Re: Overheard on the scanner
- From: mike weber <fairportfan@xxxxxxxxx>
- Date: Fri, 11 Jul 2008 00:52:05 -0400
On Thu, 10 Jul 2008 23:29:40 -0400, Joe Ellis
<synthfilker@xxxxxxxxxxxxx> wrote:
You've yet to give any indication that your "100 letter" figure is
anything but a wild-ass guess for the contemporary technology. For
example, your "100 letter table" mentioned above would have to be nearly
10 feet x 10 feet. I'm sure there are formulae that will tell us how far
away a camera (or enlarger) would have to be to capture an image of that
size on a single plate
(focal length) * ((linear dimension of subject)/(same linear dimension
of plate))
My Olympus Pen FT shoots an 18 x 24 mm negative, and has a 38mm normal
lens.
To capture a picture of a six-foot man exactly in that frame, the
distance is 38mm * (72 in/1 in) = 2736 mm = ~9 feet.
To put the same six-footer in the frame with my 500mm lens, it's 500mm
* (72 in/1 in) = 36000 mm = 36 m = ~120 feet.
So a 10 x 10 matrix of (say) six by six inch letters would be 5 feet
on a side.
To reduce if to, say, a six-inch-square plate, obviously, requires a
reduction of ten-to-one, so the distance would be ten times the focal
length of the lens.
All other things being equal, higher-quality lenses tend to be slower.
Since f-stop is aperture/focal length, but light-gathering ability is
related to the diameter of the aperture (i think to the square, but it
may be a straight proportion), making the ;lens larger is a Good
Thing, working with slow film, but that, of course, increase the focal
length, which in turn increases the necessary distance...
(The "normal" focal length for a 6 x 6 inch negative, BTW, would be
about 8.5 inches. "Normal" lenses are roughly equal in focal length
to the diagonal of the negative to be shot for a standard 35mm [24 x
36 negative], the diagonal is about 43 mm, and lenses run 45 to 52 mm
on cameras i've seen. For my Pen, the diagonal is 30 mm, so the 38 is
actually a little long...)
.
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- Re: Overheard on the scanner
- From: mike weber
- Re: Overheard on the scanner
- From: Keith F. Lynch
- Re: Overheard on the scanner
- From: mike weber
- Re: Overheard on the scanner
- From: Keith F. Lynch
- Re: Overheard on the scanner
- From: Joe Ellis
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