Digital Cameras - Pentax Optio WP Test Images
The table below shows selected representative images from our test shot series. You can see the full set of shots, including exposure information extracted from the EXIF file headers, on the Thumbnail index page. |
"Sunlit" Portrait: To view the entire exposure series from zero to +1.3 EV, see files OWPOUTMP0.HTM through OWPOUTMP4.HTM on the thumbnail index page. The lighting in this shot is deliberately awful, about what you'd expect from noontime sunshine here in the Atlanta, GA area. (In fact, the color balance has been chosen to pretty well match the hazy sunshine here in mid-August.) The reason for the harsh lighting is to provide a real "torture test" of how cameras handle conditions of extreme contrast; and in particular, how well they do holding onto highlight detail. Look for:
Contrast Series:
Saturation Series:
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Closer Portrait: To view the entire exposure series from zero to +1.0 EV, see files OWPFACAP0.HTM through OWPFACAP3.HTM on the thumbnail index page. The original intent of this shot was to illustrate why you really want a zoom lens if you intend to take close-up shots of people. Fixed focal length lenses tend toward the wide angle end of the spectrum, meaning that you have to get very close to your subjects to fill the frame with them. This results in very unnatural, chipmunk-like face shot, with exaggerated noses and rounded cheeks. These days, most digital cameras come equipped with zoom lenses, so you won't have to worry about the "Chipmunk look" in your portrait shots. (Just zoom the lens out to its telephoto position when you're taking close-in shots like this.) |
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Indoor Portrait, Flash:
This shot duplicates indoor shooting conditions in most US homes, with fairly bright incandescent room lighting. The challenge here is for the camera's flash to blend naturally with the room lighting, and produce good, neutral color overall. - Some cameras will be overly affected by the room lighting, even with their flash enabled, and the result will be a strong orange cast. Another common failing is for the highlights from the flash to take on an unnatural bluish cast. Finally, exposure is important here, and frequently a tough challenge for the cameras. Marti's white shirt is central in the scene, reflecting a lot of the light from the flash right back at the camera. As a result, most cameras underexpose this shot, and require some positive exposure compensation to produce a good result. - And that's an important consideration in itself: Does the camera even permit adjustment of its flash exposures? Many do not. These photos are a tough exposure challenge, if they come out OK, the camera in question can probably be coaxed into delivering a good flash exposure of any subject within its range. Note too, that the normal flash shot (as opposed to the slow sync one, if the camera offers that feature) will be sharply rendered, any subject or camera movement frozen by the quick pop of the flash. That makes this shot a good one to look for the effect of over-aggressive noise suppression in Marti's hair. |
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Indoor Portrait, No Flash:
The incandescent lighting used in most US homes actually has a very strong yellow color to it. Our eyes have an amazing ability to ignore color casts like this, something digital cameras struggle to emulate. The incandescent lighting used for this shot is thus not only very common here in the US, but also very difficult for most digital cameras to deal with. While we probably want a little yellow color to remain in the image (to convey some of the mood of the original scene), too much will look unnatural and distort colors. Most cameras' auto white balance systems have a great deal of difficulty with this shot, but many incandescent white balance settings struggle as well. (It seems that many cameras' incandescent settings are actually calibrated to the tungsten lighting used in professional studio systems, which isn't nearly as warm-toned as typical household lighting.) If you intend to do much shooting indoors after dark, pay careful attention to this test, as cameras vary widely in this regard. ISO Series: One additional note about this particular test series though: Because they're shot under household incandescent lighting, the camera has to boost its blue-channel signal quite a bit to get back to a neutral color balance. Since the blue channel is generally the one with the most noise, this makes this shot a real acid test of noise performance. Noise levels in high-ISO shots taken under daylight conditions usually won't show as much noise. (See the "Far Field" test for examples of high ISO shots captured in daylight.)
