Does changing film speed affect zone employment?

[138S]

It might all feel like deception until you go back to when Hurter and Driffield started verifying speed claims like Rapid and Ultra Rapid.

Yeah, the sensitometric curve is what enlights. Hurter and Driffield teached people how meal is cooked.

At the end accurate metering (IMO) consists in metering key spots in the scene and checking where they fall in our sensitometric curve.

Of course many other metering strategies are pretty valid, but when a traditional photographer understands well practical sensitometry then he has an advantage. IMO a great training excercise is performing a film calibration at least once in a lifetime, at all it's necessary to calibrate film to craft great images, but having made a single calibration helps having an open mind.

 

[Doremus Scudder]

Doremus, look, the ZS photographers routinely rate film at 1/2 (*) of its today's film speed, isn't it ?

... so pre-1960 they rated film at its Box Speed, isn't ?

______________

Of course you can refine you personal E.I. for ZS from developer, etc... if you loss 1/4 stop from Rodinal or HC-110 you will adjust that... you can say 2/3 if using Xtol (*), 1 stop if using D-76, or 1+1/3 if using Rodinal...

But Nominally the ZS table was shifted for a full zone in 1960, as the table was not modified but box speed was. There is absolutely no doubt that shift was exactly 1 Stop. If you were using ASA (ISO) box speed for ZS in 1959 then in 1961 you would have been using half the box speed, supposed your workflow was sound by 1959...


* (Well, Michael says 2/3 stop, instead 1 stop)

Careful practitioners of the Zone System did (and still do) testing to determine their own personal E.I. Box speed was, and still is, just a starting point for that determination. Choice of film developer, metering technique, enlarger type, even whether one uses multi-coated lenses vs. single-coated all make a difference here.

The fact that today, people can use 2/3-stop more exposure than box speed as a general all-round starting point that will likely deliver good results is really just a short-cut. I recommend that too, but then recommend keeping good notes and refining one's personal E.I. as needed.

How precise one needs to be with finding the minimum exposure needed to give a good negative varies with film format. It's quite important for small film, but not nearly so for larger film that can easily stand quite a bit of overexposure without unwanted grain showing up in the final prints.

And, the "Zone System table" wasn't shifted in 1960 as far as I know (really, the chart you posted applies to any speed film...). Yes, the "box speed" of films changed with the updated speed determination, but that would not have made any difference to Zone System practitioners, who had determined their own personal E.I. through testing. The films themselves didn't change... The one-stop shift only changed what was printed on the box and Zone System users did not "use ASA (ISO) box speed."

Best,

Doremus

 

[138S]

1) Careful practitioners of the Zone System did (and still do) testing to determine their own personal E.I.
2) the "Zone System table" wasn't shifted in 1960 as far as I know (really, the chart you posted applies to any speed film...).
3) the "box speed" of films changed with the updated speed determination (note by 1 exact stop)

________________________________

4) but that would not have made any difference to Zone System practitioners,
5) Box speed was, and still is, just a starting point for that determination.

Doremus, I labeled your points with numbers.

Your 1,2,3 points are totally contradictory with 4 and 5.


Note that ZS pactitiones do accurate testing. If box speed was the starting point for Z-V in 1959 then in 1961 it had to be the half, as the same film was stamped 400 instead 200... This is an hitorical fact !!!

 

[138S]

The Zone System EI is the same because the criteria has always been net 0.1D. That did not change in 1960.

Michael, yes, as shown bellow Adams places Z-I at 0.1D which is the ASA/ISO Speed Point (The Negative).

Pre 1960 this was -4.3 stops for Z-I. Post 1960 this was -3.3 Stops for Z-I.

He instructs using a calibrated meter an the "appropriate film speed."

For what maters that 0.3 stop is irrelevant because as we play N-1 that 0.3 is lost. Still if you want total formal accuracy then Z-V was at +0.3 stops overexposure pre 1960 and at +1.3 stops overexposure post 1960...

