Best method for saving TIFF's - LZW or ZIP?

[Paul_Graham]

I had a moment this morning and did some quick tests.

16bit Canon Eos 1Ds mk2 file:

TIFF: 94.86 Mb
PSD: 94.86
LZW TIFF: 113.00 (!)

then I added a curve layer and two sharpening layers, and saved the layered file as follows:

Norm TIFF / interleaved / RLE 166.08 Mb
Norm TIFF / interleaved / ZIP 103.68
LZW TIFF / interleaved / ZIP 81.37
ZIP TIFF / interleaved / ZIP 79.71
ZIP TIFF / per channel / ZIP 81.88

PSD document with layers 122.68

on these results there is a very large advantage in using both LZW tiff's and ZIP compression of layers (file size dropped under 50% of uncompressed - from 166 to 81 Mb), but no file size advantage in doing per channel over regular interleaving.

But there is not always an advantage of using LZW over regular Tiffs where there is no layers present. This seems image dependant... as I've seem it flip flop either way depending what is in the image.

I will not personally bother using ZIP files and ZIP layers - it actually added some size and is less readable to other programs. My standard layered saves will now be LZW tiff's with ZIP layer compression.


n.b. these figures are for IBM PC byte order, and there may be some small difference for Mac byte order. if someone with a similar 1Ds2 file wants to compare these on a Mac, it might be interesting to know if there's any meaningful difference.

paul

[brucefraser]

I use ZIP-compressed TIFF for my layered files, which I never send out, so the incompatibilities don't bite me much, but I sorely wish that ImagePrint could read ZIP-compressed TIFF!

I almost always deliver uncompressed flat TIFF in final print space. But for my own files the storage savings offered by ZIP/per channel, especially on 16-bit files, is too compelling to overlook. LZW can sometimes create layered 16-bit files that are bigger than the uncompressed equivalents...

[Paul_Graham]

[ QUOTE ]

I almost always deliver uncompressed flat TIFF in final print space. But for my own files the storage savings offered by ZIP/per channel, especially on 16-bit files, is too compelling to overlook. LZW can sometimes create layered 16-bit files that are bigger than the uncompressed equivalents...

[/ QUOTE ]

agreed about the LZW issues - it does seem to vary from image to image.

so what you re saying is that ZIP + ZIP is * always* a reduced file size, whereas LZW + ZIP is highly variable, from better to worse, depending on random image factors?

[brucefraser]

I've never seen LZW get worse on 8-bit files, but it often does on 16-bit ones. ZIP+ZIP always creates a significantly smaller file, usually 30-40% smaller.

[Michael_Fontana]

[ QUOTE ]
[ QUOTE ]

I almost always deliver uncompressed flat TIFF in final print space. But for my own files the storage savings offered by ZIP/per channel, especially on 16-bit files, is too compelling to overlook. LZW can sometimes create layered 16-bit files that are bigger than the uncompressed equivalents...

[/ QUOTE ]

agreed about the LZW issues - it does seem to vary from image to image.

so what you re saying is that ZIP + ZIP is * always* a reduced file size, whereas LZW + ZIP is highly variable, from better to worse, depending on random image factors?

[/ QUOTE ]

Thanks
your recommandation for the 16biters in zip make sense. With todays filesizes, the HD's are getting full pretty fast.

I had been avoiding zip-compression too, as my cataloging tool (iVMP) couldn't read the zip-compressed at all, a while ago. But I realize now, that they added this feature in the last update, for 256 x 256 pix, at least. The zip-support has been a user request I did a while ago, so that's great. BTW, the LZW-thumbnail still goes to 512 x 512pix.

Made a quick and dirt test too, and there's a approx. 25 % smaller file with zip-compression vs the LZW, on a 1 DS-2-file, too. The RGBRGB vs the RRGGBB change though didn't showed any difference.

Bruce, who owns zip?
And is there any reason, you deliver the 8biters totally uncompressed?


Paul, as maccis too, we save for IBM, it's just a matter of compatibility, as we don't have problems to read the IBM as well.

[PaulChaps]

Can someone confirm that a Mac can open a Zip tiff?

...its not just for PC's is it?

Thanks,
Paul