Film grain size as dpi

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Fri, 25 July 2003 18:05 Go to next message
Eric Gill (Photoshop expert)
"Steve Simpson" <simpson34@coxpanties.net> wrote in
news:QDgUa.18888$Bp2.11576@fed1read07:

>> Does anyone happen to have handy a table of dpi values corresponding
>> to various ASA/ISO film ratings?
>>
>> In other words, express film grain size as dpi.
>>
>
> I did a bit of research on scanners recently and there seems to be a
> consensus that 4,000 dpi is needed to capture all of the detail in
> 35mm film.

That depends on the how fine grain of the film is, as Don noted.

Blow most 35MM slides up 1300% (4,000 ppi to 300 for your average magazine
print), and you will get mush for details.

> That may not correspond directly to grain size, but it is the only
> relevant info I have on the subject.

Right. I wish someone in a good position to do so would do some work to
establish a good rule of thumb, if not the definative guide.
Fri, 25 July 2003 18:18 Go to previous messageGo to next message
i.perryman (Photoshop begginer)
Is this possible ?
Don't films with the same ISO have different RMS granularities depending on
the type and the manufacturer?
So although perhaps you could relate grain size to dpi there wouldn't
neccesarily be a correlation with the ISO although I suppose you could
construct a table for a named range of film by the same manufacturer .

"Don" <phoney.email@yahoo.com> wrote in message
news:3f205b02.11771569@news.individual.net...
> Does anyone happen to have handy a table of dpi values corresponding
> to various ASA/ISO film ratings?
>
> In other words, express film grain size as dpi.
>
> TIA!
>
> Don.
Fri, 25 July 2003 19:36 Go to previous messageGo to next message
john[1] (Photoshop begginer)
In article <3f205b02.11771569@news.individual.net>, phoney.email@yahoo.com
(Don) wrote:

> Does anyone happen to have handy a table of dpi values corresponding
> to various ASA/ISO film ratings?
>
> In other words, express film grain size as dpi.

Kodak has published metrics concerning grain size, but quite wisely
doesn't try to corelate them to so-called DPI (or SPI) probably because
the later is just a cascade of impressionistic marketing metrics/lies.

So, what do you really want to know/do?
Fri, 25 July 2003 18:39 Go to previous messageGo to next message
Bart van der Wolf (Photoshop expert)
"Don" <phoney.email@yahoo.com> wrote in message
news:3f205b02.11771569@news.individual.net...
> Does anyone happen to have handy a table of dpi values corresponding
> to various ASA/ISO film ratings?
>
> In other words, express film grain size as dpi.

Film grains, or dye clouds, have different sizes in a single emulsion. They
are also partially overlapping each other when viewed in a 2D projection of
a 3D space (film emulsion has thickness and can consist of several different
layers).
It is the irregular aggregates that are perceived as graininess.
One can measure the physical granularity with a statistical measure that
varies with density.

So, it cannot be expressed in a single scan resolution number.

Bart
Sat, 26 July 2003 11:24 Go to previous messageGo to next message
phoney.email (Photoshop expert)
There are also deviations simply because film is in the contiguous
analog domain and doesn't follow a nice uniform digital matrix, but I
was hoping for a general rule-of-thumb type table.

Don.

---

On Fri, 25 Jul 2003 22:18:25 +0000 (UTC), "i.perryman"
<i.perryman@btopenworld.com> wrote:

>Is this possible ?
>Don't films with the same ISO have different RMS granularities depending on
>the type and the manufacturer?
>So although perhaps you could relate grain size to dpi there wouldn't
>neccesarily be a correlation with the ISO although I suppose you could
>construct a table for a named range of film by the same manufacturer .
>
>"Don" <phoney.email@yahoo.com> wrote in message
>news:3f205b02.11771569@news.individual.net...
>> Does anyone happen to have handy a table of dpi values corresponding
>> to various ASA/ISO film ratings?
>>
>> In other words, express film grain size as dpi.
>>
>> TIA!
>>
>> Don.
Sat, 26 July 2003 11:24 Go to previous messageGo to next message
phoney.email (Photoshop expert)
Yes, two very good points, Bart: non-uniform (variable grain) size and
3D nature of film.

