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ISO / Sensitivity accuracy

The actual sensitivity of each indicated ISO is measured 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 a calibrated Sekonic L-358), middle gray matched. We estimate the accuracy of these results to be +/- 1/6 EV. These tests are based on the sRGB JPEG output of the cameras, in accordance with ISO 12232:2006, the standard used by camera manufacturers.

Indicated
ISO value
Sony NEX 3/5
measured value
Olympus E-PL1
measured value
Panasonic GF1
measured value
ISO 200
ISO 250
ISO 200
ISO 250
ISO 400
ISO 500
ISO 400
ISO 500
ISO 800
ISO 1000
ISO 800
ISO 1000
ISO 1600
ISO 2000
ISO 1600
ISO 2000
ISO 3200
ISO 4000
ISO 3200
ISO 4000
ISO 6400
ISO 8000
   
ISO 12800
ISO 16000
   

In these tests both Sonys produced images at least a third of a stop brighter than you would expect for a given aperture and shutter speed combination, hence their ISO ratings are above the stated values. However, in real-world use, the camera has a strong tendancy to choose shutter speed and aperture combinations that result in overexposed images.

JPEG 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.

Sony NEX-3 vs. Olympus E-P1 vs. Samsung NX10 vs. Canon EOS 550D

  • Sony NEX-3: Sony 50 mm F1.4 lens (via adapter), Manual Exposure,
    JPEG Fine, Manual WB, Default Parameters (Standard), Self-Timer
     
  • Olympus E-PL1: Olympus 50 mm F2 Macro lens (via adapter), Manual Exposure,
    JPEG Large/SHQ, Manual WB, Default Parameters (Standard), Self-Timer with Anti-Shock
     
  • Samsung NX10: Pentax 50mm F1.4 (via adapter), Manual Exposure, WB tuned to neutral,
    Default Parameters, Standard Picture Wizard, NR Off, JPEG 14MP / Super Fine

  • Canon EOS 550D: Canon 50 mm F1.4 USM lens, Manual Exposure, Manual WB,
    Default Parameters, High ISO NR (Normal), JPEG Large / Fine
  Sony NEX Olympus E-PL1 Samsung NX10 Canon EOS 550D
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200
ISO 6400    
ISO 12800    

The NEX produces results very that match the Canon very closely, showing similar amounts of noise and detail all across the ISO range (though with slightly lower chroma noise at the very highest settings). Although its images have slightly less noise than the smaller sensored Olympus, its images don't appear to have much more detail - so although its performance is very good, it doesn't stand out massively from its peers.

RAW noise

Here we look at the RAW files processed through Adobe Camera Raw (in this case version 6.2 Beta). Images are brightness matched and processed with all noise reduction options set to zero. Adobe does a degree of noise reduction even when the user-controlled NR is turned off.

The amount of NR applied 'under the hood' is not high, but it does vary by camera (Adobe is attempting to normalise output across different sensors), so we are still looking at a balance of noise and noise reduction, rather than pure noise levels. However, the use of the most popular third-party RAW converter is intended to give a photographically relevant result, rather than simply comparing sensor performance in an abstract manner.

  Sony NEX Olympus E-PL1 Samsung NX10 Canon EOS 550D
ISO 200
ISO 400
ISO 800
ISO 1600
ISO 3200
ISO 6400    
ISO 12800    

As we saw with the JPEG files, the NEX raw noise levels are comparable, even a fraction lower, than the previously class-leading Canon Rebel T2i. Noise remains managably low even at ISO 3200, clearly showing why the highest two settings produce such indistinct results in JPEG mode.

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Comments

Total comments: 2
prossi
By prossi (1 week ago)

Silver award...really?

Comment edited 25 seconds after posting
0 upvotes
Rowland Scherman
By Rowland Scherman (3 months ago)

Sony NEX-5TL?

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Total comments: 2