5 Jul
2011
5 Jul
'11
1:30 a.m.
On Tue, Jul 5, 2011 at 9:03 AM, Pete Turnbull <pete at dunnington.plus.com> wrote:
On 05/07/2011 07:50, Dave Caroline wrote:
no one image at a time not the whole fiche!
>>> I don't think you need higher
resolution, just more magnification.
>
> More magnification can make it feasable to photograph one frame of the
> fiche at a time.
> Higher resolution may make it feasable to photograph the entire fiche
> card
> at once.
You'd need an awfully high-res sensor to do that! ?Back-of-envelope
arithmetic:
If you want something equivalent to scanning a 10.5x8 page at 400dpi, you
need 3200 pixels across a (portrait) page.
The 1978 BA11-K fiche I have in front of me is a low-magnification (by DEC
standards one, and it's 16 pages across, but they're landscape format pages,
so that works out to 10.5 x 400 x 16 = 67,000 pixels wide, and therefore the sensor would have to be about 67,000 x 48,000 =
3,216,000,000 pixels. ?Thats
3216 megapixels.
The 1987 Bulletin fiche I have in front of me is 25 (portrait) pages across.
?400dpi x 8" x 25 = 80,000, which is even worse.
Even if you accepted 100dpi, you still end up needing a sensor of about 200
megapixels.
I have just done most of one fiche the
squint down the eyepiece
move fiche to fit
press button see if it can focus, repeat move till focus got
take pic hold
still 4 secs
is a crap user experience!
did you notice the qty in my other reply,
6k fiche say 71 images per fiche if we take the rrd53 as an average
and 8 secs per image
3408000 seconds of peering down the eyepiece getting backache
Also makes it feasable to use cheaper optics that
are vignetting
Possibly, but a lens that's extended (for higher magnification) will reduce
or remove the vignetting problem more quickly.
The canon with its mirror is basicly not really
suitable to the high
picture qty needed here
hence me looking for a more suitable body to scavange/use, I really
need a live PC image for lining up
So Im not investing in bits to go the canon route
Why isn't it suitable for lining up? ?It's a reflex -- so WYSIWYG. ?I could
understand that it might be hard to get at the
eyepiece when it's all set
up, but you could try getting an angle finder attachment. ?The Seagull ones
aren't "insanely great" quality compared to genuine Pentax ones (for
example) but they're easily good enough for alignment, and cheap.
cheap still does not cut it for someone out of work
probably the right way is a pair of rollers and some optics and the
scanner bar from a flatbed
and a hacked sane driver for the resultant scanner but keeping it in
focus will not be easy
Dave Caroline