Film Developing Cookbook - Does one really need to overexpose T-grain film by 1-2 stops and pull process to get satisfactory results?

[runswithsizzers]

Maybe someone could move the last few posts to a new thread.

I think the posts which discuss fine detail may have been off-topic (#30-35), but posts about ISO and exposure seem to fit...?
... but then, this is Photrio where off-topic posts are not unheard of ... ;-)

 

[chuckroast]

Which company uses ISO standards? I don't know any!

Foma's box speed definitely is too high with any standard developing process.

The Ilford film data sheets state: “It should be noted that the recommended exposure index(EI) is based on a practical evaluation of film speed and is not based on foot speed, as is the ISO standard.”

Kodak uses a Contrast Index CI, that has nothing to do with the definitions in the ISO standard. CI can only be evaluated in a graphical manner with a special ruler and cannot be converted into Ilford's G or into gamma.

The only way to deal with this is to carry out your own film tests and use your own personal EI.

The density curve used in ISO (see #29 above) has nothing in common with a typical curve of modern b&w films. This ISO standard is completely outdated and is obviously ignored by today's suppliers.

EI and ISO are different things. Anyone claiming an ISO speed should be using the relevant formal standard to compute that speed.

EI is the pragmatic speed that considers the individual's manner of metering, preferred development discipline, measurement equipment, and so on.

So, I would call into question the claim that no company uses ISO standards. They all do. That just doesn't map directly to EI.

 

[Milpool]

So, I would call into question the claim that no company uses ISO standards. They all do.

Yes that post was all kinds of wrong, as was the one further up about the ISO standard being a problem necessitating personal EI tests. That comes from not knowing about the history of the ISO standard, not understanding the test/criteria (or what the typical ZS EI test is testing) etc. Misinformation about all of this has been endlessly parroted over the years.

As far as ISO speed ratings go, Kodak and Harman test according to the standard. And in fact this is pretty easy to replicate/confirm at home. Specifically with respect to Harman, years ago when I was badgering them into making film-specific reciprocity adjustment factors, and was allowed to follow along with the work, ID-11 was the developer used for ISO speed determination.

The passage quoted by the person a few posts up has to do with the suggested processing times when an exposure index other than the ISO speed is used (for example, rating Delta 100 at EI 50 or HP5+ at EI 800, etc.)

The only case where something seems to be not quite right in my opinion is Foma. I have never used Foma films so I’m just basing this on the graphs they provide in the documentation. It’s not entirely straight forward but in many cases it does look as though if one targets a gradient similar to what you end up with in the ISO criteria, the corresponding EI is lower than the ISO rating Foma has given the film. It’s difficult for to say for sure.

 

[Stephen Benskin]

Foma webpage shows boxes using ISO, so...

Honerich's concerns are not unique. Many others have also mistakenly come to the same conclusions.

 

[Milpool]

Foma webpage shows boxes using ISO, so...

It does, however the curves on the charts they provide seem strange in some cases. It’s not entirely clear. I looked at them because at least anecdotally I’ve seen a lot of assertions these films (in particular the 200 film) are underexposed at the speeds indicated on the boxes. I don’t know for sure.

 

[Stephen Benskin]

It does, however the curves on the charts they provide seem strange in some cases. It’s not entirely clear. I looked at them because at least anecdotally I’ve seen a lot of assertions these films (in particular the 200 film) are underexposed at the speeds indicated on the boxes. I don’t know for sure.

It does appear they are reaching. Maybe one or two of the developers might be capable of achieving 200. Using Gamma doesn't make it any easier to determine where the approximate ISO contrast falls. I'm not thrilled with the inappropriate use of the ISO prefix instead of EI with the charts.

 

[Stephen Benskin]

Which company uses ISO standards? I don't know any!

Foma's box speed definitely is too high with any standard developing process.

The Ilford film data sheets state: “It should be noted that the recommended exposure index(EI) is based on a practical evaluation of film speed and is not based on foot speed, as is the ISO standard.”

Kodak uses a Contrast Index CI, that has nothing to do with the definitions in the ISO standard. CI can only be evaluated in a graphical manner with a special ruler and cannot be converted into Ilford's G or into gamma.

