ISO Sensitivity / Noise levelsISO 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.
Canon PowerShot SX1IS vs Canon PowerShot SX10 IS vs Sony DSC-HX1 vs Panasonic Lumix FZ28
Noise has always been an issue with small sensor digital cameras, and none of the four cameras shown here buck that trend - so if you were hoping that using a CMOS sensor would transform the performance of the SX1 then you're out of luck. Canon has had a history of low noise at high ISO with CMOS sensors in its EOS range of cameras, but unfortunately this does not translate to the 1/2.5" sensor in the SX1 IS. The new Digic 4 processor is working hard to reduce the amount of noise visible in the image, and this, combined with the large amount of noise, means that as ISO settings climb above 200 the amount of detail remaining in the image is greatly reduced. Compared to its sibling the SX10 IS, there is no visible advantage to using CMOS technology. In fact quite the opposite; the SX10 IS retains more detail, and less noisy at all ISO settings. The noise reduction of the Sony HX1 (the only other camera in the group with CMOS technology) really kicks in at ISO 200, which produces less visible noise in flat areas, but also means it has more trouble retaining fine detail than the Canon cameras. At lower ISO settings the Panasonic beats the SX1, narrowly, but once you get over ISO 200 the difference is marginal. ISO 1600 is an emergency setting on all these cameras, but if you were to pick a camera to shoot ISO 800 (which can be used for small prints and web) the SX10 IS would be the top choice. Luminance noise graphCameras compared:
Indicated ISO sensitivity is on the horizontal axis of this graph, standard deviation of luminosity is on the vertical axis. What is evident from this graph is that the current generation of superzoom cameras actually only differ slightly on the amount of measured noise, and it mostly depends where the noise reduction really kicks in. At all ISO settings, the SX10 IS produces less measured noise than the SX1 IS. 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 is on the vertical axis. The SX1 IS is consistently the noisiest camera in terms of RGB noise at all ISOs other then ISO 1600 compared to all the other cameras in this graph, which is the same thing that we saw in the luminance graph. Low contrast detailWhat the crops and graph don't show is the effect of noise reduction on low contrast fine detail such as hair, fur or foliage. An inevitable side effect of noise removal is that this kind of detail is also blurred or smeared, resulting in a loss of 'texture'. In this test the crops below show the effect of the noise reduction on such texture (hair) as you move up the ISO range.
What these crops show is that even at base ISO the SX1 IS is applying some noise reduction, smearing the fine detail in hair. From ISO 200 you are losing more and more fine detail, and by the time you reach ISO 1600 there is just a watercolor smudge of colour. This is one of the problems associated with packing 10 million pixels onto such a small sensor, and one that has not been overcome with the use of COMS technology. |
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