Of course, there is also aliasing so even if grain size were known in
dpi terms, according to the sampling theory, the dpi of the scanner
would have to be at least double that. I don't know how, or even if,
this applies to graphics, but it's usually problematic to express
non-discrete analog data in the discrete and finite digital domain...

Still, I believe a rough estimate should be possible to at least give
an indication of the order of magnitude (with appropriate caveats, of
course).

Don.

---

On Sat, 26 Jul 2003 00:39:05 +0200, "Bart van der Wolf"
<bvdwolf@nospam.nl> wrote:

>
>"Don" <phoney.email@yahoo.com> wrote in message
>news:3f205b02.11771569@news.individual.net...
>> Does anyone happen to have handy a table of dpi values corresponding
>> to various ASA/ISO film ratings?
>>
>> In other words, express film grain size as dpi.
>
>Film grains, or dye clouds, have different sizes in a single emulsion. They
>are also partially overlapping each other when viewed in a 2D projection of
>a 3D space (film emulsion has thickness and can consist of several different
>layers).
>It is the irregular aggregates that are perceived as graininess.
>One can measure the physical granularity with a statistical measure that
>varies with density.
>
>So, it cannot be expressed in a single scan resolution number.
>
>Bart
Sat, 26 July 2003 11:24 Go to previous messageGo to next message
phoney.email (Photoshop expert)
On Fri, 25 Jul 2003 18:36:16 -0500, john@stafford.net (J Stafford)
wrote:

>Kodak has published metrics concerning grain size, but quite wisely
>doesn't try to correlate them to so-called DPI (or SPI) probably because
>the later is just a cascade of impressionistic marketing metrics/lies.

Do you happen to have a link handy?

>So, what do you really want to know/do?

I'm about to embark on a mass scan of all my slides and negatives (for
personal use) using my 2700 dpi film scanner and was just wondering...

Don.
Sat, 26 July 2003 11:24 Go to previous messageGo to next message
phoney.email (Photoshop expert)
On Fri, 25 Jul 2003 13:41:58 -0700, "Steve Simpson"
<simpson34@coxpanties.net> wrote:

>> Does anyone happen to have handy a table of dpi values corresponding
>> to various ASA/ISO film ratings?
>>
>> In other words, express film grain size as dpi.
>>
>
>I did a bit of research on scanners recently and there seems to be a consensus that 4,000 dpi is
>needed to capture all of the detail in 35mm film.
>
>That may not correspond directly to grain size, but it is the only relevant info I have on the
>subject.

Thanks for that! I've got an older film scanner (Nikon LS30) which I
finally unpacked (it was sitting in the box for some 3 years). Even
though back then its 2700 dpi was considered quite respectable, by
today's standards - as you point out - it seems fairly modest now.

Don.
Sun, 27 July 2003 14:49 Go to previous messageGo to next message
Steve Simpson (Photoshop begginer)
> Of course, there is also aliasing so even if grain size were known in
> dpi terms, according to the sampling theory, the dpi of the scanner
> would have to be at least double that.

Actual dedicated film scanners (as opposed to high res flatbeds with film holders) do
multi-sampling, so the aliasing phenomena can be mitigated to a degree by the scanner's firmware
or software.

There is also a new piece of software specifically for that purpose and a demo is available.

http://argon.asf.com/asf/category.asp?catalog%5Fname=ASF& ;category%5Fname=Software+Plugins&pid=1000&tc=9998

Also check out:

http://www.scantips.com/

For some general info and a bunch of good links.
Mon, 28 July 2003 08:22 Go to previous messageGo to next message
phoney.email (Photoshop expert)
>> Of course, there is also aliasing so even if grain size were known in
>> dpi terms, according to the sampling theory, the dpi of the scanner
>> would have to be at least double that.
>
>Actual dedicated film scanners (as opposed to high res flatbeds with film holders) do
>multi-sampling, so the aliasing phenomena can be mitigated to a degree by the scanner's firmware
>or software.

As I mention elsewhere I do have a Nikon LS30 (2700 dpi) which is
brand new but was sitting in its box since I bought it (don't ask...).

