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Digital Cameras - Pentax Optio S4i Test Images

 

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, ISOsetting, compression setting, etc. Rather than clutter the page below with *all*that detail, we're posting the Thumber index so only those interested inthe information need wade through it!

 

Outdoor Portrait:

Good resolution and detail, but higher than average image noise and some trouble with high contrast. Good color.

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 S4i produced good color, but had a little trouble with exposure.

The shot at right was taken with a +0.7 EV exposure compensation adjustment. The strongest highlight detail is lost, despite the midtones and shadows being somewhat dark. When I shot this, I had the contrast adjustment dialed down one notch, it looks like I should have shot with the contrast set to its minimum value, as even here, the camera has difficulty with the deliberately harsh lighting. I chose the Auto white balance as the most accurate overall, though it produced a similar color balance to the Daylight setting (both are just slightly reddish). The Manual white balance resulted in a much warmer image.

Marti's skin tones here are just about right, with just a slight pinkish tinge to them, but the blue flowers in the bouquet are a bit darker and more purplish than in real life. (Many digicams have trouble with this blue, which is actually a light navy blue with just tinges of purple in it.) The strong reds, yellows, and greens look about right, although saturation is just a hint low. Resolution is high, and detail is strong in the flowers and in Marti's features, but higher than average image noise obscures some detail in the midtones and shadows. The red flowers also have an artifact-like appearance in the highlights.

To view the entire exposure series from 0 to +1.0 EV, see files S4IOUTAP0.HTM through S4IOUTAP3.HTM on the thumbnail index page.

 

Saturation Series:
Unusual to find in a subcompact digicam, the S4i has an optional color saturation adjustment that lets you boost or cut the "brightness" of its color. The range covered is a good one, with nice, small steps permitting pretty fine-grained adjustment of the camera's color response. Really, an "enthusiast" feature, but nice to find in a subcompact digicam.

Saturation Series
Lowest
Low
Normal
High
Highest

Contrast Series:
Likewise very unusual for a subcompact digicam, the S4i also has an optional contrast adjustment. It provides a reasonably good ability to deal with harsh lighting as seen in this test subject, but I'd like to see its range extend further in the low-contrast direction. The contrast adjustment seems to affect the shadows somewhat more than the highlights. It's fairly well balanced, but you'll probably want to drop the overall exposure as you decrease the contrast setting, and vice versa. Overall though, a good implementation of a very useful feature.

Contrast Series
Lowest
Low
Normal
High
Highest



 

Closer Portrait:

Higher resolution with strong detail, still slightly noisy.

Color and exposure are similar to the wider shot above, and the Optio S4i's 3x optical zoom lens helps prevent any geometric distortion of Marti's features. (Close-up portraits are one reason why it's nice to have a zoom lens on your camera.) The shot at right was taken with a +0.3 EV exposure compensation adjustment, yielding a pretty good overall exposure. Midtones are about where they should be, but the highlights are pretty hot and blown out. Detail and resolution are stronger in this close-up shot, with good definition in Marti's hair and skin. Image noise is again a bit higher than average, although I didn't find the noise in this shot as distracting as that in the wider view above. Details also seem a little soft overall.

To view the entire exposure series from 0 to +1.0 EV, see files S4IFACAP0.HTM through S4IFACAP3.HTM on the thumbnail index page.



 

Indoor Portrait, Flash:
Normal Flash
Default Exposure
Normal Flash
+ 1.3 EV

Somewhat underexposed, but good coverage. Warm color balance from the background lighting.

The Optio S4i's built-in flash illuminated the subject fairly well at its default exposure setting, but the image was a little underexposed. Unfortunately, the exposure compensation adjustment doesn't seem to affect flash exposure at all, as witnessed by the +1.3 EV adjustment sample seen at right. Overall color is a little warm, with an orange cast from the fairly strong incandescent lighting in the room. (Fairly typical of a typical home environment where you might want to shoot with the flash for added brightness. While a little dim, fairly minor exposure adjustment in software would fix up the image nicely, albeit at the cost of making the image noise more apparent. To view the entire exposure series from 0 to +1.3 EV, see files S4IINFM1.HTM through S4IINFP4.HTM on the thumbnail index page.



 

Indoor Portrait, No Flash:
Auto White Balance
Incandescent White Balance
Manual White Balance

Very good color with both manual and auto white balance, but slightly low exposure. Noise is high, and obscures detail.

