Acros II - What speed are you getting?

[Steven Lee]

Bear in mind that, at the time Adams popularized this stuff, there wasn't a lot of rigor around photography. It was a lot of secret sauce and stories around the campfire. He sought to systematize things so that a given photographer could arrive at repeatable and useful results for themselves, not set some absolute standard of accuracy.

Thank you for this perspective. I've always suspected some historical context was involved.

 

[Craig]

The target densities for pre-1960 negatives reflected a desire for more exposure.
By 1960, it had become clear that those targets were not optimum for the current films and many modern lenses.
When they changed the speed numbers, the densities were effectively reduced - both when using meters, and sunny 16.

My understanding was also that prior to 1960 most cameras/people did not have light meters and were estimating exposure. There was more danger of underexposure in those circumstances. Meters were becoming more common in the 60's and exposure could be determined more accurately than previously. Thus the need for the safety factor could be removed and the film speeds increased.

The change had nothing to do with the film, but with the rise of more accurate metering.

 

[chuckroast]

My understanding was also that prior to 1960 most cameras/people did not have light meters and were estimating exposure. There was more danger of underexposure in those circumstances. Meters were becoming more common in the 60's and exposure could be determined more accurately than previously. Thus the need for the safety factor could be removed and the film speeds increased.

The change had nothing to do with the film, but with the rise of more accurate metering.

I think that's pretty much true as well.

As an aside, I'm an engineer by training, though I started life as a commercial photographer (and quickly realized that I loved photography but hated the business of photography). As a result, I am endlessly curious about how things work and actually measure in real life situations. I can say with some confidence that - meters themselves are known to be liars on a rather large scale. I've rebuilt/recalibrated a bunch of Luna-Pros and they are highly nonlinear and frequently don't agree with one another - sometimes by a full stop or more. Ditto shutters, especially large format leaf shutters.

It was not until the advent of digital matrix metering that we actually got meters that tried to tell the truth, but even that has to be calibrated to your own way of working.

 

[pentaxuser]

chuckroast, wow my reply to you about Richard Coppnow's article and what may have been a useful discussion on it seems to have been succeeded in my absence by another vigorous exchange. Not that I am against this per se but can I say that I am still e interested in your answers to my questions and your comments on my what to me seems some puzzling statements by Richard

Just in case this appears to you to be me "piling in with the rest of those responding" I am just looking for what your comments are. I need to say for the sake of being open that I may have further questions depending on where what you say leads to


Thanks

pentaxuser

 

[chuckroast]

chuckroast, wow my reply to you about Richard Coppnow's article and what may have been a useful discussion on it seems to have been succeeded in my absence by another vigorous exchange. Not that I am against this per se but can I say that I am still e interested in your answers to my questions and your comments on my what to me seems some puzzling statements by Richard

Just in case this appears to you to be me "piling in with the rest of those responding" I am just looking for what your comments are. I need to say for the sake of being open that I may have further questions depending on where what you say leads to


Thanks

pentaxuser

I cannot speak for him (I don't know him personally) but his description of what happened and why is consistent with my own understanding. It's certainly true that we could both be wildly wrong. To the best of my understanding, "ASA" doubled overnight when the new standard was adopted, even though the films had not changed a bit. Notionally, it was like they went from measuring actual gas mileage to EPA estimates.

What isn't wildly wrong is the direct evidence that I have seen that the majority of people exposing monochrome at box speed and then developing in the ordinary manner, are getting thin negatives ... well, that's not quite true. They may be getting decent negatives, but they are missing shadow detail far too often. As just one example, look at the images posted by the OP when they kicked off this thread. Shadow detail is minimal or even completely missing.

I hope I have not come across as strident or doctrinaire about any of this stuff. People should use whatever gives them the images they like. I just have done a ton of my own testing and reached the conclusions offered here. Feel free to ignore me - certainly most people in my social orbit do

 

[DREW WILEY]

Well, Chuck, mfg flm quality film control and speed consistency wasn't anything like it now is either, when AA joined the ZS religion. Maybe that's why "Moses" in this case only factored eight dynamic zones, and not a Decalogue to ten.

