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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.)

Canon EOS-1DS Mark II Sharpness parameter

The cameras default sharpness level is 0, essentially no sharpening applied to the image at all. In reality almost all photographers are will use a setting of 1 or 2 (especially for JPEG output) with this in mind we used a setting of 1 for our noise measurement tests. This makes the test more representative of real world results and is a fairer comparison to the other cameras here, all of which apply a normal level of sharpening to their images. You can see the difference sharpening makes to noise levels in the last graph on this page.

Test notes

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

Canon EOS-1Ds Mark II vs. Nikon D2X vs. Canon EOS 20D

  • Canon EOS-1Ds Mark II: Canon 50 mm F1.4 lens, Aperture Priority (F4), Manual WB,
    Sharpness 1, 50 mm F1.4, JPEG Large / Fine
     
  • Nikon D2X: Nikkor 50 mm F1.4 lens, Aperture Priority, Manual WB,
    Default Parameters, High ISO Noise Reduction 'Normal', JPEG Large / Fine
     
  • Canon EOS 20D: Canon 50 mm F1.4 lens, Aperture Priority (F4), Manual WB,
    Parameters 1 (default), 50 mm F1.4, JPEG Large / Fine
Canon EOS-1Ds Mark II
ISO 50
(L) , 1/50 sec, F4
Nikon D2X
n/a
Canon EOS 20D
n/a
Canon EOS-1Ds Mark II
ISO 100
, 1/100 sec, F4
Nikon D2X
ISO 100
, 1/100 sec, F3.5
Canon EOS 20D
ISO 100
, 1/100 sec, F4
Canon EOS-1Ds Mark II
ISO 200
, 1/200 sec, F4
Nikon D2X
ISO 200
, 1/200 sec, F3.5
Canon EOS 20D
ISO 200
, 1/200 sec, F4
Canon EOS-1Ds Mark II
ISO 400, 1/400 sec, F4
Nikon D2X
ISO 400
, 1/400 sec, F3.5
Canon EOS 20D
ISO 400
, 1/400 sec, F4
Canon EOS-1Ds Mark II
ISO 800
, 1/800 sec, F4
Nikon D2X
ISO 800
, 1/800 sec, F3.5
Canon EOS 20D
ISO 800
, 1/800 sec, F4
Canon EOS-1Ds Mark II
ISO 1600
, 1/1600 sec, F4
Nikon D2X
ISO 1600
, 1/1600 sec, F3.5
Canon EOS 20D
ISO 1600
, 1/1600 sec, F4
Canon EOS-1Ds Mark II
ISO 3200
(H) , 1/3200 sec, F4
Nikon D2X
ISO 3200
, 1/3200 sec, F3.5
Canon EOS 20D
ISO 3200
, 1/3200 sec, F4

As you can see the EOS-1Ds Mark II has a progressive increase in noise that only really becomes intrusive at ISO 3200 (indicated as 'H' on the status LCD). At these higher sensitivities noise appears more as color blotching (chroma noise) which is a typical characeteristic of Canon's CMOS sensor (very similar to the EOS 20D also shown here). What is impressive is the camera's ability to hang on to detail even at ISO 3200, much more so than the EOS 20D or D2X.

We compared the noise characteristics of Nikon D2X and Canon EOS-1Ds Mark II in our review of the D2X, since then we have improved our noise test to include the black patch on the chart. This reveals that while the D2X has a very similar mid-tone noise profile as the EOS-1Ds Mark II its shadow noise is noticeably higher (this can be seen clearly in the crops above). There are two other significant differences; the D2X's noise appears mostly as monochromatic 'luminance' noise (more like film grain) where as the EOS-1Ds Mark II has more chroma noise (see second graph below) which does look more digital / video-like. The last difference is detail, the D2X has a fairly strong noise reduction algorithm (see the bottom of this page of our D2X review to see the difference) which smooths away detail at higher sensitivities.

Luminance noise graph

Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity on the vertical axis. Gray refers to the middle gray patch, Black refers to the black patch.

Chroma noise graph

Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of chroma (from the gray patch) on the vertical axis.

Effect of sharpness parameter on noise (Canon EOS-1Ds Mark II)

Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity (from the gray patch) on the vertical axis.

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