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Output image file quality / JPEG artifacts


Standard Test Scene

The Coolpix 8700 provides for a wide range of image sizes, there are a total of seven sizes ranging from the native eight megapixel size (3264 x 2448) down to VGA. In addition there is also a 3264 x 2176 3:2 aspect ratio mode. These sizes can be combined with three levels of JPEG compression (Fine, Normal or Basic) or the uncompressed TIFF mode (although I've no idea who would shoot TIFF these days). Of course the 8700 also provides a RAW capture mode at full resolution.

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.

3264 x 2448 RAW (Uncompressed)
12,375 KB .NEF (not for download)
3264 x 2448 TIFF (HI)
23,520 KB .TIF (not for download)
3264 x 2448 JPEG Fine
2,531 KB (2.7:1 compression, 3 bpp)
3264 x 2448 JPEG Normal
1,644 KB (4:1 compression, 2 bpp)
 
3264 x 2448 JPEG Basic
823 KB (8:1 compression, 1 bpp)
 
2592 x 1994 JPEG Fine
2,339 KB (2:1 compression, 4 bpp)
2048 x 1536 JPEG Fine
1,034 KB (2:1 compression, 4 bpp)
1600 x 1200 JPEG Fine
660 KB (2:1 compression, 4 bpp)
1280 x 960 JPEG Fine
475 KB (2:1 compression, 4 bpp)
1024 x 768 JPEG Fine
307 KB (2:1 compression)
640 x 480 JPEG Fine
133 KB (2:1 compression)

Other than a difference in sharpening between RAW and TIFF / JPEG Fine it's really difficult to see any 'file quality' differences (JPEG artifacts etc.) between these three options. It's interesting to see that Nikon appears to have chosen to go with a higher JPEG compression for its full resolution 8 megapixel JPEG Fine images, this pretty much guarantees images under 3 MB, most other manufacturers have gone for less compression. That said the Nikon images don't appear to suffer from any obvious JPEG artifacts until you get down to Basic (8:1) compression.

I was a little disappointed by the interpolation algorithm (or lack of) used for downsampling the smaller size images, both the 1024 x 768 (XGA) and 640 x 480 (VGA) images look blocky with visible 'stepping' a sure sign that the image reduction was done without interpolation.

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