Computer Graphics with Photoshop

Author

file size question

Mark Bolton

2004-01-30, 10:28 am

Ive never quite worked this out...its probably me being dumb, but I cant
work it out. When I open a Tiff in PS7, the file size at the bottom gives
the file size, as say, 30mb. If I then change it to a slightly compressed
JPEG at a smaller image size, the figures at the bottom change to maybe
10mb. This is obviously wrong, and when I then send the jpeg by email, the
attachment is listed as , say 800kb. It also lists the image as
filename.tif.jpg. How do I find the true file size, and what is a tif.jpg?
many thanks for your help in advance. Mark

--

Eric Gill

2004-01-30, 10:28 am

"Mark Bolton" <mark.bolton@blueyonder.co.uk> wrote in
news:4vtSb.3705$Q63.1409@news-binary.blueyonder.co.uk:

quote:

> Ive never quite worked this out...its probably me being dumb, but I
> cant work it out. When I open a Tiff in PS7, the file size at the
> bottom gives the file size, as say, 30mb. If I then change it to a
> slightly compressed JPEG at a smaller image size, the figures at the
> bottom change to maybe 10mb. This is obviously wrong,

Why? Smaller number of pixels, plus the layers are flattened. That's hardly
unreasonable.

quote:

> and when I then
> send the jpeg by email, the attachment is listed as , say 800kb.

Okay. You compressed the hell out of it.

quote:

> It
> also lists the image as filename.tif.jpg. How do I find the true file
> size,

In Photoshop, the figure on the left is the raw file size by pixel
dimensions. On the right, what Photoshop is using with layers and the like.

quote:

> and what is a tif.jpg?

You screwed up the filename when you saved it to a jpeg.

Tacit

2004-01-30, 2:28 pm

>When I open a Tiff in PS7, the file size at the bottom gives

quote:

>the file size, as say, 30mb. If I then change it to a slightly compressed
>JPEG at a smaller image size, the figures at the bottom change to maybe
>10mb.

When you make the image size smaller, it goes down to 10MB. That is the
uncompressed size of the layered image.

quote:

>This is obviously wrong, and when I then send the jpeg by email, the
>attachment is listed as , say 800kb.

800KB=compressed, flattened size. 10MB=uncompressed, layered size.

quote:

> It also lists the image as
>filename.tif.jpg. How do I find the true file size, and what is a tif.jpg?

The "true" file size is the size on disk--800K. The "true" image size is the
size when the image is uncompressed--10MB

A .tif.jpg is a JPEG. You did not set the name of the file correctly when you
saved it.

Virus writers use this kind of convention to trick people, but the rule is very
simple--you ONLY look at the LAST three letters. The file

myfile.tif.doc.eps.art.dxf.xls.jpg

is a JPEG. It's not a TIFF, it's not a Word file, it's not an EPS, it's not an
AOL ART file, it's not an Autocad file, it's not an Excel spreadsheet, it's a
JPEG, plain and simple.

Virus writers will sometimes send out viruses that are named something like

britneynude.jpg.exe

It is not a JPEG. It's an exe file, plain and simple. You look at the last
three letters, nothing else.

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