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Raster mosaic produces degraded image

Question asked by mhtreu on Jul 25, 2011
Use of the mosaic tool (Database Management) in ArcCatalog 9.3 to combine georeferenced aerial photographs (B&W) yields a slightly altered image quality in the mosaic.  Despite ensuring the same color ramp is used, there is a noticeable loss of sharpness in the image.  Zooming the image to a very large scale (1:50 or so) reveals a pattern of horizontal and vertical rows of pixels which are twice the height (or width in the case of columns) of the rest of the pixels (see attached screen captures for a comparison of the original image pixels with the same area in the mosaic).

This "grid" of altered pixels can be best viewed when toggling back and forth between the original image (tif image) and the same portion of the image mosaic.  In addition to some slight color ramp differences, these enlarged rows/columns of pixels are evident.

Is there a known reason for this altering of the final raster mosaic?  Is there a setting in the tool parameters which would prevent this from occurring? 

Appreciate any thoughts/help,

Marv.

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