The only way to deal with this is to carry out your own film tests and use your own personal EI.

The density curve used in ISO (see #29 above) has nothing in common with a typical curve of modern b&w films. This ISO standard is completely outdated and is obviously ignored by today's suppliers.

As far as I know, this is a standard statement used in all Ilford's black and white film technical data sheets. It is referring to how the development tables were derived as opposed to the ISO speed.

Contrast index is just one type of average gradient method, but I'm assuming you mean the ISO contrast parameter no longer applies to the development of modern film. The contrast parameter in ISO 6 doesn't indicate how to develop pictorial film (although the contrast is not unrealistic). That's not the purpose of the speed standard. One of the problems with the standards is that they don't generally contain the theory and reasoning behind them. They just explain how to do something. With ISO 6, the contrast parameters is actually part of an equation. According to C.N. Nelson in Safety Factors in Camera Exposures, "Thus when development is controlled so that ΔD remains constant, a good correlation exists between speeds based on a density of 0.1 above fog and fractional-gradient speeds."

"A new formula for speed can be derived which will make use of the 0.1 fixed-density speed criterion. If a specification is adopted requiring development to a ΔD of 0.80 or an average gradient of 0.62, for example, the log E difference (ΔX) between the two types of speed becomes 0.29, and the exposure, Ed, at a density of 0.1 above fog becomes 1.9 times greater than the exposure, Es, at the fractional-gradient speed point."

Here is the ISO contrast parameter along with the equation.

Instead of having to apply the equation, by adhering to the development conditions, the fractional gradient speed point will always fall at the same Δ log-H from the 0.10 fixed density point. The value of ΔX remains constant. The fixed density of 0.10 is where the film speed is determined. Nothing more.

If you are concerned the contrast is excessive with the ISO parameters and the speeds derived at the higher gradient won't represent the normal pictorial gradient, one: don't be, and two: adjust your shooting gradient. 0.62 is approximately 1/3 of a stop greater than the processing for statically average conditions. Small variations in a scene's luminance range, variations in flare, and LER variations in different grade 2 papers can easily make the difference. Let's not forget the difference between the negative density range for a diffusion enlarger and condenser enlarger. Also there is an "inverse" relation between ΔX and average gradient (or ΔD). As the film gradient is increased, the value of ΔX decrease which limits the change of film speed compared to just using a fixed density method. Which brings us to the next point. Any speed determination for development conditions other than the ISO parameters requires the use of the Delta-X equation. Otherwise, "The fixed-density criterion tends to underrate films that are developed to a lower average gradient and to overrate films that are developed to a higher average gradient." How many people do this? How many people notice the difference? A third of a stop is not much to complain about.

 

[honerich]

Slightly off-topic, but let me answer in more detail:

Does it make sense to discuss a proposed (but never implemented) change to the speed criterion published by C.N.Nelson in 1959, based on a standard from 1954 or even earlier? Back then, unlike today, films had an extremely S-shaped densitometric curve.

Other reasons why I think ISO 6 is outdated and no longer useful:

Modern films have a more or less straight line that starts at zone II (maybe II-III) and goes beyond zone X. Applying the ISO process to such films results in a high contrast gamma of about 0.7. ISO film speed is thus based on N+1 push development. For this you would need multigrade paper with grade 0.5, but normal contrast should fit on grade 2!

ISO places the speed point in the flat toe of the curve in zone I with a density of 0.1 over base+fog. This was a compromise that still exists today in ISO 6. The base of the density curve below D=0.2 is of no interest for practical photography, as details are no longer resolved. Many large-format photographers tend to place the shadows in zone III with a density of at least 0.35. The film density in zone I is ultimately irrelevant.

Personally, I see the ISO number on the film box as nothing more than a primitive classification into low, medium or high speed. Which EI we set on the light meter is left to our experience with a certain combination of film+developer+enlarger+paper.

 

[Milpool]

Slightly off-topic, but let me answer in more detail:

Does it make sense to discuss a proposed (but never implemented) change to the speed criterion published by C.N.Nelson in 1959, based on a standard from 1954 or even earlier? Back then, unlike today, films had an extremely S-shaped densitometric curve.

