Pentax Optio M40 Digital Camera Review

Read an expert, independent review of the Petax Optio M40 digital camera.

October 12, 2007
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A camera’s ability to reproduce accurate colors is a major factor in how good your photos turn out. Photos with dull colors can be boring, photos with oversaturated colors can look unnatural, and photos with inaccurate colors can look ugly. All cameras handle color differently, which is why we test color accuracy. We test this by photographing an industry standard GretagMacbeth ColorChecker test chart and comparing the known colors of the chart with the colors the camera reproduces. The ColorChecker consists of 24 tiles of commonly photographed colors from around the color spectrum. The image below shows the results for the Pentax M40. The outside squares show the colors the M40 reproduces, the inside squares show the ideal colors of the test chart corrected for luminance, and the inner rectangles show the ideal colors of the chart under a perfectly even exposure.


As you can see, not all of the inner squares match up perfectly with the outer squares. Note how different the blues and yellows are. The camera appears to significantly undersaturate yellows, and shift blues toward purple. This makes some blues skies look purple. The graph below confirms this in a more quantitative way. The colors of the test chart are shown on the color spectrum as squares, while the colors the camera reproduces are shown as circles. Then lines connecting the circles and squares show the extent of the color error.


The graph shows that yellows and blues are quite inaccurate. This affects many photos you will take, whether they include blue skies, yellow flowers, or light skin tones. In addition to these inaccuracies, the camera tends to undersaturate, meaning a lot of your colors will look dull, and you may have to take the time to boost them on your computer. Overall, the M40’s color accuracy is considerably below average.


*We test resolution by photographing an industry standard resolution test chart under bright, even light. We vary focal length and exposure settings to find the settings that produce the sharpest images. Imatest, our powerful third-party image analysis software, evaluates resolution in terms of line widths per picture height (lw/ph). This corresponds to the number of equally-spaced alternating black and white lines that can fit across the image frame of the camera before becoming blurred.


Click to view the high-resolution image

The 8-megapixel Pentax M40 produces the sharpest images at ISO 50, f/5.9, and a focal length of 19mm. The camera resolves 1488 lw/ph horizontally with 1.4 percent oversharpening, and 1575 lw/ph vertically with 3.3 percent oversharpening. These results put the M40 below average for 2007 point-and-shoots, though it is good to see the camera doesn’t oversharpen too much. However, the corners of the image are quite blurry and unfocused, there is some color moiré in the stripes, and there is obvious barrel distortion. These issues will show up in your photographs and won’t look nice.

Noise – Manual ISO*(6.47)

*If you have ever owned a digital camera you have probably noticed ugly graininess in photos taken in low light. This graininess is known as "noise," and is similar to the static on your TV or the background hiss from your stereo system. But unlike film grain, digital image noise almost always looks ugly. Noise appears in many varieties, from monochromatic sandy grains to colored splotches. The amount of noise in an image is intrinsically greater at high ISO sensitivities.

We test noise levels by photographing a test chart under bright, even studio light at all ISO sensitivities. The Pentax M40 has disappointingly high noise at ISO 50 and 100, but from ISO 200 to 800 noise levels stay decently low. At ISO 1600 and 3200, however, there is so much noise your images will be barely useable. The M40 doesn’t appear to apply much noise reduction, which allows more detail to show through even if noise levels are high. Despite high noise levels at ISO 1600 and 3200, the M40 scores better than average for a 2007 point-and-shoot.

Noise – Auto ISO*(1.06)

*We also set cameras to Auto ISO to test noise levels. This test is performed under the same bright studio lights as our other tests. The Pentax M40 chooses a very odd ISO 640 under the Auto setting, which yields high noise, but not notably high for such a high ISO sensitivity. This suggests that the EXIF data may be inaccurate in Auto mode. Still, the camera has significantly more noise than we would like to see in such bright shooting conditions.

