Pentax Optio Z10

Color (4.88)
Accurate colors have a big impact on image quality, whether you are shooting landscapes or people. We test color accuracy by photographing a GretagMacbeth ColorChecker test chart and comparing the colors the camera reproduces with the known colors of the chart. The image below shows how the Pentax Z10 performed. The outer squares show the colors the Z10 reproduces, the inner squares show the ideal colors of the test chart corrected for exposure, and the inner rectangles show the ideal chart colors at a perfectly even exposure.

As you can see from the image, many of the inner squares do not match up well with the outer squares, showing that the Z10 has problems with color accuracy. Yellows, blues, and reds are especially inaccurate. This information is shown graphically in the image below. The locations of the ideal chart colors are plotted on the color spectrum as squares, while the locations of the Z10’s corresponding colors are shown as circles. The lengths of the lines connecting the squares and circles show the amount of color error for each color tile.

The graph confirms the poor color accuracy seen in the first image. Many colors are drastically shifted, especially yellows, blues, and even reds. This will certainly change the appearance of landscapes and other photos. To its credit, the Z10 reproduces skin tones quite well, meaning people shouldn’t look unnaturally pale or flushed, but because the majority of colors are inaccurate, the Z10 receives a poor color accuracy score.

Resolution (5.95)
We test resolution performance by photographing an industry standard resolution test chart at varied focal lengths and exposure settings. We run the photos through Imatest, which measures resolution in terms of line widths per picture height. This unit refers to the number of equally spaced, alternating black and white lines that could fit across the image frame before becoming blurred.

Click the chart to view the high resolution image

The 8-megapixel Z10 took its sharpest photos at ISO 64, f/3.8, and a focal length of 12 mm. The camera resolved 1627 lw/ph horizontally with 6.9 percent oversharpening, and 1588 lw/ph vertically with 0.2 percent oversharpening. These are respectable numbers, but nothing special. Unfortunately, the camera also suffers from a number of optical problems related to resolution. The edges of the frames are blurry, subject to color fringing, and the corners are darkened. When lines get too small for the camera to distinguish, they turn into an ugly mush of color moiré. Despite these issues, the Z10 scores better for resolution than a several more expensive in-body lens cameras, including the Casio Exilim EX-V8 and the Nikon Coolpix S51c.

Noise – Manual ISO (4.86)
Image "noise" refers to the ugly sandy or splotchy effect that digital photos can have, especially at high ISO speeds or in low light. To test noise levels, we photograph our test chart under bright, even studio lights at all ISO speeds available. We run the photos through Imatest, which measures noise levels by the percentage of image detail they drown out.

The Z10 keeps noise levels very low at ISO 64 and 100, but above ISO 200 the noise becomes quite noticeable. At ISO 1600 and 3200, noise levels are so high they begin to wash out the entire photo, which is noticeable even in thumbnail versions (see the Still Life photos further down the page). The noise itself is very ugly, showing tiny splotches of yellow and blue and little specs of black and gray. At ISO 800 and above, some noise smoothing is apparent, which destroys some fine image detail. Overall, the Z10 is a noisy camera, and the ISO 1600 and 3200 settings are virtually useless.

Noise – Auto ISO (0.93)
We also test noise levels with the camera set to Auto ISO. Under our bright studio lights, the Z10 shot at ISO 320, yielding a large amount of noise. Keep this camera at low ISO speeds manually in order to minimize noise effects. 

Still Life Sequences
Click to view the high resolution images


White Balance (7.20)
Accurate white balance is critical to accurate color reproduction, since different types of light sources have different color casts to them. We test white balance by photographing the Colorchecker test chart under four different types of light: flash, fluorescent, outdoor shade, and tungsten. We test the auto white balance setting and the appropriate white balance presets for each type of light source. The camera has no autofocus assist light, so were were unable to take focused shots using the flash as the only light source.

Auto (7.49)
Using the auto white balance setting, the Z10 is very accurate in outdoor shade, mediocre in fluorescent light, and poor in tungsten light. The auto setting is fine for shooting outdoors, but you may want to try using the presets when shooting indoors.

Auto WB - Fluorescent Illumination

Auto WB - Shade Illumination

Auto WB - Tungsten Illumination

Preset (6.92)
The presets test very similar to the auto setting, the only notable difference being that the fluorescent preset is slightly more accurate than the auto setting. This may help if you encounter color casts to your photos when shooting indoors.