Anyway, my first few test negative scans came out quite grainy which
surprised me. Also, it seems even though stored properly, film appears
to deteriorate much faster than photographs. This was not visible to
the naked eye, of course, by once scanned it all popped out. On the
other hand, as I write elsewhere, photographs fade.

>There is also a new piece of software specifically for that purpose and a demo is available.
>
> http://argon.asf.com/asf/category.asp?catalog%5Fname=ASF& ;category%5Fname=Software+Plugins&pid=1000&tc=9998

Will do. Thanks!

>Also check out:
>
>http://www.scantips.com/
>
>For some general info and a bunch of good links.

Yes, someone else pointed it out too. It's very useful indeed!

Don.
Mon, 28 July 2003 10:38 Go to previous messageGo to next message
tacitr (Photoshop expert)
>Also, it seems even though stored properly, film appears
>to deteriorate much faster than photographs.

What kind of film?

Color print film fades and changes color over time. Color transparency film
lasts longer, but can and will still fade over time. Black and white film,
properly processed and properly stored, will last for centuries.

--
Rude T-shirts for a rude age: http://www.villaintees.com
Art, literature, shareware, polyamory, kink, and more:
http://www.xeromag.com/franklin.html
Mon, 28 July 2003 10:50 Go to previous messageGo to next message
john[1] (Photoshop begginer)
In article <20030728103855.18340.00000556@mb-m15.aol.com>, tacitr@aol.com
(Tacit) wrote:

> >Also, it seems even though stored properly, film appears
> >to deteriorate much faster than photographs.
>
> What kind of film?
>
> Color print film fades and changes color over time. Color transparency film
> lasts longer, but can and will still fade over time. Black and white film,
> properly processed and properly stored, will last for centuries.

True. Persons interested in the archival quality of color photography
materials would be well served by consulting the authoritative source:
Wilhelm Imaging Research: http://www.wilhelm-research.com/

(Now if the photographer wants to explore an interesting alternative and
he shoots largely still lives, he can shoot his color in black-and-white
film with tricolor filtration - in camera separations :))
Tue, 29 July 2003 05:35 Go to previous messageGo to next message
phoney.email (Photoshop expert)
>>Also, it seems even though stored properly, film appears
>>to deteriorate much faster than photographs.
>
>What kind of film?
>
>Color print film fades and changes color over time. Color transparency film
>lasts longer, but can and will still fade over time. Black and white film,
>properly processed and properly stored, will last for centuries.

All of the above. Color negatives didn't suffer all that much from
fading but do have a very pronounced grain and general damage not
visible to the naked eye. Transparencies did fare much better, as you
point out, and are very good indeed. B&W is also fine except I didn't
fix one film long enough (or didn't use fresh chemicals) so it turned
quite cloudy. But I only have myself to blame for that...

Don.
Fri, 25 July 2003 13:05 Go to previous messageGo to next message
phoney.email (Photoshop expert)
Does anyone happen to have handy a table of dpi values corresponding
to various ASA/ISO film ratings?

In other words, express film grain size as dpi.

TIA!

Don.
Fri, 25 July 2003 14:54 Go to previous messageGo to next message
J C (Advanced Photoshop user)
On Fri, 25 Jul 2003 17:05:10 GMT, phoney.email@yahoo.com (Don) wrote:

>Does anyone happen to have handy a table of dpi values corresponding
>to various ASA/ISO film ratings?
>
>In other words, express film grain size as dpi.
>
>TIA!
>
>Don.


I remember reading that film grain ranges from 2500 to 3500 per inch
(someone feel free to correct me if I'm remembering wrong).

However, from my darkroom experience the same film stock can yield
different results depending on the temperature and time spent in the
developing solutions.

I've never seen a chart that gives the ranges for different film
ratings though.


-- JC
Fri, 25 July 2003 19:47 Go to previous messageGo to next message
i.perryman (Photoshop begginer)
I thought film grain sizes were measured in microns.
A film with a rms granularity of 9, for example, would have grains 9 microns
across
I would have thought therefore that you could apply the math as follows

For a 35mm film with G=9 you would get
36mm/9microns across = 4000 grains
24mm/9microns down = 2467 grains

Presumably if you were to scan at this resolution (4000X2467) each grain
would be individually represented. Scanning at a higher resolution would,
at least in theory, produce no improvement in quality.

