Digital Cameras - Pentax Optio S4 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 S4 had a little trouble with the high contrast lighting.
The shot at right was taken with a +0.7 EV exposure compensation adjustment, which is about average for this shot. The S4's high native contrast leaves the midtones and shadows rather dark though, despite the highlights being blown out. Despite a cool, bluish cast, I chose the Auto white balance as the most accurate overall, since it produced nearly identical results to those of the Daylight setting, and the Manual setting resulted in a warm cast, with a strong yellow tint.
The cool color cast gives Marti's skin tones a bit of a magenta tint, but the blue flowers in the bouquet came out very good. (This blue seems to be a very difficult color for many digicams to get right.) Color is good throughout the rest of the frame (although consistently a bit on the cool side), and saturation is pretty good as well. Resolution is high, and a lot of fine detail is visible in Marti's face as well as in the flower bouquet. Shadow detail is a little limited, and noise there is on the high side.
To view the entire exposure series from zero to +1.0 EV, see files S4OUTAP0.HTM
through S4OUTAP3.HTM on the thumbnail index page.
Increased resolution and detail, but high contrast compromises highlight and shadow detail.
Color balance and exposure are similar to the wider shot above, and contrast is again high. The shot at right was taken with a +0.3 EV exposure compensation adjustment, and again, detail in the strong highlights is almost completely lost, while shadows are pretty plugged. The Optio S4's 3x zoom lens helps prevent distortion of Marti's features, and picks up sharp details in her face and hair. Resolution is much higher in this shot, with great definition in the sunlit strands of Marti's hair. However, shadow detail is again limited, with moderate amounts of noise.
To view the entire exposure series from zero to +1.0 EV, see files S4FACP0.HTM
through S4FACP3.HTM on the thumbnail index page.
Indoor Portrait, Flash:
Underexposed, but even coverage from the built-in flash.
The Optio S4's built-in flash underexposed this shot pretty badly (most
likely a reaction to the high-key background and Marti's white shirt),
but lit the subject evenly. The background incandescent lighting results
in a strong orange cast, that permeates the entire frame. - If there's
one adjustment I really missed on the S4, it'd have to be exposure compensation
for the flash. The normal exposure compensation tweak doesn't affect flash
exposures at all, so you're left with whatever the auto exposure delivers,
which can be pretty far off if the subject is brighter or darker overall
than the standard 18% gray photo exposure systems are based on.
Indoor Portrait, No Flash:
Nearly accurate color with the Manual white balance setting, and good exposure as well.
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 S4's Manual
white balance did very well here, leaving only a slight greenish cast.
The Auto setting really had trouble, producing
a strong orange cast, while the Incandescent
setting resulted in a moderate warm cast that some users may actually
prefer to the more neutral result obtained with the Manual setting. I
found the best exposure with a +1.3 EV exposure compensation adjustment,
which is a little higher than average. (Here's a shot at the default
exposure.) Skin tones look pretty good, while the blue flowers are dark
and purplish (a typical problem with this shot).
Good resolution and color, but significant softness in the corners obscures details.
The Optio S4's Auto and Daylight
white balance settings produced very similar results here. I thus chose
the Auto setting for the main shot. (The Manual
setting resulted in a cool, magenta cast.) Resolution is high, but pronounced
softness in the corners obscures the detail in the tree limbs above the
house. The clearest detail is in the house front, and in the shrubbery
in the lower left of the frame. In the other three corners, softness extends
almost to the center.
High resolution, but softness in the corners and across the whole bottom of the frame again obscures details. The default settings resulted in a slight overexposure too, which limits the camera's dynamic range.
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 S4 captures a lot of detail indeed, but there's an obvious optical defect at work here, which obscures detail all along the bottom of the frame. (This is severe enough that I'm going to ask Pentax for another sample unit, try to re-test it if I can find the time amidst the flood of new camera models I'm currently experiencing.) The tree limbs directly above the roof show a lot of fine detail, but the shrubbery in front of the house is blurry from the softness that extends all along the bottom of the frame. (The top right corner looks pretty good though, with good definition in the leaf patterns, so it's not a matter of the usual softness in the corners of the frame that I'm accustomed to seeing with many digicams.) The house details are also clear. The very bright exposure and high contrast cause the camera to lose all of the detail in the bright white paint surrounding the bay window, which is a trouble spot for many digicams. Detail is moderate in the shadow area above the front door. Overall color is good, though slightly cool. The table below shows a standard resolution and quality series, followed by ISO, sharpness, contrast, saturation, and color series.
Color Filter 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 S4's lens is equivalent to a 35-105mm zoom on a 35mm camera. That corresponds to a range from a moderate wide angle to a pretty good telephoto. Following are the results at each zoom setting.
Color casts with each white balance setting tested, but good detail. Exposure is slightly dark.