Other reasons why I think ISO 6 is outdated and no longer useful:

Modern films have a more or less straight line that starts at zone II (maybe II-III) and goes beyond zone X. Applying the ISO process to such films results in a high contrast gamma of about 0.7. ISO film speed is thus based on N+1 development (in the zone system). For this you would need multigrade paper with grade 0.5, but normal contrast should fit on grade 2!

ISO places the speed point in the flat foot of the curve in zone I with a density of 0.1 over base+fog. This was a compromise that still exists today in ISO 6. The base of the density curve below D=0.2 is of no interest for practical photography, as details are no longer resolved. Many large-format photographers tend to place the shadows in zone III with a density of at least 0.35. The film density in zone I is ultimately irrelevant.

Personally, I see the ISO number on the film box as nothing more than a primitive classification into low, medium or high speed. Which EI we set on the light meter is left to our experience with a certain combination of film+developer+enlarger+paper.

I’ll leave it to Stephen Benskin to address your points because I’m tired (it’s also probably best not to have multiple people going into detail on this to avoid muddying the waters).

However one thing you wrote which I agree with is “Which EI we set on the light meter is left to our experience…”. In my opinion that is the sensible way to depart from ISO speeds if required. If one finds he is consistently struggling with insufficient shadow information, use a lower EI (or vice versa although that is probably rare). On the other hand the kind of “personal EI” “test” people are encouraged to do at the outset is superfluous, and also isn’t really testing for anything. If you want a Zone System EI, downrate the film by 2/3 stop and you’re done.

 

[Stephen Benskin]

I’ll leave it to Stephen Benskin to address your points because I’m tired (it’s also probably best not to have multiple people going into detail on this to avoid muddying the waters).

Please don't leave it only to me. You've always been able to explain the issues without getting mired in the details. It's a big, complex, and deep topic, so maybe you or perhaps we can find a way to convey the information in a way that makes sense.

A couple quick points to start with is the standards come up for review every five years, and the Delta-X Criterion and proposals presented in Safety Factors were adopted and are part of the standard.

 

[chuckroast]

I’ll leave it to Stephen Benskin to address your points because I’m tired (it’s also probably best not to have multiple people going into detail on this to avoid muddying the waters).

However one thing you wrote which I agree with is “Which EI we set on the light meter is left to our experience…”. In my opinion that is the sensible way to depart from ISO speeds if required. If one finds he is consistently struggling with insufficient shadow information, use a lower EI (or vice versa although that is probably rare). On the other hand the kind of “personal EI” “test” people are encouraged to do at the outset is superfluous, and also isn’t really testing for anything. If you want a Zone System EI, downrate the film by 2/3 stop and you’re done.

Maybe. This assumes you have accurate thermometer, meter, and shutter. This assumes that you're either using distilled water to mix the developer or your tap water isn't a factor in developer activity (and I have seen it be exactly so). This assumes you have a fairly proper ZS way of metering the shadows. And so forth.

The whole idea of "personal ASA" as originally proposed by Adams was at a time when these things could not reliably be counted upon and the idea was to map your world onto an effective "ASA" that would give desired results.

These days, thermometer and meter variability are less of an issue. The water issue can be made moot by using distilled. But - having tested a lot of shutters over the years - I can say with some conviction that shutter variability, especially with older leaf shutters, is still very much an important variable.

 

[Augustus Caesar]

EI and ISO are different things. Anyone claiming an ISO speed should be using the relevant formal standard to compute that speed.

EI is the pragmatic speed that considers the individual's manner of metering, preferred development discipline, measurement equipment, and so on.

So, I would call into question the claim that no company uses ISO standards. They all do. That just doesn't map directly to EI.

I looked at a box of HP5 today, and the speed was given as ISO 400, not EI. When T-Max films were first introduced, they were rated as EI, because they did not reach full speed in the ISO developer (which was required at that time). Later, the ISO standard was changed to allow for other developers.

