Canon A540 Exposure

Saturation & Hue Accuracy
Slightly oversaturated color (reds and dark greens were the most affected), very typical of consumer digital cameras. Generally good hue accuracy.

In the diagram above, the squares show the original color, and the circles show the color that the camera captured. More saturated colors are located towards the periphery of the graph. Hue changes as you travel around the center. Thus, hue-accurate, highly saturated colors appear as lines radiating from the center.

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. The PowerShot follows this trend, though it tends to overdo the strong red and blue tones a bit. 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. The A540 did render skin tones slightly on the pink side in most cases, but our sense is that most consumers would find the A540's bright color very appealing.

The other important part of color rendition is hue accuracy. Hue is "what color" the color is. Here, the PowerShot did quite well. Like most digicams, it shifts cyan colors toward blue, apparently to produce better-looking sky colors, but the rest of the hues were quite accurate.

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

Our random "Gallery" shots showed very pleasing color across a wide variety of subjects. (See our PowerShot A540 Photo Gallery for more shots taken with the camera.)

Exposure and White Balance

Indoors, incandescent lighting
Moderate warm cast with Auto white balance and cool with Incandescent white balance. Roughly average exposure compensation was required.

Auto White Balance +1.0EV	Incandescent WB +1.0EV
Manual WB +1.0EV

Color balance indoors under Auto white balance was warm and slightly cool-looking with Manual white balance. The incandescent option pretty well nailed the color balance of the household incandescents used on this shot. The Canon A540 required a +1.0 EV exposure compensation boost to get a good exposure, although the Auto white balance option produced a slightly darker exposure than did the Incandescent and Manual settings. Overall color is well-balanced and hue accurate with Incandescent white balance, but all three settings produced results that we'd consider to be within acceptable limits. Our test lighting for this shot is a mixture of 60 and 100 watt household incandescent bulb, a pretty yellow light source, but a very common one in typical home settings here in the U.S.

Outdoors, daylight
Good color balance, very bright colors. Better than average exposure accuracy.

Auto White Balance Auto Exposure	Auto White Balance Auto Exposure

Outdoor shots generally showed accurate exposure with slightly blown out highlights. Shadow detail also tended to fall apart, but not more than one would expect for a consumer digicam. Sunlit shots showed high contrast and moderate oversaturation while overcast scenes managed a more accurate portrayal. Exposure accuracy overall was better than average, the camera requiring less exposure compensation than we're accustomed to seeing with consumer digicams.

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

Resolution
High resolution, 1,300 lines of strong detail.

Our laboratory resolution chart revealed sharp, distinct line patterns down to about 1,300 lines per picture height, with extinction at around 1,600. You could perhaps argue for 1,400 lines of resolution, but we felt that the level of artifacts there was too high to justify a rating at that level. (The camera did produce some artifacts even at lower line frequencies though, visible both below and in the full-sized res target shots.) 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. Beware that while you might be able to make out what looks like distinct lines at numbers higher than those we've mentioned here, the camera is just doing its best to continue interpreting the lines. If you zoom in and follow them from the wider portions, you'll see the lines converge and reappear several times, so the lines you see at 1,600 and higher are really only artifacts generated by the camera's imaging system.

Strong detail to 1,300 lines horizontal	Strong detail to 1,300 lines vertical

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

Sharpness & Detail
Fairly sharp images, relatively minorr blurring of detail from noise suppression.

Pretty good definition of high-contrast elements.	Subtle detail: Hair

The PowerShot A540's images are reasonably sharp, without any pronounced over-sharpening or edge enhancement on the camera's part. (Edge enhancement creates the illusion of sharpness by enhancing colors and tones right at the edge of a rapid transition in color or tone.) Interestingly, we reviewed this camera at the same time as the longer-zoom Canon A700, and were surprised by how noticeably sharper the very fine details in the branches against the sky in the crop above appeared with the A700. Make no mistake, the A540 takes a very good photo, but the images from the A700 are indeed somewhat sharper.

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. On the A540, noise suppression at shutter speeds above 1.3 seconds has only a relatively minor impact.

ISO & Noise Performance
Moderate noise at the normal sensitivity settings, very high noise that blurs detail at the higher settings.

