ISO Sensitivity / Noise levels

Standard Test

ISO equivalence on a digital camera is the ability to increase the sensitivity of the sensor to enable faster shutter speeds and/or better performance in low light. The way this works in a digital camera is by "turning up the volume" (gain) on the CCD's signal amplifiers. Nothing is without its price however and doing so also typically increases visible noise (random speckles visible all over the image).

We are now using a more reliable, repeatable and neutral method for evaluating noise. Shots are taken in daylight lighting in our studio. Noise is measured as the standard deviation of the medium gray patch on a Gretag MacBeth ColorChecker chart. The image is normalized before measurement of noise to remove the possibility of figures being affected by image contrast (one method of masking noise). Note that noise numbers shown on the graphs below can not be compared to those in older reviews.

Test notes:

• Shots taken at approximately 21°C (~70°F)
• Lighting was simulated daylight
• Manual white balance
• Aperture Priority (aperture selected to achieve identical shutter speeds)

Pentax *ist D vs. Canon EOS-10D

• Pentax *ist D: Pentax 50 mm F1.4 lens, Aperture Priority (F3.5), Manual WB,
  Default Parameters, JPEG Large /
   
• Canon EOS 10D: Canon 50 mm F1.4 lens, Aperture Priority (F3.5), Manual WB,
  Default Parameters (Standard), JPEG Large / Fine

	Pentax *ist D n/a	Canon EOS 10D ISO 100, 1/100 sec, F3.5
Partial crop
Red Green Blue channels
	Pentax *ist D ISO 200, 1/200 sec, F3.5	Canon EOS 10D ISO 200, 1/200 sec, F3.5
Partial crop
Red Green Blue channels
	Pentax *ist D ISO 400, 1/400 sec, F3.5	Canon EOS 10D ISO 400, 1/400 sec, F3.5
Partial crop
Red|Green|Blue channels
	Pentax *ist D ISO 800, 1/800 sec, F3.5	Canon EOS 10D ISO 800, 1/800 sec, F3.5
Partial crop
Red Green Blue channels
	Pentax *ist D ISO 1600, 1/1600 sec, F3.5	Canon EOS 10D ISO 1600, 1/1600 sec, F3.5
Partial crop
Red Green Blue channels
	Pentax *ist D ISO 3200, 1/3200 sec, F3.5	Canon EOS 10D ISO 3200, 1/3200 sec, F3.5
Partial crop
Red Green Blue channels

In comparison the *ist D appears to match the EOS 10D up to ISO 800, after that noise levels are slightly higher (although nothing particularly significant). It looks as though the *ist D has more noise in the red channel, and this dominates the noise pattern at ISO 1600 and 3200.

Pentax *ist D vs. Nikon D100

• Pentax *ist D: Pentax 50 mm F1.4 lens, Aperture Priority (F3.5), Manual WB,
  Default Parameters, JPEG Large /
   
• Nikon D100: Nikkor 50 mm F1.4 lens, Aperture Priority (F3.2), Manual WB,
  Default Parameters, JPEG Large / Fine

	Pentax *ist D ISO 200, 1/200 sec, F3.5	Nikon D100 ISO 200, 1/200 sec, F3.2
Partial crop
Red Green Blue channels
	Pentax *ist D ISO 400, 1/400 sec, F3.5	Nikon D100 ISO 400, 1/400 sec, F3.2
Partial crop
Red|Green|Blue channels
	Pentax *ist D ISO 800, 1/800 sec, F3.5	Nikon D100 ISO 800, 1/800 sec, F3.2
Partial crop
Red Green Blue channels
	Pentax *ist D ISO 1600, 1/1600 sec, F3.5	Nikon D100 ISO 1600, 1/1600 sec, F3.2
Partial crop
Red Green Blue channels
	Pentax *ist D ISO 3200, 1/3200 sec, F3.5	Nikon D100 ISO 3200, 1/3200 sec, F3.2
Partial crop
Red Green Blue channels

As we would expect the *ist D and D100 have very similar noise graphs (below) as both cameras share the same CCD sensor. That said the D100 does appear to manage noise better at ISO 1600 and 3200, perhaps through in-camera noise reduction, note that the angle of the D100 graph remains the same between ISO 800 and 1600.

Luminance noise graph

Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity (normalized) on the vertical axis. Note that we have standardized on a 0-10 scale.

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) are on the vertical axis. Note that we have standardized on a 0-10 scale.