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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 we have seen in previous reviews the Nikon cameras are right on the spot for ISO accuracy and the Canon cameras are about a third more sensitive than indicated (ISO 100 is more like ISO 125).

Indicated
sensitivity
Nikon D200
(actual sensitivity)
Canon EOS 30D / 5D
(actual sensitivity)
ISO 100 ISO 100 ISO 125
ISO 200 ISO 200 ISO 250
ISO 400 ISO 400 ISO 500
ISO 800 ISO 800 ISO 1000
ISO 1600 ISO 1600 ISO 2000
ISO 3200 ISO 3200 ISO 4000

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.

Boosted sensitivities

For the EOS 30D the ISO 3200 setting is only accessible once the 'ISO expansion' custom function has been enabled and is indicated by the camera as 'H', hence outside the recommended sensitivity range. The same is true for the Nikon D200, its ISO 3200 accessed as HI+1.0. We have indicated boosted sensitivities with a double asterisk '**' suffix.

Canon EOS 30D vs. Nikon D200 vs. Canon EOS 5D

  • Canon EOS 30D: Canon 50 mm F1.4 lens, Aperture Priority, Manual WB,
    Default Parameters (Standard PS), JPEG Large / Fine
     
  • Nikon D200: Nikkor 50 mm F1.4 lens, Aperture Priority, Manual WB,
    Default Parameters, High ISO NR 'Normal', JPEG Large / Fine
     
  • Canon EOS 5D: Canon 50 mm F1.4 lens, Aperture Priority, Manual WB,
    Default Parameters (Standard PS), JPEG Large / Fine
Nikon D200
ISO 100
Canon EOS 30D
ISO 100
(125 equiv.)
Canon EOS 5D
ISO 100
(125 equiv.)
Nikon D200
ISO 200
Canon EOS 30D
ISO 200
(250 equiv.)
Canon EOS 5D
ISO 200
(250 equiv.)
Nikon D200
ISO 400
Canon EOS 30D
ISO 400
(500 equiv.)
Canon EOS 5D
ISO 400
(500 equiv.)
Nikon D200
ISO 800
Canon EOS 30D
ISO 800
(1000 equiv.)
Canon EOS 5D
ISO 800
(1000 equiv.)
Nikon D200
ISO 1600
Canon EOS 30D
ISO 1600
(2000 equiv.)
Canon EOS 5D
ISO 1600
(2000 equiv.)
Nikon D200
ISO 3200
**
Canon EOS 30D
ISO 3200 (4000 equiv.) **
Canon EOS 5D
ISO 3200 (4000 equiv.) **

Apart from the obvious resolution difference the EOS 30D and EOS 5D produced fairly similar levels of visible noise and also limited softening at ISO 1600 and 3200. The Nikon D200 exhibits more noise above ISO 800 and pretty heavy noise reduction effect at ISO 3200. The D200's noise reduction seems to take care of chroma (color) noise better than Canon giving noise a more film like monochromatic appearance. However on balance it's clear that the EOS 30D comes away with a more usable image (compared to the D200) at ISO 1600 and 3200.

Luminance noise graph

Our new luminance noise graph shows noise levels in both the middle gray and black patches. As noted above luminance noise levels between these three cameras is pretty similar up to ISO 800, after this the Nikon's noise reduction system can no longer contain the noise. The other difference is shadow noise (the dotted line) which is higher.

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

Luminance noise graph magnified (Canon only)

The graph below represents the same data as above (except for the removal of the D200) but on a standard deviation scale of 0 to 5 instead of 0 to 10, this makes it easier to see the limited difference between the Canon cameras. As you can see any question that the EOS 30D is using a different sensor / image pipeline than the EOS 20D can be quickly quashed with a single glance at this virtual identical result.

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

Chroma (color) noise graph

In addition to measuring luminance noise we now also measure chroma (color) noise. As you can see the D200's more 'film like' monochromatic noise appearance keeps chroma (color) noise to a minimum.

Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of each of the red, green and blue channels are on the vertical axis.

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Comments

RVer
By RVer (4 weeks ago)

The 30D had a 50 mm lens and the 5D had an 85mm lens and that could account for the difference in reading the globe etc.

0 upvotes