 

[Scott J.]

My experience testing Delta 100, FP4+, and Tmax 100 using the Zone System mirrors Chuck's results -- i.e., I typically end up getting a film speed (for my use) that's around 2/3 of a stop slower than box speed with a development time that's considerably shorter than the manufacturer's ISO-based guidance (so, in effect, I pull my film). If you read the ISO standard for film speed measurement and work through the math, and then compare that to the Zone System procedure, it becomes clear why this frequently happens (you can read the ISO standard here: https://cdn.standards.iteh.ai/samples/3580/192a0f97667044f3ba51276b0ded056a/ISO-6-1993.pdf). Ultimately, the two tests appear to have different criteria for what constitutes "correct" midtone density.

The ISO test is based on finding two exposure values: one value (Hm) where the Log10 exposure produces a density on the film that's 0.10 units above base + fog, and a second Log10 exposure value (Hn) that's exactly 1.3 lux-seconds higher than the first. The film speed is calculated entirely from the first value, Hm. The purpose of the second point, Hn, is to determine the correct development time for a given developer. Specifically, the development regime (time, temperature, dilution, agitation, etc.) is adjusted until the density at point Hn is 0.9 units above base + fog.

In the simplified Zone System test, the typical procedure is to adjust exposure index (i.e., metered speed) until a Zone I exposure produces a density of 0.1 units above base + fog. From there, you adjust your development regime until the Zone V and VIII densities made with the same exposure index are roughly 0.7 and 1.3 units above base + fog, respectively. If you assume the Hm exposure in the ISO test is comparable to Zone I in the Zone System test (this isn't precisely correct, but it's a reasonable approximation), then point Hn works out to roughly a Zone 5.3 exposure.

Comparing the densities targeted by the two tests, the Zone System test appears to aim for lower midtone density (e.g., 0.7 units above base + fog versus 0.9), which Zone System users accomplish through reduced development. Reducing the development, however, necessitates giving more exposure to the film in order to maintain adequate Zone I density, which is done by downrating the effective film speed. (Here, it's important to note that, contrary to the conventional wisdom on the subject, development does impact shadow density... just not as much as it impacts the midtones and highlights.)

The ISO standard doesn't, as far as I'm aware, verbally specify a qualitative goal of the ISO test (e.g., "This procedure will produce negatives that make the best prints on a condenser enlarger," etc.). It simply gives a quantitative definition of film speed that, from the perspective of the reader, might seem somewhat arbitrary (see the equations in Section 6.1). It's a good starting point, of course; might even give you exactly what you want. For my own hybrid workflow, I've found shooting at box speed and using standard development produces negatives that are usually too contrasty for what I intend to do. One's end use will determine the best approach.

 

[DREW WILEY]

When I'm making exposures, I actually visualize in my mind the actual shape of the film curve itself, and at what point I want the shadow placement relative to that specific curve, with its specific anticipated development. I do it almost automatically, based on both a background in plotting density curves of many types, and also sheer experience. I neither need nor want any kind of calculation (that too is in the rear view mirror). I still keep a simple math calculator in my equipment drawer with log functions, but rarely need it. So in my case, the Zone System as sometimes quantified is just too complicated, yet at the same time, not specific enough. I do understand it. But I don't need my ashes to be launched into space in a silver DeLorean by a nutty professor who looks exactly like Minor White.

 

[chuckroast]

When I'm making exposures, I actually visualize in my mind the actual shape of the film curve itself, and at what point I want the shadow placement relative to that specific curve, with its specific anticipated development. I do it almost automatically, based on both a background in plotting density curves of many types, and also sheer experience. I neither need nor want any kind of calculation (that too is in the rear view mirror). I still keep a simple math calculator in my equipment drawer with log functions, but rarely need it. So in my case, the Zone System as sometimes quantified is just too complicated, yet at the same time, not specific enough. I do understand it. But I don't need my ashes to be launched into space in a silver DeLorean by a nutty professor who looks exactly like Minor White.

One more thought on all this. As has been noted elsewhere in this thread, notwithstanding the repeatability ZS brings to the table, it definitely has a problem when you're working on long SBR scenes. The ZS approach is to do contracted development, adjusting film speed downward accordingly. This is intended to "fit" the scene SBR onto the dynamic range of the film.

