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Flash Performance

The S45's slim flash unit has a rated range (at Auto ISO; 50-100) of 0.35 - 4.8 m (at wide angle) and 0.35 - 3.0 m (at telephoto). Overall results were mixed, good color balance and output control at moderate distances, less good at full wide angle and further distance. The S45 nearly always takes flash shots at maximum aperture and so wide angle flash images may be affected by vignetting (see below).

Skin tone - Good exposure, no 'blue cast' Color patches - Good color balance, good flash power, good exposure


Low Light Focus

This test measures the minimum amount of light under which the camera can still focus. The focus target is our lens distortion test chart (shown here on the right), camera is positioned exactly 2 m (6.6 ft) away.

Light levels are gradually dropped until the camera can no longer focus. This is carried out at both wide angle and telephoto zoom positions (as more light reaches the focusing systems with a larger aperture).

This test target is the optimum type of subject for most "contrast detect" AF systems (as it has a vertical line at its center), you should consider the results below the best you could expect to achieve.

Lens position Aperture Lowest light focus
Wide angle (35 mm) F2.8 Complete darkness
Telephoto (105 mm) F4.9 1.8 EV (8.7 Lux, 0.81 foot-candle)

Light intensity (Lux) = 2.5 x 2^EV (@ ISO 100), 10.76391 Lux = 1 foot-candle (fc)

The S45's AF assist lamp worked well at wide angle, but less so at telephoto where it does need a dim light (although less than a 60 W bulb is sufficient). Remember that the target is two meters (6.6 ft) from the camera.


Barrel and Pincushion Distortion

The S45 has the same lens as the S40 and therefore exhibits the same distortion characteristics, that is just under 1.0% barrel distortion at wide angle and no measurable pincushion distortion at full telephoto. This is a good performance for a compact extending digital camera lens.

Barrel Distortion, 0.9% @ wide angle Pincushion Distortion, 0% @ telephoto


Vignetting

Our vignetting test is very simple, a shot of a blank wall from two meters away, vignetting will always be most visible at wide angle and maximum aperture and will start to disappear at smaller apertures and/or further zoom. As you can see below the S45 exhibits some visible vignetting at full wide angle and maximum aperture but this soon disappears with smaller apertures or more zoom.

Some corner vignetting visible at wide angle and maximum aperture (F2.8) Vignetting better at wide angle with a smaller aperture (F5.6)
Some corner vignetting visible at wide angle and maximum aperture (F2.8) Vignetting disappears at a further zoom level


Purple Fringing (Chromatic Aberrations)

As we expected we got the same results in our chromatic aberration test shot, a very faint blue fringe but no strong purple fringing. This was supported by a hunt through our selection of 'every day' shots none of which showed any problem with purple fringing.

Hard pressed to find evidence of chromatic aberrations in "every day" shots Our standard chromatic aberration test shot


Overall Image Quality / Specific Issues

The S45 clearly has very good image quality, probably the best among the compact four megapixel class. Color balance is very good with vivid but not over-saturated color and a nice tonal balance which lifts shadow detail, images almost never look too 'contrasty'. If the image response (tone / color) isn't to your tastes you can always use one of the preset color effect settings or customize your own. Resolution is also very good, Canon's lens is certainly capable of delivering enough resolution back to the sensor to squeeze more detail into the four megapixel image than most other comparable cameras.

Just like the S40 before it the S45's only weakness could be the sharpness of its lens especially when shot at maximum aperture (F2.8 at wide, F4.9 at tele). It's certainly possible to find images which aren't as sharp as we would like and some which exhibit a sharp center but soft edges. Luckily in most well lit circumstances the camera will choose an aperture smaller than maximum to avoid any softness. In this respect the S45 is certainly no worse than other compact four megapixel digital cameras.

In my S40 review I noted a dead pixel, I didn't see anything like this on the S45. I also noted Canon's "problem" with diagonal jaggies (lines which are near 45 degrees being made up of groups of 45 degree lines), this also appears to have been addressed with the S45.

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