Canon SX20 IS Exposure

Saturation & Hue Accuracy
Good overall color and hue accuracy, with moderate oversaturation of some colors.

Saturation. The Canon SX20 IS produced good saturation overall, with moderate oversaturation in reds, greens, and blues. Some other colors such as cyan were actually undersaturated a small amount. Overall, the Canon SX20's images appeared to have punchy color that didn't look unnatural, but you can always adjust saturation to your liking. Most consumer digital cameras produce color that's more highly saturated (more intense) than found in the original subjects. This is simply because most people like their color a bit brighter than life.

Skin tones. Here, with the color balanced properly for the light source, the Canon SX20's skin tones did have a slightly pink cast, but should still be pleasing to most consumers. Where oversaturation is most problematic is on Caucasian skin tones, as it's very easy for these "memory colors" to be seen as too bright, too pink, too yellow, etc.

Hue. The Canon PowerShot SX20 IS produced a few color shifts relative to the correct mathematical translation of colors in its subjects, most visibly pushing cyan towards blue (for better-looking skies), orange toward yellow, and yellow toward green. Still, despite the shifts in red through yellow and cyans, overall hue accuracy was very good. Hue is "what color" the color is.

Saturation Adjustment
The Canon SX20 IS lets you adjust the image Saturation, Contrast, and Sharpness (as well as Red, Green, Blue, and Skin Tone settings) in five steps each. As can be seen below, the saturation adjustment was pretty effective. It also leaves the image contrast relatively unaffected, which is as it should be.

The table above shows results with the default as well as the two "extreme" saturation settings. Click on any thumbnail above, then click again to see the full-sized image.

Exposure and White Balance

Indoors, incandescent lighting
Good color with both Auto and Manual white balance settings. About average positive exposure compensation required.

Color balance indoors under incandescent lighting had a very slight magenta cast with the Auto white balance setting, but the Canon SX20 IS did much better here than the majority of digital cameras we test. The Incandescent white balance option resulted in a fairly strong reddish cast, while the Manual setting produced the most accurate color overall. The Auto setting wasn't far off the mark, though. The SX20's exposure system handled this lighting well, producing good results with an average amount of exposure compensation, +0.3 EV. Overall color looks good, though the blue flowers look a touch purplish, probably due to the SX20's tendency to punch up reds a little. (Many digital cameras reproduce the blue flowers here with more of a purplish tint, so the Canon SX20 IS actually performs a bit better than average here.) Our test lighting for this shot is a mixture of 60 and 100 watt household incandescent bulbs, a pretty yellow light source, but a very common one in typical home settings here in the U.S.

Outdoors, daylight
Good overall performance outdoors, though high contrast and hot highlights. Good color as well.

The Canon PowerShot SX20 IS performed reasonably well under harsh outdoor lighting, though contrast was quite high. An average amount of exposure compensation (+0.7 EV) was needed to keep the model's facial skin tones bright, resulting in a lot of blown highlights in her shirt and flowers. There was slight overexposure in the outdoor far-field house shot at the default exposure. Overall color is good though, if slightly pinkish, with the Manual white balance setting on the portrait (the Auto and Daylight settings were just a touch too cool). Though overall contrast is high, the shadows hold onto a fair amount of detail, even though a bit noisy. Fortunately, there's a contrast adjustment to help tame the highlights a bit, as well as bring out shadows.

See full set of test images with explanations
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Resolution
Very high resolution, 1,700 ~ 1,800 lines of strong detail.

Our laboratory resolution chart revealed sharp, distinct line patterns down to about 1,800 lines per picture height in the horizontal direction, and about 1,700 lines in the vertical direction. (Some might argue for over 1,800 lines, but artifacts begin to appear at much lower resolutions.) Extinction of the pattern occurred around 2,200 lines in both directions. Use these numbers to compare with other cameras of similar resolution, or use them to see just what higher resolution can mean in terms of potential detail.

See full set of test images with explanations
See thumbnails of all test and gallery images

Sharpness & Detail
Images are somewhat soft overall due to heavy noise suppression. Some edge enhancement artifacts on high contrast subjects as well.