The problem with this is that the contraction also contracts the midtone local contrast a bunch and has a tendency to produce images that are dull and lifeless even though all the zones you can see got mapped onto the film somehow.

This is how I ended up going deeply down the rabbit hole of semistand dilute development with compensating developers like Pyrocat-HD or D-23. It gives you you a way to independently control each aspect of tone control and exposure. To whit:

- The very long standing time gives you full shadow speed. No need to do densiometric tests. The ASA is what it says on the box. I've yet to find a counterexample.

- The very long standing time with occasional agitation, actually expands the midtone contrast - the very place where the image "snap" is created.

- The combination of a compensating developer and only occasional agitation, limits how far the highlights get developed and thereby keeps them under control. The developer exhaust rapidly at the highlights and does nothing until agitation happens next - which is rarely with semistand and only slightly more often with EMA.

So you can control shadow speed, midtone contrast, and highlights as independent elements using this approach. The cost? It's wonky and takes a while to dial in and get right. (That's why I share my notes with anyone who wants them to save them the pain.) But once you get it right, you'll never go back to Zone System and conventional development for anything that has major SBR.

The other place where it really shines is when you have really short SBRs. In a short SBR environment, the scene is naturally all clustered around Zone V and it agonizingly boring when processed normally. Even N+ development will only get you so far with most developers. Because seminstand/EMA take so long, there is plenty of time for the midtone contrast to really pop in development.

Here's a scene - 6x9 shot on Acros II - and EMA processed for an hour in highly dilute Pyrocat-HD. The actual scene was utterly flat shot on a gray day after a rain storm. There was no meaningful contrast in the midtones and it was just ... boring. Notice how those midtones pop after developing as described. Scan of silver print:

 

[pentaxuser]

I cannot speak for him (I don't know him personally) but his description of what happened and why is consistent with my own understanding. It's certainly true that we could both be wildly wrong. To the best of my understanding, "ASA" doubled overnight when the new standard was adopted, even though the films had not changed a bit. Notionally, it was like they went from measuring actual gas mileage to EPA estimates.

What isn't wildly wrong is the direct evidence that I have seen that the majority of people exposing monochrome at box speed and then developing in the ordinary manner, are getting thin negatives ... well, that's not quite true. They may be getting decent negatives, but they are missing shadow detail far too often. As just one example, look at the images posted by the OP when they kicked off this thread. Shadow detail is minimal or even completely missing.

I hope I have not come across as strident or doctrinaire about any of this stuff. People should use whatever gives them the images they like. I just have done a ton of my own testing and reached the conclusions offered here. Feel free to ignore me - certainly most people in my social orbit do

Thanks for the reply. It wasn't that I thought Richard Coppnow was wrong in all respects. For instance there clearly was a doubling of film speeds in the early 60s. I had thought it was to do with standardising on the film speed test that gave shadow detail where you'd expect it to be and this resulted in a "safe" doubling or certainly a safe increase in speed. Richard's definition of the change in criteria was that which give an image but he doesn't specify what this entails and what the actual drawbacks of this change actually were As I said a comparison of two identical negatives and their prints might have helped demonstrate his argument
The other point was what did he meant by "low end extended agitation gibberish. His use of language indicates that he doesn't rate it and yet he seems to admit that it is way of getting back to box speed so it does seem useful hence why I wondered what it consists of

Anyway it may be that you can't say either what he meant either In summary; there were places in the article where he came across as an annoyed curmudgeon which is a pity when trying to explain his stance

pentaxuser

 

[DREW WILEY]

Chuck - well it's certainly refreshing to know that you and I perceive the same flaw in the compression model of the Zone System, even though we are addressing it in different manners. If I need a heavier-handed treatment, instead of going down the minus-development rabbit-hole, I'm more likely to go ahead and give normal development for sake of full tonal richness, but then add a selective contrast mask which brings out all the microtonality (rather then suppressing it by stomping on the peanut butter sandwich to make it flatter, which the ZS prescribes).

