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ISO Sensitivity / Noise levels


Standard Test

ISO equivalence on a digital camera is the ability to increase the sensitivity of the sensor to enable faster shutter speeds and/or better performance in low light. The way this works in a digital camera is by "turning up the volume" (gain) on the CCD's signal amplifiers. Nothing is without its price however and doing so also typically increases visible noise (random speckles visible all over the image).

We are now using a more reliable, repeatable and neutral method for evaluating noise. Shots are taken in daylight lighting in our studio. Noise is measured as the standard deviation of the medium gray patch on a Gretag MacBeth ColorChecker chart. The image is normalized before measurement of noise to remove the possibility of figures being affected by image contrast (one method of masking noise). Note that noise numbers shown on the graphs below can not be compared to those in older reviews.

Test notes:

  • Shots taken at approximately 21°C (~70°F)
  • Lighting was simulated daylight
  • Manual white balance
  • Aperture Priority

Konica Minolta DiMAGE A2 vs. Canon PowerShot Pro1

  Konica Minolta DiMAGE A2
ISO 64
, 1/80 sec, F4.0
Canon PowerShot Pro1
ISO 50
, 1/50 sec, F4.5
 Partial crop
Red Green Blue
channels
  Konica Minolta DiMAGE A2
ISO
100, 1/100 sec, F4.0
Canon PowerShot Pro1
ISO 100
, 1/100 sec, F4.5
 Partial crop
Red Green Blue
channels
  Konica Minolta DiMAGE A2
ISO
200, 1/200 sec, F4.0
Canon PowerShot Pro1
ISO 200
, 1/200 sec, F4.5
 Partial crop
Red Green Blue
channels
  Konica Minolta DiMAGE A2
ISO
400, 1/400 sec, F4.0
Canon PowerShot Pro1
ISO 400, 1/400 sec, F4.5
 Partial crop
Red Green Blue
channels
  Konica Minolta DiMAGE A2
ISO 800
, 1/1250 sec, F4.0
Canon PowerShot Pro1
n/a
 Partial crop
Red Green Blue
channels

Spot the difference, at ISO 64 / 50 the Canon looks cleaner (although the measurements show it's very close). Around ISO 100 it would be difficult to say which is more preferable, the image with a little more speckle noise or the image with noise reduction. Above this the DiMAGE A2's noise reduction turns what would be speckled noise similar to what we're seeing on the Pro1 to a more blotchy result.

Konica Minolta DiMAGE A2 vs. Sony DSC-F828

  Konica Minolta DiMAGE A2
ISO 64
, 1/80 sec, F4.0
Sony DSC-F828
ISO 64
, 1/60 sec, F3.5
 Partial crop
Red Green Blue
channels
  Konica Minolta DiMAGE A2
ISO
100, 1/100 sec, F4.0
Sony DSC-F828
ISO 100
, 1/80 sec, F3.5
 Partial crop
Red Green Blue
channels
  Konica Minolta DiMAGE A2
ISO
200, 1/200 sec, F4.0
Sony DSC-F828
ISO 200
, 1/160 sec, F3.5
 Partial crop
Red Green Blue
channels
  Konica Minolta DiMAGE A2
ISO
400, 1/400 sec, F4.0
Sony DSC-F828
ISO 400, 1/320 sec, F3.5
 Partial crop
Red Green Blue
channels
  Konica Minolta DiMAGE A2
ISO 800
, 1/1250 sec, F4.0
Sony DSC-F828
ISO 800, 1/640 sec, F3.5
 Partial crop
Red Green Blue
channels

Once more at ISO 64 there's little difference, even at ISO 100 there's not a huge difference. From ISO 200 upwards the stronger noise reduction of the DiMAGE A2 becomes far more obvious.

Luminance noise graph

As you can see from the five way comparison below the Canon, Nikon and Sony have very similar noise levels throughout the ISO sensitivity range. The Olympus C-8080 Wide Zoom and Konica Minolta DiMAGE A2 both manage to keep noise levels low, examining their images it's clear that they are both achieving this through noise reduction.

So is noise actually lower on the C-8080 and DiMAGE A2? Well, yes, but probably at the expense of a little detail. This shouldn't be a big issue at lower sensitivities (ISO 100 or 200).

Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity (normalized) on the vertical axis. Note that we have standardized on a 0-10 scale.

RGB noise graph

Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of each of the red, green and blue channels (normalized) are on the vertical axis. Note that we have standardized on a 0-10 scale.

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