I am trying to save a .png as a .gif with a resolution high enough to print. It
seems set at 72 by default. When I change it to something higher, it isn't
maintained when I export as a .gif. Then when I change the .gif to a higher
resolution that doesn't stay maintained. I don't know what I am doing wrong.

Thanks, Sue

On Sat, 7 Jun 2008, pbsue wrote

>I am trying to save a .png as a .gif with a resolution high enough to
>print. It seems set at 72 by default. When I change it to something
>higher, it isn't maintained when I export as a .gif. Then when I change
>the .gif to a higher resolution that doesn't stay maintained. I don't
>know what I am doing wrong.

For an image created on a computer the so called dpi value is there for
determining the size the image will be printed, and has nothing to do
with the inherent quality of the image or "high resolution".

Image width in pixels divided by stored dpi value = print width in
inches
Image height in pixels divided by stored dpi value = print height in
inches

The dpi value stored in an image file has no value as an indicator of
quality except when scanning a document, which is a different case.
http://www.emdpi.com/imagedpi.html

There is a 'gotcha' with a gif file in that a gif does _not_ store a dpi
value. When saving to a gif from any other format the dpi value is
discarded. When reading a gif file the graphic software often 'invents'
a dpi value it likes. Get the free Irfanview at
http://www.irfanview.net/ , open a gif, and look at image ->
information. You will see that the DPI fields [1] are blank because
there is no dpi information stored in a gif file. Open it in some other
graphics app and you will likely see an invented value like 72

[1] There are two dpi fields because most graphic file formats have both
a width dpi value and a height dpi value that, in most cases, have the
same value.

--
Richard Mason
http://www.emdpi.com

Richard,

Thanks for the reply. Just as I suspected, I was missing some basic
understanding.

I visited the two sites you referenced and am trying to assimilate the info
you provided.

So, to create an image in fireworks that is of high enough resolution for
printing I need to set the pixel size of the image or canvas and then set the
print size (in the image size dialog box) and even though it will give a dpi,
that is irrelevant.

Example: if I set the print size to 2 inches and the pixel width and height to
500 the dpi will say 250 pixels/square inch but when I export it to a .gif it
will still say 500 pixels wide for the image but it will say 72dpi. So, in this
case what is the reality of the resolution of the image once the .gif is
created?

Is this the way to get a print resolution ready image in Fireworks?

Thanks, Sue

Figure out what size in pixels you need the image to be to print well, then
make your image in Fireworks that many pixels.

You need to know what the recommended dpi is for your output device and plan
accordingly. You say you need "high enough resolution to print." How high is
high? Do you have a high resolution printer (say 4800 dpi) and you are printing
a piece to be held in the hand? (Then use a high dpi to calculate with.) Are
you printing a large banner to be seen from across the room? (Then you can use
a lower dpi.) Are you printing on an inherently low-resolution medium, like
fabric?

For example, if I wanted to make a t-shirt at CafePress, and I wanted to make
the maximum size image (10 inches square) and I also went with their minimum
recommendations for dpi (200 dpi), then I would make my image 2000 pixels
square.

Note that a 2000-pixel image can be printed at 2.5 inches for an effective 800
dpi or at 20 inches for an effective 100 dpi. It isn't the dpi that determines
the information content in the image, it's the pixels. An image can be
stretched or shrunk to any physical dimension, what you want to do is have the
image be the smallest it can be to look good at the dimension you plan to print
it.

On Sun, 8 Jun 2008, pbsue wrote
>
> So, to create an image in fireworks that is of high enough resolution for
>printing I need to set the pixel size of the image or canvas and then set the
>print size (in the image size dialog box) and even though it will give a dpi,
>that is irrelevant.

Print size, pixels size, and dpi are intimately related and dpi isn't
irrelevant.
pixel size divided by print size in inches = dpi
and
pixel size divided by dpi = print size in inches

Pixels/inch and dpi are the same thing in this context.

dpi doesn't mean what a lot of books and tutorials tell you it means.
It's irrelevant for automatically determining the quality of an image
unless you know for a fact that the dpi is actually the sampling
resolution (pixels/inch) obtained from a scanning process.
When you use the term 'high resolution' in relation to an image I assume
you mean an image that is high quality in terms of image detail, and you
can't tell that from a dpi value unless you _know_ that it's an image
sampling value.

One often sees that because an image is set at 300dpi it has 'high
resolution'. Here's a cunning ploy. Give someone an image set at 50 dpi
say. When they complain it's "not a high resolution image" just use
Irfanview to change the stored dpi to 300 and give them back exactly the
same image. Now I bet they say "that's better, a high resolution image"
even though it's exactly the same image.

> Example: if I set the print size to 2 inches and the pixel width and
>height to
>500 the dpi will say 250 pixels/square inch but when I export it to a .gif it
>will still say 500 pixels wide for the image but it will say 72dpi.

250 pixels/inch not square inch.

If you export to a gif then that's when the dpi value becomes irrelevant
because that dpi value can't be stored in the gif file format. The
reason it says 72 is because when the gif is opened in Fireworks the
program has no idea what dpi you intended because there is no dpi value
stored in the gif file. Fireworks invents the value of 72 dpi for you!
It's still exactly the same image you exported! If I open any gif image
in Paint Shop Pro it tells me the image is 99 dpi because that's what is
set as a default when the image file doesn't contain a dpi value. I said
try Irfanview. It doesn't tell lies.

>So, in this
>case what is the reality of the resolution of the image once the .gif is
>created?

It's whatever you want it to be. When we talk about a high resolution
image we think of this as 'good' because a high resolution image means
lots of detail. The dpi value associated with an image is there only to
enable us to determine the _printed_ size of the image but because the
dpi value is also called 'resolution' people automatically think it is a
measure of the 'goodness' of an image. It isn't when the image is
created on a computer!! It is when the image is obtained via a sampling
process!!

> Is this the way to get a print resolution ready image in Fireworks?
If you're talking about a print shop then Fireworks is not the program
to use and gif is the wrong format. Others can give better advice on
what program to use.

If you just mean it will be printed on a laser, or whatever, then you
just juggle two of the values in the above equations to get the desired
result.

--
Richard Mason
http://www.emdpi.com

Thank You Richard and Lorraine,

I have a fundamental understanding of this now. I'll let you know how the printing turns out.

Sue

Thanks id like to hear how it goes too

Well, I used the info I learned about pixel dimensions and dpi and created a
..jpg instead of a .gif which was then printed/photocopied onto business cards
that turned out great.

Thanks to Richard and Lorraine!

website and the basic infirmation which i was unable to understand earlier have solved the issues. thanks fro that advice