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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 1.5 in this review). Click here for more information. Room temperature is approximately 22°C (~72°F), simulated daylight lighting.

Canon EOS 450D vs. Nikon D60 vs. Olympus E-420 vs Canon EOS 400D

  • Canon EOS 450D: Canon 50 mm F1.4 lens, Aperture Priority, Manual WB,
    Default Parameters (Standard PS), High ISO NR (Default; Off), JPEG Large / Fine
     
  • Nikon D60: Nikkor 50 mm F1.8 lens, Aperture Priority, Manual WB,
    Default Parameters (Normal), JPEG Large / Fine
     
  • Olympus E-420: Olympus 50 mm F2.0 Macro lens, Aperture Priority, Manual WB,
    Default Parameters (Normal), High ISO NR (Normal), JPEG Large / Fine

  • Canon EOS 400D: Canon 50 mm F1.4 lens, Aperture Priority, Manual WB,
    Default Parameters (Standard PS), JPEG Large / Fine
Canon EOS 450D
ISO 100
Nikon D60
ISO 100
Olympus E-420
ISO 100
Canon EOS 400D
ISO 100
Canon EOS 450D
ISO 200
Nikon D60
ISO 200
Olympus E-420
ISO 200
Canon EOS 400D
ISO 200
Canon EOS 450D
ISO 400
Nikon D60
ISO 400
Olympus E-420
ISO 400
Canon EOS 400D
ISO 400
Canon EOS 450D
ISO 800
Nikon D60
ISO 800
Olympus E-420
ISO 800
Canon EOS 400D
ISO 800
Canon EOS 450D
ISO 1600
Nikon D60
ISO 1600
Olympus E-420
ISO 1600
Canon EOS 400D
ISO 1600
Canon EOS 450D
n/a
Nikon D60
ISO 3200
Olympus E-420
n/a
Canon EOS 400D
n/a

From a noise and NR point of view there's little difference between any of these cameras up to ISO 400, though it's clear that Canon's CMOS sensor and DIGIC III are doing a far better job of balancing detail and noise reduction at anything over base ISO. Once you get to ISO 800 and 1600 the Olympus E-420 (and to a lesser extent the Nikon D60) is starting to struggle, with visible noise and obvious softening of detail. Whatever else you say about Canon there's no denying it still leads the pack when it comes to high ISO performance in consumer grade SLRs.

Looking at the EOS 450D (Rebel XSi) compared to the EOS 400D (Rebel XTi) it's good to see that the extra pixels haven't had a significant impact on the higher ISO capabilities of the sensor: chroma noise is a little lower but we presume this is down to a slightly higher level of NR (you can also turn high ISO NR 'on', which reduces chroma NR considerably). Looking closely it would seem that Canon has had to use a touch more luminance NR to get results that match the 400D, but the results are impressive nonetheless.

Note: like all Olympus SLRs the E-420 offers four levels of noise reduction; these samples are taken with the default 'STD' setting, which tends to produce rather soft results at higher ISOs. If you're prepared to live with more visible noise you can retain more detail and get sharper looking output. We'll look at the E-420's various noise reduction options in more depth in our forthcoming review.

Luminance noise graph (gray)

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

Luminance noise graph (black)

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

Chroma (color) noise graph

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

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