The photo quality from the S4000 is OK; good enough for small prints and Web use, but questionable for anything else. Though the camera is capable of taking decent snapshots in bright lighting conditions, quality drops off noticeably between ISO 200 and ISO 400 with increased noise and softness. The noise wouldn't be so bad if it didn't cause inconsistencies with color. The noise reduction causes smeared details, and this smearing only gets worse at higher ISOs, making it a poor choice for low-light photos.
In Auto mode there's a Fixed Auto ISO option, letting you limit the camera to using a range between ISO 80-40 or ISO 80-800. I recommend using the 80-400 range whenever you're shooting in a mixed lighting environment and don't feel like switching ISO settings. The camera also seems to have problems focusing. Regardless of mode or even using the tap-to-focus feature, it really struggled to focus on subjects, causing me to refocus again and again before shooting.
These are photos taken seconds apart with Nikon's Scene Auto Selector scene-recognition auto mode. On the left it used a 1/30-second shutter speed at ISO 160. In the photo on the right, the camera raised the sensitivity to ISO 400, presumably to get a higher shutter speed of 1/60 second. Not only is the image now overexposed, but the colors are way off.
At sensitivities at and below ISO 200, the camera produces bright, vibrant, and reasonably accurate colors, though reds seem to blow out. Though clipped highlights are certainly a problem for this camera (as well as many point-and-shoots), exposure is generally OK and white balance is fairly accurate, too.
The S4000's lens offers a good zoom range of 4x going from a 35mm-equivalent 27-108mm. It's enough to help you frame shots or get you a little closer to your subjects. However, with only electronic image stabilization, you really have to be careful when using it in low-light conditions or risk it using a higher ISO.
The wide-angle lens shows a small amount of asymmetrical barrel distortion on the left side (top). There is little discernible distortion when the lens is extended (bottom). Center sharpness is good, but there was visible softness in the top right corner of the lens on my review camera. This is only noticeable when photos are viewed at 100 percent, though.
Purple/blue fringing on high-contrast subjects is typical of this class of camera, but the S4000 displays an above average amount of it. It's especially visible on off-center subjects and background objects.
One of the few photo highlights of this camera is the inclusion of Nikon's D-lighting in Playback. The photo on the right was taken in Auto mode. Processing it through D-lighting in Playback brought out the building details lost in the shadows without overexposing the sky.