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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. 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 measurement tool which measures the standard deviation (normalized) of the middle gray patch (indicated by the red rectangle above). Additionally we now have a 'detail crop', this is currently a postage stamp (lots of fine detail) but we may replace this at a future date. Note that noise values indicated on the graphs below should not be compared to those in other reviews.

Test notes:

  • Shots taken at approximately 22°C (~72°F)
  • Lighting was simulated daylight measured as 10.1 EV (at ISO 100)

Pentax *ist DS vs. Canon EOS 300D / Digital Rebel (ISO 100 - 3200)

  • Pentax *ist DS: Pentax 50 mm F1.4 lens, Aperture Priority, Manual WB,
    Default Parameters, JPEG Large / Fine
  • Canon EOS 300D: Canon 50 mm F1.4 lens, Aperture Priority, Manual WB,
    Parameters 1 (default), JPEG Large / Fine
  Pentax *ist DS
n/a
Canon EOS 300D
ISO 100
, 1/100 sec, F4
Crops
  Pentax *ist DS
ISO 200
, 1/200 sec, F3.5
Canon EOS 300D
ISO 200
, 1/200 sec, F4
Crops
  Pentax *ist DS
ISO 400, 1/400 sec, F3.5
Canon EOS 300D
ISO 400
, 1/400 sec, F4
Crops
  Pentax *ist DS
ISO 800
, 1/800 sec, F3.5
Canon EOS 300D
ISO 800
, 1/800 sec, F4
Crops
  Pentax *ist DS
ISO 1600
, 1/1600 sec, F3.5
Canon EOS 300D
ISO 1600
, 1/1600 sec, F4
Crops
  Pentax *ist DS
ISO 3200, 1/3200 sec, F4
Canon EOS 300D
n/a
Crops

Lets talk about noise first, a visual comparison of the gray patches indicates that noise levels between the two are fairly similar, the EOS 300D perhaps a little cleaner and with the advantage of the virtually noiseless ISO 100. Next it's obvious that the Canon's in-camera image processing is far better with much clearer detail, there's a slight softening of the EOS 300D's detail at ISO 1600 but it's still revealing more of the original scene than the *ist DS.

Pentax *ist DS vs. Nikon D70 (ISO 200 - 3200)

  • Pentax *ist DS: Pentax 50 mm F1.4 lens, Aperture Priority, Manual WB,
    Default Parameters, JPEG Large / Fine
  • Nikon D70: Nikkor 50 mm F1.4 lens, Aperture Priority, Manual WB,
    Default Parameters, JPEG Large / Fine
  Pentax *ist DS
ISO 200
, 1/200 sec, F3.5
Nikon D70
ISO 200
, 1/200 sec, F3.5
Crops
  Pentax *ist DS
ISO 400, 1/400 sec, F3.5
Nikon D70
ISO 400
, 1/400 sec, F3.5
Crops
  Pentax *ist DS
ISO 800
, 1/800 sec, F3.5
Nikon D70
ISO 800
, 1/800 sec, F3.5
Crops
  Pentax *ist DS
ISO 1600
, 1/1600 sec, F3.5
Nikon D70
ISO 1600
, 1/1600 sec, F3.5
Crops
  Pentax *ist DS
ISO 3200
, 1/3200 sec, F3.5
Nikon D70
n/a
Crops

It's very difficult to see any difference in actual noise between the *ist DS and the D70, a glance out our measured noise levels in the graph below shows that the two are virtually identical. This comes as little surprise as we expect that both cameras either use the same or very similar sensors. The *ist DS does allow ISO 3200 but as you can see the noise level at this sensitivity is fairly strong. Once more the *ist DS exhibits weak in-camera image processing, the D70 exhibits more detail throughout the ISO range.

Luminance noise graph

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

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 image) are on the vertical axis.

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