Sharpness. The Canon PowerShot SX20 IS is capable of capturing fine detail, though definition of fine detail suffers from noise and the effects of noise suppression. In high contrast areas, the camera produces some visible edge enhancement artifacts, though nothing out of the ordinary. Luminance noise is also seen in the skies and particularly in the shadow under the eave. Edge enhancement creates the illusion of sharpness by enhancing colors and tones right at the edge of a rapid transition in color or tone.

Detail. The crop above right shows moderately high noise suppression, with the darker and low contrast areas of hair showing limited detail. Individual strands remain visible in the moderate shadows, but quickly lose definition. Noise-suppression systems in digital cameras tend to flatten-out detail in areas of subtle contrast. The effects can often be seen in shots of human hair, where the individual strands are lost and an almost "watercolor" look appears.

ISO & Noise Performance
Effects of noise reduction already evident at base ISO, and noise suppression becomes fairly strong at the higher settings.

The Canon PowerShot SX20 IS applies moderately strong noise reduction even at the lowest ISOs, resulting in soft detail in the mannequin's hair at ISO 80. ISO 100 shows a bit more luminance noise than ISO 80, but detail is about the same. ISO 200 has slightly less luminance noise, but detail is reduced compared to ISO 100. Beginning at ISO 400, chroma noise becomes more noticeable in the shadows, and fine detail is all but gone, smoothed away by noise reduction. At higher ISOs, chroma noise in the form of green and purple blotches is quite evident, especially in the shadows. Overall color balance becomes quite yellowish at ISO 1,600 as well. On-screen crops like this tell you only part of the story with a camera, though: To see how these images held up when printing at various sizes, read the Output Quality section below.

Extremes: Sunlit and low light tests
High resolution with good detail, but high contrast. Pretty good low-light performance.

Sunlight. The Canon PowerShot SX20 IS responded to the deliberately harsh lighting in the test above with high contrast and hot highlights. Shadow detail isn't bad, if a bit noisy, but highlights have limited detail at +0.7 EV (though this exposure was best from skin tones). Highlight detail is compromised, with clipping occurring in the shirt and some flowers. At +0.3 EV, the face, background and some shadow areas are just a little dark, so we preferred the +0.7 EV exposure, though it resulted in a lot of blown highlights. The SX20's adjustable contrast setting did a good job of decreasing the overall contrast and bringing up the shadows and midtones, without creating any strange color gradations on the face. Be sure to use fill flash in situations like the one shown above; and it's better to shoot in the shade when possible.

Contrast Adjustment
As mentioned previously, the camera's contrast adjustment helped in taming strong highlights and bringing out dark shadows.

At its lowest contrast setting, the Canon SX20 IS did a good job of holding more detail in the highlights and shadows while maintaining fairly natural-looking skin tones in the portrait shot above. It did not help much with the blown highlights in the far-field house shot, though shadow detail is slightly better.

The shots above show the results of the minimum, default and maximum contrast settings. While you can see the extremes, it's pretty hard to evaluate small differences in contrast on small thumbnails like these, click on any thumbnail, and then the interim image, to go to the full-size image.

The above images show the effect of the Canon SX20's Intelligent Contrast (i-Contrast) feature. The Auto mode did brighten the model's face quite a bit, as well as shadow areas and the background, though exposure is still a tad dim. Still, very good results here.

The above images show the effect of the Canon SX20's face detection autofocus mode (Face AiAF), which also adjusts exposure and white balance to optimize exposure for faces. The SX20's face detection AF mode did adjust exposure so that the model's face is much brighter than with it Off, but as a result the rest of the scene became a bit too bright overall, losing a lot of detail in the highlights. Still, a handy feature, if you're dealing with strong backlighting, etc.

Because digital cameras are more like slide film than negative film (in that they tend to have a more limited tonal range), we test them in the harshest situations to see how they handle scenes with bright highlights and dark shadows, as well as what kind of sensitivity they have in low light. The shot above is designed to mimic the very harsh, contrasty effect of direct noonday sunlight, a very tough challenge for most digital cameras. (You can read details of this test here.)

