ISO Sensitivity / Noise levels

ISO equivalence on a digital camera is the ability to increase the sensitivity of the sensor. This 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 (i.e. ISO 200, 1/200 sec for consistency of exposure between cameras). The image sequence is run through our own proprietary noise measurement tool (version 1.6 in this review). Click here for more information. Room temperature is approximately 22°C (~72°F), simulated daylight lighting.

Canon EOS 7D vs. Canon EOS 50D vs. Nikon D300s vs. Pentax K-7

  • Canon EOS 7D: Canon 50 mm F1.4 lens, Aperture Priority, Manual WB,
    Default Parameters (Standard PS), High ISO NR Default (Standard), JPEG Large / Fine
     
  • Canon EOS 50D: Canon 50 mm F1.4 lens, Aperture Priority, Manual WB,
    Default Parameters (Standard PS), High ISO NR Default (Standard), JPEG Large / Fine
     
  • Nikon D300S: Nikkor 50 mm F1.4 G lens, Manual Exposure, Manual WB,
    Default Parameters (Normal), High ISO NR (Normal), JPEG Large / Fine

  • Pentax K-7: Pentax 50 mm F1.4 lens, Manual Exposure, Manual WB,
    Default Parameters (Bright), High ISO NR default (Medium), JPEG Large / Premium
  Canon EOS 7D Canon EOS 50D Nikon D300S Pentax K-7
ISO 100
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200
ISO 6400
ISO 12800    

Up to ISO 800 the differences between the competitors are pretty marginal. The only camera that is visibly noisier than the rest is the Pentax K-7. As we go up the sensitivity scale the gap between the Pentax and the others widens even more but the two Canons and the Nikon D300S stay pretty close. As usual the Nikon maintains a very good balance between noise and image detail up to the highest sensitivities. The EOS 50D's approach to noise reduction is more heavy-handed and results in more blurring of fine detail than on the Nikon. Despite its higher nominal resolution and therefore smaller pixel-pitch, the EOS 7D produces a marginally cleaner image than its sister model at higher ISOs, but crucially also manages to retain some more image detail.

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All in all the EOS 7D is, considering its impressively high resolution for an APS-C camera, doing a very decent job. On a pixel level it shows comparable amounts of both luminance and chroma noise to its most direct competitor, the Nikon D300S, but its higher nominal resolution will give it an advantage when printing or displaying an image on a screen. Images taken with the two very high test ISO settings are not always pretty to look at. However, the two 'Hi' settings are there in case you need them and the output is certainly usable at smaller sizes.

Noise graphs

The graphs below pretty much confirm what we have seen in the sample crops above. In numerical terms the two Canons and the Nikon are pretty much on the same level up to the very highest sensitivities where the EOS 7D has a measurable and visible advantage over the 50D. The Pentax K-7 is by far the worst performer at higher ISOs in this comparison.

  Canon EOS 7D
Chroma
Black
Gray
Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity on the vertical axis.

RAW noise

Finally let's take a look a the EOS 7D's RAW output next to the competition. Removing any in-camera noise reduction and processing the images using Adobe Camera Raw (V5.6 Beta in this case, all NR set to 0) gives us the nearest thing to a 'level playing field' for assessing the relative noise levels of the four cameras' sensors.

With noise reduction turned off we get a more accurate idea of how noisy these sensors are and the image looks slightly different to what we've seen above in the JPEG section of this page. The Pentax K-7 is much closer to the pack but it also becomes clear that the 7D produces a cleaner image than the 50D and, at very high ISOs, also than the D300S. This explains to a degree the 50D's slightly softer JPEG output at high ISOs. Its JPEG engine has to apply more chroma noise reduction than on the 7D in order to get noise onto the same level.

  Canon EOS 7D RAW Canon EOS 50D RAW Nikon D300S RAW Pentax K-7 RAW
ISO 100
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200
ISO 6400
ISO 12800    

Raw Noise graphs

Again, the graphs below confirm what we can see in the sample crops. The 50D produces more chroma noise than the EOS 7D at higher ISOs. The Pentax K-7 is still slightly worse than the Nikon and EOS 7D at very high ISOs but the gap is smaller in RAW. At high ISOs the the 7D and its closest rival, the Nikon D300S, are more or less level in terms of chroma noise.

  Canon EOS 7D
Chroma
Black
Gray
Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity on the vertical axis.