Digital Camera Review

Digital Camera Review

Jan 30, 2007 - By Emily Raymond
The Canon PowerShot SD40 follows the SD30 by adding a few more megapixels, a whole new image processor, and a few adjustments to the specs. This 7.1-megapixel Digital Elph comes in four trendy colors and measures smaller than most cell phones. It has a 2.4x optical zoom lens and a 1.8-inch LCD screen. The biggest innovation on the SD40 is the Digic III image processor that touts face detection and noise reduction technology. In September 2006, Canon announced the SD40 along with two other PowerShot cameras. The company claims that its newer Digital Elphs, including the SD40, are designed to be a little more upscale than previous models. The Canon PowerShot SD40 looks to be just that with its stainless steel housing and trendy styling. The digital camera retails for $349.
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Color (6.98)
Canon digital cameras have typically tested well in terms of color, but the SD40 remixes the standard fare inside the camera. It has a new Digic III image processor, a 7-megapixel image sensor, and a Canon lens seen on other PowerShot models. To see how well the SD40’s combination of elements can reproduce realistic colors, we photographed the ever-colorful GretagMacbeth color chart. This chart shows colors from throughout the spectrum. We take the SD40’s photographs of the chart and upload them to Imatest imaging software, that compares the original chart’s colors to those from the camera. Below is a chart showing the original colors in the vertical rectangle of each tile, the Canon SD40’s colors in the outer square of each tile, and the ideal corrected for exposure in the inner squares.   

Some of the colors are hard to distinguish from each other, while others are obviously off. Below is another comparison chart to show just how far each color is from where it should be. The Canon PowerShot SD40’s colors are shown as circles, and the ideal colors are squares.  

The white appears to be spot on, but many of the other colors are dancing about the frame. Many of the camera’s colors move toward the outer edges of the chart, indicating that they are oversaturated. Indeed, the numbers proved this. Colors are over-saturated by an average of 119.6 percent. Most cameras oversaturate by a few percentage points to really flaunt colors, but this is a bit much! Warmer colors tended to be the most inaccurate. The Canon SD40 ended up with a mean color error of 8.59 and an overall score of 6.98, which are disappointing numbers for this digital camera.   

Still Life Scene
Below is a shot of our stock still life scene, recorded with the Canon PowerShot SD40.


Click on the image above to view the full size image.

Resolution (5.40)
The SD40 packs a 7.1-megapixel image sensor under the hood. At its top JPEG resolution, we snapped several pictures of an industry standard resolution chart to see how effective it is at capturing detail. The chart is shown below.


Click on the chart to view the full resolution file

We photographed the chart testing out different focal lengths and apertures to get the absolute sharpest shot, and our best result came from an image shot at f/5.6 and 14.9mm. Imatest ran this image through its screening and output quantitative resolution results in terms of line widths per picture height (lw/ph). This unit describes how many alternating black and white lines could fit across the SD40’s frame. On the horizontal edge of the frame, the camera resolved 2013 lw/ph, and used 10.6 percent over-sharpening. On the vertical edge of the frame, the camera read 1655 lw/ph with 9.2 percent oversharpening. 

These results are on-par with other Canon digital cameras. The Canon PowerShot A620 also has 7.1 megapixels and resolved 1708 lw/ph horizontally and 1787 lw/ph vertically. The Canon PowerShot SD40’s overall resolution score of 5.4 is very respectable for a compact digital camera. 

Noise – Auto ISO (1.86)
We tested the noise in the automatic ISO setting in our brightly lit studio. Most digital cameras choose the lowest ISO setting and produce little noise. The Canon SD40 produced the amount of noise found at the manual ISO 200 setting. Metering wasn’t the main issue in this problem, but the SD40 just produced a lot of noise all over its ISO range. Thus, the SD40 comes out with a horrible 1.86 score. 

Noise – Manual ISO (5.10)
In the bright studio lighting, we tested the noise levels at each manual ISO setting. There are plenty of options thanks to the new Digic III processor. The SD40 has a range extending from 80-1600. Below is a chart showing the noise level (on the vertical axis) for each manual ISO setting (horizontal axis). 

The Canon PowerShot SD40 produces more noise than it should at the lower ISO settings – and it only builds from there. The results are manageable until about ISO 200, then pictures start to get unbearably noisy after that. The manual ISO noise chart is almost identical to the one produced by the Canon SD700 IS. The only difference is the added ISO 1600 setting on the SD40. The Canon SD40 came out with a 5.1 overall manual ISO noise score. 

Low Light (3.0)
All of our other tests are done in optimal studio lighting. However, since not everyone shoots under perfect lighting, we dim our lights for a few tests. The first test was done at 60 lux that is equivalent to the amount of light in a living room after dusk with two soft lamps. Our second test is done at 30 lux, which is equivalent to light emitted from a 40-watt bulb. The 15 and 5 lux test are extremely dark and are meant to push the image sensor to its limit.

Low Light Tests
60 Lux
30 Lux
15 Lux
5 Lux

The Canon PowerShot SD40 doesn’t allow manual exposure settings so lengthening the shutter speed was nearly impossible. The only way to illuminate images without the flash was to bump up the ISO sensitivity, but that caused the images to come out garbled. They look spotty and honestly quite awful. This digital camera isn’t a star performer in low light, but it can at least capture fuzzy renditions of subjects that look something like watercolor paintings.

Speed / Timing
Start-up to First Shot (8.65)
The Canon Powershot SD40 can start up and take a shot in 1.35 seconds. That’s quick for a compact camera and will be useful when a chance for a spontaneous shot comes up. DSLRs usually take less than a second to start up, but it’s common for compact cameras to take over 3 seconds.

Shot-to-Shot Time (9.38)
When it was set to burst mode with maximum file size and quality, the SD40 shot at 1.6 frames per second. We shot 66 frames at that rate, and it appeared that the SD40 would have kept on going until the memory card filled up. 1.6 fps isn’t fast enough for sports or action sequences, but it allows users to get off a couple of shots at a time when shooting portraits or group pictures.

Shutter to Shot Time (8.28) 
The SD40 takes 0.36 seconds to capture a shot after the shutter button is pressed. Among compact cameras, that’s mediocre performance. Many cameras are closer to 0.2 or 0.25 but some are over 0.5. As far as practical use goes, 0.36 seconds is long enough to ruin a shot. Users of the SD40 should try to train themselves to compensate for the delay and press the shutter slightly before the peak of action.

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