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JPEG Image Size & Quality

All of the DX4900 image size options are at the 'film / print standard' 3:2 aspect ratio. This differs from most consumer digital cameras which shoot at the monitor standard 4:3 aspect ratio. There are advantages and disadvantages to both aspect ratios, 3:2 can be useful for printing.

The DX4900 provides four image size options of 4.0, 3.1, 2.2 and 1.0 mp (all JPEG). In addition there is also a 4.0 mp 'High Compr.' option which produces a smaller file size (although more highly compressed) JPEG. The DX4900 does not have a TIFF or RAW image format option.


Standard Test Scene

To give an impression of what some of the combinations of image size and quality produce the table below is a cross reference of some of them:

  • 2448 x 1632 (4.0 mp)
  • 2448 x 1632 (4.0 mp high compr.)
  • 2160 x 1440 (3.1 mp)
  • 1800 x 1200 (2.2 mp)
  • 1224 x 816 (1.0 mp)

Images below are cropped 240 x 100 area of the image magnified 200% (nearest neighbour).


 
2448 x 1632 (4.0 mp)
Fine
600 KB
High
compr.

399 KB
 

 
2160 x 1440 (3.1 mp)
Fine
433 KB
 

 
1800 x 1200 (2.2 mp)
Fine
278 KB
 

 
1224 x 816 (1.0 mp)
Fine
123 KB

The 'High compr.' 4.0 mp image does have clearly visible 8x8 block JPEG artifacts, it's unlikely you would want to use this setting for anything important. What also struck me about the normal 4.0 mp setting was how small the file is, I would have expected a JPEG file of around 1.5 MB. This means that the DX4900's best JPEG setting is already more highly compressed than other comparable 4 megapixel digital cameras.


Sharpening

The DX4900 provides three different sharpness settings of Sharp, Standard and Soft. Curiously the sharpness setting appears to actually adjust the cameras noise reduction algorithms rather than having any noticeable effect on image sharpness. You can clearly see this by looking at the 'flat area' on the crops below. On the Sharp image there is clearly distinguishable detail, on the Soft image this has been almost completely lost to the camera's noise reduction system.

Thus:

  • Sharpness: Sharp = Low Noise Reduction
  • Sharpness: Standard = Normal Noise Reduction
  • Sharpness: Soft = High Noise Reduction
Sharpness: Sharp
Sharpness: Standard
Sharpness: Soft
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