«

I tried saving a RAW image as a tiff so I could play with it in PS5.5. I was
surprised to see the file size jump from 8 meg to 35 meg. I figured raw was
the straight data from the ccd and that tif at least wouldn't compress it,
but why is it so much bigger?

Also, is there any advantage to working with the raw file as opposed to tif?

mike regish

mike regish wrote:

> I tried saving a RAW image as a tiff so I could play with it in PS5.5. I was
> surprised to see the file size jump from 8 meg to 35 meg. I figured raw was
> the straight data from the ccd and that tif at least wouldn't compress it,
> but why is it so much bigger?
>
> Also, is there any advantage to working with the raw file as opposed to tif?

You don't mention what camera you're using, but most use some
level of lossless compression when creating RAW files. This
is to save memory card space.

It sounds like you might be saving as 16 Bit TIFF.. I think
PS 5.5 can only handle 8 bit images so you're not gaining anything
by saving as 16 bit TIFF for editing.

You'll need Photoshop CS or Photoshop Elements 3.0 to do
proper 16 bit editing.

I'm using the Dimage Viewer software that came with the Minolta 7D. It has 2
choices for saving as tif-24 and 48 bit. The 48 bit was clicked when I
opened it. Is this the same thing you're referring to?

mike

"Jim Townsend" <> wrote in message
news:...

> You don't mention what camera you're using, but most use some
> level of lossless compression when creating RAW files. This
> is to save memory card space.
>
> It sounds like you might be saving as 16 Bit TIFF.. I think
> PS 5.5 can only handle 8 bit images so you're not gaining anything
> by saving as 16 bit TIFF for editing.
>
> You'll need Photoshop CS or Photoshop Elements 3.0 to do
> proper 16 bit editing.
>
>
>
>
>

mike regish wrote:
> I'm using the Dimage Viewer software that came with the Minolta 7D. It has 2
> choices for saving as tif-24 and 48 bit. The 48 bit was clicked when I
> opened it. Is this the same thing you're referring to?
>
> mike

Hi Mike...

If it helps any, saying 8 or 24 in this context is the same thing

8 bits times 3 colours = 24 bits total

and of course 16 bits times 3 colours = 48 bits.

Ken

mike regish wrote:

> I'm using the Dimage Viewer software that came with the Minolta 7D. It has 2
> choices for saving as tif-24 and 48 bit. The 48 bit was clicked when I
> opened it. Is this the same thing you're referring to?

Yes..

8 bit refers to how many bits in a single color. There are
three primary colors so the total is 8 x 3 = 24 bits.

With 48 bit you have 48 / 3 = 16 bits per color.

(Just another confusing thing

OK. I was wondering why the big difference.

Thanks.

mike

"Ken Weitzel" <> wrote in message
news2K2e.858732$8l.748846@pd7tw1no...
>
> Hi Mike...
>
> If it helps any, saying 8 or 24 in this context is the same thing
>
> 8 bits times 3 colours = 24 bits total
>
> and of course 16 bits times 3 colours = 48 bits.
>
> Ken
>

I did not see this mentioned yet, in raw data there is only one 12 bit
value for each pixel, when this is converted into color data there now
needs to be three values for each pixel, even if these values are only
8 bits you now are storing 24 bits for each pixel where you were
storing 12 before, now it you are using 16 bits / color, this jumps to
48 bits per/pixel or 4 time the space for the raw data, add to that
some losselss compression in the raw file and you have a large increase
when saving to tiff.

Scott

"Scott W" <> wrote in message
news: ups.com...
>I did not see this mentioned yet, in raw data there is only one 12 bit
> value for each pixel, when this is converted into color data there now
> needs to be three values for each pixel, even if these values are only
> 8 bits you now are storing 24 bits for each pixel where you were
> storing 12 before, now it you are using 16 bits / color, this jumps to
> 48 bits per/pixel or 4 time the space for the raw data, add to that
> some losselss compression in the raw file and you have a large increase
> when saving to tiff.
>
> Scott

Okay, now I don't get it. Compression is compression. If you compress a
file it has to come back to it's original size so you can see it. How does
a RAW file act as a lossless compression without changing anything when you
open and close it? I thought a tiff file was "no" compression at all. Does
RAW have more to do with the file coming straight from the camera with
little or no changing of the file in the camera, regardless of settings?

On 3/30/05 10:31 PM, in article npCdnVJFVaa04NbfRVn-,
"Sheldon" <> wrote:

>
> "Scott W" <> wrote in message
> news: ups.com...
>> I did not see this mentioned yet, in raw data there is only one 12 bit
>> value for each pixel, when this is converted into color data there now
>> needs to be three values for each pixel, even if these values are only
>> 8 bits you now are storing 24 bits for each pixel where you were
>> storing 12 before, now it you are using 16 bits / color, this jumps to
>> 48 bits per/pixel or 4 time the space for the raw data, add to that
>> some losselss compression in the raw file and you have a large increase
>> when saving to tiff.
>>
>> Scott
>
> Okay, now I don't get it. Compression is compression. If you compress a
> file it has to come back to it's original size so you can see it. How does
> a RAW file act as a lossless compression without changing anything when you
> open and close it? I thought a tiff file was "no" compression at all. Does
> RAW have more to do with the file coming straight from the camera with
> little or no changing of the file in the camera, regardless of settings?
>
>
It is possible to compress a file on a lossless (no-loss) basis. An example
of this is in Photoshop when you save as a Tiff you are presented with a
second dialog box that lets you select, among others, LZW compression. If
you choose LZW the file compresses without loss. A similar thing happens
with raw files. When these files are opened they open back to their true
size.

mike regish wrote:
> I tried saving a RAW image as a tiff so I could play with it in PS5.5. I was
> surprised to see the file size jump from 8 meg to 35 meg. I figured raw was
> the straight data from the ccd and that tif at least wouldn't compress it,
> but why is it so much bigger?
>
> Also, is there any advantage to working with the raw file as opposed to tif?
>
> mike regish
>
>
In spite of its name, a RAW file has been processed to some degree. A
TIFF file just stores 24 bits of information for each pixel, making very
large files.


--
Ron Hunter