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ISO Sensitivity / Noise levels

ISO equivalence on a digital camera is the ability to increase the sensitivity of the sensor. The 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.)

Panasonic DMC-FZ7 vs Panasonic DMC-FZ5

  Panasonic DMC-FZ7
ISO 80

Panasonic DMC-FZ5
ISO 80

Crops
  Panasonic DMC-FZ7
ISO 100
Panasonic DMC-FZ5
ISO 100
Crops
  Panasonic DMC-FZ7
ISO 200
Panasonic DMC-FZ5
ISO 200
Crops
  Panasonic DMC-FZ7
ISO 400
Panasonic DMC-FZ5
ISO 400
Crops

One of the biggest criticisms aimed at the FZ5 (and FZ20) was that noise was on the high side even at low ISOs, and noise reduction at higher ISOs was way too harsh, causing loss of fine detail and a 'watercolor' effect when the images are viewed full size on screen. Anyone hoping that the FZ7 would represent a significant leap forward are going to be disappointed; at 80 ISO noise is actually slightly higher (though to be honest it's not visibly different). At higher ISO's there's little to choose between the FZ7 and its predecessor; the noise reduction routines appear to have been changed, and the FZ7 exhibits more blotchy color noise than the FZ5 (which looks a little 'grittier'), especially in shadow areas. Which is better? hard to say really - the new camera appears to use slightly more gentle noise reduction (so subtle detail is more likely to be retained, and there's less of the desaturation common to strong NR), but the images look noisier in any areas darker than 'middle gray'.

Panasonic DMC-FZ7 vs Olympus SP-500UZ

  Panasonic DMC-FZ7
ISO 80

Olympus SP-500UZ
ISO 50

Crops
  Panasonic DMC-FZ7
ISO 100
Olympus SP-500UZ
ISO 100
Crops
  Panasonic DMC-FZ7
ISO 200
Olympus SP-500UZ
ISO 200
Crops
  Panasonic DMC-FZ7
ISO 400
Olympus SP-500UZ
ISO 400
Crops

At the low ISO settings the minor noise differences between these two cameras aren't really enough to show in print. At ISO 400 the FZ7 has slightly lower measurable noise, but visually there's not a lot in it - the Panasonic looks smoother, but blotchier.

Panasonic DMC-FZ7 'High sensitivity mode'

  Panasonic DMC-FZ7
ISO 800
Panasonic DMC-FZ7
ISO 1600
Crops

There's not a lot to say about the 'high sensitivity' mode when it comes to noise; yes noise is very low, but the combined effects of pixel-binning, noise reduction and interpolation have produced an image bereft of detail.

Luminance noise graph

Cameras compared:
Panasonic DMC-FZ7, Olympus SP-500UZ Ultra Zoom, Panasonic DMC-FZ5

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

Aside from the slightly anomalous gray noise measurement at ISO 80 the FZ7 follows roughly the same pattern as its predecessor (the FZ5) and the 6MP Olympus SP-500UZ - the only real difference being how the noise reduction works. Too see this graph zoomed to cover ISO 80-400 only click here.

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.

Again the noise levels at ISO 80 are higher than the FZ5 or the SP-500UZ, indicating that the strong noise reduction only kicks in at ISO 100. ISO 400 shows low measurable noise, but this is a measure of the smoothing effect of noise reduction, and certainly isn't reflected visually (see top of page) - the ISO 400 images look distinctly blotchy in the shadow areas. Again to view this graph zoomed to cover ISO 80-400 only, click here.

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