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 Optio S4i's Manual white balance setting did the best job here, despite a very slight greenish cast. The Incandescent setting also produced very good results, but with more of a reddish tint than I'd like. (Although some people will prefer the warmer cast in the Incandescent version, as being more faithful to the original lighting.) The Auto setting had a lot of trouble, and produced a strong warm cast. The shot at right was taken with a +1.0 EV exposure compensation adjustment, which is just slightly bright, with Marti's shot a little too "hot." At +0.7 EV, the white shirt came out better, but I felt that Marti's face was a bit too dark. (Yet another situation where post-capture tweaking might be in line.) Despite the greenish cast with the Manual white balance option, overall color looks pretty good, though the blue flowers are dark and purplish (usually to be expected with this light source). Detail is good, but image noise is a bit higher than average and reduces definition (especially in the flower details, particularly the red flower).

ISO Series:
Noise is moderate even at the S4i's ISO 50 setting, and only increases from there, with a strong grain pattern that interferes with subject detail. At ISO 400, the noise pattern is so strong that a visible pattern of diagonal lines develops. As with most consumer-level digicams these days, I really wouldn't consider the S4i to be usable at ISO 400. (Somewhat more disturbing though, is that the camera will boost the ISO to 400 under even moderate lighting, if you have its ISO option set to the "auto" position. This can leave the user with unexpectedly noisy images, when shooting indoors or under even slightly dim conditions.)

ISO Series
ISO 50
ISO 100
ISO 200
ISO 400



 

House Shot:
Auto White Balance
Daylight White Balance
Manual White Balance

Fairly high resolution and good color. Quite a bit of softness in the corners though.

The Optio S4i's Manual white balance setting produced the best overall color here, with nearly identical results to the Daylight setting. Surprisingly, the Auto setting was actually a bit warm. Resolution is fairly high, with good detail in the tree limbs and front shrubbery. (Not nearly up to the best full-sized four-megapixel cameras, but not bad for a subcompact model.) Image noise here is higher than average, but the biggest problem is the softness in the corners, which extends fairly far into the frame. - This seems to be a particular problem in images shot at fairly close range with the S4i: The effect is present in shots of more distant subjects as well, but not nearly to the same extent.


However, image noise and strong corner softness decrease clarity and definition. Corner softness is strongest on the left side of the frame, and extends almost to the center of the image.

 

Far-Field Test

Fairly high resolution and detail, but image quality doesn't approach that of the best full-sized four-megapixel cameras. Good overall color, but the camera overexposed the scene slightly.

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 S4i captures a lot of fine detail, but clearly not as much as the best full-sized four-megapixel cameras can manage. (It's an unfortunate fact of life that ultra-small digicams almost unavoidably require tradeoffs in image quality relative to full-sized models.) The tree limbs over the roof and fine foliage in front of the house show a fair bit of detail, but there's some loss due to flare and general softness. Once again, there's a fair bit of softness in the corners of the image, extending fairly far into the frame, but it doesn't seem quite as pronounced as with the House poster in the previous test. The S4i overexposed this subject somewhat, which leads to the loss of essentially all detail in the bright white paint of the bay window (a problem area for many cameras), but that does help with detail in the deep shadows around the front door. Overall color looks good, but the saturation is a little low from the overexposure. 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
2,304 x 1,728
S4IFARLF
S4IFARLN
S4IFARLE
1,600 x 1,200
S4IFARMF
-
 -
1,024 x 768
S4IFARSF
-
640 x 480
S4IFARTF
-


ISO Series:
Much the same results as before. Visible noise even at ISO 50, higher than average, but probably acceptable up to ISO 200, unusable (IMHO) images at ISO 400.

ISO Series
ISO 50
ISO 100
ISO 200
ISO 400


Sharpness Series:
A very useful range of sharpness options. The strongest sharpens without going too far overboard, would look good in moderate-sized inkjet prints. The lowest option takes unsharp masking in Photoshop(tm) very well, recovering surprising detail. (Try 300%, 0.4 pixel radius.)

Sharpness Series
Low Sharpness
Soft
Normal
Sharp
Very Sharp


Saturation Series:
As before, a good range of control.

Saturation Series
Lowest
Low
Normal
High
Highest

Contrast Series:
As before, good control, but mainly affects the shadows.

Contrast Series
Lowest
Low
Normal
High
Highest



 

Lens Zoom Range

A typical 3x 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 (3x, in this case), and at full telephoto with the digital zoom enabled. The Optio S4i's lens is equivalent to a 35-105mm zoom on a 35mm camera. That corresponds to an average wide angle to a moderate telephoto, a very typical range for digicams. Following are the results at each zoom setting.

