ISO Sensitivities & Noise
ISO equivalence on a digital camera is the ability to increase
the sensitivity of the CCD to allow for 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.
 The
Coolpix 5000 features four selectable ISO sensitivities of 100, 200, 400
and 800 as well as Auto mode which varies the sensitivity depending on
available light. Note that although available ISO 800 is not recommended
and shows up in red colour on the LCD monitor when selected.
I decided to use the same system created for our EOS-1D preview. This
involves shooting our standard colour patches in average light (9 EV)
at the full range of ISO sensitivities. I have chosen to compare the ISO
noise levels of the Coolpix 5000 to two other five megapixel digital cameras,
the Olympus E-20 and Sony DSC-F707.
Each of the "Patch crops" below are made up of a 100 x 80
section of patches 1, 7 (M) and 17 of the greyscale of our colour patches
(as shown above). This helps to give a better impression of noise at different
light levels within an image. Directly below this you will find the average
standard deviation of these three patches, this is a quantifiable measurement
of noise.
| Camera |
Nikon CP-5000 |
Olympus E-20 |
Sony DSC-F707 |
| Sensitivity |
ISO 100 |
ISO 80 |
ISO 100 |
| Exposure |
1/24 s, F4.4 |
1/8 s, F4.5 |
1/10 s, F4.5 |
| Patch crops |
 |
| Std dev. |
1.83 |
1.82 |
1.43 |
| |
|
|
|
| Camera |
Nikon CP-5000 |
Olympus E-20 |
Sony DSC-F707 |
| Sensitivity |
ISO 200 |
ISO 160 |
ISO 200 |
| Exposure |
1/49 s, F4.4 |
1/15 s, F4.5 |
1/20 s, F4.5 |
| Patch crops |
 |
| Std dev. |
3.21 |
2.08 |
2.18 |
| |
|
|
|
| Camera |
Nikon CP-5000 |
Olympus E-20 |
Sony DSC-F707 |
| Sensitivity |
ISO 400 |
ISO 320 |
ISO 400 |
| Exposure |
1/85 s, F4.4 |
1/30 s, F4.5 |
1/30 s, F4.5 |
| Patch crops |
 |
| Std dev. |
5.02 |
2.51 |
2.30 |
| |
|
|
|
| Camera |
Nikon CP-5000 |
Olympus E-20 |
Sony DSC-F707 |
| Sensitivity |
ISO 800 |
n/a |
n/a |
| Exposure |
1/172 s, F4.4 |
n/a |
n/a |
| Patch crops |
 |
| Std dev. |
9.11 |
n/a |
n/a |
As you can see by the visual and measured (standard deviation)
comparison above (and graph below) the Coolpix 5000 has very similar noise
levels to the other five megapixel digital cameras at ISO 100 but quickly
departs from the competition with significantly more noise from ISO 200
upwards. This is a disappointing performance from Nikon's latest "top
model".
Note: the higher shutter speeds on the Coolpix 5000 shots
can be attributed the fact that they were shot later in the day when more
light was available (shot in natural light).
A graph of the average standard deviation versus ISO
sensitivity is shown below.
White Balance
As with most digital cameras the Coolpix 5000's automatic
white balance works best under natural light. That said it did put in
a better performance under artificial light than the Coolpix 995 (which
had a strong pink cast under incandescent light and a yellow cast under
fluorescent). The pre-programmed white balance settings are fairly accurate
and of course the advantage with the 5000 is that you can always fine
tune these to exactly match your lighting. As we would expect the manual
white balance worked best.
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