But your descriptions of glacial pace development have at least piqued my interest; and one of these days I'll probably experiment with it myself, if only out of curiosity.

I've only done a little experimental printing with ACROS II so far, some involving moderate contrast scenes like the one you posted, others excessive contrast even on the same roll, just to see what one can get away with in comparison to previous Acros. But generally I shoot TMax 100 in 120 film instead, due to its exceptional SBR capacity. For this afternoon I've got TMY 400 in the 6X9 rangefinder instead, for sake of a brisk walk, with the tripod potentially left at home. We're well north of any anticipated landfall of scary hurricane Hillary, but might get a little rain anyway.

 

[chuckroast]

Chuck - well it's certainly refreshing to know that you and I perceive the same flaw in the compression model of the Zone System, even though we are addressing it in different manners. If I need a heavier-handed treatment, instead of going down the minus-development rabbit-hole, I'm more likely to go ahead and give normal development for sake of full tonal richness, but then add a selective contrast mask which brings out all the microtonality (rather then suppressing it by stomping on the peanut butter sandwich to make it flatter, which the ZS prescribes).

But your descriptions of glacial pace development have at least piqued my interest; and one of these days I'll probably experiment with it myself, if only out of curiosity.

I've only done a little experimental printing with ACROS II so far, some involving moderate contrast scenes like the one you posted, others excessive contrast even on the same roll, just to see what one can get away with in comparison to previous Acros. But generally I shoot TMax 100 in 120 film instead, due to its exceptional SBR capacity. For this afternoon I've got TMY 400 in the 6X9 rangefinder instead, for sake of a brisk walk, with the tripod potentially left at home. We're well north of any anticipated landfall of scary hurricane Hillary, but might get a little rain anyway.

For those who've not read it, I HIGHLY recommend this (and all of Kachel's other stuff as well):

http://davidkachel.com/wpNewDK/wp-content/uploads/2019/05/PrimacyOfLocalContrast.pdf

Back to the darkroom with me!

 

[albada]

@Stephen Benskin knows the history and rationale of the ISO/ASA speed standard better than (probably) all of us. The fractional-gradient method would be ideal, but is hard for most people to measure accurately, so the current standard is based on an approximation called the Delta X Criterion. You can find @Stephen Benskin's posts on them by typing the following into google/duckduckgo/bing/whatever:

Delta X Criterion site: photrio.com​

Mark

 

[chuckroast]

Chuck - well it's certainly refreshing to know that you and I perceive the same flaw in the compression model of the Zone System, even though we are addressing it in different manners. If I need a heavier-handed treatment, instead of going down the minus-development rabbit-hole, I'm more likely to go ahead and give normal development for sake of full tonal richness, but then add a selective contrast mask which brings out all the microtonality (rather then suppressing it by stomping on the peanut butter sandwich to make it flatter, which the ZS prescribes).

But your descriptions of glacial pace development have at least piqued my interest; and one of these days I'll probably experiment with it myself, if only out of curiosity.

I've only done a little experimental printing with ACROS II so far, some involving moderate contrast scenes like the one you posted, others excessive contrast even on the same roll, just to see what one can get away with in comparison to previous Acros. But generally I shoot TMax 100 in 120 film instead, due to its exceptional SBR capacity. For this afternoon I've got TMY 400 in the 6X9 rangefinder instead, for sake of a brisk walk, with the tripod potentially left at home. We're well north of any anticipated landfall of scary hurricane Hillary, but might get a little rain anyway.

When you say "selective contrast mask", are you doing physical masking of the negative or a digital post processing of a scanned negative?

 

[faberryman]

I have been part of pure-silver since its inception. I find Knoppow's many postings incredibly insightful. He may be skipping a few steps in doing the proof here, but I'd encourage you to go through the pure-silver archives and see the many useful contributions he's made. He's sort of a walking encyclopedia of this stuff.

I undertook your challenge but found searching the listserv archive so cumbersome I threw in the towel. I'll accept your assessment that Richard Knoppow made some useful contributions, although his post on film speed fell short.

