Maximum ISO

RattyMouse · Feb 26, 2018

Film or silver halide I should say is a well developed technology with more than 100 years of R & D behind it. Can we state with certainty that a maximum ISO value has been established with this technology and if so, what is it? Delta 3200 is an ISO 1000 film and to my knowledge, that is as high as film has ever gone.

Silver halide has a known ability to react with photons. What other factors influence this ability? I believe that crystal size helps make the process more efficient (larger is better) but what else?

At some point, there must be a maximum ISO value and I'm wondering what it is, given the state of film today.

trendland · Feb 26, 2018

The max. ISO is that what manufacturers are producing today (state at the art technology) for photographical use with fine characteristics.
If you lower the characteristics you possible get a factor of x2 - x4 I can't say. You may see the results in characteristics above ISO 6400/12800 via pushing.
Physical restrictions are with both (film and digital).

with regards

Gerald C Koch · Feb 26, 2018

RattyMouse said:
Film or silver halide I should say is a well developed technology with more than 100 years of R & D behind it. Can we state with certainty that a maximum ISO value has been established with this technology and if so, what is it? Delta 3200 is an ISO 1000 film and to my knowledge, that is as high as film has ever gone.

Silver halide has a known ability to react with photons. What other factors influence this ability? I believe that crystal size helps make the process more efficient (larger is better) but what else?

At some point, there must be a maximum ISO value and I'm wondering what it is, given the state of film today.

Kodak once made Royal-X Pan which had an ISO of 1250. A bit faster. Astronomers routinely increase the ISO rating by the use of latensification using nitrogen gas. This can also be done by exposing the unexposed film to hydrogen peroxide vapor. This an extra step and the actual speed increase is somewhat variable. But if you must get the photo is of use,

RattyMouse · Feb 26, 2018

michael_r said:
Given current emulsion technology, not sure there is really a "maximum speed" per se, but rather a maximum speed with acceptable image structure characteristics (and cost). For example you could go higher than ISO 1000 simply with bigger grain and lower resolution and/or sharpness but at some point the tradeoff is unacceptable. There might also be known exotic ways of increasing sensitivity but which would make the film too expensive.

Yes, that is what I meant although you said it far better. Assuming the image quality of Delta 3200 shot at ISO3200, how much higher could silver halide images go in ISO value? Others have responded with some pretty exotic ways to get there.

miha · Feb 26, 2018

30 years ago there was Konica SR-G 3200 and several 1600 ISO C41 emulsions available. I guess the sky's the limit but no one is going to invest in R&D when an alternative is readily accessible.

Patrick Robert James · Feb 26, 2018

IIRC Agfa was working on some new tech before they went belly up. I think it was color film with a speed of 1000 but the grain of 100. Don't know if anyone took advantage of the tech or if it was developed all the way. I'd bet that by now if digital hadn't taken the air out of film research we would probably have some really fast films.

By the way, as was described above, there are ways to make film faster. Peroxide is one. You can flash the film either pre or post exposure. You can also do what David Vestal used to do which is hang the film in the darkroom far away from a really dim light which is flashing it over time. I think there are other ways too, but I don't recall off the top of my head.

Young He · Feb 26, 2018

I believe Polaroid made an ISO 20,000 black and white instant film for scientific purposes.

Edit- Polaroid 612

adelorenzo · Feb 26, 2018

There are a ton of examples online of people shooting Tri-X at 6400, 12800 and even 25,600. I know it's been pushed a lot higher than that as well. So I guess box ISO speed is one thing and usable speed would be another.

AgX · Feb 26, 2018

In the last major research project done at Agfa (in conjunction with external researchers) about 20 years ago a tenfolding of sensitivity was proven.

However Agfa never released a product based on this technology....
Kodak then had a somewhat related idea that only went part of the Agfa way. It thus yielded only a minor increase, but was applied in products though.

Alan Johnson · Feb 26, 2018

http://onlinelibrary.wiley.com/doi/10.1002/14356007.a20_001/abstract
In theory the log of the !SO speed should be proportional to the surface area of the grains (p28) but in practice the speed reaches a limiting value because of " loss reactions in latent image formation".. There does not appear to be any current work on this or on sensitization.

AgX · Feb 26, 2018

The Agfa and Kodak concepts were on these loss reactions.

BrianShaw · Feb 26, 2018

michael_r said:
The discussion of emulsion speed requires a standard - ie ISO speed. Pushing is another matter.

Thank you for stating this. I feel a bit deceived when a film box says 3200 but the film speed is really 800... as an example.

Craig · Feb 26, 2018

I believe that PE said that Kodak had developed a 25,000 speed film, but the keeping properties were too poor for practical commercial sale. Being able to do something in a lab and being able to do it survive the typical distribution and sale delays is another.

Nihil Abstat · Feb 26, 2018

RattyMouse said:
Film or silver halide I should say is a well developed technology with more than 100 years of R & D behind it. Can we state with certainty that a maximum ISO value has been established with this technology and if so, what is it? Delta 3200 is an ISO 1000 film and to my knowledge, that is as high as film has ever gone.

Silver halide has a known ability to react with photons. What other factors influence this ability? I believe that crystal size helps make the process more efficient (larger is better) but what else?

At some point, there must be a maximum ISO value and I'm wondering what it is, given the state of film today.

The problem of keeping the film from reacting to gamma rays and heat is likely to limit any future increases in sensitivity. Keeping properties are also more limited.

trendland · Feb 27, 2018

Craig said:
I believe that PE said that Kodak had developed a 25,000 speed film, but the keeping properties were too poor for practical commercial sale. Being able to do something in a lab and being able to do it survive the typical distribution and sale delays is another.

