ISO Sensitivity / Noise levels

ISO equivalence on a digital camera is the ability to increase the sensitivity of the sensor to enable faster shutter speeds and/or better performance in low light. The way this works in a digital camera is by "turning up the volume" on the CCD's signal amplifiers. Nothing is without its price however and doing so also amplifies any noise that may be present and often affects colour saturation.

Compared to the DSC-F707 the DSC-F717 expands the available sensitivity range by adding ISO 800. Thus you now have the option of ISO 100, 200, 400 and 800.

Our noise comparison test involves shooting a colour patch chart (a GretagMacBeth ColorChecker) at the full range of ISO sensitivities and then measuring luminance and RGB noise at a 'mid' grey patch.

Note that our new test now provides a graph of luminance noise for each sensitivity as well as individual RGB channel noise.

Sony DSC-F717 vs. Nikon Coolpix 5700

Image sharpening set to 'Normal' on both cameras, white balance preset other settings as default, Aperture priority with a -0.3 EV exposure compensation. Measurements taken at approximately 21°C (~70°F). Lighting was daylight.

	ISO 100
	Sony DSC-F717 1/80 sec, F4.5	Nikon Coolpix 5700 1/82 sec, F4.7
Original crop
Red channel
Green channel
Blue channel
	ISO 200
	Sony DSC-F717 1/160 sec, F4.5	Nikon Coolpix 5700 1/157 sec, F4.7
Original crop
Red channel
Green channel
Blue channel
	ISO 400
	Sony DSC-F717 1/250 sec, F4.5	Nikon Coolpix 5700 1/294 sec, F4.7
Original crop
Red channel
Green channel
Blue channel
	ISO 800
	Sony DSC-F717 1/500 sec, F4.5	Nikon Coolpix 5700 1/627 sec, F4.7
Original crop
Red channel
Green channel
Blue channel

As far as we know both cameras use the same 2/3" CCD sensor, although the DSC-F717 uses a primary colour filter array (RGB filters) and the Coolpix 5700 uses a complementary colour filter array (CYGM filters). It appears as though the F717's noise reduction systems keep visible noise under control, especially at higher sensitivities. A quick look at the graph below hints that the benefits of such noise reduction begin to have a noticeable effect from ISO 400 upwards. Certainly the DSC-F717's ISO 400 and 800 crops are cleaner than that from the Coolpix 5700.

Luminance noise graph

Note that ISO sensitivity is on the horizontal axis of this graph.

RGB noise graph

Note that ISO sensitivity is on the vertical axis of this graph. Interesting to see that although the DSC-F717 does an admirable job of keeping green and blue channel noise under control that red channel noise increases relatively to them. This could lead to otherwise clean shadow areas with some visible red 'mottle' effect.

White Balance

The DSC-F717 gets the new set of white balance presets introduced into the current generation of Sony Cybershot digital cameras. This means an improvement from just two presets (indoors, outdoors) to four (daylight, cloudy, fluorescent and tungsten), this now brings the DSC-F717 in line with other brand prosumer digital cameras. Additionally there is of course Auto white balance and Manual preset which can be quickly set by pressing the 'one touch' button on the lens barrel.

While the manual white balance is excellent the pre-programmed presets are less sucessful and auto white balance can't really cope in anything other than natural light. Sony still has some way to go in this respect.

Outdoors, Auto	Outdoors, Sunny (or Cloudy)	Outdoors, Manual
Incandescent, Auto	Incandescent, Incandescent	Incandescent, Manual
Fluorescent, Auto	Fluorescent, Fluorescent	Fluorescent, Manual