IMO ZS is not trying to be 0.3 stops accurate (with 1940 meters!)... what Ansel Adams was telling people (Pre 1960) is that the Meter 0+/- point is the central Z-V. It makes no sense making a simplified System like ZS and later telling people that (in 1940 !!) they have to overexpose exactly 0.3 the 18% grey card, this would made people became crazy, IMO in his mind Z-I was (pre 1960) 4 stops underexposure, and 3 stops post 1960. If you want to split hairs then add 0.3 stops additional underexposure.

 

[Doremus Scudder]

138S,

You're missing the point somehow... First, you state: "... yes, as shown bellow Adams places Z-I at 0.1D which is the ASA/ISO Speed Point (The Negative). Pre-1960 this was -4.3 stops for Z-I. Post 1960 this was -3.3 Stops for Z-I."

I believe this is incorrect, or at least confusing. Even if the speed point was the same pre- and post-1960, the safety factor that was present earlier, in essence, moved the speed point by a stop so that, in practice, one's effective speed point was more dense on the negative than it was post-1960 when the safety factor was dispensed with.

And, you erroneously keep trying to correlate a personally-determined E.I. with a lab standard ISO. It's important to understand that a personal E.I. is dependent on many individual factors that are not laboratory standard. It varies depending on the equipment and methods of the individual photographer. Your meter reads differently than mine. You meter differently than I do. Your developer choice and method are different than mine, etc.

Sure, whatever ASA, ISO, DIN number the manufacturer gives provides a starting point testing, but the Zone System speed point that one determines for their own particular situation is not simply a given amount different than the manufacturers' standard. If that were the case, there would be no need to test; just rate your film x amount slower than box speed and get to work.

These days, one can, indeed, get a closer-to-final-result starting point for ZS testing by rating the film 2/3-stop slower than box speed rather than using box speed. Still, it's just a starting point. Personal E.I.s for the same film varies from photographer to photographer based on how they work, meter, etc. It is not just so-and-so-many stops different than ISO.

And, you seem to miss Adam's point about Zone V in the excerpt you posted above. He's not advocating using Zone V as a calibration point, rather explaining how meters read, or should be assumed to read, for use in the Zone System. Adams assumes your meter is calibrated for "middle grey" under lab conditions and that, when personal E.I. and N development time have been determined, an exposure based on an unmanipulated meter reading should render a middle grey in the print.

Be aware, however, that Adams never advocates using Zone V as a target for any calibration tests. The Zone System E.I. is determined by the ZS speed point, i.e., Zone I, which is 0.1 above fb+f. "Normal" development is determined by finding the time that puts Zone VIII right place, i.e., the "lightest tone with texture" in the final print (note that this is paper-dependent!). When both E.I. and development time for "N" have been determined, Zone V will be close to middle grey, but most likely not exactly 18% grey.

The actual reflectance of Zone V in a print made from a optimally exposed and developed "Normal" Zone-System negative in which both Zone 1 and Zone VIII are rendered correctly in the final print (according to ZS definitions), will almost invariably not match the 18% standard exactly. It will also be different for different film/developer/paper combinations.

Make a few Zone Rulers à la Minor White, Lorenz, Zakia for different films, etc. and see where Zone V ends up on them. I have (and I still do for every film I test), and Zone V only rarely ends up being 18% grey.

Short version: the outer values, Zones I and VIII define "Normal" exposure and development, respectively, in Zone System calibration. Zone V falls where it may.

The Zone System is intentionally imprecise when it comes to calibrating meters, metering technique, shutters, etc. It assumes that these things are variables and, as long as one is consistent, any deviations from "standard" will be compensated for with the personal E.I. and personally determined development times. It is a practical approach, and shouldn't be contorted into some kind of lab standard. Got a meter that reads half-a-stop off? No matter, you're personal E.I. will take care of that. Who cares if yours is different from mine for the same film as long as the results are good. Use a different developer, development method, agitation scheme than I do? Well your development time for "Normal" is likely going to be different from mine as well. For some reason, we accept this latter as self-evident, but quibble about the former...

