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ISO (Sensitivity) Adjustment

ISO equivalence on a digital camera is the ability to increase the sensitivity of the CCD to allow for faster shutter speeds and/or better performance in low light. The way this works in a digital camera is by "turning up the volume" on the CCD's signal amplifiers, nothing is without its price however and doing so also amplifies any noise that may be present and often affects colour saturation.

The Sony DSC-P71 provides an Auto ISO sensitivity mode which varies sensitivity between ISO 100 and 320 depending on light levels. In addition you can also manually select ISO sensitivity of 100, 200 or 400. The samples below are 100% crops from a ColorChecker chart shot at different sensitivities with both the Sony DSC-P71 and (for reference) Nikon Coolpix 995. As you can see the P71 has comparable noise levels (if visibly slightly different) to the 995 at all sensitivities.

  Sony DSC-P71 Nikon Coolpix 995
ISO 100
ISO 200
ISO 400


White Balance

The DSC-P71 is part of a new line of Sony digital cameras which finally offer us a good range of white balance options. At this level there's no manual preset white balance but we do get the full range of Auto, Daylight, Cloudy, Tungsten and Fluorescent. The results are mixed, under natural light the Daylight / Cloudy options provide a useful way to 'lock' the white balance (although Auto had always been fairly good under natural light). It looks however as though the pre-programmed Incandescent needs a little tuning and that the Fluorescent setting really needs an additional 'Fluorescent High' mode to cope with different coloured tubes.

Outdoors, Auto Outdoors, Cloudy Outdoors, Daylight
 
Incandescent, Auto Incandescent, Incandescent  
 
Fluorescent, Auto Fluorescent, Fluorescent  


Macro Focus

The DSC-P71's macro mode is hardly that, it allows you to get 'a bit closer' than normal but certainly doesn't come close to providing a usable macro capability. The closest focus distance and best frame coverage appeared to be at wide angle which provided a horizontal frame coverage of approximately 98 mm (3.8 in).

Barrel Distortion, 1.2% @ wide angle Pincushion Distortion, 0% @ telephoto


Flash Performance

The DSC-P71's internal flash has a quoted range of 0.5 - 3.8 m (1.6 - 12.5 ft), this we can only assume is at automatic sensitivity as it's a fairly big range for such a small unit. In use the flash appeared to have fairly good power and even illumination. When we tested the pre-production unit it did have a tendancy to produce a random blue cast, I'm glad to report this has been rectified in the final production camera.

Skin tone test - no sign of any colour cast, slightly warm white balance. Slightly under-exposed. Wide angle wall test (from 2 m) - fairly good coverage for this level of camera, note the very slight 'bulb shadow' across the top third of the image. Color patches test - good colour, average metering (a little underexposed). Similar 'warm' white balance seen on the skin tone test.


Barrel and Pincushion Distortion

Unfortunately the DSC-P71 does seem to exhibit clear barrel distortion at wide angle, we measured this as 1.2% (total distortion at the center of the frame as a percentage of the total image height). The news is better at full telephoto with no measurable pincushion distortion.

Barrel Distortion, 1.2% @ wide angle Pincushion Distortion, 0% @ telephoto


Purple Fringing (Chromatic Aberrations)

The DSC-P71 did exhibit some slight purple fringing, although at this level it's not something we would be overly concerned about. Mostly the fringing seems to be amplified by the presence of some blooming.

Hard to find any purple fringing in an "every day" shot
Our now standard chromatic aberration test shot, slight fringing.


Overall Image Quality / Specific Issues

Overall the DSC-P71 produced decent three megapixel images, typical bright Sony colours, fairly good exposure and excellent resolution. Noise was visible in most images, even at ISO 100, which is surprising considering this camera is supposed to feature a new noise reduction algorithm. That said noise was never intrusive and wasn't visible at normal viewing sizes or in print.

Clipped / Over-saturated Reds

The DSC-P71 did occasionally deliver over-saturated reds especially in sunlight, in the sample below much of the red channel in the flower petal is clipped at 255 (full saturation), this does deliver super-vivid colour but it also means that some petal detail has been lost, this can never be retrieved.

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