RE: Advice on designing graphics and mis-information

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"Carol Geary" wrote:
>Are there any sources on the web that explain this in more detail. When
>I was saving TIFFs from my Macintosh to PC, I decided to save them as
>BMPs. They seemed to be about the same size file. For example a 1MB Mac
>TIFF = 1MB BMP. Since Mac and PC use the same BMPs, that seemed to be
>the best cross-platform format. The files looked equivalent to me on my
>computer screen. They were 32-bit scans of photographs. I had worried
>about BMPs, but couldn't see any problems. Do the problems mainly come
>up when printing?

I usually just lurk in the background in the mailing lists but the poor
information being spread by Mr. Durham brought me out of hiding. Since I
contribute so infrequently my answers are always a bit long winded.
Information concerning the myraid image file formats can be found at
http://www.faqs.org - they seem to be having server trouble of late. An
alternate link would be
http://www.onlyamiga.freeserve.co.uk/graphics.fileformats-faq.part3.txt --
all image file formats are not covered in these FAQ's but the major players
are.

To clear up the BMP format... Mr. Durham wrote that "BMPs are among the low
end of graphics -- only really good for Powerpoint and word docs ---
especially for cheesy clip art. BMPs are meant for low-res graphics-- "
This is incorrect. Disgustingly so. The BMP format is NOT low-end. BMP is a
perfectly acceptable image format so long as you don't need greater then 16
million colors and don't mind large file sizes. The limitation of BMP is
it's color depth and file size (even with RLE compression). BMP format
supports RGB but not CMYK. It is NOT a lossy format. It is not just meant
for low-resolution graphics or for "cheesy clip art" -- BMP is just an
image format created by Microsoft to be used within the Windows OS. There
are OS/2 and Alpha BMP formats as well. Working in the print profession on
both Mac and PC systems, I usually use TIFF as my cross platform image file
format. It supports CMYK and TIFF was designed to be as compatible as
possible and I have NEVER had a problem using it.

To clear up the question pertaining to problems in printing. If you are
trying to print an RGB image on a CMYK output device you will have problems
with matching colors as there are colors contained in the RGB color space
that cannot be faithfully reproduced in the CMYK color space. A quick
explanation of why what you see isn't what you get (when printing) can be
read at
http://www.adobe.com/supportservice/custsupport/TECHGUIDE/PSHOP/CMS3/wysiwyg
.html -- If you're really all that interested you can read about color
gamuts at http://www.wasatchinc.com/digigrafix.gamut.html or
http://www.adobe.com/supportservice/custsupport/SOLUTIONS/c9fe.htm

There is plenty of information regarding image formats and color
information for you on the web. Kodak (www.kodak.com), Adobe
(www.adobe.com),etc. etc. etc.

So *I* am not accused of spreading bad information I'll pass the blame...
BMP information came from ZDNet. Typically, I couldn't find information on
the BMP format on Microsoft's website. ZDNet's information about BMP files
(in short is as follows): ".BMP files encode color information using 1, 4,
8, 16, or 24 bits per pixel (bpp). The bits-per-pixel count, also known as
the image's color depth, determines the maximum number of colors the image
may have. A 1-bpp image is limited to 2 colors, while a 24-bpp image can
contain more than 16 million different colors." The full article can be
found at http://www.zdnet.com/pcmag/pctech/content/15/21/tu1521.002.html

TIFF Information came from Adobe. Adobe chairs the TIFF Advisory Committee,
which is a group of imaging experts who define future versions of TIFF
specifications. This is what they have to say about the TIFF image format:
"TIFF is a tag-based image file format that is designed to promote the
interchange of digital image data. TIFF is now the defacto standard for
desktop images and is supported by all major imaging hardware and software
developers. It provides a general purpose data format and is compatible
with a wide range of scanners and image-processing applications. It is
device independent and is used extensively in most operating environments,
including Windows, Macintosh, UNIX, and NeXT. This non-proprietary industry
standard for data communication has been implemented by most scanner
manufacturers and desktop publishing applications."
The full article (most of it is above) can be found at
http://www.adobe.com/supportservice/custsupport/NOTES/2596.htm

I hope that I have answered some of your questions Carol. If you have any
others ask and I may stop lurking once again.
 
Paul


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Paul Clark
pclark(at)gate.net

Art History / Graphic Design / HTML / JS / Perl / VB
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