Fujifilm X-T1 Optics

Zoom Lens
A typical zoom ratio for a kit lens, with very good performance.

The Fuji X-T1's XF 18-55mm f/2.8-4R OIS kit lens has an equivalent focal length of about 27-83mm lens on a full-frame body. Optical performance at full wide angle (18mm) is quite good at f/8, with very good sharpness and contrast across most of the frame. Upper corners look a bit soft, though the depth of this scene makes judging corner performance difficult (see sections below for corner performance, as well as distortion, etc.) There are hints of flare around bright objects, though the camera overexposed the building at wide angle, blowing quite a few highlights in the white areas of the building. Chromatic aberration is very low, though the camera suppresses it. Far-field performance at 34.3mm (51mm eq.) is similar, with very good sharpness except in the extreme corners. At full telephoto (55mm), optical performance is still well above average for a 3x zoom kit lens, with very good sharpness and contrast across the frame.

Macro
A larger than average minimum area, with slightly soft detail. Flash throttled down well.

As always, the Fuji X-T1's macro performance will depend entirely on the lens in use. However, with the 18-55mm kit lens at 55mm, the Fuji X-T1 captures a much larger than average minimum area measuring 5.43 x 3.62 inches (138 x 92 millimeters). Detail is good, just a touch soft across the frame at f/8, with additional softening in the corners. (Most lenses have some additional softening in the corners at macro distances.) The bundled flash throttled down well at this distance, resulting in a pretty good exposure.

Geometric Distortion
Low geometric distortion with the 18-55mm kit lens in JPEGs, though strong distortion in uncorrected RAW files.

In JPEGs, the Fuji X-T1's 18-55mm kit lens produces about 0.3 percent barrel distortion at wide angle, which is much less than average and just slightly noticeable in its images. Pincushion distortion at full telephoto is only about 0.1 percent, also much lower-than-average and hardly noticeable, though somewhat unsymmetrical (the bottom edge shows a tiny bit of barrel distortion). This is the tendency for the lens to bend straight lines outward (like a barrel -- usually at wide-angle). The Fuji X-T1 compensates for most of the distortion in JPEGs, though. See below for uncorrected distortion.

Chromatic Aberration and Corner Sharpness
Low levels of chromatic aberration from the kit lens in JPEGs. Uncorrected RAW files show higher amounts. Very good corner performance at wide angle, however corners are a bit soft at full telephoto.

Chromatic Aberration. Chromatic aberration in the corners of JPEGs taken with the Fuji X-T1's 18-55mm kit lens is quite low at both wide angle and telephoto, but the camera does suppress it (see below for uncorrected RAW files).

Corner Softness. Corner sharpness is excellent at wide angle when wide open at f/2.8, almost as sharp as the center which is remarkable for f/2.8. Corners are slightly soft at full telephoto though performance is still pretty good, while the center is sharp.

Vignetting. Only minor corner shading ("vignetting") is noticeable at both wide angle and telephoto, as can be seen from the difference in brightness of the center versus corner crops above, however the camera does appear to be applying shading correction.

F8: Stopped down to f/8, corner sharpness actually got a little worse, which is a bit odd. We saw similar results in our test of another sample of this lens on SLRgear.com. Chromatic aberration remains very low, and vignetting (corner shading) improves a bit but is still slightly visible.

Lens Corrections

The Fuji X-T1 applies a number of lens corrections to JPEGs. Distortion, chromatic aberration and shading correction are all performed "under the hood" and have no associated settings. (Note that when using the Fuji M-mount Adapter, Distortion Correction, Color Shading Correction and Peripheral Illumination Correction are available, however the type and strength is manually set.)

Geometric Distortion Correction. To see how much correction is taking place in the camera, we converted matching .RAF files from the above shots with RawDigger, which ignores distortion correction instructions in RAW files. Note that RawDigger does not perform sophisticated demosaicing like typical RAW converters (it actually uses a simple binning algorithm to interpolate full color which is better suited for sensor analysis), so the full-res images here are a little rough, but it's a very useful tool to examine uncorrected lens characteristics as well as sensor performance.

As can be seen above, actual barrel distortion at wide angle is quite high at about 1.6%, while pincushion at telephoto is fairly high, at about 1.0%. We expect this for smaller interchangeable lenses though, so it's nothing to be concerned about unless you are using a RAW converter which does not understand the embedded "opcodes" to perform distortion corrections automatically. Most RAW converters these days (including Adobe Camera Raw and SilkyPix) are capable of applying distortion correction automatically, as specified by the manufacturer. There is however going to be some loss of resolution in some areas of the frame as a result of such correction, because pixels are being "stretched" to correct for the distortion. Obviously, a lens that doesn't require such correction, and is also sharp in the corners to begin with would be preferable, but relaxing constraints on distortion brings other benefits in the lens design, such as a more compact design or better sharpness in the center.

Chromatic Aberration Suppression. As mentioned above, the Fuji X-T1 suppresses lateral chromatic aberration in its JPEGs. Uncorrected RAW files (right) show moderate but bright magenta and green coloration along high-contrast edges at wide angle, and some minor blue and yellow fringing at telephoto. As you can see, C.A. has been effectively suppressed in the matching camera JPEGs (left). Also notice the artifacts at the corners of the square and rectangular components of the resolution target in the camera JPEGs, likely side effects of correction interacting with the special desmosaicing required for the X-Trans sensor's unique color filter array.

Shading Correction. The Fuji X-T1 also appears to be applying some shading correction as can be seen by mousing over the above two links comparing an in-camera JPEG to uncorrected RAW at 18mm and f/2.8. Notice how the corners are quite a bit dimmer than the center in the uncorrected RAW file.

Lens Modulation Optimizer. Fuji's Lens Modulation Optimizer technology applies variable sharpening depending on the lens and aperture used.

Mouse over the above links to compare the effect of Fuji's Lens Modulation Optimizer on our test target at 18mm and f/8. It's a pretty subtle difference, but the On settings does produce a crisper-looking image. If you look closely, sharpening halos are more visible than with the Off setting which still applies standard sharpening.

Overall, very good optical performance for a kit zoom lens, especially one that is faster (brighter) than average.

Accuracy
Good coverage accuracy from the electronic viewfinder and LCD monitor.

The Fuji X-T1's electronic viewfinder and LCD monitor both proved fairly accurate in record mode, showing just over 98% coverage. Good results here, though we're a little surprised it's not 100% given both previews are derived from the sensor.