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ISO / Sensitivity accuracy

In this section of our reviews we are measuring the actual sensitivity of each indicated ISO sensitivity. This is achieved using the same shots as are used to measure ISO noise levels, we simply compare the exposure for each shot to the metered light level (using Sekonic L-358), middle gray matched. We estimate the accuracy of these results to be +/- 1/6 EV.

Like its predecessor the E-420 proved to have inconsistently indicated ISO sensitivities. In reality ISO 100 proved to be marginally more sensitive than indicated (more like ISO 125).

Indicated
sensitivity
Olympus E-420
(actual sensitivity)
Canon EOS 450D
(actual sensitivity)
Nikon D60
(actual sensitivity)
ISO 100 ISO 125 ISO 100 ISO 100
ISO 200 ISO 200 ISO 200 ISO 200
ISO 400 ISO 400 ISO 400 ISO 400
ISO 800 ISO 800 ISO 800 ISO 800
ISO 1600 ISO 1600 ISO 1600 ISO 1600
ISO 3200 n/a n/a ISO 3200

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). Room temperature is approximately 22°C (~72°F), simulated daylight lighting.

Olympus E-420 vs. Canon EOS 450D (Digital Rebel XSi) vs. Nikon D60

  • 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 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-410: Olympus 50 mm F2.0 Macro lens, Aperture Priority, Manual WB,
    Default Parameters (Normal), High ISO NR (Normal), JPEG Large / Fine
Olympus E-420
ISO 100
Nikon D60
ISO 100
Canon EOS 450D
ISO 100
Olympus E-410
ISO 100
Olympus E-420
ISO 200
Nikon D60
ISO 200
Canon EOS 450D
ISO 200
Olympus E-410
ISO 200
Olympus E-420
ISO 400
Nikon D60
ISO 400
Canon EOS 450D
ISO 400
Olympus E-410
ISO 400
Olympus E-420
ISO 800
Nikon D60
ISO 800
Canon EOS 450D
ISO 800
Olympus E-410
ISO 800
Olympus E-420
ISO 1600
Nikon D60
ISO 1600
Canon EOS 450D
ISO 1600
Olympus E-410
ISO 1600
Olympus E-420
n/a
Nikon D60
ISO 3200
Canon EOS 450D
n/a
Olympus E-410
n/a

As you would almost expect there is little difference in terms of noise between the digital SLRs in this comparison up to ISO 400. At ISO 800 and 1600 the Olympus clearly applies more luminance noise reduction than the Canon and Nikon, resulting in a 'cleaner' but less detailed image. The Canon 450D (Rebel XSi) provides the most balanced output, managing noise well and preserving a lot of detail up until the high ISO regions.

Gray luminance noise graph

The E-420's noise curve is almost identical to its predecessor's. It keeps measurable noise virtually flat from ISO 100 (125) to 800, rising only slightly at ISO 1600 (1250).

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

Black luminance noise graph

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

 

Chroma (color) noise graph

Chroma noise reduction works pretty much the same way system as the luminance variant, the curve is being kept very flat throughout the entire sensitivity range.

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

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