scanning old negatives

In article , Dale wrote:

Phillip Helbig (undress to reply):
Does it appear possible that re-scanning the film in higher
resolution would produce better results? (Of course one can scan
it in arbitrarily high resolution and produce arbitrarily large
JPEG files. The point is, what resolution is meaningful and what
file size should that produce.)

I think film is around 4000 dpi

Yup.

--
Sandman

On 05/28/2015 12:20 PM, Sandman wrote:
In article , Peter Irwin wrote:

nospam:
if the scanner can resolve individual film grains, then it is
capturing *all* of the detail the film holds.

That is true in the sense that if you could run 300 km/h you would
be faster than any taxicab.

But in fact a 4000 dpi scanner can't resolve anything smaller than
12.7 microns, and that is larger then the largest film grains in any
normal film. Film grains are on average less than a micron in size,
but there is a large variation especially in fast films.

Film resolution isn't measured in grain size, however. It's mesaured in lines/mm,
and the absolut best film you could get back in the day was rated at 200
lines/mm.

And this 200 lines/mm is only valid for scenarios where you use a perfect lens,
camera on tripod, mirror up etc etc. The most ideal parameters possible. I use to
settle for a 75 lines/mm as a "really good" analog shot.

Each "line" is one complete light/dark cycle so in order to represent it, you
need at least 2 pixels per line. A 35mm frame is 36x24mm and 75 lines/mm
translates thus to 150 pixels/mm, which means that the comparable pixel
resolution of a very sharp analog film shot is 5400 x 3600 pixels, or 19.4
megapixel.

So, how big will a 36x24mm film negative be with a 4800dpi scanner? Well the end
result will be a 6803x4535 image, or a 30.8 megapixel image.

If your scanner maxes out at 4000DPI, the end result is a 21.4 megapixel, just
above the threshold of max resolution you can get out of a film negative, which
is probably why most scanner manufacturers have stopped at 4000 DPI. Epson has
the V750 that goes up to 6400DPI, which results in a 55 megapixel image, but
again, that's pretty wasted since the original only holds about 20 megapixels of
information.

snip
I won't argue your math; it appears correct. But, you base your math on
75 lines/mm, which you say is "really good". And I won't argue that. But
you also say that "the absolute best film you could get back in the day
was rated at 200 lines/mm", and this is only valid for a perfect world.
Probably also true.

My point is: Let's strive for that perfect world scenario. I normally
shoot on a tripod. I use manufacturer's lenses designed for the camera,
and I often raise the mirror. What if I am getting better than 75
lines/mm? Why should I be limited by the neg scan? Why not print
optically, so that everything on the negative appears on the print?

And so far, we've only considered getting maximum info from the neg into
a data file- we haven't looked at any losses from the printer, whether
it's laser jet, ink jet, or light jet.

Check out the test photos on this page:
http://petapixel.com/2014/12/18/comp...-film-digital/

--
Ken Hart

On 5/28/2015 2:55 PM, Ken Hart wrote:


snip
I won't argue your math; it appears correct. But, you base your math on
75 lines/mm, which you say is "really good". And I won't argue that. But
you also say that "the absolute best film you could get back in the day
was rated at 200 lines/mm", and this is only valid for a perfect world.
Probably also true.

My point is: Let's strive for that perfect world scenario. I normally
shoot on a tripod. I use manufacturer's lenses designed for the camera,
and I often raise the mirror. What if I am getting better than 75
lines/mm? Why should I be limited by the neg scan? Why not print
optically, so that everything on the negative appears on the print?

And so far, we've only considered getting maximum info from the neg into
a data file- we haven't looked at any losses from the printer, whether
it's laser jet, ink jet, or light jet.

Check out the test photos on this page:
http://petapixel.com/2014/12/18/comp...-film-digital/


Thank you for that posting. It makes me htink about starting to play
with my old film cameras.



--
PeterN

In article , Ken Hart wrote:

Sandman:
Film resolution isn't measured in grain size, however. It's
mesaured in lines/mm, and the absolut best film you could get back
in the day was rated at 200 lines/mm.

And this 200 lines/mm is only valid for scenarios where you use a
perfect lens, camera on tripod, mirror up etc etc. The most ideal
parameters possible. I use to settle for a 75 lines/mm as a
"really good" analog shot.

Each "line" is one complete light/dark cycle so in order to
represent it, you need at least 2 pixels per line. A 35mm frame is
36x24mm and 75 lines/mm translates thus to 150 pixels/mm, which
means that the comparable pixel resolution of a very sharp analog
film shot is 5400 x 3600 pixels, or 19.4 megapixel.

So, how big will a 36x24mm film negative be with a 4800dpi
scanner? Well the end result will be a 6803x4535 image, or a 30.8
megapixel image.

If your scanner maxes out at 4000DPI, the end result is a 21.4
megapixel, just above the threshold of max resolution you can get
out of a film negative, which is probably why most scanner
manufacturers have stopped at 4000 DPI. Epson has the V750 that
goes up to 6400DPI, which results in a 55 megapixel image, but
again, that's pretty wasted since the original only holds about 20
megapixels of information.

snip I won't argue your math; it appears correct. But, you base your
math on 75 lines/mm, which you say is "really good". And I won't
argue that. But you also say that "the absolute best film you could
get back in the day was rated at 200 lines/mm", and this is only
valid for a perfect world. Probably also true.

My point is: Let's strive for that perfect world scenario. I
normally shoot on a tripod. I use manufacturer's lenses designed
for the camera, and I often raise the mirror. What if I am getting
better than 75 lines/mm? Why should I be limited by the neg scan?
Why not print optically, so that everything on the negative appears
on the print?

Youä're preaching to the choir, I agree that optical enlargement is better, but
only because - then you know.

As for your question, since the resolution increases massively if you increase
the lines/mm, here are some end results:

75 lines/mm: 19.4 MP
100 lines/mm: 34.5 MP (still in line with the D810)
150 lines/mm: 77.7 MP
200 lines/mm: 138 MP

These are all theoretical of course.

And I must stress, 200 lines/mm was extraordinarliy good film when available,
and the math is only valid if it was used on a rock steady tripod, mirror up,
100% perfect focus, completely still subject etc etc.

Model and product photos are the only thing that probably matches that, and
most of those would be shot on medium format.

A 200 lpmm medium format would be a 2.7 *giga*pixel image, but a 75 lpmm film
would be a "low" 391 MP

So, for 999 out of a 1000 35mm shots taken in this world, I'd say 20 MP is more
than enough to represent the quality. There are exceptions, which is only
important to the very high end studio photographers available.

Hey, maybe I should buy that autofocus Mamiya 645 anyway... :-D

And so far, we've only considered getting maximum info from the neg
into a data file- we haven't looked at any losses from the printer,
whether it's laser jet, ink jet, or light jet.

True, we haven't. But most consumer scanners and printers match when it comes
to DPI, most prosumer scanners/printers do as well.

--
Sandman