Best,

Doremus

 

[138S]

138S,

You're missing the point somehow... First, you state: "... yes, as shown bellow Adams places Z-I at 0.1D which is the ASA/ISO Speed Point (The Negative). Pre-1960 this was -4.3 stops for Z-I. Post 1960 this was -3.3 Stops for Z-I."

I believe this is incorrect, or at least confusing. Even if the speed point was the same pre- and post-1960, the safety factor that was present earlier, in essence, moved the speed point by a stop so that, in practice, one's effective speed point was more dense on the negative than it was post-1960 when the safety factor was dispensed with.

Not confusing at all, just ISO/ASA norms rigosously applied: Pre 1960 density 0.1D+B+F (Z-1) has nominally obtained at 4.3 underexposure. Post 1960 it is 3.3. What is it confusing in that ? This is exactly the Industrial Norms in force at each moment

Safety factor was for the consumers that were toasting negatives more in 1959 than in 1961, but not for Ansel Adams and his mates... that people by 1960 had SEI meters (for example) and exposed perfectly, LOL if Ansel Adams had to expose differently because of something stamped on the box

IMO most ZS practitioners rate film around half of what the Box says, and they don't realize this is because film speed was doubled in 1960 while the ZS table is the 1940 one !!! Those using box speed have to shift one zone which is the same !!!

That 1960 speed change was straight for consumers, but it organized an incredible mess that 60 years later still it is controversial... Many opinions around but little realize why they rate film around the half, the formula says all...

>Today we calculate speed like this:

> Pre 1960 that 0.8 was a 0.4. Impossible to tell it easier. If Z-I is 0.1D + FB... then you have to rate film to the half to conserve 0.1 at Z-1. Kid's math...

The Zone System is intentionally imprecise when it comes to calibrating meters, metering technique, shutters, etc.

Not at all... Ansel Adams says that Z-I is the Speed Point. And the Speed point is well defined at 0.1D+FB, so definition is perfect. Manufacturers and consumers had problems to know if one speed was ok or if the good one was the half, but Ansel had no problem:

Speed Point = Z-1, and you count zones from there !!! Where the imprecision is ?

 

[Sirius Glass]

Not confusing at all, just ISO/ASA norms rigosously applied: Pre 1960 density 0.1D+B+F (Z-1) has nominally obtained at 4.3 underexposure. Post 1960 it is 3.3. What is it confusing in that ? This is exactly the Industrial Norms in force at each moment

Safety factor was for the consumers that were toasting negatives more in 1959 than in 1961, but not for Ansel Adams and his mates... that people by 1960 had SEI meters (for example) and exposed perfectly, LOL if Ansel Adams had to expose differently because of something stamped on the box

IMO most ZS practitioners rate film around half of what the Box says, and they don't realize this is because film speed was doubled in 1960 while the ZS table is the 1940 one !!! Those using box speed have to shift one zone which is the same !!!

That 1960 speed change was straight for consumers, but it organized an incredible mess that 60 years later still it is controversial... Many opinions around but little realize why they rate film around the half, the formula says all...

>Today we calculate speed like this:
View attachment 265401

> Pre 1960 that 0.8 was a 0.4. Impossible to tell it easier. If Z-I is 0.1D + FB... then you have to rate film to the half to conserve 0.1 at Z-1. Kid's math...




Not at all... Ansel Adams says that Z-I is the Speed Point. And the Speed point is well defined at 0.1D+FB, so definition is perfect. Manufacturers and consumers had problems to know if one speed was ok or if the good one was the half, but Ansel had no problem:

Speed Point = Z-1, and you count zones from there !!! Where the imprecision is ?

Placing an object or area in Zone i is a scientific wildassed guess, based on an option. It goes downhill from there.

 

[138S]

Placing an object or area in Zone i is a scientific wildassed guess, based on an option. It goes downhill from there.

