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!|
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.
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:
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:
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).
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
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.
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.
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.
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
"Davebox" Test Target
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.
Color Filter Series:
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.)
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.
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
Resolution Test, Wide Angle
Resolution Test, Telephoto
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 Test Images
S4i "Picky Details"
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