 

[Stephen Benskin]

Most of the ISO standards are about defining how to do something. ISO 6 is the determination of ISO speed for B&W pictorial films. To understand the theory, one must look to the scientific papers. The reasoning for the 1960 standard change is explained in the paper by C.N. Nelson, Safety Factors in Camera Exposures.

Found on a site generously maintained by Bill Burk.
Safety Factors in Camera Exposures

Matt King correctly pointed out that methodology affects the results and to simply present a value without stating the conditions under which it was determined can cause confusion and misunderstandings. Placing the ISO prefix before the speed value indicates the film was tested according to the standard. Zone System testing generally uses a camera and meter. The speed point is determined 4 stops below the meter's exposure point. While the ISO doesn't use a camera, the speed point is determined 3 1/3 stops below Hg (the meter's exposure point). Apart from experimental error, that is where most of the ISO / Zone System film speed discrepancy originates. To put it bluntly, in most cases, people aren't taking about the same thing.

Figure 1 diagram in the ISO standards does not correlate to the metered / speed point relationship. Hn does not equal Hg. That information can be found in D. Connelly's, Calibration Levels of Films and Exposure Devices. Again, the ISO standards, in most cases, don't explain theory.

Found here:
Calibration Levels of Films and Exposure Devices

Jack Dunn in Exposure Manual has a very nice illustration of the relationship of exposure on the film characteristic curve. Other sources do the same but Dunn's is clean and easy to read.

Most manufacturers base their development on the statistically average luminance range and for the resulting negative to be printed on a diffusion enlarger or approximately a CI 0.56 - 0.58. If someone prints with a different type of enlarger or uses something other than silver paper, the aim average gradient will be different therefore the printing conditions should be stated with any processing recommendation that doesn't include the CI value or similar average gradient method value.

Read quickly through Musings on "Real ASA" and Development Methods and found it not too far off with the facts but biased in the editorializing. The ISO/DIN part had the biggest transgressions. The same goes for the excerpt from Tim Daneliuk and the "real" ASA speculation.

​

 

[DREW WILEY]

I do zero digital anything. The only exception will be when I use the copystand to document my print collection for sake of cataloging and estate purposes. At one time I did employ a basic scanner for 35mm slides taken on the copy stand of actual darkroom color and b&w prints for sake of my former website. But I have never printed anything from a scan, nor ever intend to.

So yes, I am referring to physical masking with actual film. But by stating, "selective", I'm implying masking as a full toolbox in its own right, and not any single specific variety of it. It can get pretty involved in color printing; lesser so, and less frequent, in relation to black and white films and prints.

 

[MattKing]

My understanding was also that prior to 1960 most cameras/people did not have light meters and were estimating exposure. There was more danger of underexposure in those circumstances. Meters were becoming more common in the 60's and exposure could be determined more accurately than previously. Thus the need for the safety factor could be removed and the film speeds increased.

The change had nothing to do with the film, but with the rise of more accurate metering.

Quoting from the C.N. Nelson article linked to by Stephen above:

"If a large safety factor is undesirable at the present time, why was it thought to be necessary when the American Standards for film ratings and exposure meters were first adopted in the 1940's? The first reason is that exposure meters, camera shutters, and lens apertures were not as accurate in the 1940's as they are in 1959. The second reason is that the camera-exposure latitude of black-and-white films was effectively greater in those earlier years, largely because the increase in print graininess with increase, in camera exposure was not as evident with the large cameras, large negatives, and small degree of enlargement or contact printing then commonly used. The great increase in the number of small cameras in recent years and the increase in the degree of enlargement has made the graininess problem more acute. Many photographers have adopted the practice of giving less exposure than is indicated by the use of ASA exposure indexes with exposure meters. The American Standard indexes for black-and white films are used by them only as a starting point for deriving a new kind of exposure index which is obtained by the simple procedure of doubling the Standard exposure index. This practice, of course, has the effect of cutting the safety factor in half, giving the preferred thinner negatives."

 

[Arvee]

If memory serves, (best check the archives, though), I believe PE stated that he exposed Kodak films at 1/3 to 2/3 stop over as a rule for best results. He was, of course, intimately engaged in the design and production of Kodak films.