If it is a guess or not it depends on you... when you know what you are doing then when you place something in Z-I you place it in the "m" point, pointed by the red arrow:

Zone-V is the "n" point: what meter aimed Pre 1960. Today (Post 1960) the meter aims one stop less, at Delta Log H = 1.0 (instead 1.3).

_______

If our workflow is accurate then we may expect to obtain just degradated detail for Z-I. If our process is not that accurate then for Z-I we may obtain better detail than expected or pure black, depending on the direction our pitfall has.

If we don't want to make the effort to have an accurate workflow then we simply can consider that what is in Z-I is at risk.

 

[Sirius Glass]

If it is a guess or not it depends on you...

 

[Sirius Glass]

If it is a guess or not it depends on you...

Which proves the point. Setting the exposure is an estimate, not based on a measurement. Therefore it cannot be scientific. To believe otherwise is a guess, not at all scientific.

 

[138S]

Which proves the point. Setting the exposure is an estimate, not based on a measurement. Therefore it cannot be scientific. To believe otherwise is a guess, not at all scientific.

No, at all...

First you are teached in engineering or science is that any measurement and calculations operating mesurements always have an error, the second thing you learn is to know the probable error interval of a calculation from the precision of operated data.

Therefore it is totally scientific, to the point you want.

You don't guess, you know what you are aiming and the probable error amount, science is like this: While 2+2=4 you don't have all the Pi decimals, nor all the decimals of Plank constant of the Gravitational constant, in science you know you have errors but you know their nature.

 

[138S]

Setting the exposure is an estimate, not based on a measurement.

Let me add that it depends on how you meter, if you use an averaged metering you cannot say if something will be in Z-1 or Z-0...

But if you simply check key areas with the spot meter (the easiest thing in the world) then you have an accurate scientific prediction about the density the negative will reach in every spot:

>> B+F for Z-0, no detail

>> 0.1+FB for Z-1

If standard ISO development:

>> Add 0.185D for each additional Zone

>> For Z-V add 0.8D to the density in Z-I...

Of course you also need to know the precision of your workflow to know how accurate your prediction is, using a suitable safety margin when we want to ensure some image quality in some shadow detail recording, for example.

At all it is necessary to make those calculations because we may have feedback to know how each under/over exposure level results in our workflow. Averaged metering can be perfectly valid, but there is nothing wrong in checking resulting exposure in interesting spots, if we want to know it...

Still, knowing what is Speed Point and learning to use spot meter in a scene area to know how far/close we are from it... this makes a photographer quite more proficient (but not artistically better).

 

[Doremus Scudder]

Not confusing at all, just ISO/ASA norms rigosously applied: Pre 1960 density 0.1D+B+F (Z-1) has nominally obtained at 4.3 underexposure. Post 1960 it is 3.3. What is it confusing in that ? This is exactly the Industrial Norms in force at each moment

What part of "personal E.I. has nothing to do with box speed" don't you understand? Give me a film with no markings at all. I'll test, come up with a usable film speed for me, a development time that gives me the contrast I want and I'll go out and make photographs. That's basically what Zone System practitioners do. Give me a time machine and I'll do the same thing pre1960 With the same film, I'll end up with the same personal E.I.

There are no industrial norms that apply when you do your own testing. ZS practitioners arrive at their own personal values to make sure they are getting sufficient density on the film (Zone I or III or whatever) with the meter and techniques they use. They don't give a hoot what it says on the box...

You're stuck in a mental rut that's not letting you see the forest for the trees...

Doremus

 

[138S]

There are no industrial norms that apply when you do your own testing.

Doremus, the ISO speed provided (by principal manufacturers) do apply perfectly, Kodak graphs in the dataheets have absolute Lux.Second units, so it's totally precise information.

Of course your particular procesing may vary the Speed Point (exposure for 0.1D+FB) by some 1/3 stop exposure, but not by 1 stop or the like, what probably you adjust.

