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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

Nikon Coolpix 8700 vs. Konica Minolta DiMAGE A2

  Nikon Coolpix 8700
ISO 50
, 1/50 sec, F3.9
Konica Minolta DiMAGE A2
ISO 64
, 1/80 sec, F4.0
 Partial crop
Red Green Blue
channels
  Nikon Coolpix 8700
ISO
100, 1/100 sec, F3.9
Konica Minolta DiMAGE A2
ISO 100
, 1/100 sec, F4.0
 Partial crop
Red Green Blue
channels
  Nikon Coolpix 8700
ISO
200, 1/200 sec, F3.9
Konica Minolta DiMAGE A2
ISO 200
, 1/200 sec, F4.0
 Partial crop
Red Green Blue
channels
  Nikon Coolpix 8700
ISO
400, 1/400 sec, F3.9
Konica Minolta DiMAGE A2
ISO 400, 1/400 sec, F4.0
 Partial crop
Red Green Blue
channels
  Nikon Coolpix 8700
n/a
Konica Minolta DiMAGE A2
ISO 800, 1/1250 sec, F4.0
 Partial crop
Red Green Blue
channels

At ISO 50 / 64 noise is so low from both cameras that it's not noticeable. However even at ISO 100 the DiMAGE A2's noise reduction really does deliver cleaner images, higher still and it's much more noticeable although as with all noise reduction systems it would be a compromise between visible noise and a slight loss in detail.

Nikon Coolpix 8700 vs. Canon PowerShot Pro1

  Nikon Coolpix 8700
ISO 50
, 1/50 sec, F3.9
Canon PowerShot Pro1
ISO 50
, 1/50 sec, F4.5
 Partial crop
Red Green Blue
channels
  Nikon Coolpix 8700
ISO 100
, 1/100 sec, F3.9
Canon PowerShot Pro1
ISO
100, 1/100 sec, F4.5
 Partial crop
Red Green Blue
channels
  Nikon Coolpix 8700
ISO 200
, 1/200 sec, F3.9
Canon PowerShot Pro1
ISO
200, 1/200 sec, F4.5
 Partial crop
Red Green Blue
channels
  Nikon Coolpix 8700
ISO 400, 1/400 sec, F3.9
Canon PowerShot Pro1
ISO
400, 1/400 sec, F4.5
 Partial crop
Red Green Blue
channels

In this comparison things are much closer, both cameras exhibiting roughly the same levels of noise throughout their sensitivity range. Interestingly the Nikon tends towards a green shift at higher sensitivities, this only seemed to occur in our studio and we weren't able to replicate this in normal 'everyday' situations.

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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