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If you brought a slew of different cameras to the Grand Canyon and photographed your family, each camera would reproduce the colors of the landscape differently. Some might make the sky a duller gray, some may give the sky a brilliant but exaggerated blue, some may bring out reds in your family’s faces, and some will make those same faces look paler. The closer to realistic colors the camera produces, the better it scores.
We tested the color accuracy of the Canon SD850 IS to see how it reproduces colors. To test this, we photographed an industry standard GretagMacbeth ColorChecker test chart and compared the colors the camera reproduced with the colors of the chart. The image below shows how well the camera performed. The outer squares show the colors the camera reproduced, the inside squares show the ideal color of the chart corrected for the exposure, and the small rectangles show the ideal chart color at an even exposure.
For most colors, the outside and inside squares are very similar, meaning the camera’s colors are, for the most part, accurate. Only in a couple of the blue squares do the colors stray significantly. The graph below shows this information in another way. The ideal colors of the test chart are placed in their known locations on the color spectrum, and are represented by squares. The colors the SD850 IS reproduced are the circles, and the lines connecting the squares and circles show the color error.
Imatest measured a color error of 5.44 in L**a**b* color space, which is fantastic. As you can see on the graph, most of the colors are very close to their ideal colors. The blues stray from their ideals the most, but this is often the case in digital cameras because shifting the blues enhances to the look of skies in a photograph. Overall, there is also a trend toward oversaturation, meaning colors appear more saturated in photos than they do in reality.
**Resolution ***(6.11) *
We tested the resolution of the 8-megapixel SD850 IS by photographing an industry standard resolution test chart and varying the focal length and exposure settings. We ran the images through Imatest to determine the combination of settings that produced the sharpest images. Imatest measures resolution in units of line widths per picture height (lw/ph), which correspond to the number of equally spaced alternating black and white lines that could fit in the image frame before it blurred.
The sharpest image, shown above, was taken at ISO 80, f/4, and a focal length of 12mm. Imatest measured a resolution of 1710 lw/ph horizontally with 8.1 percent oversharpening, and 1532 lw/ph vertically with 11.6 percent undersharpening. These scores are decent, though there isn’t as much vertical sharpening as we would like to see in a point-and-shoot camera. Also, there is evident chromatic aberration, even in the middle of the frame. Chromatic aberration makes edges turn blue or red, and is caused by lens elements in the camera not being perfectly focused. This could be distracting in large prints.
**Noise – Manual ISO ***(4.72) *
Noise refers to the "static" you can see in digital camera images, often in low light shots. This random signal noise comes from inside the camera, not from the scene being photographed. It can take the form of sandy grains or splotchy gray or colored patches. To test the amount of noise produced by the Canon SD850 IS, we photographed our test chart under bright studio lights at every ISO sensitivity the camera offers.
The SD850 IS kept noise levels low from ISO 80 to 200, but at higher sensitivities noise was very high. The noise was very apparent in images shot with high ISO settings, and had both fine grained noise as well as splotchy blue and yellow patches, making the images quite ugly and resulting in the mediocre manual noise score.
Noise – Auto ISO*(1.68)*
We also shot the test chart at Auto ISO to see how much noise it produced in Auto mode. The camera chose ISO 200, and the noise level was 1.49 percent, meaning much of the image was drowned out by noise. This is a lot of noise for shooting under such bright lights, and yielded a poor auto noise score. This camera doesn’t seem to provide much in-camera noise reduction, which means you will see grainy noise in any photo not shot in very bright light. There is a good side to this, however: the lack of - or limited - noise reduction smoothing means photos shot in low light will stay sharp.
White Balance*** (14.4)*
****White balance accuracy is very important when shooting with a point-and-shoot, especially if you don’t plan to spend time fiddling with your photos on a computer later. Poor white balance can create a color cast over an entire image. If you have ever owned a camera, you have very likely observed a yellow cast come across an indoor shot. Good white balance settings help to accurately depict colors.
We tested the white balance of the SD850 IS by photographing the ColorChecker test chart under four different types of light: Outdoor Cloudy, Flash, Fluorescent, and Tungsten. We took shots to test the auto white balance setting and the white balance presets.
The SD850 IS performed extremely well in white balance accuracy with both the auto setting and the presets. Using flash on the auto white balance setting was almost perfectly accurate. The only time it performed poorly was in tungsten light using the auto setting, which is an issue many cameras have. Overall, the auto white balance is accurate, though the preset is a better option for shooting indoors under tungsten light.
The SD850 IS has no flash preset, but that didn’t matter in the least because the white balance was nearly spot-on using the auto setting. The presets were very accurate in fluorescent, outdoor cloudy, and tungsten light.