Kodak tells you that (developed with D-76) gray spots at 3.33 underexposure will deliver around that 0.1D+FB, and belive me, they are not wrong. If you use HC-110 then it would be 3 stops, and if you use Xtol it would be around 3.5.

Of course one may test all what he wants to correct his own repetitive errors...

What you don't understand in these graphs ?



They tell you exactly at what exposure you'll get the Z-I in lux.second, so what your meter has to aim. It's about knowing how to read datasheet, and predicting the (max) 0.3 stop shift from the developer kind, at that point we all know if a particular developer will gain or loss a (mostly irrelevant) 1/4 of stop.

We may have some variability for the constrast index (agitation, temperature, etc)... but Z-I exposure is precisely known from datasheet !!!

 

[Doremus Scudder]

138S,

Now we're getting somewhere!

Doremus, the ISO speed provided (by principal manufacturers) do apply perfectly, Kodak graphs in the datasheets have absolute Lux.Second units, so it's totally precise information.

Of course it's totally precise information. The thing is, it doesn't necessarily apply to a particular practical application. I don't have Kodak's meters. I meter real-life things in lots of different lighting; my readings aren't going to be anywhere close to as precise as Kodak's when it comes to getting the same amount of photons onto the film. I'm aware of that. I certainly believe Kodak gets the results they get. I simply cannot duplicate that. Nor can you.

Of course your particular processing may vary the Speed Point (exposure for 0.1D+FB) by some 1/3 stop exposure, but not by 1 stop or the like, what probably you adjust.

Just one of many variables that can influence the total outcome and just another reason to do one's own testing and arrive at a personal E.I. FWIW, some contractions require even more than a stop of compensation. But even if we're talking "Normal" development, developer choice and agitation method can deviate from the ISO standard development by a significant amount.

Kodak tells you that (developed with D-76) gray spots at 3.33 underexposure will deliver around that 0.1D+FB, and believe me, they are not wrong. If you use HC-110 then it would be 3 stops, and if you use Xtol it would be around 3.5.

Yes, I believe Kodak can do that. And, with my much-less-precise metering, etc. I can easily get within a stop or so of that. I'd just like to refine that a bit. You seem to think that we photographers have equipment and conditions that can duplicate Kodak's laboratory results. That's simply not true. We're lucky if we come close.

Of course one may test all what he wants to correct his own repetitive errors...

Well, I don't know if I'd call deviations from Kodak's lab results "errors." I do as well as I can with what I have. My Pentax spotmeter has flare that influences the shadow readings. I'll bet Kodak didn't have that problem. I've also got flare from other sources (camera bellows, enlarger, etc.) that needs to be compensated for; Kodak didn't have to do that either. Etc., etc... The point is, I'm not "correcting" anything, but compensating for the real-life situation that I find myself in. If I have to rate my film a couple thirds of a stop differently than ISO standard to get consistently better results, I'm going to do it.

What you don't understand in these graphs ?

I understand the graphs. They're great for comparing films and learning about a specific film's characteristics. Still, they don't help me with a choice for rating my film speed in my particular situation.

They tell you exactly at what exposure you'll get the Z-I in lux.second, so what your meter has to aim. It's about knowing how to read datasheet, and predicting the (max) 0.3 stop shift from the developer kind, at that point we all know if a particular developer will gain or loss a (mostly irrelevant) 1/4 of stop. We may have some variability for the contrast index (agitation, temperature, etc)... but Z-I exposure is precisely known from datasheet !!!

I really do believe that x-amount of lux-seconds will get my x density on x film with x developer for x time with x agitation. Really, I do. I'm just not able to measure light and expose that precisely in the real world. My meter isn't Kodak's, and it doesn't read the same nor is it as precise. (If you've got a light meter that works that accurately in practice, I'd love to get my hands on one!)

So, how do I get my meter to match Kodak's? Well, I can never be that precise, but I can come up with an average value based on lots of metered shadows that allows me to find a factor to change my meter settings so that, in general, I get similar results. It's called a personal E.I. It is not based on sensitometry, but from my personal negatives and my particular meter.