 

[DREW WILEY]

honerich - you seem to assume film curves are much more similar to one another than they actually are. Yes, some Zonies do subscribe to the motheaten old generic advice to expose shadow gradation threshold value way up belly-button high on Zone III, as if Triassic-X were the only film in existence; but that would have been a counterproductive waste of valuable real estate further down the curve even back in the days of Super-XX. Having mentioned Super-XX proves that films back in the 50's were by no means all analogous back then either - certainly not all with a pronounced S-curve. Just get ahold of a Kodak film handbook from that era. There was quite a diversity of curves, tailored to a wide range of applications.

 

[Milpool]

Maybe. This assumes you have accurate thermometer, meter, and shutter. This assumes that you're either using distilled water to mix the developer or your tap water isn't a factor in developer activity (and I have seen it be exactly so). This assumes you have a fairly proper ZS way of metering the shadows. And so forth.

The whole idea of "personal ASA" as originally proposed by Adams was at a time when these things could not reliably be counted upon and the idea was to map your world onto an effective "ASA" that would give desired results.

These days, thermometer and meter variability are less of an issue. The water issue can be made moot by using distilled. But - having tested a lot of shutters over the years - I can say with some conviction that shutter variability, especially with older leaf shutters, is still very much an important variable.

All I can say is if you look at the methodology and criteria for the typical personal EI test, the test is not doing what you’re describing.

If the purpose of a personal EI test was to find an adjustment to the ISO speed to account for any of the variables you listed, the test would have the same speed determination criteria. But we know right off the bat a typical personal EI test targets a fixed density of 0.1 (net) 4 stops below the metered exposure while in the ISO criteria that density is 3 1/3 stops below the metered exposure. Not a good start if a speed test is ostensibly supposed to adjust the box speed for personal metering/processing conditions, and could do a pretty good job explaining why (barring extreme processing) personal/ZS EI tests typically find something roughly 2/3 stop slower than the ISO speed.

Even if the test methodology is altered to ISO targets/criteria in an attempt to find an EI that corrects for personal conditions, I’m not sure how that works:

Unless a shutter gives the same exposure error at all settings, wouldn’t you potentially need many EIs?

How specifically is the personal EI test accounting for metering and meter variability?

How specifically is the personal EI test accounting for an inaccurate thermometer?

What about other things such as flare, which could creep into a methodology?

As an aside, the water variable puzzles me. It would be a very long shot (or horrendously bad water) if somehow that played a role, and if something like that was going on I doubt it would be a consistent effect either.

 

[Stephen Benskin]

Does it make sense to discuss a proposed (but never implemented) change to the speed criterion published by C.N.Nelson in 1959, based on a standard from 1954 or even earlier? Back then, unlike today, films had an extremely S-shaped densitometric curve.

I just want to first make a few factional corrections before moving forward.

On page 443 of Theory of the Photographic Process, 3rd edition.

The Delta-X Criterion is discussed for 1 1/2 pages. Towards the bottom of page 443.

“In view of the data presented by Nelson and Simonds, it is clear that the poor correlation which Jones and Nelson found between speed numbers obtained from the D=0.10 criterion and speeds obtained from a statistical determination of the “first-excellent” print can be attributed to the use in their investigation of negatives that had been developed to widely different average gradients.”

And on page 444, “It is now feasible to restrict the use of the speed criterion to those cases in which the negative material is developed to a fixed average gradient corresponding to that realized in commercial practice. With this restriction incorporated in the development specifications, it follows from the studies of Nelson and Simonds (Simple Methods for Approximating the Fractional Gradient Speeds) that the fixed-density (D=0.10) speed criterion is a valid correlate of the fractional-gradient criterion.

In 1957, the responsible committees of the American Standards Association undertook the drafting of a revised American Standard Method for Determining Speed of Photographic Negative Materials (Monochrome, Continuous Tone). One of the primary objective in writing the standard was to specify a method of testing which would permit the use of a fixed-density speed criterion. The view was held that by abandoning the fractional-gradient criterion, which had been specified in previous American Standards, and adopting a fixed-density criterion, a serious obstacle in the way of international agreement on the method for determining speed would be removed. Because, in addition, the use of a 0.10 fixed-density criterion in combination with a suitable development specification offers the convenience and precision characteristic of this criterion and retain the practical significance of the fractional-gradient criterion, this method was adopted in the new American Standard."

