Brilliant! Thanks very much Robert, that answers my question very well. I
remember now that my low compression example was indeed with a 16-bit
file. I use both, but hadn't cottoned on to the fact that compression
varies with bits per pixel / no of bitplanes.
Cheers,
Julian
At 09:28 01/03/03, you wrote:
>One other possibility is that he works with 16-bit TIFFs and you with 8-bit
>TIFFs. If you go beyond 8 bits the compression ratio falls pretty fast. As a
>matter of fact, jpeg2000 even allows to bypass parts of the algorithm after
>5 bitplanes because compression is not very significant anymore (because
>there isn't much correlation anymore). Therefore, for images with many
>bitplanes it makes sense to use a bigger compression ratio as not that much
>is lost.
>
>Robert
Julian
Canberra, Australia
Satellite maps of fire situation Canberra and Snowy Montains
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