**Still Life Sequences
***Click to view the high-resolution images.*
|Still Life Scene|
|ISO 80||*ISO 80*|
|*ISO 100*||ISO 100|
|ISO 200||ISO 200|
|*ISO 400*||*ISO 400*|
|*ISO 800*||*ISO 800*|
|*ISO 1600*||*ISO 1600*|
**Low Light ***(7.60) *
We dimmed the studio lights to get a look at how the SD850 IS performed in low light. We took shots of the ColorChecker test chart at light levels of 60, 30, 15, and 5 lux. 60 lux corresponds to a room softly lit with two lamps, and 30, 15, and 5 lux get progressively darker, testing the limits of the camera’s sensor.
All the shots were taken at ISO 1600.
Color accuracy held up well at 60 and 30 lux, but deteriorated at 15 and 5 lux, hitting a mean color error of 10.6 at 5 lux. Noise was very high at all the low light levels, drowning out almost 5 percent of the image. Even in the reduced size images above, the noise is quite pronounced.
We also tested the long exposure performance of the SD850 IS. We took the shots at ISO 400, as we do with every camera we test. The exposure compensation menu on the SD850 IS has a secondary menu that reveals the long exposure settings, from 1 to 15 seconds. The camera had trouble manually white balancing with long exposures, and consequently the color accuracy suffered. The long processing time of each photo indicates the SD850 IS applies automatic noise reduction. Noise levels stayed moderately low, never rising above 2 percent of the image.
**Dynamic Range ***(5.03) *
Dynamic range is an important image quality factor because it tells how many shades of gray - from pure black to paper white - a camera can discern. This is especially important in bright outdoor photography, when there are bright sunny highlights and dark shadows in the same scene. High dynamic range allows you to see detail in the highlights and the shadows in a scene and poor dynamic range blows them out.
We tested the dynamic range of the SD850 IS by photographing a backlit Stouffer test chart and running the images through Imatest. The Stouffer chart is made up of a long row of rectangles, each a slightly different shade of gray, ranging from brightest white to darkest black. The more rectangles the camera can discern, the better its dynamic range.
The SD850 IS had solid dynamic range at ISO 80, but then dropped off significantly at higher ISO settings. If you are shooting in a situation where there are strong bright and dark areas of the image, keep this camera at as low an ISO sensitivity as possible. Overall, the SD850 IS had a mediocre dynamic range score compared to other point-and-shoot cameras.
Speed/Timing – All speed tests were conducted using a Kingston Ultimate 120X 2GB SD Card
*Startup to First Shot (8.3) *
The SD850 IS took 1.7 seconds to take a picture after it was turned on. This is pretty reasonable, and should allow users to capture an unexpected moment.
*Shot-to-Shot (9.2) *
In Continuous shooting mode, the SD850 IS takes a shot every 0.8 seconds for at least 250 shots. This is very good for a point-and-shoot, and will be great for capturing action shots.
*Shutter-to-Shot (9.0) *
With the shutter held halfway down and prefocused, the Canon fired a shot instantly. Without being prefocused, the camera took 0.4 seconds to take a shot.
*Processing (7.8) *
The SD850 IS took 1.1 seconds to process one shot. This is how long you will have to wait for the little green light to stop blinking before you take another photo.
**Video Performance ***(3.85) *
Bright Indoor Light – 3000 lux
We tested the Video mode of the SD850 IS by recording footage of our color test charts under bright studio lights. We shoot our video color tests with auto white balance, and you can see in the images below that the colors were far from accurate. The camera had a mean color error of 24.5, and saturation of 136.8. However, this is very normal for camera video. Aside from the horrendous color error, the noise was quite low, at 0.54 percent.
*Low Light – 30 lux *
The SD850 IS did much better with video color accuracy in low light, with a color error of 9.84, which was less than half the error in bright light. Noise levels were high, however, at 1.8 percent – definitely noticeable.
We recorded video of our resolution test chart under studio lights at 1700 lux. The SD850 IS resolved 293 lw/ph horizontally with 7.8 percent undersharpening, and 312 lw/ph vertically with 2.6 percent oversharpening. For standard definition video recorded at a resolution of 640 x 480, this is quite decent, and didn’t cause any severe image artifacts.
We took the SD850 IS outside to see how it handled moving objects on the street. Overall, the video looked quite good, with nice handling of exposure and contrast. Motion looked very good, but with a little stuttering when objects moved off the frame. However, there was a little moiré on the grills of moving cars, and a lack of detail in distant objects.
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