Film grain size as dpi

PE
Posted By
phoney.email
Jul 25, 2003
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3181
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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.

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JC
J C
Jul 25, 2003
On Fri, 25 Jul 2003 17:05:10 GMT, (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
EG
Eric Gill
Jul 25, 2003
"Steve Simpson" wrote in
news:QDgUa.18888$:

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.
IP
i.perryman
Jul 25, 2003
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" wrote in message
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.
BV
Bart van der Wolf
Jul 25, 2003
"Don" wrote in message
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
J
john
Jul 25, 2003
In article ,
(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?
IP
i.perryman
Jul 25, 2003
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" wrote in message
On Fri, 25 Jul 2003 17:05:10 GMT, (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
PE
phoney.email
Jul 26, 2003
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" 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" wrote in message
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.
PE
phoney.email
Jul 26, 2003
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" wrote:

"Don" wrote in message
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
PE
phoney.email
Jul 26, 2003
On Fri, 25 Jul 2003 18:36:16 -0500, (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.
PE
phoney.email
Jul 26, 2003
On Fri, 25 Jul 2003 13:41:58 -0700, "Steve Simpson" 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.
PE
phoney.email
Jul 26, 2003
On Fri, 25 Jul 2003 18:54:49 GMT, J C wrote:

On Fri, 25 Jul 2003 17:05:10 GMT, (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.
PE
phoney.email
Jul 26, 2003
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" 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" wrote in message
On Fri, 25 Jul 2003 17:05:10 GMT, (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

SS
Steve Simpson
Jul 27, 2003
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&amp ;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.
PE
phoney.email
Jul 28, 2003
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&amp ;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.
T
tacitr
Jul 28, 2003
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
J
john
Jul 28, 2003
In article ,
(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 :))
JC
J C
Jul 29, 2003
On Sat, 26 Jul 2003 15:24:42 GMT, (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
JC
J C
Jul 29, 2003
On Sat, 26 Jul 2003 15:24:42 GMT, (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 8×10 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
PE
phoney.email
Jul 29, 2003
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.
PE
phoney.email
Jul 29, 2003
On Tue, 29 Jul 2003 01:21:25 GMT, J C 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.
PE
phoney.email
Jul 29, 2003
On Tue, 29 Jul 2003 02:12:13 GMT, J C 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 8×10 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.
JC
J C
Jul 29, 2003
On Tue, 29 Jul 2003 18:40:21 GMT, (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 5×7 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 5×7 to 3×5 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 5×7 image from 2 feet away then from 4 feet away (would the magification change?). How about if the image had been submitted as an 8×10, 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
DL
Donald Link
Jul 30, 2003
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" wrote in message
On Tue, 29 Jul 2003 01:21:25 GMT, J C 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.

Master Retouching Hair

Learn how to rescue details, remove flyaways, add volume, and enhance the definition of hair in any photo. We break down every tool and technique in Photoshop to get picture-perfect hair, every time.

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