Olympus TG-5 Optics

Zoom
A 4x wide-angle zoom, with about average performance for its type.

The Olympus TG-5 is equipped with a 4.5-18mm lens, offering an optical zoom ratio of 4x, translating to a 35mm-equivalent focal range of about 25-100mm. The lens is quite fast (bright) at the wide end, with a maximum aperture ranging from f/2.0, however at the tele end maximum aperture is a bit dim at f/4.9.

The TG-5's lens features a 1-stop diaphragm plus 3-stop ND filter aperture mechanism, offering settings of f/2, f/2.8 and f/8 at full wide angle, and f/4.9, f/6.3 and f/18 at full telephoto. (The ND filter cannot be enabled with the diaphragm wide open.) The following table reflects the maximum and minimum apertures as reported by the camera at popular approximate focal lengths:

Far-field performance is about average for its type, which is to say decent but not great. At maximum wide angle, sharpness is quite good in the center, but corners are soft and there's some noticeable purple fringing, as well as flare and loss of contrast around bright objects. At medium focal length, the lens preforms well across the frame, but it's still not tack sharp. The lens isn't as sharp at full telephoto and there's still some noticeable purple fringing, but the corners are reasonably sharp. Unlike prior models, the TG-5 does not offer digital zoom in normal shooting modes.

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

Macro
A tiny minimum coverage area, with very good detail in the center. Flash throttled down well, but illumination was not even.

The Olympus TG-5 allows you to zoom to maximum telephoto ("4x") in Microscope mode with the subject essentially touching the front of the lens! This allowed it to capture a tiny minimum area measuring only about 0.36 x 0.27 inches (9.2 x 6.9 millimeters). Sharpness in the center of the frame is pretty good, however corners and edges are quite soft (most lenses show some softening in the corners at macro distances). The flash did a good job throttling down, though illumination was not even as the lens bezel was practically touching the subject.

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 very little geometric distortion in the TG-5's JPEG files, though what distortion there is asymmetrical. At full wide angle, we measured about 0.1% barrel distortion along the top edge, and about 0.3% barrel distortion along the bottom edge. At full telephoto, distortion was practically zero along the top edge, increasing to just under 0.1% along the bottom edge. Still, very low geometric distortion overall. 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 RawDigger, which does not correct for distortion. At wide angle, barrel distortion is very high, between 3.2 and 3.4% depending on which edge is measured, while telephoto has about 0.9% pincushion distortion at both edges.

We expect to see fairly significant distortion in uncorrected RAW files in fast, compact lenses, as allowing this gives the 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 a lens profile built into the TG-5's RAW files.

Chromatic Aberration and Corner Sharpness
Moderate chromatic aberration in JPEGs. The lens produces some soft corners, though corner sharpness improves stopped-down.

Chromatic Aberration. Thanks to in-camera chromatic aberration suppression in JPEGs, there's moderate lateral chromatic aberration in the corners at wide angle and at telephoto. At wide angle, there's moderate amounts of blue and yellow fringing while at telephoto, there is slightly milder magenta fringing. As expected, though, uncorrected RAW files (see below) show much more CA than seen above.

Corner Softness. Wide-open at full wide angle, the exhibits extreme corners that are quite soft, and some softening extends into the frame about a quarter of the way. Most of the frame is pretty sharp, though, including the center. Wide-open at full telephoto, corner sharpness is much better than wide angle, but still soft. The center is fairly sharp though not as sharp as wide angle, and exhibits lower contrast as well.

Vignetting. There's some moderate vignetting (corner shading) wide-open, shown by how much darker the corner crops above are than those from the center, at both wide angle and telephoto

Stopped-down: Stopping down to f/2.8 (one stop) improved corner performance at wide angle, however corners were still much softer than the center. Contrast and vignetting in corners improved along with sharpness, though chromatic aberration remained moderate. The center also became slightly sharper at f/2.8. While contrast, chromatic aberration and vignetting improved in the corners at full telephoto when stopping down one step, sharpness actually fell due to diffraction at f/6.3. Sharpness in the center also fell, but contrast and CA improved.

Note that "stopping down" further to the minimum "apertures" of f/8 at wide angle and f/18 at telephoto uses a 3-stop ND filter to avoid additional diffraction, but we found it reduced sharpness at the telephoto end in some real-world shots.

Chromatic Aberration Correction

As you can see in the crops from uncorrected RAW images on the right (taken from .ORF files converted with RawDigger which didn't correct for chromatic aberration), the TG-5's lens produces fairly high and bright chromatic aberration at maximum wide angle and at full telephoto with the fringing shifting from magenta/green to blue/yellow. The TG-5's processor does a decent job suppressing CA in camera JPEGs (crops on the left), though it does leave some behind and shifts the colors due to slight overcorrection.

Overall, about average optical performance for its class with good sharpness in the center at maximum wide angle but with soft corners, a noticeable drop in sharpness and contrast at full telephoto, and a lot of digital corrections applied to in-camera JPEGs.

Coverage
Very good accuracy from the LCD monitor.

The Olympus TG-5's LCD monitor provided about 99% coverage at full wide angle and at full telephoto. This is very good performance, especially considering the amount of geometric distortion correction taking place.