Fujifilm X100S Review
Resolution Chart Comparison (JPEG and RAW)
Images on this page are of our standard resolution chart which provides for measurement of resolution up to 4000 LPH (Lines Per Picture Height). A value of 20 equates to 2000 lines per picture height. For each camera we use the relevant prime lens (the same one we use for all the other tests in a particular review). The chart is shot at a full range of apertures and the sharpest image selected. Studio light, cameras set to aperture priority (optimum aperture selected), image parameters default. Exposure compensation set to deliver approximately 80% luminance in the white areas.
What we want to show here is how well the camera is able to resolve the detail in our standard test chart compared to the theoretical maximum resolution of the sensor, which for the charts we shoot is easy to work out - it's simply the number of vertical pixels (the chart shows the number of single lines per picture height, the theoretical limit is 1 line per pixel). Beyond this limit (which when talking about line pairs is usually referred to as the Nyquist frequency) the sensor cannot faithfully record image detail and aliasing occurs.
This limit is rarely attained, because the majority of sensors are fitted with anti-aliasing filters. Anti-aliasing filters are designed to reduce unpleasant moiré effects, but in doing so, they also reduce resolution (the relative strength and quality of these filters varies from camera to camera). In theory though, a sensor without an AA filter, when coupled with a 'perfect' lens, will deliver resolution equal to its Nyquist limit. Therefore, even though it may be effectively unattainable with normal equipment in normal shooting situations, an understanding of a sensor's theoretical limit provides a useful benchmark for best possible performance. Nyquist is indicated in these crops with a red line.
On this page we're looking at both JPEG and Raw resolution. For a (more) level playing field we convert the latter using Adobe Camera Raw. Because Adobe Camera Raw applies different levels of sharpening to different cameras (this confirmed) we use the following workflow for these conversions:
- Load RAW file into Adobe Camera RAW (Auto mode disabled)
- Set Sharpness to 0 (all other settings default)
- Open file to Photoshop
- Apply a Unsharp mask tuned to the camera, here 200%, Radius 0.3, Threshold 0
- Save as a TIFF (for cropping) and as a JPEG quality 11 for download
|JPEG (4896 x 3264) 3.9MB||RAW (4896 x 3264) 3.2MB|
Like the X-Pro1 and X-E1 the X100S shows visibly higher resolution in this chart test than a conventional 16MP Bayer-type camera such as the Sony NEX-6 (which has a particularly weak AA filter). In fact, in terms of resolution the Fujifilm is very close indeed to the 24MP Sony NEX-7 or the Sigma SD1, which uses a 15MP Foveon X3 sensor to record full color information at every pixel, and therefore (like the X-100S) uses no AA filter.
These chart shots also show very little of the false color that we'd expect from a Bayer camera with no AA filter - there's a tiny bit on the RAW version, just around the point where the X-100S begins to struggle to accurately resolve the lines on our chart, but none at all in the JPEG. This supports Fujifilm's claim that the X-Trans CMOS is less susceptible to moiré than a Bayer sensor. Last but not least, the X-100S's JPEG processing can deliver just as much resolution as the converted RAW.
We were impressed by the X-Pro 1's and X-E1's JPEG processing, and the X-100S is at least as good, if not better than its peers. As we often see for a camera with no AA filter, the X-100S continues to show line structure beyond its Nyquist limit. As usual this is false detail (i.e. it's not an accurate representation of the chart) but in real-world use it often helps give an impression of increased detail anyway.
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