Low light. The Canon PowerShot SX20 IS performed reasonably well on the low-light test, capturing bright images at the lowest light level down to ISO 200. At ISOs 80 and 100, the images at 1/16 foot-candle are a bit dim, due to the SX20's maximum exposure time of 15 seconds (reported in the EXIF file header as 16s), but still usable. At ISO 3,200, the maximum exposure is limited to 1/8, which results in bright exposures down to about 1/3 foot-candle. Auto exposure metering struggled a bit at lower light levels, requiring the use of manual exposure for these shots. Color balance was pretty good with the Auto white balance setting, though, only very slightly cool. The camera's AF system was able to focus down to just below the 1/4 foot-candle light level unassisted, but in complete darkness with the AF assist enabled. (A useful trick when shooting under dim lighting is to just prop the camera on a convenient surface, and use its self-timer to release the shutter. This avoids any jiggling from your finger pressing the shutter button, and can work quite well when you don't have a tripod handy. With its ability to focus in very dim lighting, the SX20 IS should do quite well in such situations.)

How bright is this? The one foot-candle light level that this test begins at roughly corresponds to the brightness of typical city street-lighting at night. Cameras performing well at that level should be able to snap good-looking photos of street-lit scenes.

NOTE: This low light test is conducted with a stationary subject, and the camera mounted on a sturdy tripod. Most digital cameras will fail miserably when faced with a moving subject in dim lighting. (For example, a child's ballet recital or a holiday pageant in a gymnasium.) For such applications, you may have better luck with a digital SLR camera, but even there, you'll likely need to set the focus manually. For information and reviews on digital SLRs, refer to our SLR review index page.

Coverage and Range
Good flash power, though coverage is very uneven at wide-angle. Our standard flash shots required about average exposure compensation.

Coverage. Flash coverage was very uneven at wide-angle (not surprising, given the wider-than-average 28mm equivalent focal length), with much more uniform results at telephoto. (Note that the full 20x zoom is too long for this shot, so we shot at approximately 17x or 481mm eq. for our telephoto results here. We also shot telephoto coverage at ISO 1,600, as ISO 100 resulted in a very dark image which did not reveal coverage.)

Exposure. In the Indoor test, the Canon PowerShot SX20 IS' flash underexposed our subject slightly at its default setting, requiring a flash exposure boost of +0.7 EV, which is about average for this shot. The camera's Slow-Sync flash mode did not require flash compensation, though it produced a warm cast from the background lighting.

ISO 100 Range. At wide-angle and ISO 100, flash shots started out bright at 6 feet, peaked at about 9 feet and remained fairly bright out to about 12 feet, becoming gradually dimmer from there. Still, flash images were usable all the way out to 16 feet, the limit of our test. At telephoto, flash shots were bright to 9 feet, decreasing in brightness from that point on. Very good results here.

Manufacturer Specified Flash Test. In the wide-angle shot above, the Canon SX20 IS doesn't appear to perform to specification at the rated distance, as the target is very dim, even though the camera selected ISO 250. However, we'd call these results inconclusive, as the white doors may have thrown the camera's flash metering off. (The camera may have "thought" the doors were part of the intended subject, and may have reduced flash power to expose for them.) At full telephoto, the SX20 IS did perform to specification resulting in a reasonably bright image, but also boosted ISO to 250. Our standard test method for flash range uses a fixed setting of ISO 100, to provide a fair basis of comparison between cameras. We've now also begun shooting two shots using the manufacturer-specified camera settings, at the range the company claims for the camera, to assess the validity of the specific claims.

Print Quality
Good print quality at 13x19 inches. ISO 400 images are soft but usable at 11x14, ISO 3,200 shots are produce a decent 4x6.

Printed results from the Canon SX20 are good, despite the softness at 100 percent onscreen, producing a good 13x19-inch print at ISO 80 and 100 with good, vibrant color.

ISO 200 shots, though, are too soft at that size, looking better at 11x14 inches.

ISO 400 shots are usable at 11x14 when viewed at arm's length, but get better at 8x10 inches.

ISO 800 shots still look good at 8x10, though some detail in red areas will be quite soft.

ISO 1,600 and 3,200 shots are soft but usable at 4x6.

Overall, printed performance from the Canon SX20 IS is good for a long zoom digital camera.

Testing hundreds of digital cameras, we've found that you can only tell so much about a camera's image quality by viewing its images on-screen. Ultimately, there's no substitute for printing a lot of images and examining them closely. For this reason, we now routinely print sample images from the cameras we test on our Canon Pro9000 Mark II studio printer, and on the Canon Pixma MP610 here in the office. (See the Canon Pixma Pro9000 Mark II review for details on that model.)