Canon EOS 40D Review: 18. Photographic tests: Digital Photography Review

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.

Unlike the EOS 30D the EOS 40D proved to have the same sensitivity as indicated, much in line with what we've seen from other recent Canon digital SLRs and has been the case for most other brand SLRs.

Indicated sensitivity	Canon EOS 40D (actual sensitivity)	Nikon D200 (actual sensitivity)	Pentax K10D (actual sensitivity)
ISO 100	ISO 100	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	ISO 3200	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). Room temperature is approximately 22°C (~72°F), simulated daylight lighting.

Canon EOS 40D vs. Nikon D200 vs. Pentax K10D

Canon EOS 40D: Canon 50 mm F1.4 lens, Aperture Priority, Manual WB,
Default Parameters (Standard PS), High ISO NR (Default; Off), JPEG Large / Fine
Nikon D200: Nikkor 50 mm F1.4 Macro lens, Aperture Priority, Manual WB,
Default Parameters (Normal), High ISO NR (Normal), JPEG Large / Fine
Pentax K10D: Pentax 50 mm F1.4 lens, Aperture Priority, Manual WB,
Default Parameters (Natural), JPEG Large / Fine

Canon EOS 40D ISO 100	Nikon D200 ISO 100	Pentax K10D ISO 100


Canon EOS 40D ISO 200	Nikon D200 ISO 200	Pentax K10D ISO 200


Canon EOS 40D ISO 400	Nikon D200 ISO 400	Pentax K10D ISO 400


Canon EOS 40D ISO 800	Nikon D200 ISO 800	Pentax K10D ISO 800


Canon EOS 40D ISO 1600	Nikon D200 ISO 1600	Pentax K10D ISO 1600


Canon EOS 40D ISO 3200	Nikon D200 ISO 3200	Pentax K10D n/a

From ISO 100 to 400 there's very little to choose between these three cameras, at ISO 800 we begin to see some chroma noise in the K10D's gray crop as well as the effects of luminance noise reduction in the detail of the D200 crop. At ISO 1600 the difference grows, the EOS 40D and K10D maintaining more detail than the D200 but both with more visible chroma noise (thanks to Nikon's stronger chroma noise reduction). At ISO 3200 the 40D is looking much better than the D200 with considerably better detail reproduction and lower (although color mottled; this can be reduced, see next page) noise levels overall.

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

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

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