Why is Photoshop enlarging TIFF?

[stoltz01]

Hi,
I've been playing with Photoshop, and there is one thing that I have not found an answer for.
I even know how to calculate the size of the file if it is RGB/8 or 16, but this one is mistery to me.

I open up a TIFF file from my scanner - plain text page B/W.
It is a 170K file.
Now I open it in Photoshopw and suddenly 5M !!
And if I save as a TIFF and not doing anything at all with the image it becomes larger!?

Why? I want to have the same resolution, work with the file, and maintain much about the same file size...
I use CS3 by the way.

[zipykido]

A tiff the size of a 8.5x11 piece of paper that's only white should be about 5 megs. Perhaps your scanner is telling you the size of a jpeg.

[stoltz01]

Hmm, the file is 170 K when I look at it in the file list... Can it somehow be compressed as it comes out of the scanner, and unpacked when PS opens it:?:

[stoltz01]

And now i got a bit confused.
I thought a TIFF B/W file for a A4 size page with text would take 100KB-200KB at 300 ppi resolution?
But maybe it is just a container file for a JPEG, that gave me some ideas...

[zipykido]

I'm guessing that the preview is 170k. Check the settings on your scanner. Going from one format to another isn't uncompressing, it's conversion. So I'm guessing you have it saving as a jpeg but your scanner wants to save as a tiff.

[BamBam]

most likely a layered Tiff

[stoltz01]

Thanks for the help - it cleared some of the fog (not all).
I made a few mistakes , but is looks better...

I downloaded a TIFF header decoder - and found out that the file is in did TIFF with some CCITT compression (for fax). Not layered, not embedded JPEG, just plain compressed monochrome TIFF.

When opening the file, photoshop probably converts the format in order to be able to read it, the 170 KB become immediatelly 1M - What I hade missed before is avoiding to use pixel aspect ration=1 THAT'S WHAT MADE THE FILE 5M . And I found out that using pixel aspect ratio of 2 makes the file only 2M, why I have no clue.

Next step, I forgot when cropping to clear the settings, so that PS was actually resampling the image instead of just cutting the file.
Not so speak of that I had to convert it to grayscale in order to work with it. Then using the ruler and rotate canvas arbitraly I finally managed to get my text straight and looking good.
Once I saved as TIFF with LZW compression, it became just a bit larger, somewhat over 200K, I guess that's the price of being able to work with it.



Still crazy about that thing of opening a 170K file and ending up with 1M, but is must be something with the compressing of the scanner.