If you want to work this in inches
1 inch = 25.4mm
for a film with G=9
25.4mm/9microns =2822 grains per inch ( = maximum dpi of 2822?)

For a higher definition film with smaller grains - say G=8
25.4mm/8microns =3175 grains per inch (= maximum dpi of 3175?)


"J C" <null@nowhere.net> wrote in message
news:4HwhP3qevRZ3WWJYI2q1tHijZZCx@4ax.com...
> On Fri, 25 Jul 2003 17:05:10 GMT, phoney.email@yahoo.com (Don) wrote:
>
> >Does anyone happen to have handy a table of dpi values corresponding
> >to various ASA/ISO film ratings?
> >
> >In other words, express film grain size as dpi.
> >
> >TIA!
> >
> >Don.
>
>
> I remember reading that film grain ranges from 2500 to 3500 per inch
> (someone feel free to correct me if I'm remembering wrong).
>
> However, from my darkroom experience the same film stock can yield
> different results depending on the temperature and time spent in the
> developing solutions.
>
> I've never seen a chart that gives the ranges for different film
> ratings though.
>
>
> -- JC
Sat, 26 July 2003 11:24 Go to previous messageGo to next message
phoney.email (Photoshop expert)
On Fri, 25 Jul 2003 18:54:49 GMT, J C <null@nowhere.net> wrote:

>On Fri, 25 Jul 2003 17:05:10 GMT, phoney.email@yahoo.com (Don) wrote:
>
>>Does anyone happen to have handy a table of dpi values corresponding
>>to various ASA/ISO film ratings?
>>
>>In other words, express film grain size as dpi.
>>
>>TIA!
>>
>>Don.
>
>
>I remember reading that film grain ranges from 2500 to 3500 per inch
>(someone feel free to correct me if I'm remembering wrong).

My 2700 dpi scanner puts me in the lower half end of that, then.

>However, from my darkroom experience the same film stock can yield
>different results depending on the temperature and time spent in the
>developing solutions.

Indeed, so I was really looking for a rough estimate.

>I've never seen a chart that gives the ranges for different film
>ratings though.

Over in "comp.graphics.apps.photoshop" the opinions as to why that is
range from physical inaccuracies of the analog domain (variable grain
size, 3D nature of emulsion, etc) to "shy" marketing departments
reluctant to admit the truth...

Don.
Sat, 26 July 2003 11:24 Go to previous messageGo to next message
phoney.email (Photoshop expert)
Excellent! Thanks very much for that. What film speed is the 9 micron
figure for?

And you're probably going to guess my next question now... ;-)

Do you happen to have a chart of how rms granularity relates to other
common ASA/ISO ratings?

Don.

---

On Fri, 25 Jul 2003 23:47:20 +0000 (UTC), "i.perryman"
<i.perryman@btopenworld.com> wrote:

>I thought film grain sizes were measured in microns.
>A film with a rms granularity of 9, for example, would have grains 9 microns
>across
>I would have thought therefore that you could apply the math as follows
>
>For a 35mm film with G=9 you would get
>36mm/9microns across = 4000 grains
> 24mm/9microns down = 2467 grains
>
>Presumably if you were to scan at this resolution (4000X2467) each grain
>would be individually represented. Scanning at a higher resolution would,
>at least in theory, produce no improvement in quality.
>
>If you want to work this in inches
>1 inch = 25.4mm
>for a film with G=9
>25.4mm/9microns =2822 grains per inch ( = maximum dpi of 2822?)
>
>For a higher definition film with smaller grains - say G=8
>25.4mm/8microns =3175 grains per inch (= maximum dpi of 3175?)
>
>
>"J C" <null@nowhere.net> wrote in message
>news:4HwhP3qevRZ3WWJYI2q1tHijZZCx@4ax.com...
>> On Fri, 25 Jul 2003 17:05:10 GMT, phoney.email@yahoo.com (Don) wrote:
>>
>> >Does anyone happen to have handy a table of dpi values corresponding
>> >to various ASA/ISO film ratings?
>> >
>> >In other words, express film grain size as dpi.
>> >
>> >TIA!
>> >
>> >Don.
>>
>>
>> I remember reading that film grain ranges from 2500 to 3500 per inch
>> (someone feel free to correct me if I'm remembering wrong).
>>
>> However, from my darkroom experience the same film stock can yield
>> different results depending on the temperature and time spent in the
>> developing solutions.
>>
>> I've never seen a chart that gives the ranges for different film
>> ratings though.
>>
>>
>> -- JC
>
>
Mon, 28 July 2003 21:21 Go to previous messageGo to next message
J C (Advanced Photoshop user)
On Sat, 26 Jul 2003 15:24:42 GMT, phoney.email@yahoo.com (Don) wrote:

>"shy" marketing departments
>reluctant to admit the truth...
>
>Don.

"Shy?" -- way too kind.

I was once in a CompUSA store talking about a laser printer with an
HP sales rep who was there for a promotion. Another HP rep walked up
to him and asked whether when scanning with HP scanner model XXX if
the image was digitized. The response from the rep was, "No, it's just
in there. It's saved and he can print it out."

True story.


-- JC
Mon, 28 July 2003 22:12 Go to previous messageGo to next message
J C (Advanced Photoshop user)
On Sat, 26 Jul 2003 15:24:42 GMT, phoney.email@yahoo.com (Don) wrote:


>
>My 2700 dpi scanner puts me in the lower half end of that, then.
>

Not really, because there is actually detail IN the grain. If you look
under a microscope you see a crystal in, for example, black and white
emulsion. That crystal has somewhat irregular shape and contains
details and imperfections. Additionally, not all crystals are the same
size.

As another poster commented, to scan the detail in the film grains
you'd need to scan at a MUCH higher resolution.

But since the human eye cannot resolve the grain details in prints
scanning all that detail is (in my opinion) futile.

Generally, you should scan at 300 dpi for every inch of final print
size. Period. I suggest you run a test. Take the same 8x10 image at
150 dpi, 300 dpi, 600 dip, and 1200 dpi and print four versions on
your inkjet. Compare them. You *might* see a difference between the
150 and 300 dpi images, but you will not see any difference between
300, 600 and 1200, even though your injet is capable of 1400 or more.

Rather than the march of technology making today's scans obsolete, it
will be your decision to print the image greatly enlarged that is
more likely to cause you worry.


-- JC
Tue, 29 July 2003 14:40 Go to previous messageGo to next message
phoney.email (Photoshop expert)
On Tue, 29 Jul 2003 01:21:25 GMT, J C <null@nowhere.net> wrote:

>>"shy" marketing departments
>>reluctant to admit the truth...
>
>"Shy?" -- way too kind.

Oh, it's just my subdued understatement... ;-)

>I was once in a CompUSA store talking about a laser printer with an
>HP sales rep who was there for a promotion. Another HP rep walked up
>to him and asked whether when scanning with HP scanner model XXX if
>the image was digitized. The response from the rep was, "No, it's just
>in there. It's saved and he can print it out."
>
>True story.

Oh, I believe it! There's nothing more frustrating then, when trying
to get some specs or information out of a company, you realize that
the person you're dealing with knows even less than you do. And yet
the incompetent continues to pretend they know what they're talking
about. "Yeah, it goes up to 11!" type of thing... (Spinal Tap).

Don.
Tue, 29 July 2003 14:40 Go to previous messageGo to next message
phoney.email (Photoshop expert)
On Tue, 29 Jul 2003 02:12:13 GMT, J C <null@nowhere.net> wrote:

>As another poster commented, to scan the detail in the film grains
>you'd need to scan at a MUCH higher resolution.
>
>But since the human eye cannot resolve the grain details in prints
>scanning all that detail is (in my opinion) futile.

I guess the only exception is aliasing. I was surprised at how grainy
my test film scanner images were but someone pointed out that this may
be due to aliasing, which makes sense.

>Generally, you should scan at 300 dpi for every inch of final print
>size. Period. I suggest you run a test. Take the same 8x10 image at
>150 dpi, 300 dpi, 600 dip, and 1200 dpi and print four versions on
>your inkjet. Compare them. You *might* see a difference between the
>150 and 300 dpi images, but you will not see any difference between
>300, 600 and 1200, even though your injet is capable of 1400 or more.

