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ISO Sensitivities & Noise

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 Coolpix 5000 features four selectable ISO sensitivities of 100, 200, 400 and 800 as well as Auto mode which varies the sensitivity depending on available light. Note that although available ISO 800 is not recommended and shows up in red colour on the LCD monitor when selected.

I decided to use the same system created for our EOS-1D preview. This involves shooting our standard colour patches in average light (9 EV) at the full range of ISO sensitivities. I have chosen to compare the ISO noise levels of the Coolpix 5000 to two other five megapixel digital cameras, the Olympus E-20 and Sony DSC-F707.

Each of the "Patch crops" below are made up of a 100 x 80 section of patches 1, 7 (M) and 17 of the greyscale of our colour patches (as shown above). This helps to give a better impression of noise at different light levels within an image. Directly below this you will find the average standard deviation of these three patches, this is a quantifiable measurement of noise.

 Camera Nikon CP-5000 Olympus E-20 Sony DSC-F707
 Sensitivity ISO 100 ISO 80 ISO 100
 Exposure 1/24 s, F4.4 1/8 s, F4.5 1/10 s, F4.5
 Patch crops
 Std dev. 1.83 1.82 1.43
       
 Camera Nikon CP-5000 Olympus E-20 Sony DSC-F707
 Sensitivity ISO 200 ISO 160 ISO 200
 Exposure 1/49 s, F4.4 1/15 s, F4.5 1/20 s, F4.5
 Patch crops
 Std dev. 3.21 2.08 2.18
       
 Camera Nikon CP-5000 Olympus E-20 Sony DSC-F707
 Sensitivity ISO 400 ISO 320 ISO 400
 Exposure 1/85 s, F4.4 1/30 s, F4.5 1/30 s, F4.5
 Patch crops
 Std dev. 5.02 2.51 2.30
       
 Camera Nikon CP-5000 Olympus E-20 Sony DSC-F707
 Sensitivity ISO 800 n/a n/a
 Exposure 1/172 s, F4.4 n/a n/a
 Patch crops
 Std dev. 9.11 n/a n/a

As you can see by the visual and measured (standard deviation) comparison above (and graph below) the Coolpix 5000 has very similar noise levels to the other five megapixel digital cameras at ISO 100 but quickly departs from the competition with significantly more noise from ISO 200 upwards. This is a disappointing performance from Nikon's latest "top model".

Note: the higher shutter speeds on the Coolpix 5000 shots can be attributed the fact that they were shot later in the day when more light was available (shot in natural light).

A graph of the average standard deviation versus ISO sensitivity is shown below.


White Balance

As with most digital cameras the Coolpix 5000's automatic white balance works best under natural light. That said it did put in a better performance under artificial light than the Coolpix 995 (which had a strong pink cast under incandescent light and a yellow cast under fluorescent). The pre-programmed white balance settings are fairly accurate and of course the advantage with the 5000 is that you can always fine tune these to exactly match your lighting. As we would expect the manual white balance worked best.

Outdoors, Auto Outdoors, Cloudy Outdoors, Manual
Incandescent, Auto
Incandescent, Incandescent
Incandescent, Manual
Fluorescent, Auto Fluorescent, Fluorescent Fluorescent, Manual
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