In article , RJH
wrote:
The main problem for future historians and academics is how to *know*
the results are always perfectly accurate when they may have no access
to an original or a plain scan. If they need to refer to a more
'reliable' version then they may as well use that!


Yes, I see what you mean now. Can't say it would have occurred to me to
be *that* important! But of course libraries and so on would need some
form of standard.

Is there a preferred method of archiving documents to pdf? I'd assume
it'd be a page-to-image type arrangement? A quick search shows PDF/A:

https://www.pdfa.org/pdfa-faq/

And from there, Adobe Acrobat appears to offer the option.

The problem being that this may not be something someone 100 years from now
may have to hand. And the more layers of tweaking there are, the more ways
to get mistakes or problems there will be.

So PDF isn't 'preferred' at all. Although, as will millions of Word docs,
future historians may have to struggle with them when MicroSoft have long
gone.

Wonder why Keith saved them in that way?

I've exchanged a couple of emails with him about this. I think he felt this
was the best way to minimise file size whilst keeping visual quality.
Certainly OCR is useful for that. Problem is that this makes a number of
implicity assumptions about what rendering software people are using, etc.
Which may not be so for the far future.

Indeed, he said to me he scans at 600 dpi and doesn't use jpegs. But the
patchwork images in the file I looked at *are* jpegs, and not all 600 dpi.
I'm not sure yet if he knows that his PDF software may be doing that
without him realising.

Simple example of potential causes of problems. When rendered on-screen the
tendency for many OS is to assume a base of 72dpi. Yet the main OS I use a
lot of the time is based on 90 dpi. So the same 'size' of image on-screen
calculated in terms of a paper size specified by a PDF in inches (or mm)
may look better on one machine than the other. Then consider rips or
renderers for paper. There you'd have to rely on an lpi that is large
enough to ensure this won't matter.

What dpi will screens on devices 100 years from now be based upon? Seems
doubtful it will be as low as 72 or 90. But who knows (yet)?

Hence even if a PDF 'optimally' scales things for reading, that
'optimisation' includes some assumptions that may be false. And some PDFs I
see have no dpi values for some images.

Hence the simplest approach is to keep to plain bitmaps with a specificed
dpi. One bitmap per page/scan. This removes all the added 'clever'
processes that give more ways to slip up.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

"Jim Lesurf" wrote in message
...
In article , RJH
wrote:
The main problem for future historians and academics is how to *know*
the results are always perfectly accurate when they may have no access
to an original or a plain scan. If they need to refer to a more
'reliable' version then they may as well use that!


Yes, I see what you mean now. Can't say it would have occurred to me to
be *that* important! But of course libraries and so on would need some
form of standard.

Is there a preferred method of archiving documents to pdf? I'd assume
it'd be a page-to-image type arrangement? A quick search shows PDF/A:

https://www.pdfa.org/pdfa-faq/

And from there, Adobe Acrobat appears to offer the option.

The problem being that this may not be something someone 100 years from
now
may have to hand. And the more layers of tweaking there are, the more ways
to get mistakes or problems there will be.

So PDF isn't 'preferred' at all. Although, as will millions of Word docs,
future historians may have to struggle with them when MicroSoft have long
gone.

Wonder why Keith saved them in that way?

I've exchanged a couple of emails with him about this. I think he felt
this
was the best way to minimise file size whilst keeping visual quality.
Certainly OCR is useful for that. Problem is that this makes a number of
implicity assumptions about what rendering software people are using, etc.
Which may not be so for the far future.

Indeed, he said to me he scans at 600 dpi and doesn't use jpegs. But the
patchwork images in the file I looked at *are* jpegs, and not all 600 dpi.
I'm not sure yet if he knows that his PDF software may be doing that
without him realising.

Simple example of potential causes of problems. When rendered on-screen
the
tendency for many OS is to assume a base of 72dpi. Yet the main OS I use a
lot of the time is based on 90 dpi. So the same 'size' of image on-screen
calculated in terms of a paper size specified by a PDF in inches (or mm)
may look better on one machine than the other. Then consider rips or
renderers for paper. There you'd have to rely on an lpi that is large
enough to ensure this won't matter.

What dpi will screens on devices 100 years from now be based upon? Seems
doubtful it will be as low as 72 or 90. But who knows (yet)?

Hence even if a PDF 'optimally' scales things for reading, that
'optimisation' includes some assumptions that may be false. And some PDFs
I
see have no dpi values for some images.

Hence the simplest approach is to keep to plain bitmaps with a specificed
dpi. One bitmap per page/scan. This removes all the added 'clever'
processes that give more ways to slip up.

Jim

I think you have to distinguish between amateurs putting past printed
material online in a format suitable for interested readers to enjoy and
professionals creating long term historical archives. The Bristish Museum
has Wireless World in its collection and no doubt will get around to a
digital archive before the paper deteriorates too far. That will use
something like JPEG2000 which would not be very convenient for direct use by
a casual reader wanting to download and browse the magazine.

In article , MikeS
wrote:
I think you have to distinguish between amateurs putting past printed
material online in a format suitable for interested readers to enjoy and
professionals creating long term historical archives.

Yes, I'd agree. I can see why PDF is very convenient as things stand for
many people. More so than a set of 'one file per page' with larger file
sizes. Similarly, for various current 'e-books' formats.

FWIW UKHHSoc do use and accept PDFs, even ones that have the problems.
You'll find examples on the public site. Simply because having access to
the information content is much better than *not* having it. But as soon as
archiving for the future is concerned, the kinds of points I made begin to
be things we need to consider. So they are something I worry about and try
to alert people to take into account.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html