High contrast, but a very nice job overall, with good color and great resolution.

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 Optio 550 had a little trouble with the harsh lighting.

The shot at right was taken with a +1.0 EV exposure compensation adjustment, which resulted in slightly dark midtones, even while losing some highlight detail. At its default setting, the Optio 550 produced even higher contrast, thus I shot the image at right using the low contrast setting. Still, contrast is slightly high. I chose the Daylight white balance as the most accurate overall, though the Manual setting produced nearly identical results. The Auto setting was close but slightly warm.

Skin tones look very good, though the blue flowers in the bouquet are dark and just a little purplish. This is a very difficult blue for many digicams to get right, and for reference, the flowers are actually a light navy blue, with only hints of purple. The Optio 550 did a good job with the strong red and green tones, and managed not to lose detail in the bright highlights of the red flowers. Resolution is very high, with excellent detail visible throughout the frame. Detail is also very good in the shadow areas, with very low noise, and details are also quite sharp. Overall, a good performance.

To view the entire exposure series from zero to +2.0 EV with the low contrast adjustment, see files O55OUTLCDP0.HTM through O55OUTLCDP6.HTM on the thumbnail index page.

Contrast Series:
The Optio 550's contrast adjustment helps a little with this shot (notice how the shadows get a bit lighter with the "low" setting), but I'd really like to see a bit broader range. (Kudos to Pentax for including this feature at all on a compact camera though.)

Contrast Series
Low	Normal	High

Closer Portrait:

Excellent resolution and detail, but once again somewhat high contrast.

Exposure and color balance are similar to the wider shot above, and the Optio 550's 5x zoom lens does an excellent job of preventing distortion of Marti's features. Detail is even stronger in this shot, with great definition in Marti's face and hair. (Probably more than she'd like to see full-screen.) The shot at right was again taken with a +1.0 EV exposure compensation adjustment, which is a bit more compensation than this shot typically requires. Contrast is again high, as with the Outdoor Portrait above. Despite the strong shadows though, there's good detail in them, with relatively low noise.

To view the entire exposure series from -0.3 to +1.7 EV, see files O55FACDM1.HTM through O55FACDP5.HTM on the thumbnail index page.

Indoor Portrait, Flash:

Normal Flash +1.7 EV

Quite a bit of positive exposure compensation required for the best exposure, reasonably good color.

The Optio 550's flash illuminated the subject fairly evenly, though intensity was quite dim at the default exposure setting. The camera actually required a pretty substantial positive exposure boost, at +1.7 EV, to get the best exposure. The background incandescent lighting results in a fairly strong orange cast across the image, particularly on the back wall. Still, overall color is pretty good.

To view the exposure series at zero and from +1.0 to +2.0 EV, see files O55INFP0.HTM and O55INFP3.HTM through O55INFP6.HTM on the thumbnail index page.

Indoor Portrait, No Flash:

Auto White Balance

Incandescent White Balance

Manual White Balance

Excellent color with the Manual and Auto white balances, and good exposure (though with a significant boost).

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. Overall, the Optio 550 handled this tough subject much better than most cameras I test. Both the its Manual and Auto white balance options produced very good color here, though I preferred the slightly warmer tone of the Auto setting to the slight green tint of the Manual setting. (The Incandescent produced good results as well, but left a slightly greenish cast in the image.) Skin tones are very good, though the blue flowers are quite purple. (A common problem with this shot.) The shots at right have +1.3 EV exposure compensation adjustments, slightly more than this shot typically requires. Still a great job overall.

ISO Series:
Noise is very low on the Optio 550. Even at ISO 400, while the noise level is very high, the noise pattern is very tight and fine-grained, making it less objectionable than that of many other cameras.

ISO Series
ISO 64	ISO 100	ISO 200	ISO 400

House Shot:

Auto White Balance

Daylight White Balance

Manual White Balance

Slight color casts with each white balance tested, but great detail and resolution.

