ISO / Sensitivity accuracy

In a new addition to our reviews we are now 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.

As is typical of almost every Canon digital SLR the EOS 5D is about a third of a stop more sensitive than indicated, hence its ISO 100 is actually more like ISO 125. The Nikon D2X is (as with most Nikon digital SLR's) right on the spot, the Fujifilm S3 Pro turned out to be about a third (to a quarter) less sensitive.

Indicated
sensitivity
Canon EOS 5D / EOS 20D / EOS-1Ds Mk II
(actual sensitivity)
Nikon D2X

(actual sensitivity)
Fujifilm S3 Pro

(actual sensitivity)
ISO 50 ISO 64 n/a n/a
ISO 100 ISO 125 ISO 100 ISO 80
ISO 200 ISO 250 ISO 200 ISO 160
ISO 400 ISO 500 ISO 400 ISO 320
ISO 800 ISO 1000 ISO 800 ISO 640
ISO 1600 ISO 2000 ISO 1600 ISO 1250
ISO 3200 ISO 4000 ISO 3200 n/a

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.)

Test notes

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

Canon EOS 5D vs. EOS-1Ds Mark II vs. Nikon D2X

  • Canon EOS 5D: Canon 50 mm F1.4 lens, Aperture Priority, Manual WB,
    Default Parameters (Standard), JPEG Large / Fine
     
  • Canon EOS-1Ds Mark II: Canon 50 mm F1.4 lens, Aperture Priority, Manual WB,
    Sharpness 1, 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 5D
ISO 50 (L)
Canon EOS-1Ds Mark II
ISO 50 (L)
Nikon D2X
n/a
Canon EOS 5D
ISO 100
Canon EOS-1Ds Mark II
ISO 100
Nikon D2X
ISO 100
Canon EOS 5D
ISO 200
Canon EOS-1Ds Mark II
ISO 200
Nikon D2X
ISO 200
Canon EOS 5D
ISO 400
Canon EOS-1Ds Mark II
ISO 400
Nikon D2X
ISO 400
Canon EOS 5D
ISO 800
Canon EOS-1Ds Mark II
ISO 800
Nikon D2X
ISO 800
Canon EOS 5D
ISO 1600
Canon EOS-1Ds Mark II
ISO 1600
Nikon D2X
ISO 1600
Canon EOS 5D
ISO 3200
Canon EOS-1Ds Mark II
ISO 3200
Nikon D2X
ISO 3200

The EOS 5D's performance up to ISO 800 is very similar to that of the EOS-1Ds Mark II, however there's a distinct difference at ISO 1600 and 3200 where the EOS-1Ds Mark II appears to utilize less noise reduction and hence maintains more detail (at the expense of visible noise). This would appear to be an example of the difference in the ethos behind Canon's professional EOS-1D series cameras and the rest of the range. The overall noise performance from the EOS 5D is very good and by our measurements almost identical to the EOS 20D.

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.

Luminance noise graph (just Canon, zoomed)

This graph shows the same data as above but with the Nikon D2X removed and the standard deviation scale halved (to provide a clearer view of the differences).

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

The EOS 5D exhibited slightly lower chroma noise (colored speckles) than both the EOS-1Ds Mark II and EOS 20D, although couldn't match the D2X which has a more monochromatic appearance to noise.

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