I’ve found papers explaining the theory behind a new photographic standard were common, like Safety Factors in Camera Exposure. Some of the papers could be about proposing a change to a standard, but as Safety Factors was published in 1960, the same year as the new speed standard, and the above quote has the committee working on the new standard in 1957, it appears it was at least being written concurrently with the standard. So, for a better understanding of the choices in the ISO speed standard, two of the papers one should read are Safety Factors and Simple Methods of Approximating the Fractional Gradient Speed.

Other reasons why I think ISO 6 is outdated and no longer useful:

As for being outdated, the standards are reviewed every 5 years. While the ASA standard was later adopted as an ISO standard in 1974, and then revised in 1993, the changes were primarily methodological and didn’t change the core theory. It has not been revised since.

Modern films have a more or less straight line that starts at zone II (maybe II-III) and goes beyond zone X. Applying the ISO process to such films results in a high contrast gamma of about 0.7. ISO film speed is thus based on N+1 push development. For this you would need multigrade paper with grade 0.5, but normal contrast should fit on grade 2!

ISO places the speed point in the flat toe of the curve in zone I with a density of 0.1 over base+fog. This was a compromise that still exists today in ISO 6. The base of the density curve below D=0.2 is of no interest for practical photography, as details are no longer resolved. Many large-format photographers tend to place the shadows in zone III with a density of at least 0.35. The film density in zone I is ultimately irrelevant.

There's a lot to unpack in there. I'm going to ignore the Zone System stuff as that has more to do with metering and setting an EI than the ISO speed standard. There are a few points I'd like to make. As I said in a previous post, the ISO parameters produces a film with a gradient of 0.62 especially in the case of short toed films. Because gradient is calculated as Rise / Run, the length of the run and how it relates to the film curve is important. In another thread, I should how the value of the gradient can change depending on the type of film curve and the length of the run. As the ISO standard uses Δ1.30 for its run, developing a long toed curve to a ΔD = 0.80 tends to produce a negative with a CI higher than 0.62. I emphasis once again the standard isn't suggesting this is how to process a pictorial negative. It is used for the speed determination of the ISO standard, so much of the point in the first paragraph moot. Considering a normal negative to be contact printed or printed on a diffusion enlarger is considered to have a CI of 0.58 based on a paper LER of 1.05, Luminance range of 2.20, and 0.40 of flare, a CI of 0.62 is about 1/3 more contrast as stated in a previous post.

A good paper that addresses print quality from different film types is Simonds, J.L., Factors Affecting the Quality of Black-and-white Reflection Prints, The Journal of Photographic Science, Vol, 11, 1963.

As for density being a deciding factor in exposure placement, there's a favorite quote by Lyod Jones, "From the standpoint of tone reproduction theory, there seems to be no justification for the adoption of any value of density as a significant criterion of the speed of a photographic negative material. The primary function of the negative material is to record brightness differences existing in the scene. Density, per se, has no significance as an indication of the ability of the photographic material to perform this function. The value of negative density by which any particular object brightness is rendered, as, for instance, the deepest shadow, is of no consequence except insofar as it may have some bearing on the exposure time required to make a print from the negative."

 

[Milpool]

Incidentally if anyone is interested, before the requirement was removed this is the developer specified (g/l)

Metol 0.5
Sodium sulfite (anh.) 40.0
HQ 1.0
Sodium carbonate (anh.) 1.5
Sodium bicarbonate 1.0
KBr 0.2

pH 9.4 +/- 0.2 @ 20C

 

[Stephen Benskin]

Which EI we set on the light meter is left to our experience with a certain combination of film+developer+enlarger+paper.

This is the only part of the post I can agree with. You find what works for you and has the results you like. Here's the thing. It doesn't go against the ISO speed standard. There's no contradiction if a person is willing to understand the theory. Sure the standards need to be tweaked from time to time, but for the most part, any blame directed toward the speed standard is generally misplaced. You don't need to understand theory to photograph, as the next section from a Kodak data sheet demonstrates, but theory helps it all make sense so we can stop misplacing blame.

This is from the exposure section in Kodak's technical data sheet for TMX.