 

[Stephen Benskin]

If memory serves, (best check the archives, though), I believe PE stated that he exposed Kodak films at 1/3 to 2/3 stop over as a rule for best results. He was, of course, intimately engaged in the design and production of Kodak films.

We need to be careful not to conflate exposure with speed.

 

[Arvee]

We need to be careful not to conflate exposure with speed.

I have to assume that in his sharing his behavior to get best results with Kodak films, he was downrating the ISO when programming his exposure meter. That would be a speed modification.
Also, I believe he shared the information as practical matter to achieve real world results, not impugning the scientific method.

 

[Stephen Benskin]

I have to assume that in his sharing his behavior to get best results with Kodak films, he was downrating the ISO when programming his exposure meter. That would be a speed modification.
Also, I believe he shared the information as practical matter to achieve real world results, not impugning the scientific method.

He did share the recommendation as a practical matter, but not as film speed. Film speed is a way to sensitometrically evaluate different films so they equate to a psychophysically determined level of quality. It doesn't suggest the film speed must be strictly adhered to but uses it as a way to compare film emulsions equally and consistently. Film speed purposefully uses a limiting variable in order to express the usable range. A photographer is free to make adjustments based on personal preference and aesthetics; however, don't forget film speed relates to the results from controlled tests using people to judge perceived excellent results. The data from the tests does show a slight change in the perception of quality with additional exposure which could be attributed to a problem with the judges actually being able to perceive a change in quality with the additional exposure. Up until the first excellent print choice, the ordering of the prints from the judges were consistent. After that point, the print order was not.

An example that might help the concept of film speed vs exposure has to do with the pre 1960 ASA speed being an EI. The actual speed was determined at the fractional gradient point. A constant was then applied which has come to be known as the safety factor.

The fractional gradient speed is 1/Es. This can be considered the actual film speed. k then is applied creating an EI for the film. This is no different than changing the speed setting on a camera or exposure meter. It doesn't change the speed of the film. It only adjusts how the photographer exposes it.

For example, if Es = 0.0032 mcs, the fractional gradient speed would be 312. Applying k makes the EI 78. Under the conditions of the current ISO standard, the fractional gradient point falls around 0.30 log-H below the 0.10 fix density speed point. Based on that and using the ISO speed equation, Film Speed = 0.8 / Hm, the current speed for the same film would be 125. Since the current ISO speed uses the Delta-X Criterion which continues to use the fractional gradient speed as a basis, the current ISO speed can technically be considered an EI. The fractional gradient speed point was never intended to be used as the applied film speed, but a point where film speed is determined.

 

[MattKing]

Following up what Stephen says, it is important to differentiate between the light sensitivity of the film, and how we prefer to expose it.
When my friends in my Darkroom Group compare negatives, we have enough experience with each other's preferences to know each other's tendencies.
I recently took my Retinette Ib - the one in my avatar - out of the drawer after not using it for longer than I should have and ran a roll through it, relying on the built in selenium meter for the exposure settings. After developing the film and examining the negatives, I jokingly described the response of that camera as tending to give me "Bruce" negatives, because Bruce is one of the group who generally prefers to give negatives more generous exposure than I do. Everyone in the group understood the reference.
That is why, if you are asking a question about what "speed" people are getting from a film, it is useful to both determine how they are evaluating that speed and, if they are actually sharing the Exposure Index that they use, what sort of negatives they prefer.

 

[chuckroast]

He did share the recommendation as a practical matter, but not as film speed. Film speed is a way to sensitometrically evaluate different films so they equate to a psychophysically determined level of quality. It doesn't suggest the film speed must be strictly adhered to but uses it as a way to compare film emulsions equally and consistently. Film speed purposefully uses a limiting variable in order to express the usable range. A photographer is free to make adjustments based on personal preference and aesthetics; however, don't forget film speed relates to the results from controlled tests using people to judge perceived excellent results. The data from the tests does show a slight change in the perception of quality with additional exposure which could be attributed to a problem with the judges actually being able to perceive a change in quality with the additional exposure. Up until the first excellent print choice, the ordering of the prints from the judges were consistent. After that point, the print order was not.

