Re: SUMMARY AND FOLLOWUP QUESTIONS: Re: Acrobat file sizes

[Max Wyss <prodok -at- prodok -dot- ch>]

You're welcome, Gilda.

The reason why I prefer TIFF is that it behaves a bit better in Frame on
Mac, compared to GIF, and that it seems to run a bit snappier (because
Frame does not need to decompress the GIF on the fly, but can simply load
in the TIFF). It also does not have the 256 color limitation of the GIF
format. Otherwise, if your screenshots are always below 256 colors, I don't
see much of a problem using GIF instead.

That the GIFs are smaller than the TIFFs is understandable, as the GIF
format is a compressed format by design, whereas TIFF may or may not be
compressed. As you have noticed, when you end up in the PDF, there is no
real difference in size.

You pretty well have described artefacts. They are pixels with another
color than intended around sharp contrasts. They can be lines, particularly
when the contrast follows a sharp straight line.

When you have those artefacts, you can no longer get rid of them. The
conversion to GIF is essentially to prevent further degradation of the
quality. As you have noticed, only when you come from a "clean" screenshot
directly to GIF (or TIFF), you will have a "clean" image in your PDF.

Hope, this can help further.


Max Wyss
PRODOK Engineering
Low Paper workflows, Smart documents, PDF forms
CH-8906 Bonstetten, Switzerland

Fax:  +41 1 700 20 37
e-mail:  mailto:prodok -at- prodok -dot- ch
http://www.prodok.ch



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Thanks again for your detailed explanation. I've experimented with a few
files, and I can see why TIFF or GIF would be better than JPG.

I hope you don't mind - I have a few more questions:

   The original reason we switched from BMP to JPG was that we're now using
   Quadralay WebWorks Publisher to create online help in HTML format. WWP
   was automatically converting the BMP files to either JPG or GIF, and I
   was told by a friend that we'd be better off doing the conversion
   ourselves, before the WWP stage. As you know, we chose JPG, hence all
   our current problems. So my question is - if WWP seems to want GIF or
   JPG, should we switch to GIF, even though you preferTIFF?

   I've compared file sizes. While the Acrobat file sizes are virtually
   identical, the original GIFs are much smaller than the TIFFs. I assume
   that's to be expected? And if so, wouldn't this be a good argument for
   choosing GIF?

   I'm not familiar with the term "artefact", but I'm guessing it refers to
   funny lines in the JPG picture. Is that correct?

   As for converting JPGs in batch to GIF, I've experimented with the batch
   conversion facility in Paint Shop Pro (I don't have Photoshop), and I
   don't think it will work . It seems to keep the funny lines from the
   JPG. The pictures only look good if I capture them straight from the
   software. Am I missing something obvious?


Thanks for the tip on 8-bit ZIP compression in Distiller.  No matter which
format I finally choose, 8-bit ZIP compression seems to be the best choice
regardless.

Gilda