Wide Angle
3x Telephoto
4x Digital Telephoto



 

Musicians Poster
Auto White Balance
Daylight White Balance
Manual White Balance

A slightly reddish color cast, and a dim exposure, but pretty good detail. Image noise is again higher than average.

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 S4i's Auto white balance setting fell victim to this trap, producing a very warm color balance. The Daylight setting produced better results, though with a slight red cast. I chose the Manual setting for the main shot, though it too was just slightly reddish. Still, overall color is good. The blue background is purplish in spots from the red cast, and the deep shadows of the blue robe are also purplish. Skin tones are pretty good, if a bit pale. Resolution is high, with pretty good definition in the embroidery of the blue robe. However, as I've noticed in some of the other shots, higher than average image noise obscures the finer details, making them appear pixilated. The S4i also slightly underexposed this shot, increasing the color saturation a little, and probably contributing at least somewhat to the higher noise levels.



 

Macro Shot
Standard Macro Shot
Super Macro Shot
Macro Shot with Flash

A small macro area with good detail. Flash does well up close.

The Optio S4i captured a small macro area in its normal macro mode, measuring 3.26 x 2.44 inches (83 x 62 millimeters). In Super Macro mode, performance is even better, with a minimum area of only 1.58 x 1.18 inches (40 x 30 millimeters). Resolution is high in both shots, although the color is slightly yellowish. Corner softness is strong in all four corners of the frame (a common failing in digicam ultra-macro modes), but is the most obvious on the left side. The Optio S4i's flash throttled down pretty well for the macro area, the glare from the brooch isn't really the camera's fault, it's just that the brooch is reflecting the flash right back into the lens.



 

"Davebox" Test Target
Auto White Balance
Daylight White Balance
Manual White Balance

Slightly warm color balance, but still very good color overall. Limited shadow detail though.

The Optio S4i's Auto and Daylight white balance settings produced similar, slightly warm results here, while the Manual option produced a nearly perfect color balance. Exposure is good, and the camera distinguishes the subtle tonal variations of the Q60 target pretty well. The large color blocks show excellent hue accuracy, and only very slightly low saturation. That said, the large red and blue blocks are quite vibrant. The shadow area of the charcoal briquettes shows rather limited detail though, and image noise there is fairly high.


ISO, Saturation, and Contrast controls all produced essentially identical results to what we saw above, so I won't bother repeating my earlier comments here. - This target is useful for making very quantitative evaluations of the various controls' action, so I've included a full set of sample images here.

ISO Series:
ISO Series
ISO 50
ISO 100
ISO 200
ISO 400

 


Saturation Series:
Saturation Series
Lowest
Low
Normal
High
Highest

 

Contrast Series:
Contrast Series
Lowest
Low
Normal
High
Highest

 

Color Filter Series:
Color Filter Series
Blue
Red
Green
Yellow
Pink
Black and White
Sepia

 

Effects Series:
Effects Series
Posterization
Slim
Unslim
Soft



 

Low-Light Tests

Limited low-light performance, with higher than average image noise. Autofocus works down to about 0.75 foot-candle. (Should just handle typical city night scenes.)

The Optio S4i produced bright, usable images down to 1/2 foot-candle at ISO 50, and 1/4 foot-candle at ISO 100 and above. Like some other cameras, the S4i's maximum exposure time varies with the ISO setting chosen. At ISO 50 and 100, the maximum exposure time is 4 seconds, but that drops to 2 seconds at ISO 200, and 1 second at ISO 400. Thus, while higher ISO settings will help you maintain higher shutter speeds at any given light level, they don't extend the camera's ultimate low light ability. The color balance is warm from the Auto white balance, and image noise is higher than average at all ISO levels. The S4i's autofocus system works down to light levels of about 0.75 foot-candle, and there's no autofocus-assist light to help at darker light levels. Typical city street lighting at night corresponds to a light level of about one foot-candle, so the S4i should have little trouble shooting under such conditions, but it won't be able to go much darker than that. 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.

(Note: If you'd like to use a light meter to check light levels for subjects you might be interested in shooting, a light level of one foot-candle corresponds to a normal exposure of two seconds at f/2.8 and ISO 100.)

