On Thu, 20 Nov 2008, Peter Alefounder wrote:
>
> Gordon Scott <gordon@???> wrote:
> > > 2. At least 10 megapixels.
> >
> > It seems this is not necessarily a good thing.
>
> Maybe so... but that is what I want. Some old documents can be
> quite hard to read, even the original item. What I want to achieve
> is at least 300dpi for an A4 page, or a little larger (these
> documents are not always convenient sizes), because I might have to
> join several images together. I expect to have to re-size, rotate
> and change perspective: for that, I find it is best to start with a
> higher resolution than I want to finish with.
But if the quatlity is worse than, say, an 5Mpx camera, it's still not
delivering what you _need_.
This sounds like a time that you need to take a tough sample to a camera
shop and try some real cameras.
If you need 10Mpx for the resolution, that my push you to a digital SLR,
together with a comensurate price.
BTW I think my earlier CCD pixel size should have read nanometers not
micrometers. Doh!
> My thoughts exactly. No problem with a viewfinder for a distant
> target, but close-up I would rather see exactly what is on the CDD
> - particularly if the item needs to be done in sections. I've come
> across manorial court rolls with some pages several feet long. How
> do these cameras cope with things that are not flat? - not just
> because they've been rolled up for centuries, but parchment that
> wasn't flat to start with? Is there sufficient depth of focus?
Depth of field should not be a problem given half-decent lighting. I've
been known to use a cheap (about a tenner) halogen floodlight
reflecting from foil or card to give a reasonably even and bright light.
Flash from the camera often gives hotspots and glare on documents.
You'll presumably be using wide-ish angle lenses, to depth of field
should be huge.
BTW, you'll need a colour balancing option or manual exposure control,
as photographing white paper for example tends to fool auto exposures.
> [3], earlier MJU series cameras all appeared as USB mass storage,
> so I expect this one would do so as well.
The three Olympus digitals we have/nad (one was stolen) have all
appeared as mass storage devices, though are also recognised as a camera
.. I guess that may also offer PC control, but I've never tried it.
--
Gordon Scott http://www.gscott.co.uk
Haiku: Tragic Irony
Imagined Life Without Walls
Windows Crash to Floor.
Linux ... Because I like to *get* there today.