But, you're still overlooking some things: what if I want my Zone I to be higher than 0.1 above fb-fog? Or what if I want to base my effective film speed on Zone III? Well, my E.I. is likely going to be a bit different than the ISO, but I digress...

Really, finding what gives you the shadow detail and separation you want is what finding a personal E.I. is all about. It is not sensitometry! You seem to be confusing the two.

Look, Kodak was the first to recognize that their lab results don't always apply exactly to real-life scenarios. Their advice shows this. I'm paraphrasing here, but it goes something like this: If your negatives are consistently to thin, give more exposure (by rating your film differently from the ISO rating!) and vice versa. Kodak is, in essence, suggesting you find your own personal E.I. if your results are not acceptable at the ISO rating.

I think that's good advice. The Zone System simply takes that a bit further and helps quantify things more by testing a bit. Still, one can just follow Kodak's advice and arrive at the same point; a personal working E.I. that takes one's particular situation into account.

And, don't get me wrong. If my personal E.I. were way different than the ISO, I'd be looking for errors in my processing or faulty equipment. I've never had an E.I. for "Normal" that was more than a stop different from the ISO. So, one could likely do just fine using box speed most of the time, especially with negative film. But that's not the issue here. What I'm trying to convince you is that all the science you present, while perfectly good, is not what finding a personal E.I. is about. Finding your own E.I. is simply about finding a setting on your meter that, although it might be different from ISO speed for whatever reason, gives you better exposures. That's all.

Best,

Doremus

 

[138S]

Now we're getting somewhere!

Of course it's totally precise information. The thing is, it doesn't necessarily apply to a particular practical application. I don't have Kodak's meters. I meter real-life things in lots of different lighting; my readings aren't going to be anywhere close to as precise as Kodak's when it comes to getting the same amount of photons onto the film. I'm aware of that. I certainly believe Kodak gets the results they get. I simply cannot duplicate that. Nor can you.

Doremus, personally I see it different... For feedback I often take notes about the spots being at just -3 (with kodak/ilford film), and I find those spots consistently in the speed point...

I usually spot meter TTL with a Nikon SLR and I've no doubt that readings are totally accurate within 1/6 stop. When using those readings for a view camera (that may have slightly higher flare) I also have perfect expoures.

 

[Bill Burk]

I'm supposed to be in the darkroom tonight not arguing about ASA pre-1960, post-1960 and Zone System.

My understanding is that Zone System would have been pretty close to the pre-1960 ASA.

Then when the ASA speeds were doubled, Zone System did not change.

My evidence is that light meters did not have to change to support the 1960 ASA standards (for the meters labeled ASA such as Weston Master III).

 

[138S]

Then when the ASA speeds were doubled, Zone System did not change.
My evidence is that light meters did not have to change to support the 1960 ASA standards (for the meters labeled ASA such as Weston Master III).

Bill, what is clear is that today the ZS table is inconsistent with box speeds... in nominal terms. (if we use a personal speed then we simply do what we want)

Z-I was stated (by Ansel Adams himself) to have 0.1D (over FB), if we use Box Speed and we meter for Z-V (stated to be a 18% grey card) then our Z-I won't be at 0.1D as it will be pure black, a -4 underexposure is lower than the the Speed Point exposure by a fair amount, you in particular are proficient in film calibration, so no need to insist in that...

Even if metering/exposing very accurately, even if performing a lab grade ISO calibration... we won't get the Z-I detail if we use the perfectly calibrated ISO speed for ZS, we have to shift a zone or to use half the EI!

IMO that speed change generated an incredible amount of confusion for the ZS, as ZS table was not changed we have 3 choices:

1> Using (Nominally) half of the Box Speed.

2> Exposure compensation +1

3> Shifting a zone, so expecting start having detail in Z-2 instead Z-1 which will be pure black.

Nominally:

With 1 and 2 we expose like Pre 1960, we overexpose the neutral 18% grey by +1 (in modern terms) and we have 4.33 stops shadow latitude.

