ISO Sensitivity / Noise levels

Standard Test

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 measurement tool which measures the standard deviation (normalized) of the middle gray patch (indicated by the red rectangle above). Additionally we now have a 'detail crop', this is currently a postage stamp (lots of fine detail) but we may replace this at a future date. Note that noise values indicated on the graphs below should 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)

Konica Minolta Maxxum 7D vs. Nikon D70 (ISO 100 - 1600)

• Konica Minolta 7D: Minolta 50 mm F1.4 lens, Aperture Priority, Manual WB,
  Default Parameters, JPEG Large / Fine
  
• Nikon D70: Nikkor 50 mm F1.4 lens, Aperture Priority, Manual WB,
  Default Parameters, JPEG Large / Fine

	Konica Minolta 7D ISO 100, 1/100 sec, F3.5	Nikon D70 n/a
Crops
	Konica Minolta 7D ISO 200, 1/200 sec, F3.5	Nikon D70 ISO 200, 1/200 sec, F3.5
Crops
	Konica Minolta 7D ISO 400, 1/400 sec, F3.5	Nikon D70 ISO 400, 1/400 sec, F3.5
Crops
	Konica Minolta 7D ISO 800, 1/800 sec, F3.5	Nikon D70 ISO 800, 1/800 sec, F3.5
Crops
	Konica Minolta 7D ISO 1600, 1/1600 sec, F3.5	Nikon D70 ISO 1600, 1/1600 sec, F3.5
Crops

Two different approaches to dealing with similar levels of noise. Nikon has chosen the purer approach, less noise reduction but better detail throughout the sensitivity range. Konica Minolta has chosen some noise reduction and by the looks of things some automatic reduction of sharpening at higher sensitivities. The other primary difference between the two is the type of noise, the D70's noise is fairly uniformly monochromatic where as the 7D's appears as colored blotches (most noticeable at ISO 1600 and above).

Konica Minolta Maxxum 7D vs. Canon EOS 20D (ISO 100 - 3200)

• Konica Minolta 7D: Minolta 50 mm F1.4 lens, Aperture Priority, Manual WB,
  Default Parameters, JPEG Large / Fine
  
• Canon EOS 20D: Canon 50 mm F1.4 lens, Aperture Priority, Manual WB,
  Parameters 1 (default), JPEG Large / Fine

	Konica Minolta 7D ISO 100, 1/100 sec, F4	Canon EOS 20D ISO 100, 1/100 sec, F4
Crops
	Konica Minolta 7D ISO 200, 1/200 sec, F4	Canon EOS 20D ISO 200, 1/200 sec, F4
Crops
	Konica Minolta 7D ISO 400, 1/400 sec, F4	Canon EOS 20D ISO 400, 1/400 sec, F4
Crops
	Konica Minolta 7D ISO 800, 1/800 sec, F4	Canon EOS 20D ISO 800, 1/800 sec, F4
Crops
	Konica Minolta 7D ISO 1600, 1/1600 sec, F4	Canon EOS 20D ISO 1600, 1/1600 sec, F4
Crops
	Konica Minolta 7D ISO 3200, 1/3200 sec, F4	Canon EOS 20D ISO 3200, 1/3200 sec, F4
Crops

The 7D has the visibly cleaner gray patch but it also appears to be losing some detail to its stronger noise reduction algorithms and drop off in automatic sharpening. The EOS 20D maintains good detail through to ISO 1600 where the 7D's image has become quite soft. At ISO 3200 (the 7D's "boost sensitivity") colored red and blue speckles are fairly noticeable on the gray patches.

Luminance noise graph

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

RGB noise graph

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.