As Kodak's statement suggests, the ISO standard is a guide. ISO 6 is not intended to be universally applicable. It is designed to accurately work under certain conditions. The further from those conditions, the less accurate the results. There are a number of caveats involved including both physical and psychophysical. In the forward to ISO 6, "the ISO speeds will provide correct exposures for average scenes with the exposure meters conforming to ISO 2720 or ISO 2721 when the film is processed as specified in this international standard." As a scene moves further from the average scene or if the film is processed differently, the agreement is reduced.

Jones says in The Psychophysical Evaluation of the Quality of Photographic Reproductions, PSA Journal, Vol 17, Dec 1951. "In this discussion, the term photographic quality will be used in referring to the degree of perfection with which the photographic picture reproduces in the mind of the observer the subjective impression which he received when looking at the original." What if the intention wasn't a realistic reproduction of how something looks but an interpretation that departs from a realistic impression of the subject or for lack of a better term, an artistic interpretation? A situation where the emotional element supersedes a strictly technically reproduction. How would this affect Jones' print judgement speeds and consequently sensitometric speeds? Or looking at it from a different perspective, how would film speeds based on Jones' print judgement speeds be applicable to the artistic work of photographers like Bill Brant, Brett Weston, or Michael Kenna?

The fractional gradient speed point has excellent correlation with psychophysical testing and is used to accurately compare the limiting gradient across films of various characteristics. It means the same for all film types. This is the basis for black and white film speeds. The old ASA standard had an ASA speed and an ASA film exposure index. The ASA standard was the fractional gradient speed while the exposure index takes into consideration the meter's characteristics, a scene's luminance range and distribution, flare, and other factors including any safety factors. In other words the factional gradient speed is the film speed and the EI is how the film is to be applied. While the current ISO speed standard doesn't make a distinction between the two, the ISO speed is still determined in relation to the fractional gradient speed and can be considered an EI. A user’s choice of EI can then be further based on an individual's situation which may include many additional variables including taste, but the actual speed of the film is defined. It's common for people to conflate speed with exposure.

Apart from all that, what makes more sense, people who use EIs other than the ISO value have a better understanding or more ridged testing procedures than the people that researched and developed the methodology or that they have found a value which works for them?

 

[Chuck_P]

What if the intention wasn't a realistic reproduction of how something looks but an interpretation that departs from a realistic impression of the subject or for lack of a better term, an artistic interpretation?

So the intention was a simple realistic interpretation of the subject. What was the manner in which those negatives were actually printed for a psychophysical evaluation of the print for film speed. Sorry if I have missed it stated somewhere. For me, an enlarged proof print at a standard 5x7 or 8x10 enlarger height with the exposure time based on the minimum time to print the paper's D-max through the fb+f density of the negative is an excellent way to evaluate the negative.

 

[Stephen Benskin]

So the intention was a simple realistic interpretation of the subject. What was the manner in which those negatives were actually printed for a psychophysical evaluation of the print for film speed. Sorry if I have missed it stated somewhere. For me, an enlarged proof print at a standard 5x7 or 8x10 enlarger height with the exposure time based on the minimum time to print the paper's D-max through the fb+f density of the negative is an excellent way to evaluate the negative.

It's fine as long as it works for you; however, that method is more about exposure than speed, and it's a somewhat arbitrary method at that (see what Jones says about density).

 

[Augustus Caesar]

It's fine as long as it works for you; however, that method is more about exposure than speed, and it's a somewhat arbitrary method at that (see what Jones says about density).

Bear in mind that different lenses will have different transmittance and different levels of contrast depending on their age and design. Also, in dealing with leaf-shutter lenses, the efficiency varies with the aperture, making precisely equivalent exposures difficult.

 

[chuckroast]

All I can say is if you look at the methodology and criteria for the typical personal EI test, the test is not doing what you’re describing.

If the purpose of a personal EI test was to find an adjustment to the ISO speed to account for any of the variables you listed, the test would have the same speed determination criteria. But we know right off the bat a typical personal EI test targets a fixed density of 0.1 (net) 4 stops below the metered exposure while in the ISO criteria that density is 3 1/3 stops below the metered exposure. Not a good start if a speed test is ostensibly supposed to adjust the box speed for personal metering/processing conditions, and could do a pretty good job explaining why (barring extreme processing) personal/ZS EI tests typically find something roughly 2/3 stop slower than the ISO speed.

