ISO Sensitivity / Noise levels
Standard Test Scene
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" (gain) on the CCD's signal amplifiers. Nothing is without its price however and doing so also typically increases visible noise (random speckles visible all over the image).
Just like the F700 and S5000 the S7000 appears to use a combination of a noise reduction algorithm and decrease in image sharpening to achieve lower noise levels at higher sensitivities. Additionally the S7000 uses 'pixel binning' (combining adjacent pixel values) to achieve ISO 800 at a forced lower resolution. The combination of strong noise reduction, sharpening decrease and forced low resolution at ISO 800 made it impossible to compare directly against other cameras. Thus instead of posting crops of gray patches I thought it more appropriate to provide examples of what effect this has on image detail.
As you can see from the 100% crops below the S7000's noise reduction system is either softening the images or works in conjunction with the rest of the image processing system to turn down sharpening. Note how the detail in George Washington's face is 'smoothed away' at ISO 400. The ISO 200 and 400 images were taken at the 6MP image size.
|ISO 200, 1/6 sec, F5.6|
|ISO 400, 1/10 sec, F5.6|
|ISO 800, 1/20 sec, F5.6 (Forced 3MP: 2016 x 1512)|
Outdoors in natural light the S7000's automatic white balance was good although tending towards a cooler white balance (slight cyan cast). In incandescent and fluorescent light we saw the same pink / magenta cast. As expected manual preset white balance was as pretty much perfect.
|Outdoors, Auto||Outdoors, Cloudy, Sunny||Outdoors, Manual|
|Incandescent, Auto||Incandescent, Incandescent||Incandescent, Manual|
|Fluorescent, Auto||Fluorescent, FL2, FL1, FL3||Fluorescent, Manual|
Just like the S602 Zoom (and the 6900 Zoom before that) the S7000 has two macro focus modes. Normal macro focus provides a limited zoom range and the least image distortion, Super macro focus provides the closest possible focus distance but is locked at wide angle zoom, this means soft corners and high lens distortion.
Underexposed, in a word. Although fortunately there's no obvious color cast and the S7000 does provide for flash exposure compensation. It looks to me as though the white background behind the hand and color patches shots reflected back the pre-flash used for flash metering.
|Skin tone - No color cast, underexposed||Color patches - No color cast, fairly good color balance, underexposed|
The S7000 appears to use dark frame subtraction noise reduction, this means that the camera uses a second 'dark image' to subtract fixed pattern 'hot pixel' noise from the main image. Interestingly the S7000 exhibited some hot pixels in short exposures but not in longer, this is the opposite of what we expect.
|Manual exposure, ISO 200, 5 sec, F8.0|
|Manual exposure, ISO 200, 10 sec, F8.0|