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. Indeed, I found it difficult to choose the best
white balance setting here, as each of the three tested produced color
casts. The Auto setting fell prey to the too-much-blue
problem, producing a strong warm cast, while the Daylight
setting was slightly pinkish. The Manual setting
had a green tint. Despite the pink cast, I settled on the Daylight setting
for the main image. The reddish color cast affects the models' skin tones,
and produces purplish tints in the blue background and in the shadow areas
of the blue robe. Resolution is high, and the embroidery of the blue robe
shows a lot of detail. There's some softness in the corners here, but
nothing like what I saw in the Far-Field test above. The image is also
a bit underexposed, albeit not severely.
Excellent performance with the Super Macro mode, standard macro is about average. Flash has trouble up close.
The Optio S4 performed about average in its normal
macro mode, capturing a minimum area of 4.44 x 3.33 inches (113 x
85 millimeters). However, the Super Macro setting
produced very good results, with a minimum area of just 1.73 x 1.30 inches
(44 x 33 millimeters). Resolution is high in both shots, with good detail
in the dollar bill, coins, and brooch. There's a fair bit of corner softness
again, most noticeable along the left side of the frame, but at least
in the case of super-macro shots, this isn't as unusual an occurrence
among digicams I've tested. The camera's flash
had trouble throttling down for the macro area, and greatly overexposed
the shot, so plan on using external lighting with the Optio S4 for macro
"Davebox" Test Target
A slight underexposure darkens the large color blocks, but overall results are very good.
The Optio S4's Auto and Daylight
white balance settings produced similar, slightly warm images here, while
the Manual setting was a hint cool. Despite
the slight cool cast, I preferred the Manual setting overall. The S4's
default exposure underexposed the shot slightly, which helped it distinguish
the subtle tonal variations of the Q60 target. Colors are dark in the
large color blocks, but pretty hue-accurate. Saturation is about right,
but the large red and blue blocks are slightly oversaturated. The shadow
area of the charcoal briquettes shows only modest detail, albeit with
Pretty good low-light performance for a point-and-shoot digicam, with bright exposures at light levels just under below that of typical city street lighting at night.
The Optio S4 operates in Program AE mode at all times, meaning that the
camera is in charge of shutter speed and aperture. With a maximum exposure
time of four seconds, the S4 is slightly limited when shooting at night.
Still, the camera fared pretty well on my low-light test, capturing bright
images down to the 1/4 foot-candle (2.7 lux) light level with good color
at the 100 and 200 ISO settings. At ISO 50, images were bright only as
low as 1/2 foot-candle (5.5 lux). At the darker light levels, the target
was still visible, but the underexposure resulted in a strong magenta/purplish
color cast. Since average city street lighting at night corresponds to
about one foot-candle (11 lux), the camera should be able to handle slightly
darker situations quite well. Noise is low at the 50 and 100 ISO settings,
but becomes moderately high at ISO 200. 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
Good intensity until about 10 feet, then slight falloff thereafter.
In my testing, the Optio S4's flash illuminated the test target all the way out to 14 feet, but with a progressive decrease in intensity from 11 feet on. (Also interesting to note is that the camera seems to set its default ISO to 100 when the flash is in use, trading off a little image noise in favor of greater flash range.) Below is the flash range series, with distances from eight to 14 feet from the target.
Good resolution, 1,150 - 1,200 lines of "strong detail." High barrel distortion at wide angle.
The Optio S4 performed fairly well on the "laboratory" resolution test chart. It started showing artifacts in the test patterns at resolutions as low as 600 lines per picture height horizontally, and about 700 lines vertically. I found "strong detail" out to 1,200 lines in the horizontal axis and 1,150 lines vertically. "Extinction" of the target patterns didn't occur until about 1,400 lines.
Optical distortion on the Optio S4 is quite high at the wide-angle end, where I measured approximately 1.0 percent barrel distortion. The telephoto end fared much better, as I found only 0.1 percent barrel distortion there. Chromatic aberration is pretty low, showing only faint color around the edges of the target lines in the corners. (This distortion appears as faint colored fringes around the res target elements in the corners of the frame.) The most pronounced distortion I found was fairly severe "coma," causing blurring in the corners that extended nearly to the center of the frame on a number of my tests.
Resolution Series, Wide Angle
Resolution Test, Telephoto
Viewfinder Accuracy/Flash Uniformity
A very tight optical viewfinder, though the LCD monitor is pretty accurate.
The Optio S4's optical viewfinder is very tight,
showing only about 71 percent of the final frame at wide angle, and
about 78 percent at telephoto. (This is quite a bit worse than average,
and one of the S4's worst liabilities, IMHO.) Images framed with the
optical viewfinder are also shifted toward the left side of the frame,
resulting in extra space on the right side. The LCD monitor proved to
be much more accurate, but still slightly tight at wide angle, showing
approximately 95 percent frame accuracy. At telephoto however, the LCD
monitor was more accurate, showing about 99 percent of the final frame.
Given that I like LCD monitors to be as close to 100 percent accuracy
as possible, the Optio S4's LCD monitor did pretty well, but the optical
viewfinder should really be more accurate.
Flash distribution is uneven at wide angle, with a bright center and
falloff at the corners and edges of the frame. At telephoto, flash distribution
is more uniform.
S4 Test Images
S4 "Picky Details"
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