Previous page Next page

ISO / Sensitivity accuracy

To get an accurate picture of noise levels at different sensitivities it is important to understand just how sensitive the indicated ISO really is. Many cameras differ slightly in sensitivity and that could make the difference between having to use ISO 1600 or 800.

This test 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.

The Olympus E-330 turned out to be about a third of a stop (0.3 EV) more sensitive than indicated, which is the same as the Canon EOS 350D. This in contrast to the E-300 and E-500 which both proved to be the same as their indicated sensitivity.

Indicated
sensitivity
Olympus E-330
(actual sensitivity)
Canon EOS 350D
(actual sensitivity)
Sony DSC-R1
(actual sensitivity)
ISO 100 ISO 125 ISO 125 n/a *
ISO 200 ISO 250 ISO 250 ISO 200
ISO 400 ISO 500 ISO 500 ISO 400
ISO 800 ISO 1000 ISO 1000 ISO 800
ISO 1600 ISO 2000 ISO 2000 ISO 1600
ISO 3200 n/a n/a ISO 3200

* The Sony DSC-R1's lowest sensitivity is ISO 160

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), lighting simulated daylight.

Boosted sensitivities

For the E-330 higher sensitivities are only accessible once the 'ISO boost' has been enabled.Hence outside the recommended sensitivity range. The same is true for some of the other cameras here. We have indicated boosted sensitivities with a double asterisk '**' suffix.

E-330 Noise Filter option

We first explored Olympus's Noise Filter option on the E-500 and weren't terribly impressed. It turned out that even with the Noise Filter option switched off (with ISO Boost set to 'On') the camera was already applying quite a lot of noise reduction, enabling the noise filter simply increased this and softened the image even further. We haven't included noise filter crops below but have plotted the measurement on our graphs.

Olympus E-330 vs. Olympus E-300 vs. Olympus E-500

  • Olympus E-330: Olympus 50 mm F2.0 Macro lens, Aperture Priority, Manual WB,
    Default Parameters (Vivid), JPEG Large / Fine, ISO Boost: On
     
  • Olympus E-300: Olympus 50 mm F2.0 Macro lens, Aperture Priority, Manual WB,
    Default Parameters, JPEG Large / Fine, ISO Boost: On
     
  • Olympus E-500: Olympus 50 mm F2.0 Macro lens, Aperture Priority, Manual WB,
    Default Parameters (Vivid), JPEG Large / Fine, ISO Boost: On
Olympus E-330
ISO 100
(125 equiv.)
Olympus E-300
ISO 100
Olympus E-500
ISO 100
Olympus E-330
ISO 200
(250 equiv.)
Olympus E-300
ISO 200
Olympus E-500
ISO 200
Olympus E-330
ISO 400
(500 equiv.)
Olympus E-300
ISO 400
Olympus E-500
ISO 400
Olympus E-330
ISO 800
(1000 equiv.) **
Olympus E-300
ISO 800
**
Olympus E-500
ISO 800
**
Olympus E-330
ISO 1600
(2000 equiv.) **
Olympus E-300
ISO 1600
**
Olympus E-500
ISO 1600
**

Below ISO 800 it's difficult to distinguish much of a difference between these three Olympus digital SLR's, except for the slight resolution disadvantage the E-330 carries. At ISO 800 the E-330's gray patch looks cleaner but a look at the detail crop reveals why, softening due to noise reduction. At ISO 1600 the E-330's gray and black patches do appear noticeably cleaner but we've lost considerable amounts of detail, and this with the 'Noise Filter' option switched off. It's a pity Olympus have chosen to chase low luminance noise figures at the expense of detail (and without the option to disable / turn down noise reduction).

Olympus E-330 vs. Canon EOS 350D (Digital Rebel XT) vs. Sony DSC-R1

  • Olympus E-330: Olympus 50 mm F2.0 Macro lens, Aperture Priority, Manual WB,
    Default Parameters (Vivid), JPEG Large / Fine, ISO Boost: On
     
  • Sony DSC-R1: Aperture Priority, Manual WB,
    Default Parameters, JPEG Large / Fine

  • Canon EOS 350D: Canon 50 mm F1.4 lens, Aperture Priority, Manual WB,
    Parameters 1 (default), 50 mm F1.4, JPEG Large / Fine
Olympus E-330
ISO 100
(125 equiv.)
Canon EOS 350D
ISO 100
(125 equiv.)
Sony DSC-R1
ISO 160
Olympus E-330
ISO 200
(250 equiv.)
Canon EOS 350D
ISO 200
(250 equiv.)
Sony DSC-R1
ISO 200
Olympus E-330
ISO 400
(500 equiv.)
Canon EOS 350D
ISO 400
(500 equiv.)
Sony DSC-R1
ISO 400
Olympus E-330
ISO 800
(1000 equiv.) **
Canon EOS 350D
ISO 800
(1000 equiv.)
Sony DSC-R1
ISO 800
Olympus E-330
ISO 1600
(2000 equiv.) **
Canon EOS 350D
ISO 1600
(2000 equiv.)
Sony DSC-R1
ISO 1600

Similar results as we observed in the Olympus comparison above, the E-330 looks clean and almost as detailed as the EOS 350D up to ISO 400 but beyond that the blurring effect of the cameras noise reduction has a seriously detrimental effect on detail. (Note: the DSC-R1's lowest sensitivity is ISO 160 and also has an ISO 3200 option).

Previous page Next page
53
I own it
1
I want it
45
I had it
Discuss in the forums

Comments