Panasonic ZS100 Optics

Zoom
A 10x zoom, with mixed optical performance.

The Panasonic ZS100 is equipped with a 9.1-91mm lens, offering an optical zoom ratio of 10x, translating to a 35mm-equivalent focal range of about 25-250mm. The lens features a maximum aperture ranging from a relatively fast f/2.8 at wide angle to a somewhat dim f/5.9 at telephoto. As is often the case, maximum aperture does fall-off rather quickly as you zoom, already reaching f/5.9 at around 160mm equivalent. The following table reflects the maximum and minimum apertures as reported by the camera at various focal lengths:

Far-field performance is pretty good at 25mm equivalent at f/5.6, with very good sharpness and good contrast across most of the frame, though corners and edges do show some softness and some minor flare is visible around very bright objects. Chromatic aberration is well-controlled, suppressed by the ZS100's JPEG engine. Performance at 49mm equivalent is also pretty good at f/5.6, but full telephoto at 250mm equivalent and f/5.9 is a touch soft across the frame, with some additional blurring and loss of contrast in extreme corners.

See below for lab results on macro performance, geometric distortion, corner softness, etc.

Macro
An average-sized minimum coverage area, with very good performance in the center. Flash is partially blocked at minimum focus distance.

The Panasonic ZS100 captured an average-sized minimum area at maximum wide-angle (25mm eq.), measuring 2.83 x 1.89 inches (72 x 48 millimeters). Sharpness in and around the center of the frame is pretty good, but corners and edges show quite a bit of softness even at the smallest aperture of f/8 (most lenses show some softening in the corners at macro distances). Exposure with the flash is very uneven with the top portion of the frame well-exposed, but the bottom is dark due a shadow caused by the lens. You'll likely want to use external lighting for the closest ZS100 macro shots.

Geometric Distortion
Very low distortion in camera JPEGs, but very high in uncorrected RAW files at wide angle.

Thanks to in-camera distortion correction, there's low geometric distortion in the ZS100's JPEGs. At maximum wide angle, we measured just over 0.3% barrel distortion which is pretty low and not very noticeable. At full telephoto, distortion was even lower, at just over 0.1% of complex (wavy) barrel distortion. This is the tendency for the lens to bend straight lines outward (like a barrel -- usually at wide-angle) or inward (like a pincushion -- usually at telephoto).

To see how much correction is taking place in the camera, we converted RAW files from the above shots with dcraw, which does not correct for distortion. As you can see at wide angle, barrel distortion is very high, at about 3.7%, while telephoto shows about the same very low distortion as JPEGs. This is not unusual, though. We expect to see fairly significant distortion in uncorrected RAW files in fast, compact lenses allowing lens designers greater flexibility in optimizing center sharpness and other aberrations, as well as in reducing cost, size, and weight. The downside is that the distortion correction contributes additional blurring to the corners of the frame where pixels are "stretched" during correction and where lenses are usually already a bit soft. Note that most RAW converters are capable of applying distortion correction automatically, as specified by the manufacturer in an embedded lens profile.

Chromatic Aberration and Corner Sharpness
Moderately low to very low chromatic aberration in JPEGs. The lens produces soft corners wide-open, though corner sharpness improves stopped-down.

Chromatic Aberration. Thanks to effective in-camera chromatic aberration suppression, there's moderately low CA in the corners at wide angle and telephoto in JPEGs. As expected, though, uncorrected RAW files (see below) show much more CA than seen in the JPEG crops above.

Corner Softness. Wide-open at maximum wide angle, the ZS100's lens is soft in all four corners, and blurring extends fairly deep into the frame. The center is however quite sharp. Corners are a little better at full telephoto when wide-open, but they are still slightly soft, and the center isn't as sharp as it is at wide angle.

Vignetting. There's some minor vignetting (corner shading) but mostly just at wide angle, as shown by the darker the corner crops compared to the center.

Stopped-down: Stopping down a few clicks (in this case to f/5.6 at wide angle and f/8 at telephoto) improved corner sharpness and contrast significantly at wide angle, but less so at full telephoto. However, corners were still not as sharp as the center, and full telephoto was slightly softer than wide-open near the center of the frame, due to diffraction.

Chromatic Aberration Correction

As you can see in the crops from uncorrected RAW images on the right (taken from RW2 files converted with dcraw), the ZS100's lens produces moderately high and bright lateral chromatic aberration at both maximum wide angle and full telephoto. But the ZS100's processor does a pretty good job at suppressing CA in camera JPEGs (crops on the left). Note that most RAW converters should also automatically suppress CA when converting the ZS100's RW2 files.


Overall, decent performance from the ZS100's lens when considering size and zoom ratio, but it's not very sharp at telephoto and it's a bit soft in the corners even when stopped down at both ends.

Coverage
Excellent accuracy from the LCD monitor and electronic viewfinder.

The Panasonic ZS100's LCD monitor and EVF both provide essentially 100% coverage. This is excellent performance, especially considering the amount of geometric distortion correction taking place at wide angle.