Output image file quality / JPEG artifacts

Standard Test Scene

The D2X provides three different image size options in combination with three JPEG compression levels (Fine, Normal and Basic) as well as TIFF format and RAW. In a new feature to the D2X you can also define that JPEG compression is carried out to Size priority or Optimal quality. In Size priority mode output file sizes will be approximately the same, in Optimal quality mode the file size will vary depending on the amount of detail (can be up to 80% larger than in Size priority mode). The output image size is obviously also different when using High-speed crop mode (which records a smaller area of the sensor). RAW captures in High-speed crop mode are also smaller. The table below sets out the different image sizes in each mode:

Size setting	Normal mode	High-speed crop mode
L	4288 x 2848	3216 x 2136
M	3216 x 2136	2400 x 1600
S	2144 x 1424	1600 x 1024

Below you will find crops of the same 240 x 180 portion of the center of a sequence of images taken at some of the available combinations of image size and quality. Crops shown are at 100%, saved as extremely high quality JPEG. The RAW file was converted to a TIFF using Nikon Capture 4.2.1. The 'approx. quality' values beside the JPEG file sizes are an approximation of the quality factor of the JPEG (0-100) by analyzing the file's quantization table.

Full resolution, different quality levels

4288 x 2848 (L) TIFF (Uncompressed) 37,402 KB .TIF (not for download)	4288 x 2848 (L) RAW (Uncompressed) 17,074 KB .NEF (not for download)
4288 x 2848 (L) JPEG Fine (Optimal quality) 5,801 KB .JPG (approx. quality 99)	4288 x 2848 (L) JPEG Normal (Optimal quality) 3,860 KB .JPG (approx. quality 97)
4288 x 2848 (L) JPEG Basic (Optimal quality) 2,396 KB .JPG (approx. quality 92)
4288 x 2848 (L) JPEG Fine (Size priority) 4,898 KB .JPG (approx. quality 98)	4288 x 2848 (L) JPEG Normal (Size priority) 3,056 KB .JPG (approx. quality 95)
4288 x 2848 (L) JPEG Basic (Size priority) 1,491 KB .JPG (approx. quality 83)

It's virtually impossible to see a difference between the three JPEG compression qualities available, indeed even at 200% magnification only the Basic (Size Priority) setting produces some artifacts, and even they are not that significant. In these samples the 'Optimal quality' Fine JPEG is approximately 20% larger than the 'Size priority' version, but again it's difficult to see any visible difference.

Smaller image sizes

3216 x 2136 (M) JPEG Fine (Optimal quality) 3,598 KB .JPG (approx. quality 99)	2144 x 1424 (S) JPEG Fine (Optimal quality) 1,974 KB .JPG (approx. quality 99)

A high quality downsampling algorithm makes for clean crisp looking smaller size images.

Color space

In a change compared to the D2H the D2X now has a separate menu option for color space, however slightly confusingly the 'color mode' option still exists allowing you to select the two different sRGB color response modes. Images taken in the Adobe RGB color space have their filename prefixed with an underscore (_) this complies with DCF 2.0 (Exif 2.21); and plays havoc with the order of images if you sort by filename.

Place your mouse over the label to see a ColorChecker chart shot in the respective mode.

Mode I (sRGB)	Mode II (Adobe RGB)*	Mode III (sRGB)

* Note that the Adobe RGB image has been converted to the sRGB color space for correct display in your web browser.

Color space: CIE u'v' Color Distribution chart

Note that in these samples the Adobe RGB image has not been converted to sRGB and so to view it correctly you will have to load it into a color space aware photo application and assign the Adobe RGB color space. Below each sample is the CIE u'v' Color Distribution chart; larger gray triangle approximately represents the range of color which the human eye can resolve, the inner triangle the available gamut in each color space (sRGB or Adobe RGB).

Mode I (sRGB)	Mode II (Adobe RGB)	Mode III (sRGB)