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

Olympus C-8080 WZ vs. Konica Minolta DiMAGE A2

  Olympus C-8080 WZ
ISO 50
, 1/50 sec, F4.5
Konica Minolta DiMAGE A2
ISO 64
, 1/80 sec, F4.0
 Partial crop
Red Green Blue
channels
  Olympus C-8080 WZ
ISO
100, 1/100 sec, F4.5
Konica Minolta DiMAGE A2
ISO 100
, 1/100 sec, F4.0
 Partial crop
Red Green Blue
channels
  Olympus C-8080 WZ
ISO
200, 1/200 sec, F4.5
Konica Minolta DiMAGE A2
ISO 200
, 1/200 sec, F4.0
 Partial crop
Red Green Blue
channels
  Olympus C-8080 WZ
ISO
400, 1/400 sec, F4.5
Konica Minolta DiMAGE A2
ISO 400, 1/400 sec, F4.0
 Partial crop
Red Green Blue
channels
  Olympus C-8080 WZ
n/a
Konica Minolta DiMAGE A2
ISO 800, 1/1250 sec, F4.0
 Partial crop
Red Green Blue
channels

Both of these cameras appear to implement noise reduction at higher sensitivities which reduces the more noticeable 'speckle' noise to a more blotchy noise which blends into the image far better. Overall I would say that I prefer the appearance of the C-8080's noise which also appears to be more even across all color channels. The graph below shows that in fact measured levels are almost identical.

Olympus C-8080 WZ vs. Nikon Coolpix 8700

  Olympus C-8080 WZ
ISO 50
, 1/50 sec, F3.9
Nikon Coolpix 8700
ISO 50
, 1/50 sec, F3.9
 Partial crop
Red Green Blue
channels
  Olympus C-8080 WZ
ISO 100
, 1/100 sec, F3.9
Nikon Coolpix 8700
ISO
100, 1/100 sec, F3.9
 Partial crop
Red Green Blue
channels
  Olympus C-8080 WZ
ISO 200
, 1/200 sec, F3.9
Nikon Coolpix 8700
ISO
200, 1/200 sec, F3.9
 Partial crop
Red Green Blue
channels
  Olympus C-8080 WZ
ISO 400, 1/400 sec, F3.9
Nikon Coolpix 8700
ISO
400, 1/400 sec, F3.9
 Partial crop
Red Green Blue
channels

The C-8080 looks cleaner than the Coolpix 8700 from ISO 100 upwards, although interestingly the 8700 may look a little cleaner at ISO 50, though there's very little in it. Olympus's noise reduction system appears to work well, but remember that any noise reduction like this can lead to a softening of the image or a slight loss in detail.

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.