That's probably the key point.
I personally reached ISO 100.000 with an original ISO 400 Agfa emulsion.
[outside the ISO definition] via push processing.
But what about the characteristic?
I noticed two microscopic smal points on the negative. At ISO 50.000 I noticed one more (3 microscopic smal points).
I doubt on dust particles on the film.
At ISO 25.000 I noticed theses little points came bigger. And I imagine a very thin line in the negative.
With ISO 12800 it came more clear - these little spots seemed to be highlights
(from headlights) and at ISO 6400 the first time a picture was imaginable.
(best negatives with E.I. ISO 200...)
So it is very relative on characteristic.
with regards

removed account4 · Feb 27, 2018

for max iso you need to contact an astronomer, they had ways of treating film to get the maximum iso out of it.

that said, i pushed tmx(100) sheets by 6 or 7 stops (by mistake) on a job and had to think on my feet to process it.
it was done using straight sprint film developer for something like 20mins hangers in a tank. then the film was enlarged onto
some sort of agfa grade 5 rc paper. if i had a scanner they would have come out perfect, but this was like 1992.

klaus3428 · Feb 27, 2018

FWIW, many years ago I pushed Kodak 3200 to 64000, using a Praktika MTL3. I don't have any records from that time (maybe the negs are still in a file somewhere) but the dev time must have been in the region of 20 minutes with useable results. Now I am curious, let me search through my files...

voceumana · Feb 27, 2018

ISO defines film speed in a way that no practical photographer uses, so when Kodak and Ilford offer films with a box speed rating that is higher than a true ISO speed it is far from deceptive--photographers looking for the fastest speed possible need practical ratings, not speeds designed to meet a standard. Both Ilford and Kodak always identified that the speed rating was an EI (Exposure Index) and not based on ISO if you read the detailed product information.

ISO speeds are based on a developer that no one uses and agitation techniques that are not commonly used, but they are necessary to provide 100% repeatable results, something that is essential in a standard.

One of the practical limits of film speed is the inaccuracy of shutters and f/ stops because of mechanical limitations--if speeds got too high, it would be much harder to accurately expose them. Lots of photographic process decisions were based on practicality, I am sure.

Bill Burk · Feb 27, 2018

Jus a couple easy things... Polaroid doubled their ISO by putting a mirror-type reflective coating at the back, and X-ray film coats emulsions on both sides for increased response to a particular exposure.

ic-racer · Feb 28, 2018

Bill Burk said:
Jus a couple easy things... Polaroid doubled their ISO by putting a mirror-type reflective coating at the back, and X-ray film coats emulsions on both sides for increased response to a particular exposure.

Also, x-ray 'intensifying screens' accept the x-rays and emit blue or green light to expose the film with more intensity than the x-rays themselves. Further increasing the effective speed.

Film can use similar technology with electronic intensification like night vision systems.

removed account4 · Feb 28, 2018

voceumana said:
ISO speeds are based on a developer that no one uses and agitation techniques that are not commonly used, but they are necessary to provide 100% repeatable results, something that is essential in a standard.

not sure how accurate this is .. from what i remember reading by PE, iso is determined in a lab with a test chart ( macbeth? ) and d76 ( or whatever plain vanilla developer xyz company has ) using normal processing techniques ..
the difference is that one is real-life is one is in a lab .. its a lab-standard, and pretty accurate for some applications
most photographers aren't scientists ( as much as they wish they were )
and they don't process the same way every time ( make mistakes ),
and lighting isn't like a lab,
and our camera shutters tend not to be accurate

... that is why all of this stuff iso and developing times are recommendations, not set in stone.

i wish i could gugglufu PE's remarks on the subject ..

klaus3428 · Feb 28, 2018

klaus3428 said:
FWIW, many years ago I pushed Kodak 3200 to 64000, using a Praktika MTL3. I don't have any records from that time (maybe the negs are still in a file somewhere) but the dev time must have been in the region of 20 minutes with useable results. Now I am curious, let me search through my files...

I got a bit carried away here: found the negs with an undated note saying "TMZ @ ISO 12500". Some of the frames look quite good, need to scan when I got a moment. Pushing to 64000 was probably too difficult with that old camera. Anyway, will share a few scan in due course.
Generally I stick with the "box speed" but then haven't really experimented lately.

AgX · Feb 28, 2018

ic-racer said:
Also, x-ray 'intensifying screens' accept the x-rays and emit blue or green light to expose the film with more intensity than the x-rays themselves. Further increasing the effective speed.
Film can use similar technology with electronic intensification like night vision systems.

This is not what this thread is about.

Ko.Fe. · Feb 28, 2018

From practical and up to date active and regular film user PoV, I could tell you what I not going to use Kodak 3200. Ten bucks per roll of film? No, thank you.
I'm just confident and consistent with far less expensive HP5+ @3200 and even cheaper Kentmere 400 does it for me @1600.

Nihil Abstat · Feb 28, 2018

Ko.Fe. said:
From practical and up to date active and regular film user PoV, I could tell you what I not going to use Kodak 3200. Ten bucks per roll of film? No, thank you.
I'm just confident and consistent with far less expensive HP5+ @3200 and even cheaper Kentmere 400 does it for me @1600.

Why?
In 1957...Kodak Tri-X... Twenty exposures were 85 cents, and a 36 exposure roll was $1.15.

Allowing for inflation, film is cheaper today than ever!

$1.15 in 1957 → $10.14 in 2018

Maximum ISO

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