Digital Cameras - Canon PowerShot S230 Digital ELPH Test Images
(Originally Posted: 11/13/02)
|I've begun including links in our reviews to a Thumber-generated index page for the test shots. The Thumber data includes a host of information on the images, including shutter speed, ISO setting, compression setting, etc. Rather than clutter the page below with *all* that detail, we're posting the Thumber index so only those interested in the information need wade through it!|
The extreme tonal range of this image makes it a tough shot for many digicams, which is precisely why I set it up this way, and why I shoot it with no fill flash or reflector to open the shadows. The object is to hold both highlight and shadow detail without producing a "flat" picture with muddy colors, and the S230 performed fairly well, although its final image was a little contrasty.
The shot at right was taken with a +0.7 EV exposure compensation adjustment, which brightened the midtones just a little, but blew the stronger highlights. I chose the Manual white balance as the most accurate overall, since the Daylight and Auto settings were on the cool side.
Skin tones look good, and the blue flowers in the bouquet are almost perfect. (This is a very difficult blue for many digicams to get right, and the S230 does produce some purplish tints in them. For reference, the flowers are a fairly pure light navy blue.) The red flowers are a little oversaturated, and show a slight "glow" around their edges. Resolution is very good, with a lot of fine detail visible throughout the frame, even in the shadows. Details are just slightly soft all over, but still have good definition. (This is a reflection of Canon's conservative approach to in-camera sharpening. By going easy on the sharpening in-camera, the maximum subject detail is preserved. As a result, the images from Canon digicams generally take sharpening in Photoshop, etc, very well, but look a little soft onscreen.) Image noise the shadows is quite low. Despite the high contrast, the S30 did a very good job here.
To view the entire exposure series from zero to +1.0 EV, see files
S23OUTMP0.HTM through S23OUTMP3.HTM on the thumbnail
Great resolution and detail, though some distortion from the lens.
Overall results are similar to the wider shot above, but the S230's 2x zoom lens distorts Marti's features slightly. - A longer zoom ratio would be preferable for close-in portrait shots like this. Detail is outstanding, however, with sharper details in Marti's face and hair. The shot at right was taken at the default exposure setting, which resulted in slightly high contrast and only the strongest highlights blown out. Shadow detail is moderate, with low noise.
To view the entire exposure series from zero to +0.7 EV, see files S23FACDP0.HTM through S23FACDP2.HTM on the thumbnail index page.
Indoor Portrait, Flash:
Good intensity and coverage with the built-in flash, though a pronounced color cast from the incandescent room lighting.
The S230's built-in flash is a bit dim at the default exposure setting, with a strong orange cast from the background incandescent lighting. The orange cast spills over onto Marti's features, but increasing the exposure compensation only blows the highlights on her shirt and does nothing about the orange cast. I preferred the +0.7 exposure compensation adjustment, which brightened Marti's features without losing too much detail in her white shirt. I also shot with the Slow-Sync flash mode, which produced a much dimmer shot, with a very strong orange cast from the room lighting. (Slow-Sync on the S230 will be best used outdoors at night, to brighten backgrounds.)
To view the entire exposure series from zero to +1.0 EV in the normal
flash mode, see files S23INFP0.HTM through S23INFP3.HTM on the thumbnail
Indoor Portrait, No Flash:
Excellent color with both Incandescent and Manual white balance options.
This shot is always a very tough test of a camera's white balance capability, given the strong, yellowish color cast of the household incandescent bulbs used for the lighting. The S230 was very much up to the challenge though. The S230's Incandescent white balance produced the best color overall, with only the faintest green cast. The Manual option produced an acceptable picture as well, though the greenish cast was slightly stronger. (The Auto had a lot of trouble though, producing a very warm sepia cast.) Marti's skin tone is pretty good here, but the blue flowers in the bouquet are quite dark and purplish. (Probably to be expected, considering the color cast of the light source.) The shots at right were shot with an exposure compensation of +0.7 EV, to compensate for the effect of the light background and Marti's white shirt on the exposure metering.
Great resolution, detail, and color, though details are a little soft. Significant softening in the corners.
The S230's Manual white balance setting produced great results here, with the most accurate white value on the house trim. Both the Auto and Daylight white balances resulted in warm, yellow casts. Resolution is moderately high, with good detail in the tree limbs and shrubbery. Details are a little soft throughout the frame, however, with increased softness in the corners. (In fact, the S230's corner softness extends a fair distance into the frame along the left side.) Since I didn't see corner softness to this extent in the Far Field test below, I assume it's something associated with close-in focusing. (When shooting this test target, the S230 was only a bit over a meter from the poster. Lenses frequently show corner softness as you get toward the near end of their focusing range.)
Excellent resolution and detail, with a good dynamic range.
This image is shot at infinity to test far-field lens performance. NOTE that this image cannot be directly compared to the other "house" shot, which is a poster, shot in the studio. The rendering of detail in the poster will be very different than in this shot, and color values (and even the presence or absence of leaves on the trees!) will vary in this subject as the seasons progress. In general though, you can evaluate detail in the bricks, shingles and window detail, and in the tree branches against the sky. Compression artifacts are most likely to show in the trim along the edge of the roof, in the bricks, or in the relatively "flat" areas in the windows.
This is my ultimate "resolution shot," given the infinite range of detail in a natural scene like this, and the S230 did quite well with it, particularly for a subcompact camera. The tree limbs over the roof and fine foliage in front of the house show strong detail, especially in the leaves of the cherry tree in front of the house on the right. In-camera sharpening does a better job here than in the closer shot of the house poster above, with sharper details throughout the frame. The left corners of the frame are still quite soft, however. (Here's an example at the Low Sharpness setting.) The camera picks up most of the detail in the bright white paint surrounding the bay window, a trouble spot for many digicams. Detail is moderate in the shadow area above the front door, showing the S230's slightly limited dynamic range. Overall color looks good, but the shot is contrasty overall, and a little dark as well. (The camera apparently tried to hold onto the very bright highlights, leading it to underexpose the rest of the frame.) The table below shows a standard resolution and quality series, followed by ISO and color series.
