Previous page Next page

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 1.5 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-FZ18 (NR STD) vs Fuji S8000 vs Olympus SP560 UZ

Panasonic DMC-FZ18
ISO 80

Fuji S8000
ISO 64

Olympus SP560 UZ
ISO 50

 

Panasonic DMC-FZ18
ISO 100
Fuji S8000
ISO 100
Olympus SP560 UZ
ISO 100
Panasonic DMC-FZ18
ISO 200
Fuji S8000
ISO 200
Olympus SP560 UZ
ISO 200
Panasonic DMC-FZ18
ISO 400
Fuji S8000
ISO 400
Olympus SP560 UZ
ISO 400
Panasonic DMC-FZ18
ISO 800
Fuji S8000
ISO 800
Olympus SP560 UZ
ISO 800
Panasonic DMC-FZ18
ISO 1250
n/a n/a
   
Panasonic DMC-FZ18
ISO 1600
Fuji S8000
ISO 1600

Olympus SP560 UZ
ISO 1600

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).

Once again Panasonic is applying fairly heavy noise reduction at all settings from ISO 100 up, and though the FZ18 doesn't show quite the same level of color smearing at ISO 400+ that we saw with the last generation of FZ cameras it does sacrifice a lot of fine detail in order to keep the noise under control, and at ISO 200 and up the output actually looks less detailed than the 7MP FZ8.

At ISO 100 the output looks a bit grubby close up, with obvious noise reduction artefacts and some smearing of the finest low contrast detail. In a print however or normal on-screen view this will not be a problem. Besides, shooting with the NR set to low (or even better, shooting Raw) allows you to reduce the rather unpleasant 'painterly' effect you see when looking at the actual pixels (viewing at 100%).

At higher ISO settings the Venus III engine 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, though as mentioned above the visible bleeding of colors observed on the FZ8 has been significantly reduced on its new sister camera. All low-contrast chroma information (hair, foliage, fine texture) is lost entirely at ISO 400 and above. How important this is depends on personal preference (and photographic subjects). Outdoor portraits in bright light entirely will look ok, foliage on an overcast day might look a little disappointing. 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's can be very impressive. Just stick to ISO 100 whenever possible.

Low vs Standard NR

As the crops below (and on the next page) show there's little difference between shooting with the noise reduction on 'standard' (the default) or 'low', either in terms of the noise level or in the detail preserved.

 
Panasonic DMC-FZ18
ISO 100
NR Std
Panasonic DMC-FZ18
ISO 100 NR low
100% CROPS
 
Panasonic DMC-FZ18
ISO 200
NR Std
Panasonic DMC-FZ18
ISO 200 NR low
100% CROPS
 
Panasonic DMC-FZ18
ISO 400
NR Std
Panasonic DMC-FZ18
ISO 400 NR low
100% CROPS
 
Panasonic DMC-FZ18
ISO 800
NR Std
Panasonic DMC-FZ18
ISO 800 NR low
100% CROPS

Luminance noise graph

Cameras compared: Panasonic DMC-FZ18, Fuji S8000 FD, Olympus SP650 UZ

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's luminance noise reduction on the FZ18 is more or less in line with the competition, although at low ISO settings the Fuji is noisier but therefore preserves more image detail which is clearly visible in our sample shots.

RGB noise graph

Cameras compared: Panasonic DMC-FZ18, Fuji S8000 FD, Olympus SP650 UZ

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 ISO 100 is low. At ISO 200 and 400 it is virtually the same which is in line with our real world observations, where blurring of chroma noise becomes very obvious at ISO 400 and higher using the default JPEG settings.

Previous page Next page
29
I own it
0
I want it
52
I had it
Discuss in the forums

Comments

Pranay Verma

This is a fantastic camera. Shooting with lights gives a very good output. This camera is not meant for shooting in the night, inspite of that the results are spectacular.

On Diwali (a celebration of lights in India) I shot this video and you would be amazed with the quality. Mind it, this is a VGA output and not 720 or HD.

The link is http://youtu.be/GJGF0nl-7NY

0 upvotes