Though slightly reddish, the Optio 550's Auto white balance option produced the most pleasing overall color here. The Daylight setting was a bit greenish, and the Manual setting had a cooler, bluish cast. Resolution is very high, with practically all the detail to be found in this target visible in the tree limbs and shrubbery. (Cameras like the Optio 550 really stretch the limits of this poster, even though it was made from a 500MB scan of a 4x5 negative shot with a tack-sharp lens.) Details are also sharp, though the top right corner betrays some softness. (There's also a little softness in the top left corner as well.)

Far-Field Test

Excellent resolution, detail and color, though slightly high contrast.

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 Optio 550 performed very well. Detail is excellent in the tree limbs over the roof and in the fine foliage in front of the house, with great definition in the intricate details of the leaf patterns. Details are also sharp throughout the frame, though the left corners of the frame are just slightly soft. Contrast is a little high, and as a result, the camera loses a fair amount of detail in the bright white paint surrounding the bay window (a trouble spot for many digicams). That said, detail is reasonably strong in the shadow area above the front door. Color is about right, although the image is just a little dark overall. The table below shows a standard resolution and quality series, followed by ISO, sharpness, saturation, and contrast series.

Resolution Series:

Wide Angle	"Fine" JPEG	"Normal" JPEG	"Economy" JPEG
2,592 x 1,944	O55FARLF	O55FARLN	O55FARLE
2,048 x 1,536	O55FARM1F	-	-
1,600 x 1,200	O55FARM2F	-	-
1,024 x 768	O55FARSF	-	-
640 x 480	O55FARTF	-	-

ISO Series:

ISO Series
ISO 64	ISO 100	ISO 200	ISO 400

Sharpness Series:

Sharpness Series
Soft	Normal	Sharp

Saturation Series:

Saturation Series
Low	Normal	High

Contrast Series:

Function Series
Low	Normal	High

Lens Zoom Range

Excellent 5x 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 (5x, in this case), and at full telephoto with the digital zoom enabled. The Optio 550's lens is equivalent to a 37.5-187.5mm zoom on a 35mm camera. That corresponds to a moderate wide angle to a pretty substantial telephoto. Following are the results at each zoom setting.

Musicians Poster

Auto White Balance

Daylight White Balance

Manual White Balance

Good color with the Daylight white balance, and good resolution. However, underexposed at the default setting.

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 Optio 550's Auto white balance option somewhat fell prey to this tendency, producing a rather warm image, while the Daylight white balance setting showed good color overall, with good skin tones, despite a very slight red color tint. By contrast, the Manual setting was quite cool. The slight red cast of the Daylight setting creates faint purple tints in the blue background, as well as in the deep shadows of the blue robe. Resolution is very high, with great detail in the embroidery of the blue robe. The original data file for this poster was only 20MB however, so the Optio 550 can definitely show more detail than the poster has in it. Exposure was a bit dim at the default setting, so I shot the images at right with a +0.7 EV exposure compensation adjustment.

Macro Shot

Super Macro Shot

Standard Macro Shot

Macro with Flash

A slightly large macro area, but great resolution.

In its "Super Macro" mode, the 550 does indeed deliver "super" macro performance, with a tiny minimum area of only 1.04 x 1.38 inches (16 x 35 mm). In normal macro mode, the minimum area is a slightly large 4.61 x 3.46 inches (117 x 88 millimeters). Resolution was very high, with great detail in the dollar bill, coins, and brooch. Details were also quite sharp, though with slight softness in the corners. Exposure was pretty good, though the corners of the frame were slightly dark. The Optio 550's flash had trouble throttling down for the macro area, overexposing the shot, and is completely unusable in Super Macro mode. (Plan on using external illumination for close-in macro shots.)

"Davebox" Test Target

Auto White Balance

Daylight White Balance

Manual White Balance

Very slight color casts with each white balance setting, and significant underexposure at the default setting.

