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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 DX4900 provides the sensitivities of ISO 100, 200 and 400. It also includes an Auto sensitivity which automatically varies sensitivity between ISO 100 and 400 depending on light levels.

Our noise testing method involves shooting a colour patch chart (a GretagMacBeth ColorChecker) at the full range of ISO sensitivities.

Each of the comparison samples below are made up of 150 x 80 crops of patches 19, 22 and 24 of the ColorChecker chart (as indicated right). This helps to give a better impression of noise at different light levels within an image. Both cameras were set to automatic white balance, default internal processing parameters.

Noise levels: Kodak DX4900 vs. Minolta DiMAGE F100

  Kodak DX4900 Minolta DiMAGE F100
ISO 100
ISO 200
ISO 400
  Kodak DX4900 Minolta DiMAGE F100

Overall noise levels are pretty similar. The primary difference is in the appearance of the noise. The DX4900 seems to be using a noise reduction algorithm (as mentioned on the previous page). This algorithm acts primarily on 'flat areas' (such as the grey patches above) and reduces the noise to a mottled 'water-colour paint' effect.

White Balance

The DX4900 has a limited selection of white balance options. Apart from Auto mode there are only three other settings of Daylight, Tungsten and Fluorescent. I really would have liked to have seen Cloudy / Shade and Manual Preset white balance options. As you can see from the samples below the DX4900's auto white balance does well under natural (daylight) as well as incandescent bulbs. The fluorescent auto white balance shot has a yellow cast but is still relatively good.

Outdoors, Auto Outdoors, Daylight
Incandescent, Auto Incandescent, Tungsten
Fluorescent, Auto Fluorescent, Fluorescent

Macro Focus

The DX4900's optimum zoom position when using macro mode was full wide angle. Typically wide angle macro's lead to barrel distortion, but luckily Kodak have that under control. However, one thing which can't be avoided when shooting so close at wide angle are soft edges which can be seen if you take a closer look at the ruler shot below. Best horizontal frame coverage was 84 mm (3.3 in).

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