Let's go back to basics. Is the 42MB size variable with content? If so, does that represent a typical low-moderate ISO shot of a mixed scene, or some high ISO complex scene? And how big a variation? If you were to losslessly compress it with something like 7zip, does it go down significantly?
Taking the 18MP canon raw for comparison, we know that's 18MP at 14 bit, for a maximum around 31.5MB. The biggest raw I can find in a quick search of my hard disk is 33.6MB for a complex scene at ISO3200. If we assume that's low compressibility, and there is other data contained within the raw such as the jpeg preview and other camera data, then the size is in a reasonable ball park. A typical file is around 25MB.
Taking the 18MP canon raw for comparison, we know that's 18MP at 14 bit, for a maximum around 31.5MB. The biggest raw I can find in a quick search of my hard disk is 33.6MB for a complex scene at ISO3200. If we assume that's low compressibility, and there is other data contained within the raw such as the jpeg preview and other camera data, then the size is in a reasonable ball park. A typical file is around 25MB.
<a class="bbc_url" href="http://snowporing.deviantart.com/">dA</a> Canon 7D2, 7D, 5D2, 600D, 450D, 300D IR modified, 1D, EF-S 10-18, 15-85, EF 35/2, 85/1.8, 135/2, 70-300L, 100-400L, MP-E65, Zeiss 2/50, Sigma 150 macro, 120-300/2.8, Samyang 8mm fisheye, Olympus E-P1, Panasonic 20/1.7, Sony HX9V, Fuji X100.