White Balance*(5.25)*

A camera cannot reproduce accurate colors without good white balance. A camera must be able to adjust to different lighting conditions in order to accurately reproduce colors. Without proper white balance, images can take on odd color casts, often yellow or blue. We test white balance by photographing the ColorChecker test chart under four types of light: flash, fluorescent, outdoor shade, and tungsten. We test the Auto white balance setting as well as the appropriate white balance presets found in the White Balance menu.

*Auto (4.07)

*We could not test the white balance accuracy using flash because the lack of a focus assist light prevents the camera from focusing in the dark. White balance accuracy under fluorescent light is good, though it fares poorly under outdoor shade and tungsten light. Images taken outdoors have a blue color cast, and in tungsten light they take on a strong yellow cast.


Auto WB - Fluorescent Illumination


Auto WB - Shade Illumination


Auto WB - Tungsten Illumination

Preset (6.43)

The white balance presets are more accurate than the auto setting. Outdoor shade and tungsten light are significantly more accurate, though still not great. Accuracy under fluorescent light is fairly accurate, though not quite as accurate as the Auto setting. Using manual white balance will always be the best way to white balance the M40.


Fluorescent WB - Fluorescent Illumination


Shade WB - Shade Illumination


Tungsten WB - Tungsten Illumination

Still Life Sequences

Click to view the high-resolution images.

Still Life Scene
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 ISO 50  *ISO 50*
 {{article.attachments['PentaxM40-ColorSL-ISO100_1.jpg']}}  {{article.attachments['PentaxM40-PeopleSL-ISO100_1.jpg']}}
 *ISO 100*  ISO 100
** {{article.attachments['PentaxM40-ColorSL-ISO200_1.jpg']}}**  {{article.attachments['PentaxM40-PeopleSL-ISO200_1.jpg']}}
 ISO 200  ISO 200
** {{article.attachments['PentaxM40-ColorSL-ISO400_1.jpg']}}**  {{article.attachments['PentaxM40-PeopleSL-ISO400_1.jpg']}}
 *ISO 400*  *ISO 400*
{{article.attachments['PentaxM40-ColorSL-ISO800_1.jpg']}}   {{article.attachments['PentaxM40-PeopleSL-ISO800_1.jpg']}}
 *ISO 800*  *ISO 800*
** {{article.attachments['PentaxM40-ColorSL-ISO1600-2_1.jpg']}}**  {{article.attachments['PentaxM40-PeopleSL-ISO1600_1.jpg']}}
 *ISO 1600*  *ISO 1600*
{{article.attachments['PentaxM40-ColorSL-ISO3200-3_1.jpg']}}   {{article.attachments['PentaxM40-PeopleSL-ISO3200_1.jpg']}}
 *ISO 3200*  *ISO 3200*
** Low Light***(6.42)* We also test camera performance in less-than-ideal light conditions. We dim the studio lights to 60, 30, 15, and 5 lux to see how well the camera maintains color accuracy and noise levels. Sixty lux corresponds to a room softly lit with two lamps, 30 lux is approximately a room lit by a single 40-watt bulb, and 15 and 5 lux are quite dark and test the limits of the camera sensor. All shots are taken at ISO 1600 so the results can be compared to other cameras. Color accuracy suffers in low light, resulting in a mean color error of 12.5 at 5 lux. Noise levels are very high, as well, as are any shots taken with the M40 at ISO 1600 (which shows how absurd the camera’s ISO 3200 setting is). At 30 lux, 3.4 percent of the image is drowned out by noise. The good news is the camera has no trouble properly exposing in very low light, even though the noise prevents the photos from looking very good. We also test low light performance using long exposures. In Night Scene mode, the M40 can take exposures as long as four seconds, and allows control of ISO and white balance. All shots are taken at ISO 400. Color accuracy suffers greatly, though noise levels are not as high as at ISO 1600. If you have a tripod, it may be worth lowering your ISO and taking longer exposures when you need a shot in low light. Otherwise, you’ll end up with lots of noise in your low light photos.
**Dynamic Range***(5.44)* Dynamic range, which describes the tones a camera can distinguish, is another important factor in image quality. For example, a camera with good dynamic range will be able to make out lots of detail in a bride’s white dress and a groom’s black tux in the same shot. A camera with poor dynamic range blows out white highlights or fails to detect detail in dark areas. We test dynamic range by photographing a backlit Stouffer test chart. The Stouffer chart is made up of a row of rectangles, each a slightly different shade of gray, ranging from brightest white to darkest black. The more rectangles a camera can discern, the better its dynamic range.
The M40 has excellent dynamic range at ISO 50, but at higher ISO settings it quickly drops off. Dynamic range is decent up to ISO 200, but at 400 and above it is quite bad. It is certainly worth your while to keep this camera at as low an ISO setting as possible whenever you can. Overall, the M40’s dynamic range is average for point-and-shoots released so far this year.
**Speed/Timing** – All speed tests are conducted using a Kingston Ultimate 120X 2GB SD Card, with the camera set to highest resolution and best quality. *Startup to First Shot (6.7)* The Pentax M40 takes a sloth-like 3.3 seconds to turn on and take its first shot. *Shot-to-Shot (9.2) *In Continuous shooting mode, the M40 takes three shots 0.8 seconds apart, then pauses for 3 seconds before continuing to take shots every 1 second. This is the only Burst mode the camera offers. *Shutter-Shot (9.0)* There is no measurable lag time if the shutter is held down halfway and prefocused. If the camera is not prefocused, the lag is 0.5 seconds while the camera autofocuses. *Processing (7.0)* It takes the M40 1.5 seconds to process one full resolution, best-quality 3.3 MB photo taken at ISO 160. **Video Performance***(3.53) Bright Indoor Light – 3000 lux *We test digital cameras’ Movie modes by capturing footage of the ColorChecker under bright studio lights set to 3000 lux. The graph below shows color accuracy in the same way as the graph in the Color section. As you can see, there is extreme color error, though this is actually quite normal for a camera set to Auto white balance under tungsten light. Noise levels are very low in bright light.

