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 is set to deliver approximately 80% luminance in the white areas.
In order to eliminate any potential sources of vibration from adversely affecting the results, we illuminate the scene using flash, which provides an effective shutter speed many times faster than the camera's own shutter speed would allow.
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.
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 an Unsharp mask tuned to the camera, in this case Amount 150%, Radius 0.6, Threshold 0
- Save as a TIFF (for cropping) and as a JPEG quality 11 for download
|JPEG (6000 x 4000)||Raw (6000 x 4000)|
|JPEG 100% crop|
|Raw 100% crop|
|JPEG 100% crop||Raw 100% crop|
Based on pixel count alone, the 24MP D7100 ranks among the highest resolution DSLRs of any class, falling shy only of the 36MP full frame Nikon D800. Add to that the fact that the D7100 has no OLPF filter and you'd expect nothing less than impressive performance on our resolution chart. As you can see, the D7100 doesn't disappoint. JPEG output is very good, retaining fine detail arguably close to 3000LPH, which is a bit beyond what we've seen from the best 24MP sensors that use an OLPF filter. Impressively, it does this without introducing the sharpening-inducing halos that we've observed in APS-C rivals like the 24MP Sony SLT-A77.
Raw files can resolve a bit more detail here and can tolerate slightly more aggressive than usual low-radius sharpening for output that again places it atop its peers. One trade-off for the removal of the OLPF filter is an increased presence of moire patterning on our resolution chart compared to 24MP APS-C models which employ the filter, like the Nikon D5200. And if you look carefully along the edges of the numerals in the chart, you can make out some jagged edges which appear smooth in the JPEG rendering.