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House Shot:
Like several of our tests, these images are actually photos of a high-resolution poster, shot under studio lighting. As of this writing, the poster in question was produced from a high-resolution scan of a 4x5-inch transparency, scanned to a resolution of about 150 megapixels. Even at that, it's starting to show its age, as the combination of camera lens, film emulsion and scanner resolution mean that many of the current 5+ megapixel cameras come close to capturing all the detail that's present. (We have a new poster under production, produced from 45 separate digital images, "stitched" into a single 400+ megapixel image, that should comfortably outpace the resolution of portable digital cameras for years to come. - Expect to start seeing shots of this new poster sometime in Fall, 2005.) Why did we choose to shoot a picture of a picture? The idea was to show a typical subject (a house and surrounding foliage) in a way that would be absolutely consistent from camera to camera. Any outdoor subject is going to vary considerably from day to day, as the lighting changes with the weather, atmospheric conditions, and season. Shooting a poster lets us compare images from cameras shot weeks, months, or even years apart, with the sure knowledge that nothing has changed from one shot to another. Things to look for here are fine detail, as seen in the foliage and tree limbs against the sky, sharpness in the corners, and the preservation of subtle detail in the shaded brick patterns. - Many cameras with overactive noise suppression severely blur the brick patterns that are in shadow. |
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Far-Field Test While the House poster in the shot above provides absolute repeatability from test to test, it doesn't offer the range of brightness (dynamic range) that the original scene had, nor does it contain the nearly infinite range of fine detail found in nature. For these reasons, we still shoot the original house, even though the vagaries of nature mean that no two shots will ever be directly comparable. (In fact, over the eight or so years since we first shot this subject, the trees in front of the house have now grown so large that they obscure much of the subject. - We're unfortunately going to have to switch to a different subject in the near future.) Things to look for here are how well the camera handles the range of light levels from very bright to quite dark, and how well it renders the very fine detail visible in various parts of the image. Note though, that because this is shot outdoors, the character of the light is unavoidably going to change quite a bit, depending on the atmospheric humidity and the time of year. - You thus shouldn't rely on it for absolute comparisons between cameras, since it's unlikely that conditions will be identical from one test to the next. For this subject, we shoot examples of pretty much anything the camera is capable of, with a resolution series to show how well the camera "downsamples" its images to make lower-resolution copies, an ISO series, color effects, contrast and saturation adjustments if they're available, etc. Resolution Series:
ISO Series:
Sharpness Series:
Contrast Series:
Saturation Series:
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Lens Zoom Range Simply reading "4x zoom range" doesn't do a lot to help you visualize what that means. It also says nothing regarding just how wide the wide-angle end of that range is. To give you an idea of exactly what each camera's zoom lens does, we shoot this series of images, showing results at maximum wide angle, maximum telephoto, and telephoto with "digital zoom" enabled. (Note of course though, that so-called "digital zoom" just crops out and enlarges the central pixels of the image, achieving increased size at the cost of reduced resolution.)
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Musicians Poster
This is another poster, shot in the studio under controlled lighting. It's intended to give an idea of how well various cameras render a range of skin tones, but it often winds up as more of a referendum on the camera's white balance system. The background of the image has a lot of blue in it, which frequently tricks white balance systems into overcompensating toward warmer hues. The poster is also rather low resolution, having been made from a 20 megabyte digital file. As such, it can't be relied upon to reveal much about detail rendition of modern, high-megapixel cameras. |
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Macro Shot
Many are interested in close-up or "macro" photography. This test shows the best results we could obtain using each camera's macro mode. What to look for:
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"Davebox" Test Target
This subject is a good all-around laboratory test target, useful for the more analytically-minded in making objective comparisons between cameras. Things to look for:
ISO Series:
Contrast Series:
Saturation Series:
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Low-Light Tests Low light photography is an area where there are really enormous differences between digital camera models. This test starts at a light level about equivalent to typical city street lighting at night (one foot-candle), and then progresses down from there, each successive test being at half the light level of the preceding one. You may also see the effect of poor low-light autofocus in some of these shots, although we use a different test setup to check autofocus performance more directly. (The results of which are reported on in the main Test Results section.) Things to look for here include:
(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.) |
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Flash Range Test Digital camera makers have gotten better with their flash-range ratings. In the early days, many cameras had rather "optimistic" flash range specs, to put it politely. These days, the manufacturers seem to be toeing the line. (No doubt at least in part because of tests like this.) Consistent with our philosophy of testing worst-case conditions, this test also involves some use of each camera's zoom lens. Flash range is greater at wide angle focal lengths than at telephoto ones. If you're shooting at the wide angle end of the lens' range, you might get better flash range than what's shown here. - But you'll never get a nasty surprise if you let the test shots below be your guide to flash capability.
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ISO-12233 (WG-18) Resolution Test This is the standard ISO-12233 resolution target. It can be used with automated image-analysis tools like Imatest, but for our reviews, we generally just report the number of lines of resolution that we can see cleanly resolved in it. The chart numbers correspond to hundreds of lines of resolution per picture height. - The reference to picture height is to provide a consistent measure of resolution, regardless of image aspect ratio. (Height to width ratio.) In evaluating lines of resolution, it's important to set as a threshold the point at which artifacts (jaggies or blurring of the lines) start to overcome the target details themselves. We tend to be a bit more conservative than some reviewers in the number of lines we'll say a camera has: The point here isn't to try to figure out the point at which you can just barely convince yourself that you're still seeing the target lines, but rather to call a halt when the camera is no longer cleanly resolving the target detail. We also report the point at which the target lines entirely merge into oblivion, as the "extinction point." This last point doesn't relate to image resolution in any sense, but does correlate somewhat with perceived edge sharpness. Things to look for on this target include:
Resolution Series, medium focal length
Sharpness Series:
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Viewfinder Accuracy/Flash Uniformity Viewfinder accuracy is an important parameter, especially for shots where framing is critical. The optical viewfinders on most digital cameras match the (poor) accuracy of those on film cameras, typically showing only about 85% of the actual final frame area. It's likely that this is a deliberate design choice by the camera engineers, to help avoid users accidentally cutting off the heads of their subjects. We disagree with this approach, or at least feel that it should be mitigated a bit, perhaps by increasing the accuracy to 90 to 95%. Unlike the optical viewfinders, the LCD viewfinders on most digital cameras tend to be quite accurate. There are exceptions though, and it's unfortunately not uncommon to find an LCD monitor that only shows 90% or less of the final frame. Things to look for on this test chart are:
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