I chose the Manual white balance as the most accurate here, though it had a very slight greenish tint in the large white color block. The Auto and Daylight settings also produced nearly accurate images, with very slight color casts as well. The images were quite dim at the default setting, so I shot the images at right with a +0.7 EV exposure compensation adjustment. (This is very unusual, very few digicams have significant problems with these well-controlled and well-lit studio shots.) Still, the Optio 550 distinguishes the subtle tonal variations of the Q60 target well. The large color blocks are just slightly dark, but saturation is very good, as is hue accuracy. Detail is great in the shadow area of the charcoal briquettes, with very low noise.

Low-Light Tests

Pretty good low-light capabilities, sensitive enough for average city street lighting at night and darker.

The Optio 550 has a maximum exposure time of eight seconds, and a variable ISO setting, which serve the camera well in low-light shooting conditions. In my testing, the 550 produced clear, bright, usable images down to the 1/8 foot-candle (1.3 lux) light level, with good color at the 400 ISO setting. (Though just slightly dim, you could arguably use the image taken at the 1/16 foot-candle, 0.67 lux, light level.) Minimum usable light level closely tracked ISO all the way back to ISO 64, with which images were bright only as low as one foot-candle (11 lux).

The 550's low-light Achilles' heel was autofocus performance though. It could only focus reliably down to just under one foot-candle (11 lux), as it has no AF-assist illuminator. Since average city street lighting at night equates to about one foot-candle, the Optio 550 will work well for city night scenes. It can bring back good-looking pictures from darker environments, but you'll need to plan on focusing manually in those situations.

The Optio 550 does a good job managing image noise too: There's no hot-pixel noise evident anyplace in these shots, and while the noise level is generally higher than average, the grain pattern is very tight and uniform, making the noise that is present less objectionable (IMHO, anyway) than that from cameras with more open, blotchy noise patterns. The table below shows the best exposure I was able to obtain for each of a range of illumination levels. Images in this table (like all sample photos) are untouched, exactly as they came from the camera.

Flash Range Test

A somewhat dim flash, but consistent all the way to 12 feet from the test target.

In my testing, the Optio 550's flash illuminated the test target all the way out to 14 feet, with only a slight decrease in intensity beyond 12 feet or so. Flash illumination was a bit dim from the start, but maintained a consistent level. Below is the flash range series, with distances from eight to 14 feet from the target.

8 ft	9 ft	10 ft	11 ft	12 ft	13 ft	14 ft
1/ 76 secs F4	1/ 87 secs F4.2	1/ 103 secs F4.4	1/ 103 secs F4.4	1/ 125 secs F4.6	1/ 125 secs F4.6	1/ 125 secs F4.6

ISO-12233 (WG-18) Resolution Test

Very high resolution, 1,200 lines of "strong detail." Better than average barrel distortion, but slightly high pincushion.

The Optio 550 performed very well on the "laboratory" resolution test chart. It started showing artifacts in the test patterns at resolutions as low as 1,000 lines per picture height, in both horizontal and vertical directions. I found "strong detail" out to at least 1,200 lines. "Extinction" of the target patterns didn't occur until about 1,450 lines.

Optical distortion on the Optio 550 is about average at the wide-angle end, where I measured an approximate 0.54 percent barrel distortion. The telephoto end fared about the same, as I measured a 0.62 percent pincushion distortion. The barrel distortion figure is a bit lower than the 0.8% average I've found among cameras I've tested (which is too high, IMHO), but the pincushion figure is a fair bit higher than average. On the other hand though, the 550 does have a 5x zoom lens, making for a tougher optical design than a typical 3x lens would. Chromatic aberration is very low, showing only relatively faint color 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.)

Resolution Series, Wide Angle

Wide Angle	"Fine" JPEG	"Normal" JPEG	"Economy" JPEG
2,592 x 1,944	O55RESWGF	O55RESWGN	O55RESWGE
2,048 x 1,536	O55RESWLF	-	-
1,600 x 1,200	O55RESWMF	-	-
1,024 x 768	O55RESWSF	-	-
640 x 480	O55RESWTF	-	-

Resolution Test, Telephoto

2,592 x 1,944 (Fine, Tele)

O55RESTGF