Previous page Next page

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.

Like many recent digital SLRs all four in this comparison proved to be right on the spot with their indicated sensitivity, that is to say an indicated sensitivity of say ISO 200 was exactly that (unlike some older digital SLRs which were slightly more or less sensitive than indicated).

Indicated
sensitivity
Nikon D300
(actual sensitivity)
Sony DSLR-A700
(actual sensitivity)
Canon EOS 40D
(actual sensitivity)
Olympus E-3
(actual sensitivity)
ISO 100 ISO 100 ISO 100 ISO 100 ISO 100
ISO 200 ISO 200 ISO 200 ISO 200 ISO 200
ISO 400 ISO 400 ISO 400 ISO 400 ISO 400
ISO 800 ISO 800 ISO 800 ISO 800 ISO 800
ISO 1600 ISO 1600 ISO 1600 ISO 1600 ISO 1600
ISO 3200 ISO 3200 ISO 3200 ISO 3200 ISO 3200
ISO 6400 ISO 6400 ISO 6400 n/a 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.

Nikon D300 vs. Canon EOS 40D vs. Sony DSLR-A700 vs. Olympus E-3

  • Nikon D300: Nikkor 50 mm F1.4 lens, Manual exposure, Manual WB,
    Default Parameters (Normal), High ISO NR (Normal), JPEG Large / Fine
     
  • Canon EOS 40D: Canon 50 mm F1.4 lens, Manual exposure, Manual WB,
    Default Parameters (Standard), High ISO NR (Default; Off), JPEG Large / Fine
     
  • Sony DSLR-A700: Minolta 50 mm F1.4 lens, Manual exposure, Manual WB,
    Default Parameters (Standard), High ISO NR (Normal - default), JPEG Large / Fine
     
  • Olympus E-3: Olympus 50 mm F2.0 Macro lens, Manual exposure, Manual WB,
    Default Parameters (Natural), JPEG Large / Fine
Nikon D300
ISO 100
Canon EOS 40D
ISO 100
Sony DSLR-A700
ISO 100
Olympus E-3
ISO 100
Nikon D300
ISO 200
Canon EOS 40D
ISO 200
Sony DSLR-A700
ISO 200
Olympus E-3
ISO 200
Nikon D300
ISO 400
Canon EOS 40D
ISO 400
Sony DSLR-A700
ISO 400
Olympus E-3
ISO 400
Nikon D300
ISO 800
Canon EOS 40D
ISO 800
Sony DSLR-A700
ISO 800
Olympus E-3
ISO 800
Nikon D300
ISO 1600
Canon EOS 40D
ISO 1600
Sony DSLR-A700
ISO 1600
Olympus E-3
ISO 1600
Nikon D300
ISO 3200
Canon EOS 40D
ISO 3200
Sony DSLR-A700
ISO 3200
Olympus E-3
ISO 3200
Nikon D300
ISO 6400
Canon EOS 40D
n/a
Sony DSLR-A700
ISO 6400
Olympus E-3
n/a

From ISO 100 to 400 there is virtually no difference from a noise point of view between any of these cameras, none exhibit noticeable any noise. Indeed visible noise only begins to creep into the D300 shots at around ISO 1600, at which point it has a very 'natural' monochromatic grain appearance (not want to be too cliched but 'film like'). At ISO 3200 the effects of the D300's noise reduction are more obvious if you look closely at the detail crop. ISO 6400 really is only for the brave or those emergency situations. It has to be said that out of these four cameras the D300 has the nicest appearance to its higher sensitivity images, Nikon's decision to preserve as much luminance detail as possible by using mostly chroma noise reduction really pays off.

* These results are with the cameras in their default modes, the EOS 40D for example does have an optional stronger chroma noise reduction option which delivers images with almost no chroma noise.

Noise graphs

Note that we normally show both gray and black results on the same graph, comparing four cameras this became too difficult to read hence we have two separate graphs, one for the gray patch (middle gray) and one for the black patch (shadows).

Luminance noise graph (gray patch)

The D300's noise reduction kicks in at ISO 800 from their upwards noise around the middle gray level increases in a steady manner to ISO 3200 then there's a fairly obvious jump at ISO 6400 (which can also be seen in the crops above as fine grain).

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

Luminance noise graph (black patch)

Much the same story for the black patch (which generally represents shadow noise), noise reduction drops the noise level at ISO 800, consistent growth from there to ISO 3200 then a jump at ISO 6400.

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

Chroma (color) noise graph

Because the D300's noise reduction appears to be mostly chroma based we get the biggest change in noise levels when measuring chroma (color) noise, at ISO 800 chroma noise is actually lower than at ISO 200.

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

Previous page Next page
768
I own it
10
I want it
437
I had it
Discuss in the forums

Comments