Even if the test methodology is altered to ISO targets/criteria in an attempt to find an EI that corrects for personal conditions, I’m not sure how that works:

Unless a shutter gives the same exposure error at all settings, wouldn’t you potentially need many EIs?

How specifically is the personal EI test accounting for metering and meter variability?

How specifically is the personal EI test accounting for an inaccurate thermometer?

What about other things such as flare, which could creep into a methodology?

As an aside, the water variable puzzles me. It would be a very long shot (or horrendously bad water) if somehow that played a role, and if something like that was going on I doubt it would be a consistent effect either.

In order to your comments:

The normal ZS methodology attempts to take those variables (and others) into account to achieve two things: Maintain a sufficient level of shadow detail (via EI adjustment) and keep the highlights in bounds for printing (via development time). Unfortunately this has several drawbacks - not all films have the same toe so the nominal 0.1 FB+F for Zone 1 isn't really a universal constant. The other issue is that doing this almost always introduces some midtone compression which is typically kind of ugly.

Yes, for a shutter, there are corrections potentially necessary for every different speed.

By meter "variability" I mean from meter to meter not across the range of the same meter. So if my meter is miscalibrated by 1/2 stop against the standard, I can dial in 1/2 stop of compensation via EI adjustment. Much like having many corrections for different shutter speed errors on the same shutter, handling things like meter nonlinearity across its range has to be done on an exposure-by-exposure basis.

Ditto the thermometer if its off by some fixed amount in the normal range of use.

I have directly observed the better part of 1/2-2/3 stop variability in film development in a new home I bought years ago as the water changed across the seasons. This may have been attributable to new pipes needing to clear and coat, but I never bothered to check. I eliminate this one by using distilled water.

All of these things are essentially an attempt to get to a common goal: Consistent repeatable outcomes.

 

[DREW WILEY]

Errors in meter function, shutter speed, or temp control should be addressed as exactly that - errors needing some kind of corrective recognition, and not as part of what is termed personal E.I. Otherwise, things get unnecessarily convoluted.

There are numerous variations to the Zone System, and it's malleable enough as a concept to be leveraged to your own needs. What I personally dislike about traditional versions of it is that they rely too much on compression or minus development to handle high contrast situations rather than opting for a film with a longer straight line deeper down into the shadows. So yes, a less than ideal film for those kind of situations can be salvaged in certain respects, but at a penalty to fine intermediate tonal gradation.

During the heyday, although Kodak itself did not espouse the Zone System, they did provided a wide range of films, which most prominently included Super-XX with its extremely long straight line, Plus-X Pan with its "all toe" upswept curve favoring high values, especially in studio portraiture applications, and then, TriX 320, which was basically in the middle. One can go to the guidebooks to note many other films in their past selection. But when my older brother was in a commercial photography academy, the three specific films I just mentioned were the ones they were expected to master.

Back then, anything smaller than 4x5 was considered a miniature format, so there wasn't as much emphasis on fine grain as now.
But as small cameras became more and more important, that was one of the driving forces to re-engineer their predominant film lineup with T-grain technology.

 

[Stephen Benskin]

So the intention was a simple realistic interpretation of the subject. What was the manner in which those negatives were actually printed for a psychophysical evaluation of the print for film speed.

I may have missed the meaning of your question before. I read it as using the just black method as a determinant of proper camera exposure and speed rating. If you are asking about the printing methodology of the psychophysical testing done in the first excellent print tests, it is explained in great detail in Jones' paper The Evaluation of Negative Film Speeds in Terms of Print Quality, Journal of The Franklin Institute, 1939.

