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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.)

Panasonic DMC-FZ8 vs Panasonic DMC-FZ7 vs Canon S3 IS

Panasonic DMC-FZ8
ISO 80

Panasonic DMC-FZ7
ISO 80

Sony DSC-H5
ISO 80

 

Panasonic DMC-FZ8
ISO 100
Panasonic DMC-FZ7
ISO 100
Sony DSC-H5
ISO 100
Panasonic DMC-FZ8
ISO 200
Panasonic DMC-FZ7
ISO 200
Sony DSC-H5
ISO 200
Panasonic DMC-FZ8
ISO 400
Panasonic DMC-FZ7
ISO 400
Sony DSC-H5
ISO 400
Panasonic DMC-FZ8
ISO 800
Panasonic DMC-FZ7
ISO 800
Sony DSC-H5
ISO 800
Panasonic DMC-FZ8
ISO 1250
n/a Sony DSC-H5
ISO 1000
 
Panasonic DMC-FZ8
ISO 3200
Panasonic DMC-FZ7
ISO 1600
n/a
 

With tiny, high pixel count chips noise is always going to be an issue, and to a large degree this is more a test of the effectiveness (both measurable and visible) of a camera's noise reduction system. Designers have to balance the desire to produce smooth, clean results with the need to retain as much detail as possible (if you blur away the noise, you blur away image detail too).

At ISO 100 the FZ8 produces output that is very similar to its predecessor, and not that different to any of its direct competitors, noise-wise. Once you get to ISO 400 the difference in noise reduction between this camera and its predecessor is distinct; it looks a lot less noisy, but the chroma blurring used by the Venus III engine has a destructive effect on low contrast detail and color information. Obviously ISO 800 is a huge improvement on the FZ7, though I prefer the noisier, but more detailed approach taken by Sony with the H5 (and Canon with the S3 IS for that matter). ISO 1250 is firmly in the 'emergency use only' camp, whilst ISO 3200 is so bereft of detail you'd be better off with a camera phone.

So then, does the Venus III's much-trumpeted two stage noise reduction system work - and more importantly, is it producing pleasing photographic results? The answer isn't that simple.

At ISO 100 the FZ8 - like other current Lumix models - looks a bit grubby close up, with obvious noise reduction artefacts. But it's only really a problem at the 'pixel peeping' level; if you produce prints or reduce the images to fit on-screen you won't see it. Besides, shooting with the NR set to low (or even better, shooting Raw) allows you to reduce - or eliminate - the rather unpleasant 'painterly' effect you see when looking at the actual pixels (viewing at 100%).

At higher ISO settings it's less clear-cut. The Venus III splits the luminance (brightness) from the chroma (color) information in the image, and applies heavy noise reduction to the latter. This has the effect - in theory - of removing the unsightly 'digital looking' multicolored speckled noise without affecting the grainy 'photographic looking' noise. Since, in theory, the detail in the scene is mostly found in the luminance channel, and luminance noise doesn't look that offensive anyway, this is an admirable and sensible approach to noise reduction.

The problem is that the amount of chroma 'smearing' is so high that images with very detailed color information lose an awful lot of texture, and there is visible bleeding of colors. All low-contrast chroma information (hair, foliage, fine texture) is lost entirely at ISO 400 and above. How important this is depends entirely on the content of the picture you're taking, and the amount of low contrast / color in the shot. Fill the frame with someone's face in bright light and it looks OK, but try to take a landscape on a dull day and you're going to be disappointed. The effect on very detailed scenes is like someone trying to do a 'paint by numbers' with a brush that's too big and paint that's too watered down. And yet at other times, when the majority of the information is contained in the luminance channel, the result is superb.

Luminance noise graph

Cameras compared: Panasonic DMC-FZ8, Panasonic DMC-FZ7, Sony Cyber-Shot DSC-H5

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

As observed from our samples Panasonic is using far less luminance noise reduction than it has before, so it is actually quite high compared to its predecessor and most competitor product. This is no bad thing; the noise is always going to be there, and the use of lower NR helps preserve detail.

RGB noise graph

Cameras compared: Panasonic DMC-FZ8, Panasonic DMC-FZ7, Sony Cyber-Shot DSC-H5

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.

Chroma noise at lower ISO settings is low, and at ISO 400 is actually lower than it is at ISO 100; this is in line with our real-world observations that chroma noise is heavily blurred away using the default JPEG settings.

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Comments

Roald46
By Roald46 (11 months ago)

You can find a VIDEO test of the LUMIX DMC-FZ72 here:
http://youtu.be/csSFrNPx2CI
Filmed in 1920 x 1080 50i

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