than it should have in such brightly lit conditions.
Noise – Manual ISO* (4.88)
*The Pentax Optio W30 has an expansive manual ISO range that reaches from 64 to 3200. We measured the noise at each ISO setting and plotted it on the chart below. The horizontal axis shows the ISO settings and the vertical shows the percentage of the image lost to the speckled stuff.
Noise steadily rises with each increase in ISO sensitivity. The first two ISO settings are comparable with the Pentax W10’s, but the W30 has much more noise at ISO 200. At ISO 400, the Pentax W30 has much more noise than the older W10. Beyond ISO 400, the speckled noise is easily seen to the naked eye in even a 4 x 6-inch print. The scary thing is that these images were taken in optimal studio lighting – just wait until the lights go dim!
The studio lights were dimmed for the next test, which challenged the camera’s ability to photograph subjects in low light. We took pictures of the color chart at diminishing light levels of 60, 30, 15, and 5 lux. At 60 lux, reading is still a comfortable endeavor. At 30 lux, readers resort to squinting but can still get the job done. 15 and 5 lux is very dark and is when most people simply put their books away and give up. The first two tests are fairly common situations for photography; think places like dimly lit restaurants and night clubs. The last two tests are more useful for determining any limitations the camera may have.
And the Pentax Optio W30 has its limitations. At and below 15 lux, the camera had trouble focusing because there was no assist lamp. That doesn’t bode well for low light photography. The pictures shown above get darker, noisier, and discolored the dimmer the lights are. At 30 lux, the color error still held at 12.8 and saturation was very good. It is just the darkest two tests that really fell apart.
The longest exposure available from the Pentax W30 is 4 seconds and because shutter speeds can’t be manually adjusted, it is found in the night scene mode. We measured the amount of noise produced from this long exposure in low light and it came out to 2.37 percent of the image. In the end, if you can’t read without squinting, don’t even think about picking up the W30. It’s not built for low light photography.
To see how well the Pentax W30 could capture a full range of blacks, whites, and details in between, we photographed a backlit Stouffer test film. This film has a row of rectangles that are completely black on one side and transparent on the other. We uploaded the pictures into our imaging software and it measured how many exposure values the camera could capture at different ISO settings because ISO greatly affects the amount of details captured.
Below is a chart showing the manual ISO settings on the horizontal plane and the number of exposure values captured in a single image on the vertical plane.
Once again, the PentaxW30’s first two ISO settings performed similarly to the older W10’s. The W10’s ISO 200 and 400 settings capture more detail but then that camera crashed at ISO 800 with only 2 exposure values. The comparable setting on the W30 sits just under 3. The ISO 3200 is about as bad as it gets: pictures taken with this setting won’t show much detail at all. The ISO 64 setting yields the best dynamic range on the Pentax Optio W30 and should be used whenever possible.
The automatic white balance setting was most accurate when shooting in fluorescent lighting and it also performed better than the tungsten setting, which usually isn’t the case.
In general the presets didn’t perform as well as they should. The fluorescent preset was less accurate than the auto setting as well as tungsten, although both the preset and auto settings were horribly inaccurate. The Pentax W30’s most accurate white balance preset was shade. There was no flash preset and it was hard to test the flash at all even in the auto mode because the camera couldn’t focus on the test chart in the dark.
Still Life Sequences
Click to view high-resolution images.
|Still Life Scene|
|ISO 64||*ISO 64*|
|*ISO 100*||ISO 100|
|ISO 200||ISO 200|
|*ISO 400*||*ISO 400*|
|*ISO 800*||*ISO 800*|
|*ISO 1600*||*ISO 1600*|
|*ISO 3200*||*ISO 3200*|
*Low Light -30 lux *
When the lights were dimmed and a video of our test chart recorded, the mean color error jumped to 22.6 but the saturation returned to within normal range at 113 percent. This figure describes the overall saturation though and there were outliers in both directions. The blue end of the spectrum was very undersaturated and many of the reds were very oversaturated. The noise was the most bothersome aspect of the video in low light; noise reached an average of 2.69 percent of the video.
The video’s resolution wasn’t phenomenal by any stretch. We recorded a movie of a standard video test chart and ran it through Imatest software. The program output results using the same lw/ph measurement. The Pentax Optio W30 read 272 lw/ph horizontally with 17.6 percent undersharpening and 358 lw/ph vertically with 3 percent undersharpening. These aren’t impressive numbers but not many digital cameras have impressive movie modes anyway. That’s why there’s still a market for camcorders: they’re better.
We took the Pentax W30 outside and videoed some cars and other moving objects. The 30 fps frame rate still wasn’t enough to render smooth motion; subjects stuttered quickly along. There was also a lot of moiré visible, but the contrast outdoors was still good.
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