Fluorescent WB - Fluorescent Illumination

Shade WB - Shade Illumination

Tungsten WB - Tungsten Illumination

Low Light (4.89)
Not all your shots will be taken in perfectly lit situations, which is why we also test cameras in less-than-ideal shooting conditions. To test low light performance, we photograph the ColorChecker chart at light levels of 60, 30, 15, and 5 lux. This corresponds to the amount of light in a room lit softly by two table lamps (60 lux), down to very dim light levels that would make you squint. All shots are taken at ISO 1600.

Low Light Tests
60 Lux	30 Lux
15 Lux	5 Lux

The camera cannot expose properly at 5 lux, showing the sensor has clear limits. You could get closer with ISO 3200, but, as it is,  ISO 1600 is really pushing it in terms of noise levels. Color accuracy suffers a bit in low light, which is especially a problem because it isn’t even very good in bright light. Noise levels are very high and distracting. This is not a great camera for low light shooting.

We also test performance for long exposure photos in low light, this time at ISO 400. The Z10 can take exposures as long as 4 seconds in Night Scene mode, but we couldn’t get it to focus on anything dark enough to need an exposure that long. The longest exposure we could get out of the camera with sharp autofocus was 0.5 seconds, which produced strong color error and high noise levels. Again, this camera is not your best bet for low light shooting.

Dynamic Range (5.08)
Dynamic range is a measure of a camera’s tonal range, i.e. how many shades of gray it can distinguish. This is particularly important for scenes with high contrast, such as a wedding photo or a landscape in bright sunlight. A camera with good dynamic range will keep detail in both the highlights and shadows of the same scene. We test dynamic range by photographing a backlit Stouffer step chart at all ISO speeds. The Stouffer chart consists of a long row of gray rectangles, varying slightly in tone from brightest white to darkest black. The more rectangles a camera can discern, the better its dynamic range.

The Z10 has decent dynamic range at ISO 64 and 100, but then drops quickly at higher ISO speeds. This is important to realize when shooting scenes with high contrast; lowering your ISO speed will greatly improve image quality. Dynamic range is limited by noise levels, and the Z10 is very noisy at high ISO speeds.

Speed/Timing – All speed tests were conducted using a Kingston Ultimate 120X 2GB SD Card, with the camera set to highest resolution and best quality, unless otherwise noted.

Startup to First Shot (7.6)
The Z10 takes 2.4 seconds to turn on and fire its first shot. This is a bit slower than many small point-and-shoots.

Shot-to-Shot (9.1)
In continuous mode, the Z10 takes 3 shots 0.9 seconds apart, and then pauses for roughly 3 seconds before shooting again every 2.1 seconds. In HS mode, the camera takes 4 3-megapixel photos 0.3 seconds apart. This is not a terrific burst mode, and will make it difficult to capture some action shots.

Shutter-Shot (9.0)
The Z10 has no measurable lag when the shutter is held halfway down and prefocused, but has a short lag of 0.2 seconds when not prefocused.

Processing (1.0)
The camera takes 4.5 seconds for the little green light to stop blinking, though another photo can still be taken during that time. This was measured for a 3.3 MB full resolution photo taken at ISO 160.

Video Performance (4.05)
Bright Indoor Light – 3000 lux
We shoot video of our color charts under bright indoor studio lights set to 3000 lux. Under such bright light, the Z10 had relatively good color accuracy (especially for auto white balance), and very low noise.


Low Light – 30 lux
We also take footage of our color charts with the lights dimmed to 30 lux, roughly the amount of light in a room lit only by a 40 watt bulb. In this low light, the Z10 has good color accuracy, but a lot of jumpy noise.

Resolution
We test video resolution by recording footage of our resolution chart under bright studio lights set to 1700 lux. The camera resolved 305 lw/ph horizontally with 3.4 percent undersharpening, and 363 lw/ph vertically with 37.4 percent oversharpening. This is extreme oversharpening, and leads to very ugly image artifacts, such as jagged lines and moiré.


Outdoor Motion
To get a look at how movie modes handle moving subjects, we take our cameras down to the street to shoot footage of cars and pedestrians in action. The Z10’s video look decent overall, though it was a bit noisy, showed some overexposure and motion moiré, and a bit of stuttering to objects moving off of the frame. Overall though, it isn’t bad video for a point-and-shoot digital still camera.