Digital BW, The Print

Strange.
Mark

On Feb 7, 2006, at 12:52 PM, Roger Howard wrote:

>
> On Tuesday, February 07, 2006, at 09:37AM, Mark Savoia  
> <mark@...> wrote:
>
> >Why do you say LZW is not?
> >Mark
> >
> >On Feb 7, 2006, at 11:58 AM, Roger Howard wrote:
> >
> >> ZIP compression within TIFF is generally well supported these days
> >> and is fairly effective with 16bit/channel files (LZW is not).
>
> Sorry if I wasn't clear enough.
>
> LZW works fine; it's lossless. So is ZIP. But in my experience LZW  
> on 16bit/channel TIFFs rarely does anything but actually increase  
> the filesize! Quick example using a 16bit RGB image of a manuscript  
> page:
>
> Uncompressed TIFF - 82.4MB
> ZIP compressed TIFF - 78.6MB
> LZW compressed TIFF - 105MB
>
> This is consistent with my experience; depending on the nature of  
> the image ZIP might save you 10-40% on filesize compared with  
> uncompressed; LZW on the other hand seems to almost always INCREASE  
> the filesize.
>
> This may just be a bug in Photoshop's TIFF/LZW implementation for  
> 16bit, or may be fundamental to LZW, but since Photoshop is pretty  
> much ubiquitous I use its results as my guide. For lossless  
> compression of 16bit grayscale or RGB from Photoshop, TIFF/ZIP is  
> the best option weighing compatibility, etc. Of course you might  
> decide the performance hit (opens/saves) from ZIP outweigh any  
> minor storage capacity savings (I agree for flat TIFFs - but I do  
> use ZIP compression on layered TIFFs).
>
> -R
>
>
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