I found a very clever and revealing resolution test which comes at it
from a slightly different angle. It's based on the fact that
interpolation does not create any new detail. The test comprises
scanning the same image twice, once at high resolution (say, 2400) and
once at lower resolution (say, 600). The low resolution scan is then
interpolated, or should that be extrapolated? ;-) to 2400 dpi.

Putting these two images side by side (now of identical sizes and so
much easier to compare), examining them closely and even going down to
pixel level will show that the genuine 2400 dpi scan does not reveal
any more detail than the "make believe" pixels "invented" by the
interpolation process in the other image! Game, set and match!

Don.
Tue, 29 July 2003 15:20 Go to previous messageGo to next message
J C (Advanced Photoshop user)
On Tue, 29 Jul 2003 18:40:21 GMT, phoney.email@yahoo.com (Don) wrote:

>I found a very clever and revealing resolution test which comes at it
>from a slightly different angle. It's based on the fact that
>interpolation does not create any new detail. The test comprises
>scanning the same image twice, once at high resolution (say, 2400) and
>once at lower resolution (say, 600). The low resolution scan is then
>interpolated, or should that be extrapolated? ;-) to 2400 dpi.
>
>Putting these two images side by side (now of identical sizes and so
>much easier to compare), examining them closely and even going down to
>pixel level will show that the genuine 2400 dpi scan does not reveal
>any more detail than the "make believe" pixels "invented" by the
>interpolation process in the other image! Game, set and match!
>
>Don.

BUT I have two rhetorical a question about that...

1. Is the judgment just a visual inspection or did you actually
measure the color value of pixels in the same position in each scan?
The reason to ask this is that a greyscale image pixel can be any of
256 colors and subtle changes would mean that your 2400 dpi scan would
still be more accurate (though how significant the difference I'll
leave up to statisticians).

2. I wouldn't expect that the majority of pixels would be different in
the two scans cited above. After all, adjacent pixels in, for example,
the white area in a cloud would not be that different in the native
2400 dpi or in the 600 to 2400 dpi conversion. The real differences
only come into play at the edges where the pixels are changing color
to convey a new structure (detail).


AND NOW... Just as a complete aside, here's another completely
different image size conundrum:

We often publish photomicrographs and electron microscopy images. The
authors typically submit them as 5x7 prints and in the captions to the
photos they specify the microscopic magnification (i.e., X200, X400,
etc.).

We've has a few authors that insist that if we resize the image from
5x7 to 3x5 then the magnification in the photo's caption should change
in the same proportion.

In an explanation to one author of why not to do that I gave the
example of viewing the 5x7 image from 2 feet away then from 4 feet
away (would the magification change?). How about if the image had been
submitted as an 8x10, would they have increased the magification used
on the microscope?

Then when you layer the fact that the image is going to be printed
with a 150 halftone line screen, some authors seem to get really
confused about exactly what resolution that the microscopes lens is
conveying.


-- JC
Tue, 29 July 2003 20:08 Go to previous message
Donald Link (Photoshop expert)
You think the reps in CompUSA are ignorant. Go to Best Buy and ask
different sales person the same question in the computer department if you
really want a chuckle.



"Don" <phoney.email@yahoo.com> wrote in message
news:3f268625.7123317@news.individual.net...
> On Tue, 29 Jul 2003 01:21:25 GMT, J C <null@nowhere.net> wrote:
>
> >>"shy" marketing departments
> >>reluctant to admit the truth...
> >
> >"Shy?" -- way too kind.
>
> Oh, it's just my subdued understatement... ;-)
>
> >I was once in a CompUSA store talking about a laser printer with an
> >HP sales rep who was there for a promotion. Another HP rep walked up
> >to him and asked whether when scanning with HP scanner model XXX if
> >the image was digitized. The response from the rep was, "No, it's just
> >in there. It's saved and he can print it out."
> >
> >True story.
>
> Oh, I believe it! There's nothing more frustrating then, when trying
> to get some specs or information out of a company, you realize that
> the person you're dealing with knows even less than you do. And yet
> the incompetent continues to pretend they know what they're talking
> about. "Yeah, it goes up to 11!" type of thing... (Spinal Tap).
>
> Don.
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