Previous page Next page

ISO Sensitivity / Noise levels

ISO equivalence on a digital camera is the ability to increase the sensitivity of the sensor. This works by turning up the "volume" (gain) on the sensor's signal amplifiers (remember the sensor is an analogue device). By amplifying the signal you also amplify the noise which becomes more visible at higher ISO's. Many modern cameras also employ noise reduction and / or sharpness reduction at higher sensitivities.


To measure noise levels we take a sequence of images of a GretagMacBeth ColorChecker chart (controlled artificial daylight lighting). The exposure is matched to the ISO (ie. ISO 200, 1/200 sec for consistency of exposure between cameras). The image sequence is run through our own proprietary noise measurement tool (version 1.4 in this review). Click here for more information. (Note that noise values indicated on the graphs here can not be compared to those in other reviews.)

Kodak EasyShare Z650 vs Oympus SP-500UZ

  Kodak Z650
ISO 80

Olympus SP-500UZ
ISO 80

Crops
  Kodak Z650
ISO 100

Olympus SP-500UZ
ISO 100

Crops
  Kodak Z650
ISO 200

Olympus SP-500UZ
ISO 200

Crops
  Kodak Z650
ISO 400

Olympus SP-500UZ
ISO 400

Crops

There's not a huge difference in the noise levels here - the Kodak has slightly higher luminance noise at higher ISO settings, but uses heavier noise reduction to produce slightly less grainy - but also less detailed - results. Neither camera handles chroma noise very well, with both showing fairly strong - and quite big - color blotches at ISO 400. It's fair to say that at lower ISO settings (80 and 100) the Z650 isn't going to trouble you with noise, but the loss of detail caused by the heavy-handed noise reduction at ISO 200-400 will limit how big you'll want to print images taken at the higher settings.

Kodak EasyShare Z650 vs Pansasonic DMC-FZ7

  Kodak Z650
ISO 80

Panasonic FZ7
ISO 80

Crops
  Kodak Z650
ISO 100

Panasonic FZ7
ISO 100

Crops
  Kodak Z650
ISO 200

Panasonic FZ7
ISO 200

Crops
  Kodak Z650
ISO 400

Panasonic FZ7
ISO 400

Crops

Ignoring the differences in sharpness the difference here is down to noise reduction - Panasonics approach is much more subtle at lower ISO settings (so luminance noise makes the images look grainier), whereas Kodak goes for the ultra-smooth look. At higher ISO's the noise levels appear to be broadly similar, and the choice is between Kodak's smooth look (which lacks detail) or Panasonic's sharp, but slightly 'watercolor' result. The Kodak noise reduction does a fairly good job with luminance noise, but Panasonic has tne edge on chroma noise at ISO 400, where there are visible blotches in the Kodak image.

Luminance noise graph

Cameras compared:
Kodak Z650, Panasonic FZ7, Olympus SP-500UZ

Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity is on the vertical axis.

Broadly speaking all three cameras have the similar noise characteristics at ISO 80-200, with the main differences at ISO 400 coming down to the effectiveness of their respective noise reduction systems. It's worth noting that measured noise at high ISO settings in these small sensor cameras is to some extent irrelevant - it doesn't show how much noise reduction has been used to keep the levels down, and how destructive (or not) this is to the image. For a better idea of how these three cameras compare take a look at the studio comparison shots on the following pages. It's also worth noting that the noise levels on all these cameras are higher than we've seen so far with the newer 6MP (as used in the Canon A700, for example).

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 is on the vertical axis.

The Z650 and SP-500UZ have very similar noise levels, and again, both are a fair bit higher than we've seen so far from cameras using the newer 6MP sensor now appearing in models from Canon and Sony.

Previous page Next page
2
I own it
0
I want it
0
I had it
Discuss in the forums

Comments