  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
50
Click to see S4ILL0503.JPG
2 sec
f2.6
Click to see S4ILL0504.JPG
4 sec
f2.6
Click to see S4ILL0505.JPG
4 sec
f2.6
Click to see S4ILL0506.JPG
4 sec
f2.6
Click to see S4ILL0507.JPG
4 sec
f2.6
ISO
100
Click to see S4ILL1003.JPG
1 sec
f2.6
Click to see S4ILL1004.JPG
2.5 sec
f2.6
Click to see S4ILL1005.JPG
4 sec
f2.6
Click to see S4ILL1006.JPG
4 sec
f2.6
Click to see S4ILL1007.JPG
4 sec
f2.6
ISO
200
Click to see S4ILL2003.JPG
1/1 sec
f2.6
Click to see S4ILL2004.JPG
1.3 sec
f2.6
Click to see S4ILL2005.JPG
2 sec
f2.6
Click to see S4ILL2006.JPG
2 sec
f2.6
Click to see S4ILL2007.JPG
2 sec
f2.6
ISO
400
Click to see S4ILL4003.JPG
1/3 sec
f2.6
Click to see S4ILL4004.JPG
1/1 sec
f2.6
Click to see S4ILL4005.JPG
1 sec
f2.6
Click to see S4ILL4006.JPG
1 sec
f2.6
Click to see S4ILL4007.JPG
1 sec
f2.6



 

Flash Range Test

A weak flash, underexposing even at the shortest range.

Limited flash range is a very common shortcoming of subcompact digicams, and the S4i is no exception. In my testing, the Optio S4i's flash was quite dim even at the shortest distances I test at (8 feet). The flash will probably be adequate for supplemental illumination in night shots at very close range, but it clearly wouldn't be your first choice if nighttime photography is at all important to you. 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
Click to see S4IFL08.JPG
1/60 sec
f4.8
ISO 50
Click to see S4IFL09.JPG
1/60 sec
f4.8
ISO 50
Click to see S4IFL10.JPG
1/60 sec
f4.8
ISO 50
Click to see S4IFL11.JPG
1/60 sec
f4.8
ISO 50
Click to see S4IFL12.JPG
1/60 sec
f4.8
ISO 50
Click to see S4IFL13.JPG
1/60 sec
f4.8
ISO 50
Click to see S4IFL14.JPG
1/60 sec
f4.8
ISO 50



 

ISO-12233 (WG-18) Resolution Test

High resolution, 1,200 lines of "strong detail." High barrel distortion and corner softness.

The Optio S4i performed fairly well on the "laboratory" resolution test chart. It started showing artifacts in the test patterns at resolutions as low as 800 lines per picture height vertically, but as low as about 600 lines horizontally. I found "strong detail" out to at least 1,200 lines horizontally, and to around 1,100 lines in the vertical direction. "Extinction" of the target patterns occurred around 1,500 lines.

Optical distortion on the Optio S4i is very high at the wide-angle end, where I measured approximately 1.1 percent barrel distortion. The telephoto end fared much better, as I found only 0.1 percent barrel distortion there (about three pixels). Chromatic aberration is moderate, showing about seven or eight pixels of relatively 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 biggest optical shortcoming of the S4i's lens though, is the fairly severe softness in the corners of its images, extending quite far into the frame.

Resolution Series, ~50mm equivalent focal length
Wide Angle "Fine"
JPEG
"Normal"
JPEG
"Economy"
JPEG
2,304 x 1,728
S4IRES2304F
S4IRES2304N
S4IRES2304E
1,600 x 1,200
S4IRES1600F
-
-
1,024 x 768
S4IRES1024F
-
-
640 x 480
S4IRES0640F
-
-

 

Resolution Test, Wide Angle
2,304 x 1,728
(Fine, Wide)
S4IRES_W



Resolution Test, Telephoto
2,304 x 1,728
(Fine, Tele)
S4IRES_T



Sharpness Series
Sharpness Series
Low Sharpness
Soft
Normal
Sharp
Very Sharp



 

Viewfinder Accuracy/Flash Uniformity

A very tight optical viewfinder, but an accurate LCD monitor.

The Optio S4i's optical viewfinder is very tight, showing only about 72 percent frame accuracy at wide angle, and about 77 percent at telephoto. Images framed with the optical viewfinder are also tilted slightly, likely due to a shifted CCD chip. The LCD monitor performed much better, showing approximately 99 percent frame accuracy at both zoom settings. Given that I like LCD monitors to be as close to 100 percent accuracy as possible, the Optio S4i's LCD monitor is essentially perfect in that regard. Flash distribution is uneven at wide angle, with significant falloff at the corners and edges of the frame. At telephoto, flash distribution is more even, but very dim.




S4i Review
S4i Test Images
S4i Specifications
S4i "Picky Details"
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