Fortunately, a nice summary is available in all the editions of Theory of the Photographic Process. From the 3th edition, page 440, "A statistical method was used by Jones to determine the relationship between the exposure of the negative and the quality of the resultant prints. A series of twelve negatives in which the camera exposure was increased progressively from a very low to a very high value was made on each material to be studied. To secure the best possible print from each negative thus obtained, skilled operators were asked to print each negative on several grades of paper, use several printing exposures, quality of the resultant prints. A series of twelve negatives in which the camera exposure was increased progressively from a very low to a very high value was made on each material to be studied. To secure the best possible print from each negative thus obtained, skilled operators were asked to print each negative on several grades of paper, use several printing exposures, and then select from this group of prints the best one that each negative was capable of giving. These series of prints were then arranged in order and were judged by two hundred observers, each observer being requested to pick the first print in each series which he considered “excellent”. This is, of course, a very laborious method of working, but it allowed a statistical selection of the negative which the average observer would consider “satisfactory.” It was also possible to select a print inferior to the “first-excellent” print."

 

[Augustus Caesar]

This is the only part of the post I can agree with. You find what works for you and has the results you like. Here's the thing. It doesn't go against the ISO speed standard. There's no contradiction if a person is willing to understand the theory. Sure the standards need to be tweaked from time to time, but for the most part, any blame directed toward the speed standard is generally misplaced. You don't need to understand theory to photograph, as the next section from a Kodak data sheet demonstrates, but theory helps it all make sense so we can stop misplacing blame.

This is from the exposure section in Kodak's technical data sheet for TMX.

View attachment 383365

As Kodak's statement suggests, the ISO standard is a guide. ISO 6 is not intended to be universally applicable. It is designed to accurately work under certain conditions. The further from those conditions, the less accurate the results. There are a number of caveats involved including both physical and psychophysical. In the forward to ISO 6, "the ISO speeds will provide correct exposures for average scenes with the exposure meters conforming to ISO 2720 or ISO 2721 when the film is processed as specified in this international standard." As a scene moves further from the average scene or if the film is processed differently, the agreement is reduced.

Jones says in The Psychophysical Evaluation of the Quality of Photographic Reproductions, PSA Journal, Vol 17, Dec 1951. "In this discussion, the term photographic quality will be used in referring to the degree of perfection with which the photographic picture reproduces in the mind of the observer the subjective impression which he received when looking at the original." What if the intention wasn't a realistic reproduction of how something looks but an interpretation that departs from a realistic impression of the subject or for lack of a better term, an artistic interpretation? A situation where the emotional element supersedes a strictly technically reproduction. How would this affect Jones' print judgement speeds and consequently sensitometric speeds? Or looking at it from a different perspective, how would film speeds based on Jones' print judgement speeds be applicable to the artistic work of photographers like Bill Brant, Brett Weston, or Michael Kenna?

The fractional gradient speed point has excellent correlation with psychophysical testing and is used to accurately compare the limiting gradient across films of various characteristics. It means the same for all film types. This is the basis for black and white film speeds. The old ASA standard had an ASA speed and an ASA film exposure index. The ASA standard was the fractional gradient speed while the exposure index takes into consideration the meter's characteristics, a scene's luminance range and distribution, flare, and other factors including any safety factors. In other words the factional gradient speed is the film speed and the EI is how the film is to be applied. While the current ISO speed standard doesn't make a distinction between the two, the ISO speed is still determined in relation to the fractional gradient speed and can be considered an EI. A user’s choice of EI can then be further based on an individual's situation which may include many additional variables including taste, but the actual speed of the film is defined. It's common for people to conflate speed with exposure.

Apart from all that, what makes more sense, people who use EIs other than the ISO value have a better understanding or more ridged testing procedures than the people that researched and developed the methodology or that they have found a value which works for them?

The speed of T-Max films is now listed as ISO, not EI. In any case, a little more exposure than the absolute minimum is not in any way deleterious. It's best to err on the side of generous exposure, especially in rapidly changing situations.

 

[Stephen Benskin]

The speed of T-Max films is now listed as ISO, not EI. In any case, a little more exposure than the absolute minimum is not in any way deleterious. It's best to err on the side of generous exposure, especially in rapidly changing situations.

The except from the Kodak technical data sheet is from around 2017. It isn't implying the film doesn't have an ISO. The only time T-Max films didn't have an ISO was prior to the 1993 standard. Kodak's use of EI is referring to how you set the camera's exposure meter. The film has an ISO of 400. You set the your camera / meter to EI 400.

Again, let's remember there is a distinction between film speed and exposure.