5 Jul
2011
5 Jul
'11
1:03 a.m.
On 05/07/2011 07:50, Dave Caroline wrote:
>>> 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.
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.
--
Pete