Document Sizes

RA
Posted By
Richard_Archer-Jones
Apr 18, 2007
Views
313
Replies
7
Status
Closed
It’s no good folks, I’ll have to ask this question again, I know I’ve asked it before but I can’t find it. I’m running PSCS2 in Windows Professional 2000 and I don’t understand the vast discrepancy between the left document size figure displayed in the status bar of a PS document and the file size given by Explorer. I’ve read that the left figure "…. represents the printing size of the image – approximately the size of the saved, flattened file in Adobe Photoshop format". So should not that figure be near enough the same as the figure given by Explorer?

For example, a photograph I have that is 1.98MB according to Explorer is down as 11.6M in that left figure in the status bar. So, I have two questions:-

1. Is ‘MB’ in Explorer the same as ‘M’ in PS?
2. Why such a difference? I don’t expect them to be exactly the same but crumbs!!!!

I think I understand the second figure in the status bar. That should get bigger and bigger the more layers there are, but shouldn’t the first figure stay virtually the same as the Explorer figure.

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C
chrisjbirchall
Apr 18, 2007
Depends what type of file.

When an image is open in Photoshop, the size given is based upon the actual pixel dimensions. If you save it as a Jpeg a considerable amout of compression takes place resulting in a much smaller file size.

A PSD will also save at a slightly smaller size, despite being a "lossless" format. Generally TIFFS save at the size shown in Photoshop.

Hope this helps.

Chris.
RA
Richard_Archer-Jones
Apr 18, 2007
Mmmm, well, thanks Chris, but I’ve had a look at some TIFF files and so far I’ve only found one that was the same size, and that one even had a path. They are normally nowhere near the same, and they haven’t got any layers or paths or anything (as far as I can see). A TIFF file can be 1.32MB in Explorer and 28.3M in the PS status bar. This is all mighty confusing.

I would have thought that the one file format that should be the same would be the PSD file, if there were no layers etc., or the same as a flattened version (as the Help explains that it should be).
B
Bernie
Apr 18, 2007
TIFFs can be compressed (using one of three different compression schemes: LZW, ZIP and JPEG)

PSD also incorporates some compression
CH
clifford_hager
Apr 18, 2007
While an image is open in photoshop, it also containcs a little extra information used by the program that allows editing, final saving, a guess at how the image will be saved, etc. Once you actually save it, a lot of this info is stripped out and the resulting smaller file size saved on disk. This is further changed by the choices you make when youi save it as described above.
RA
Richard_Archer-Jones
Apr 19, 2007
Ah, I see, it’s all to do with compression. When a file is saved on the hard disk there is usually a certain amount of compression, sometimes a heck of a lot, as my example above shows (depending on the type chosen). When a file is opened it is decompressed and also given more size to cope with such things as mentioned by Clifford. So both figures, the one in Explorer and in the PS status bar, are correct.

So presumably this means when I open up a file in PS, the space used up in my RAM is not the amount stated in Explorer but the amount stated in the status bar, plus a certain amount made available on the scratch disk.
C
chrisjbirchall
Apr 19, 2007
….and if you think that’s fun, you’ll find this:

< http://www.adobe.com/cfusion/knowledgebase/index.cfm?id=3200 05>

an interesting read.
RA
Richard_Archer-Jones
Apr 24, 2007
Wow, that actually is interesting Chris. Thanks, I’ve made a start at reading it and I’m even understanding most of it 🙂

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