Pentax Optio A20 Review
As well as the default auto setting, the A20 has four white balance presets (daylight, shade, tungsten, and fluorescent) and a manual/custom setting that can be used with a white or gray card to accurately measure the color of light in a scene. Our standard studio tests showed the A20 to be fairly reliable, and real-world shots rarely suffer from white balance problems though inevitably in low incandescent lighting there is a distinct orange cast).
|Auto White Balance||Fluo Preset||Auto White Balance||Incandescent preset|
|Fluorescent light - Auto white balance average, preset white balance excellent||Incandescent light - Auto white balance average, Preset white balance good|
The A20 has two macro modes; standard macro (closest focus 12cm / 4.7-inches), usable only in the wide to mid-zoom range (up to about 55mm equiv.), and super macro (closest focus around 6cm). The Super Macro mode fixes the focal length at the wide end, but does allow some pretty impressive close ups for such a small camera.
- Click here for wide macro test chart (captured area 163 x 122mm)
- Click here for Super macro test chart (captured area 60 x 45mm)
- Click here for tele macro test chart (55mm equiv.) (captured area 75 x 56mm)
The Optio A10 was one of the top 8MP cameras in pure resolution terms, and the A20 is even better, though the difference isn't huge. The results are pretty clean too, and overall this is impressive stuff from such a compact camera.
WIDE LENS Crops
|Click here for the full resolution test chart||
resolution 1800 LPH
resolution 1850 LPH
Distortion and other image quality issues
The A20 exhibits higher than average distortion at the wide end of the zoom - 1.7% barrel distortion (click here for test chart) and there is some pincushion distortion (0.4%) at the telephoto end (click here for test chart). Nothing to worry about for normal 'everyday' photography but worth knowing about if these things are important to you.
Overall the results from the A20 - when it gets everything right - will give little cause for complaint; they have good color, a decent level of detail and exposure / focus are pretty reliable. Compared to the A10 we had fewer problems with camera shake (so the SR has been improved), fewer metering issues and fewer focus problems (though it still focuses too slowly), but the pixel-level output doesn't look quite as clean. Like the A10 the results have a nice natural feel to them, without the over-saturation and over-sharpening we so often see with these little cameras.
On the downside the extra megapixels are obviously stretching the lens to its limit and looking too closely at the output reveals slight corner softness and a lack of biting sharpness across the frame (this is not a problem at normal print sizes of course). At a pixel level noise is also visible in shadows and blue skies even at ISO 64, though again it's not something that will bother you unless you want to produce a poster print or have an eight foot high screen to show them on - or are shooting in very low light (when long exposures produce a lot of noise at all settings). Less easy to sweep under the carpet is the highlight clipping; a common problem with this type of camera but slightly disappointing here because it is worse than the A10. As with the A10 you also have to watch the exposure if you're shooting in very bright, contrasty conditions, when the metering can be fooled into under or over exposing a little too easily for our liking.
The Optio A10 was the first Pentax compact to offer mechanical image stabilization (Shake Reduction) using a CCD-shift system, and of course the A20 has the same system. By placing the CCD sensor on a movable platform the system can compensate for a certain amount of the blur caused by camera shake at lower shutter speeds and longer focal lengths. The system works by analyzing input from two internal gyro sensors and producing an inverse movement in the CCD.
In use we found the system to be effective, though by no means foolproof, and certainly not as consistently capable of reducing the effect of camera shake as other systems we've tested, particularly those that use moving lens elements rather than a moving CCD. There is no doubt that the system reduces blur, but it just doesn't inspire total confidence, especially at longer focal lengths. It also seems much more effective when the shake is in a single direction (up and down or left to right) than when it is more random.
There is no doubt that SR works, and it significantly decreases the proportion of shots ruined by camera shake, but having looked at the results when I got back after a day's shooting I wouldn't say I would trust it unquestioningly. The SR is only activated when you actually press the release; you can preview it by pushing a button, but it's kind of pointless. It's also worth noting that we had far fewer examples of the dramatic failure of the SR system seen with the A10 (where high shutter speeds resulted in blurred images), though there where still a couple.
Below are a couple of comparative 'real world' examples. Note also that all the images in the samples gallery are hand held.
|113mm equiv, 1.10th sec. Hand-held|
|Shake Reduction on||Shake Reduction off|
|113mm equiv, 1.80th sec. Hand-held with intentional shake|
|Shake Reduction on||Shake Reduction off|
With tiny, high pixel count chips noise is always going to be an issue, and to a large degree this is more a test of the effectiveness (both measurable and visible) of a camera's noise reduction system. Designers have to balance the desire to produce smooth, clean results with the need to retain as much detail as possible (if you blur away the noise, you blur away image detail too)
At ISO 64 there is some visible noise, but it's fairly low unless you're shooting in very low light, and the noise reduction very subtle, meaning lots of detail. As you move up the ISO scale the noise increase is almost linear, meaning that Pentax is avoiding the temptation to damp up the noise reduction at higher sensitivities. It is obvious is that - compared to many of its competitors - the A20 does a good job of balancing the need to reduce visible noise with the need to retain sharp detail, so that even at ISO 400 the results look pretty detailed, if noisy (note that in much lower light the visibility of noise is much higher). We praised the A10 for it's 'hands off' handling of noise, and the A20 offers more of the same.
|ISO 64||ISO 100||ISO 200||ISO 400||ISO 800|
Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity is on the vertical axis.
Noise is higher than the A10 - and at ISO 200 and up it's higher than most cameras in this class. Of course the flip side of this is that what we're looking at is noise reduction more than noise, and the A20 uses a very light touch, which means even at higher ISO settings there's plenty of detail. It's easy to apply heavy noise reduction in post processing, but impossible to bring back detail smeared in-camera.
Low contrast detail
What the crops and graph don't show is the effect of noise reduction on low contrast fine detail such as hair, fur or foliage. An inevitable side effect of noise removal is that this kind of detail is also blurred or smeared, resulting in a loss of 'texture'. In this test the crops below show the effect of the noise reduction on such texture (hair) as you move up the ISO range.
|ISO 64||ISO 100||ISO 200|
|ISO 400||ISO 800|
The A20 might not use noise reduction as heavy as some of its competitors, but it still uses noise reduction and the loss of fine texture is obvious at a pixel level. As the crops show, low contrast detail is perfectly good at ISO 64 - 200. Once you get to ISO 400 the noise - and noise reduction - has a visible blurring effect on all the low contrast detail, though it's still better than a lot of cameras we see.
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