An example that might help the concept of film speed vs exposure has to do with the pre 1960 ASA speed being an EI. The actual speed was determined at the fractional gradient point. A constant was then applied which has come to be known as the safety factor.

The fractional gradient speed is 1/Es. This can be considered the actual film speed. k then is applied creating an EI for the film. This is no different than changing the speed setting on a camera or exposure meter. It doesn't change the speed of the film. It only adjusts how the photographer exposes it.

View attachment 347063

For example, if Es = 0.0032 mcs, the fractional gradient speed would be 312. Applying k makes the EI 78. Under the conditions of the current ISO standard, the fractional gradient point falls around 0.30 log-H below the 0.10 fix density speed point. Based on that and using the ISO speed equation, Film Speed = 0.8 / Hm, the current speed for the same film would be 125. Since the current ISO speed uses the Delta-X Criterion which continues to use the fractional gradient speed as a basis, the current ISO speed can technically be considered an EI. The fractional gradient speed point was never intended to be used as the applied film speed, but a point where film speed is determined.

IOW, the formal ISO definition of "speed" doesn't directly translate into a pragmatic use of EI for purposes of exposure. The formal definition was intended to bring sensiometric consistency and rigor to the measurement of film emulsions to exposure to light.

In my early career, I spent some time in applied research on how people perceive sound in loud environments - aka "psychoacoustics". Our interest was in determining whether there pre- or post stimuli materially affects speaking cognition. Like anything having to do with human responses (that is to say, "psycho"-anything), there is great variability of results from person to person, and any valid outcomes, even with tightly controlled experiments, barely poked through the statistical noise floor. We found no consistent causal relationship between pre/post aural stimulus and whether a person would - on average - hear better or worse in a noisy environment.

I suspect that "perceived quality" of a photographic image is much the same thing. Getting someone to point at a print and say "That one is better" is influenced by so many variables and is variable from person to person so significantly, that there is no straight line from cause to effect.

What is, however, clear to me, lo these many years later, is that - if it's not on the negative - you cannot even print it. The current ISO standard as described, simply doesn't present the likelihood of significant shadow detail being present. The much abused 0.1DU over FB+F for Zone I gives us a higher probability of shadows having some content, at least for normal development schemes. On that basis - assuming reasonably accurate meters, thermometers, clean water etc. - pretty much all films need the better part of 1 full stop of increased exposure above ISO recommendation.

But the whole discussion is, at some level, sort of moot. Zone System was specifically designed to help the photographer calibrate exposure speed to their _personal_ way of working. Who cares if you expose Tri-X sheet film at 12 or 1200 so long as it yields rich and printable negatives in your standard workflow. ZS and its variants were never intended to be a replacement for formal manufacturer's densiometric specification, but rather a way to bring rigor and consistency to the working photographers.

tl;dr A lot of ink is spilled on "What is the REAL ASA?", but it simply doesn't matter. The real question is, "What is YOUR ASA?"

 

[MattKing]

tl;dr A lot of ink is spilled on "What is the REAL ASA?", but it simply doesn't matter. The real question is, "What is YOUR ASA?"

Which unfortunately is akin to saying: don't bother to ask on an internet forum: "Acros II - What speed are you getting?" Because the answer would only be usable by those using the exact same method and criteria as the respondent.

If I used Acros II, and I decided to give Steven as fulsome a response as possible, it would be something like:

"1) I develop it in replenished X-Tol;
2) my preference is for negatives that provide excellent highlight and high mid-tone separation, and in high SLR lighting conditions I am more willing to sacrifice detail in the deep shadows than in the highlights;
3) I prefer to print from negatives that are not too dense;
4) I print with a diffusion light source. I scan with a relatively inexpensive flatbed scanner;
5) I have a spot meter, and I'm generally willing and happy to walk up to my subject to take close readings of highlight and shadow areas, but more frequently than not I use incident metering when the option is available.
Based on all those factors and preferences, I find that I get results that I like if I use an EI of XXXXX.
Here is a backlit digital image of some negatives that I am happy with, where I used that EI."

That answer includes the terms of reference that might help make it meaningful.