ISO 80	ISO 100
ISO 200	ISO 400
ISO 800

The PowerShot A540's sensitivity ranges from ISO 80 to 800 equivalents. Up to ISO 200, the PowerShot produced relatively little noise, with only slightly blurred detail in the dark areas. At ISO 400 and especially at 800, the noise level and the amount of blurring that results increased noticeably. Taken as a whole though, the Canon A540's noise levels seem to be lower than we've seen in most camera models that compete at its price point.

Extremes: Sunlit and low light tests
High resolution, good overall detail, though high contrast and limited shadow detail. Excellent low-light performance, capable of capturing bright images under the darkest conditions we test at. (More than good enough for typical city scenes after dark.)

+0.3EV	+0.7EV	+1.0EV

Sunlight:
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.)

The Canon A540 had a little trouble with the deliberately awful lighting in the test above, producing somewhat high contrast with some lost highlight detail and deep shadows. The A540 required a bit les exposure compensation than is common on this shot, a correction of +0.7EV vs the +1.0 that is often needed. (In "real life" though, be sure to use fill flash in situations like the one shown above; it's better to shoot in the shade when possible.)

	1 fc 11 lux	1/2 fc 5.5 lux	1/4 fc 2.7 lux	1/8 fc 1.3 lux	1/16 fc 0.67 lux
ISO 80	1.3 sec f2.6	2.5 sec f2.6	5 sec f2.6	13 sec f2.6	15 sec f2.6
ISO 100	1 sec f2.6	2 sec f2.6	4 sec f2.6	10 sec f2.6	15 sec f2.6
ISO 200	1/2 sec f2.6	1 sec f2.6	2 sec f2.6	5 sec f2.6	10 sec f2.6
ISO 400	1/4 sec f2.6	1/2 sec f2.6	1 sec f2.6	2.5 sec f2.6	5 sec f2.6
ISO 800	1/8 sec f2.6	1/4 sec f2.6	1/2 sec f2.6	1.3 sec f2.6	2.5 sec f2.6

Low light:
The Canon PowerShot A540 did very well in our low light tests, producing bright images at the lowest light levels at ISO 200 and above. At ISO 80 and 100, images were bright down to the 1/8 foot-candle level, about 1/8 as bright as average city street lighting at night. As seen by the type in even the darkest images, the auto focus system worked well, and in fact managed to focus properly at the darkest levels of this test, even with its AF-assist light turned off.

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
The A540's small flash is limited to about 9 feet, and produces a slight blue cast in combination with typical incandescent room lighting. Our standard shots required more roughly average exposure compensation.

35mm equivalent	140mm equivalent
Normal Flash +1.0EV	Night Portrait Mode, +1.0EV

Flash coverage was a bit uneven at wide angle but very good at telephoto. In the Indoor test, the flash on the A540 underexposed our subject at its default setting (pretty standard for this shot), requiring a +1.0 EV exposure compensation adjustment to get reasonably bright results. The camera's Night mode produced brighter results, though with a stronger pinkish-orange cast from the room lighting.

At 11 feet, the flash did not quite illuminate the DaveBox target adequately.

8 ft	9 ft	10 ft	11 ft	12 ft	13 ft	14 ft
1/60 sec f5.0	1/60 sec f5.5	1/60 sec f5.5	1/60 sec f5.5	1/60 sec f5.5	1/60 sec f5.5	1/60 sec f5.5

Print Quality
Very good print quality, nice bright color, very usable 13x19 inch prints. ISO 400 images are cleaner than average at 8x10 inches, ISO 800 may be acceptable to some users at 8x10 inches, but look better at 5x7 inches.

Testing hundreds of digital cameras, we've found that you can only tell just 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 i9900 studio printer, and on the Canon iP5000 here in the office. (See the Canon i9900 review for details on that model.)

With the Canon A540, we found that it had plenty of resolution to make very crisp 8x10 inch prints. At 13x19, its prints were a bit softer looking, but should be more than adequate for wall or table display for most users. At high ISO, image noise levels were held in check very well up to ISO 400, but the ISO 800 shots were a fair bit noisier. We think most consumers would be quite satisfied by the quality of 8x10 inch prints made from ISO 400 shots. At ISO 800, the images looked a rough at 8x10 (but perhaps acceptable to some consumers), and fine at 5x7 inches.

Color-wise, the PowerShot A700's images looked just beautiful when printed on the i9900, with bright, vibrant color, yet not to the point that most users would consider it overdone. A few users who prefer more subdued, technically accurate color saturation levels may find the A700's images a little too bright, but we think most consumers will probably find the A700's bright, snappy images very appealing.