With 3 we have 3.3 stops shadow latitude, and our 18% mid gray is exposed 0+/-. Our Z-1 is in the speed point so staring to have detail.


The question is: Do we aim a 3.33 or a 4.33 shadow latitude ?

 

[Bill Burk]

I’m feeling better since I got to do some darkroom work last weekend.

All our Zone System, ASA/ISO and EI talk is an “overlay” to the characteristic curve which is cast in silver once the film processing is done.

To quote my best friend Jim... “Reality is reality and anything you say about it is just something you say about it.”

Same with the characteristic curve.

We all want to be able to predict what we will get. So we talk about planning how we will expose and develop our film to get what we want. I love talking about this so I will use a common language the reader can grasp. Zone System is a great language with a vocabulary that people can wrap their heads around.

But I really just want to know a meter setting that will guide me to expose so that my densities in the negatives of my pictures come in about 0.2 to 1.2 generally, with as few bad surprises as possible.

Last weekend I had a pretty bad surprise and fell far short of my target. But it worked out alright in the long run because I shot all this film at EI 32

That is exactly what I got (I used up all the tolerance).

 

[Stephen Benskin]

If it is a guess or not it depends on you... when you know what you are doing then when you place something in Z-I you place it in the "m" point, pointed by the red arrow:

View attachment 265410

Zone-V is the "n" point: what meter aimed Pre 1960. Today (Post 1960) the meter aims one stop less, at Delta Log H = 1.0 (instead 1.3).

_______

If our workflow is accurate then we may expect to obtain just degradated detail for Z-I. If our process is not that accurate then for Z-I we may obtain better detail than expected or pure black, depending on the direction our pitfall has.

If we don't want to make the effort to have an accurate workflow then we simply can consider that what is in Z-I is at risk.

The ISO Film Speed Diagram is used to determine film speed and not exposure placement. It is a graphical method of the Delta-X Criterion. Fractional Gradient speed point is derived by psychophysical testing and produces the most consistently accurate B&W film speed. When the ISO diagram's parameters are adhere to, the difference between 0.10 over Fb+f is always Δ0.296 log-H from the fractional gradient speed point.

Any point of density is not an adequate way to determine consistent print quality.

If you are interested in better understanding film speed, I suggest checking out these two papers. This forum has a number of ways you can obtain them.

Nelson, C.N., Safety Factors in Camera Exposures, Photographic Science and Engineering, Vol 4, No 1, Jan-Feb 1960.
Nelson, C.N. and Simonds, J.L., Simple Methods for Approximating the Fractional Gradient Speeds of Photographic Materials, JOSA, Vol, 46, No. 5, May 1956.

 

[Bill Burk]

Thanks Stephen!

p.s. My site came down because my hosting provider went offline. I will try to get it back online soon.

 

[MattKing]

Whenever Stephen refers to those criteria, I tend to translate what he says in my mind to "If you use the ISO criteria for film speed, more of your prints will look good".

 

[Bill Burk]

I’m still looking for a print of Willow Pond, but Mark Osterman retired from George Eastman House. He was my best bet for possibly finding one.

He did sell me this nice sector wheel though... I am thinking of using it under my enlarger driven by an 8mm projector to make “test strips”

 

[Stephen Benskin]

I’m still looking for a print of Willow Pond, but Mark Osterman retired from George Eastman House. He was my best bet for possibly finding one.

He did sell me this nice sector wheel though... I am thinking of using it under my enlarger driven by an 8mm projector to make “test strips”

Years ago I tried to get a print too, but even before the digital revolution, Kokak was cutting back. They no longer had an archivist or librarian. No one knew where to look. I did get a nice information packet on Loyd Jones. It included a head shot of Jones.

 

[Stephen Benskin]

Thanks Stephen!

p.s. My site came down because my hosting provider went offline. I will try to get it back online soon.

I'm sure one or both have been uploaded in a thread or two.