Pentax Optio M20 Digital Camera Review

by James Murray
Published on December 20, 2006

Navigation
Intro	Testing / Performance
Physical Tour	Components
Design / Layout	Modes
Control Options	Image Parameters
Connectivity / Extras	Overall Impressions
Conclusion	Specs / Ratings

 
 

Color (7.09)

Like all other digital cameras that are reviewed at our office, we put the Pentax Optio M20 through a series of tests to determine exactly how good its pictures are. For starters, we tested its ability to reproduce color. We did this by photographing the industry standard GretagMacbeth color chart, which displays 24 different colors. The M20’s images of the chart were uploaded to Imatest imaging software, which is programmed to compare cameras’ produced colors to the original colors of the chart. Below is a chart modified by the software to show the original colors (vertical rectangle), Pentax M20’s colors (outer portion of tile), and luminance-corrected ideal colors (inner square).

Below is another chart that explains the M20's color reproduction characteristics further. The center of the chart is completely unsaturated, and the edges of the chart are fully saturated. The 24 squares represent the ideal colors on the GretagMacbeth chart. The circles represent the colors produced by the Pentax Optio M20. The line connecting the two shows the degree of error. Ideally, the two shapes should be atop each other, but as seen below, there is a lot of variance.

Many of the Optio M20's cooler hues are off. In addition, the colors are undersaturated (notice the circles leaning toward the inner portion of the chart). The M20 came out with an average saturation of 97.15 percent, which is a little strange because most compact models oversaturate by a few percentage points to enhance skin tones and make images look more flattering than reality. This Pentax has a mean color error of 8.37, which isn’t anything worth bragging over. A 7.09 overall color score isn’t impressive, but it’s better than the Pentax Optio W10’s horrible 5.56 rating.

 

Still Life Scene
Below is a shot of our still life scene recorded by the Pentax M20.

The Pentax Optio M20 has a 1/2.5-inch CCD with 7 effective megapixels on it. We mounted the digital camera on a stable tripod and used the self-timer to get the absolute sharpest shots. We varied the aperture and focal length to find where the lens was its sharpest. We found the best shot the M20 delivered was taken at f/5.1 and 14.3mm; it is shown below.

If you click on the image, a full-resolution file can be seen. It shows serious barrel distortion, especially noticeable by the black lines on the top and bottom of the chart. Those lines run straight horizontally on the actual ISO resolution chart we used, but the lines show up bowed into the frame of the Pentax M20’s images. The sharpness of the edges suffers significantly too. Although, it looks the worst on the right side; it is apparent on both edges.

 

This image was analyzed by Imatest software, and its resolution was quantified in units of line widths per picture height (lw/ph). This tells how many theoretical alternating black and white lines the camera could clearly discern before the lines began to blur together. The Pentax Optio M20 resolved 1682 lw/ph horizontally with 11 percent oversharpening, and 1670 lw/ph vertically with 10.1 percent oversharpening. These numbers aren’t impressive since compact digital cameras with the same advertised resolution produced much better results. The 7.1-megapixel Canon PowerShot A620 read 1708 lw/ph horizontally and 1787 lw/ph vertically. The lack of detail garnered a 3.77 overall resolution score, but the barrel distortion that will visibly warp pictures when printed is most disturbing.

Many users of this digital camera will use the automatic ISO setting, so we tested to see how well it worked. In our brightly lit studio, the Pentax Optio M20 automatically set the camera to 400, which is much too high. The amount of noise at this rating is terrible, resulting in an overall auto ISO noise score of 1.31. This is worse than the Pentax W10 and WP that we’ve tested.

 

Using the bright studio lighting and the color chart, we adjusted the ISO settings and tested each one to see how much noise was produced. The results are shown below with the horizontal axis representing the manual ISO settings and the vertical axis showing the amount of noise produced at each.

There is a lot of noise to start with even at the lowest ISO 64 setting. It continues to build until it is basically unusable at ISO 1600. Pictures at the highest setting will look grainy. The Pentax Optio M20 managed a 5.72 overall score derived from a regression analysis on the individual ISO settings’ noise levels.

 

Low Light (3.75)

The Pentax M20 has a host of automated modes, few of which cater to low light photography. Nevertheless, we tested the camera at 60, 30, 15, and 5 lux. The lighting in the first test at 60 lux is comfortable enough to read a book. The 30 lux test would cause the eyes to strain a little. The 15 lux test necessitates squinting, and the 5 lux test is nearly impossible to read unless you have a flashlight.

 

Low Light Tests
60 Lux	30 Lux
15 Lux	5 Lux

 

This digital camera kept colors illuminated more than the Pextax W10 did, but the noise level in the M20’s images is still very disappointing. The M20 also had trouble focusing in low light and often used short exposures. Even considering the short exposures, there was a lot of noise in pictures. Below is a chart showing just how much, with the horizontal axis representing the shutter speed and the vertical axis representing the noise level.

The Pentax Optio M20 had trouble keeping noise under control beyond just 1/15^th of a second. Overall, this digital camera isn’t made for shooting in low light. Its exposures are too short, its focus too finicky, and its high ISO settings too noisy to produce anything decent. The M20 is best fit for shooting outdoors in daylight.

 

Speed / Timing
Startup to First Shot (6.58)
The Pentax Optio M20 took 3.42 seconds from the time we turned it on until it took its first shot. Many compact cameras take about 2 seconds to start up, which can still be a long delay. M20 users should turn the camera in advance of picture-taking opportunities.

Shot to Shot (8.84)
The Pentax Optio M20 has a burst mode, but in our tests, the mode doesn’t have a steady burst rate. The second shot is 0.9 seconds after the first shot, the third shot is 0.72 seconds after the second shot, the fourth shot is 2.7 seconds later, and the subsequent shots are spaced at about 1.35 seconds apart. The average for the first 6 shots is 0.7 frames per second.

Shutter to Shot (9.37)
The Optio M20 took 0.63 of a second from the time we pressed the shutter to take a picture. That’s a long time – long enough to miss really great shots. Users can press the shutter just before they expect the perfect moment but anticipating a great moment by half a second is tough. We consider a 0.2 of a second delay to be good for compact cameras but anticipating by that much can still be difficult. The M20 is not a strong option for action photography. A delay of more than half a second can be frustrating even for posed pictures.