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).

ISO Sensitivity / Noise levels

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.

Notes

• Where's the EOS 20D? - We haven't included the EOS 20D in the samples below because its noise level / reduction effect is as good as identical to the EOS 5D.
   
• Boosted sensitivities? - Nikon rate the optimum usable range of sensitivity for the D200 as being up to ISO 1600, you can access ISO 3200 equivelant by selecting the 'HI +1.0' boosted sensitivity option. For the D2X the designed sensitivity range is up to ISO 800, ISO 1600 and 3200 are both 'boosted'. We have indicated such with a double asterisk '**' suffix.

Nikon D200 vs. Canon EOS 5D vs. Nikon D2X

• 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), JPEG Large / Fine
   
  
• Nikon D2X: Nikkor 50 mm F1.4 lens, Aperture Priority, Manual WB,
  Default Parameters, High ISO NR 'Normal', JPEG Large / Fine

Nikon D200 ISO 100	Canon EOS 5D ISO 100 (125 equiv.)	Nikon D2X ISO 100
Nikon D200 ISO 200	Canon EOS 5D ISO 200 (250 equiv.)	Nikon D2X ISO 200
Nikon D200 ISO 400	Canon EOS 5D ISO 400 (500 equiv.)	Nikon D2X ISO 400
Nikon D200 ISO 800	Canon EOS 5D ISO 800 (1000 equiv.)	Nikon D2X ISO 800
Nikon D200 ISO 1600	Canon EOS 5D ISO 1600 (2000 equiv.)	Nikon D2X ISO 1600 **
Nikon D200 ISO 3200 **	Canon EOS 5D ISO 3200 (4000 equiv.)	Nikon D2X ISO 3200 **

Up to ISO 800 there's very little noticeable difference in noise (in the gray and black patches). At ISO 1600 the EOS 5D's black patch (representing shadow areas in a normal image) looks cleaner than both Nikon's, however both also present a more 'film like' monochromatic noise pattern, the EOS 5D exhibits some chroma (color) noise. At ISO 3200 the EOS 5D performs much better than either Nikon. The biggest difference from ISO 800 upwards is the effect Nikon's noise reduction has on detail, becoming gradually more blurred as sensitivity increases, in this respect Canon has it.

Nikon D200 (NR Off) vs. Canon EOS 5D vs. Nikon D2X (NR Off)

Here we're only comparing the 'high sensitivities' (above ISO 400) with Nikon's High ISO noise reduction turned off. Note though that even in the 'Off' position Nikon still applies some (minimal) noise reduction above ISO 400.

Nikon D200 (NR Off) ISO 800	Canon EOS 5D ISO 800 (1000 equiv.)	Nikon D2X (NR Off) ISO 800
Nikon D200 (NR Off) ISO 1600	Canon EOS 5D ISO 1600 (2000 equiv.)	Nikon D2X (NR Off) ISO 1600 **
Nikon D200 (NR Off) ISO 3200 **	Canon EOS 5D ISO 3200 (4000 equiv.)	Nikon D2X (NR Off) ISO 3200 **

With noise reduction turned off the D200 image exhibits more detail and with only a slight increase in noticeable noise, at ISO 3200 however noise dominates the image. My personal preference would be to leave Nikon's High ISO noise reduction switched off unless I intended to use ISO 3200, the difference it makes to visible noise at ISO 1600 is minimal but the blurring effect on fine detail (when enabled) is noticeable.

Luminance noise graph

Our new luminance noise graph shows noise levels in both the middle gray and black patches. As you can see up to ISO 1600 the D200 has a fairly similar noise curve as the D2X (surprising considering the different sensor technologies). The main difference between the Nikon's and the Canon EOS 5D (apart from loss of detail due to noise reduction) is shadow noise (the dotted line on these graphs).

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

Chroma (color) noise graph

In addition to measuring luminance noise we now also measure chroma (color) noise. Both the D200 and D2X present a more 'film like' noise response with a mostly monochromatic noise, chroma (color) noise is kept 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 (normalized image) are on the vertical axis.