Lens Zoom Range
Average 2x zoom range.
I routinely shoot this series of images to show the field of view for each camera, with the lens at full wide angle, at maximum telephoto (2x, in this case), and at full telephoto with the digital zoom enabled. The S230's lens is equivalent to a 35-70mm zoom on a 35mm camera. That corresponds to a moderate wide angle to a very modest telephoto. (A more limited zoom range is frequently one of the tradeoffs you must accept in a subcompact camera design.) Following are the results at each zoom setting.
Good color with the Manual setting, albeit a tad magenta, and good detail too.
This shot is often a tough test for digicams, as the abundance of blue in the composition frequently tricks white balance systems into producing a warm color balance. The S230's Auto and Daylight settings both responded with warm casts, with the Auto setting producing the strongest cast. Though results are slightly magenta, the Manual setting produced the best overall color, and the most natural skin tones to my eye. Skin tones are quite good here, naturally rendered, without strong casts, or over- or undersaturation. The magenta cast results in a blue background with purplish tints that aren't in the original image. The blue robe looks nearly right, although again purplish in the shadow areas. Resolution is very high, with great detail in the embroidery of the blue robe.
Good macro performance with great detail, though flash has trouble.
The S230 performed pretty well in the macro category, capturing an average-sized minimum area of 3.47 x 2.61 inches (88 x 66 millimeters). Resolution is very high, with strong detail in the dollar bill, as well as in the coins and brooch. Corner softness is slightly less in this shot than what I noticed in the House poster, though this time is stronger on the right side of the frame. The S230's flash had trouble throttling down for the macro area, overexposing the entire frame.
"Davebox" Test Target
Very slight underexposure, but great color and good saturation.
All three white balance settings produced good results here, though the Auto and Daylight settings are a touch greenish. I preferred the Manual setting, though it has a very slight reddish cast. Exposure looks about right, and the S230 has no trouble distinguishing the subtle tonal variations of the Q60 target. Colors are just a hint dark in the large color blocks, although I found the red and blue additive primary color blocks a tad oversaturated. The shadow area of the charcoal briquettes shows moderate detail, though with low noise.
Great low-light performance, although slightly warm color balance.
The S230's limited manual exposure controls include a Long Shutter mode, with adjustable shutter speeds from one to 15 seconds. Combined with the ISO adjustment, the S230's low-light shooting capabilities are well above the average point-and-shoot digicam. Add in the bright autofocus assist light (which lets the camera focus in near complete darkness), and you have a subcompact camera that's an excellent low-light shooter.
The S230 produced clear, bright, usable images down to the 1/16 foot-candle (0.67 lux) limit of my test, at ISO equivalents from 100 to 400. (At ISO 50, the darkest usable image was at 1/8 foot-candles, or 1.3 lux, which is still very good.) Color was a bit warm from the Auto white balance setting, but saturation was good, considering the low light levels.
The table below shows the best exposure we were able to obtain for each of a range of illumination levels. Images in this table (like all of our sample photos) are untouched, exactly as they came from the camera.
Flash Range Test
A somewhat weak flash, barely effective even at eight feet from the test target.
In my testing, the S230's flash was rather dim, even at the eight foot minimum distance I test at. This isn't terribly surprising, since compact digicams very often have underpowered flashes. (The limited space inside the case prevents use of a larger energy-storage capacitor in the flash system.) Intensity decreased noticeably with each foot of distance, and the flash became very dim at 14 feet. The decreased intensity resulted in a bluish cast, that intensified with the shooting distance. Below is the flash range series, with distances from eight to 14 feet from the target.
High resolution, 1,050-1,100 lines of "strong detail." Better than average barrel distortion.
The S230 turned in a roughly average performance on our "laboratory" resolution test chart. It started showing artifacts in the test patterns at resolutions as low as 600 lines per picture height, in both horizontal and vertical directions. I found "strong detail" out to 1,100 lines horizontally, and 1,050 lines vertically. "Extinction" of the target patterns didn't occur until about 1,300 lines.
Optical distortion on the S230 is a bit better than average (although still too much, IMHO) at the wide-angle end, where I measured an approximate 0.6 percent barrel distortion. The telephoto end fared better, as I measured a 0.2 percent pincushion distortion. Chromatic aberration is very low, showing only about two or three pixels of faint coloration on either side of the target lines. (This distortion is visible as a very slight colored fringe around the objects at the edges of the field of view on the resolution target.) The strongest distortion I noticed from the S230's lens was corner softness, which intruded a fair amount into the frame.
Resolution Series, Wide Angle
Resolution Test, Telephoto
Viewfinder Accuracy/Flash Uniformity
A tight optical viewfinder, but the LCD monitor is nearly 100 percent accurate.
The S230's optical viewfinder is somewhat tight, showing 83 percent of the frame at wide angle, and 82 percent at telephoto. The LCD monitor proved much more accurate, showing almost exactly 100% of the final image area. Given that I like LCD monitors to be as close to 100 percent accuracy as possible, the S230's LCD monitor performs very well. Flash distribution is somewhat uneven at wide angle, with dark falloff at the corners and edges of the frame. At telephoto, flash distribution is more even, but with still with a little falloff at the corners of the frame.
S230 Test Images
S230 "Picky Details"
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