RAW image format
RAW is simply pixel data as it comes directly off the CCD, no in-camera processing is performed. Typically this data is 8, 10 or 12 bits per pixel. The advantage being that file sizes are considerably smaller than an equivalent TIFF file. The image has not been processed or white balanced which means you can correct the image, and it's a better representation of the "digital negative" captured. The disadvantage is you can't open these image files with a normal photo package, in the case of Minolta RAW files (.MRW) you must use the Minolta DiMAGE Viewer.
A little background: each pixel of a CCD can only see one colour, depending on the CFA (colour filter array) placed over the CCD this is either Red/Green/Blue or Cyan/Magenta/Green/Yellow. The cameras internal image processing engine then interpolates colours from the value of neighbouring pixels to calculate a full 24-bit colour for each pixel.
Minolta's RAW (.MRW) files are larger than we would expect. Minolta report the camera as having a 12-bit A/D converter, thus MRW files should be around 7.5 MB. In reality they are approximately 9.5 MB, this appears to be because Minolta are recording a 16-bit value for each pixel location, a very space inefficient system.
Minolta DiMAGE Viewer
DiMAGE Viewer is the supplied image browsing / conversion application (Version 2.10 used in this review). It allows you to browse, view and organize images from the camera. It also provides the ability to convert RAW files (.MRW extension) to JPEG, TIFF or BMP. Double-click on a MRW file in the DiMAGE Viewer browser window and you will see the options dialog shown below.
This RAW file dialog allows you to change any of the following parameters:
- Color Mode (Color / B&W)
- White Balance (Camera, Daylight, Cloudy, Tungsten, Fluorescent, Manual from image, Kelvin temp)
- Filter (-3 to +3)
- Saturation (-3 to +3)
- Contrast (-3 to +3)
- Sharpness (Soft, Normal, Hard)
The only setting we normally see which is unfortunately missing is digital exposure compensation, it would be nice to have this option because it is one of the most useful features of RAW files. A group of settings can be saved as a 'RAW Job' and retrieved later when converting another image.
RAW vs. JPEG (Scene)
|RAW (.MRW) (click below for re-saved JPEG)||JPEG FINE (.JPG)|
A few things are immediately noticalbe. The first is the undesirable dotted Bayer artifacts around line detail (see the watch face), this points towards an unsophisticated de-mosaic algorithm in the Minolta DiMAGE Viewer application, compared to the camera. It's also fairly clear that the DiMAGE Viewer produces softer, less detailed (but equally less noisy) images than JPEG. Results here are identical to the DiMAGE 7i, to see more examples of the difference between Minolta RAW and JPEG click here (DiMAGE 7i review).