*Low Light – 30 lux

*We also test video quality in low light at 30 lux. The Pentax M40 has decent color accuracy in low light, and quite low noise. The problem, however, is that it has trouble focusing in low light. Regardless of how much noise there is, you want videos to be in focus.



*We record footage of the resolution test chart to determine the sharpness of video clips. Video is shot in Standard Definition, 640 x 480, so video resolution will always be much less than still photo resolution. In Movie mode, the M40 records 255 lw/ph horizontally with 14.6 percent undersharpening, and 350 lw/ph vertically with 13 percent undersharpening. This undersharpening actually helps the video detail by not introducing image artifacts when it is compressed. There are very few signs of moiré or jagged lines.

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Outdoor Motion

To evaluate the motion capture of digital camera video, we shoot moving cars and pedestrians on the street. The M40’s video is significantly overexposed in bright sunlight, and the highlights smear the frame. The exposure also changes drastically, creating a flashing effect, and the motion stutters. The good news is the camera effectively captures detail, and doesn’t show significant image artifacting. Overall, like most digital cameras’ Movie modes, the M40’s video quality leaves a lot to be desired.

Our editors review and recommend products to help you buy the stuff you need. If you make a purchase by clicking one of our links, we may earn a small share of the revenue. Our picks and opinions are independent from any business incentives.


  1. Testing/Performance
  2. Components
  3. Design / Layout
  4. Modes
  5. Control Options
  6. Image Parameters
  7. Connectivity / Extras
  8. Overall Impressions
  9. Conclusion
  10. Sample Photos
  11. Photo Gallery
  12. Specs / Ratings
Our editors review and recommend products to help you buy the stuff you need. If you make a purchase by clicking one of our links, we may earn a small share of the revenue. Our picks and opinions are independent from any business incentives.
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Our editors review and recommend products to help you buy the stuff you need. If you make a purchase by clicking one of our links, we may earn a small share of the revenue. Our picks and opinions are independent from any business incentives.
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