Film speed test in winter

markbarendt · Jan 14, 2013

Stephen Benskin said:
Mark, this is a really important insight. I've been toying with the idea of starting a thread to pose just such a question. What if some of the assumptions in a testing method are simply wrong, or are only accurate or acceptable under limited conditions, or contain justifications that require clarification? Wouldn't this lead to erroneous results? Sure, probably not disastrously so, but what's the point of putting in the effort if it's only going to be little better than using rule of thumb or guesswork?

It's always a bit of a surprise when people accept a testing method without first questioning its legitimacy. Let's take as example that Steve Simmons' article that kbrede linked to. Within the first couple of paragraphs, Simmons introduces three concepts that are key to the methodology: just black printing time, a wall for a target, and stopping down four stops from the metered exposure. As they are stated in the article, all three are flawed. How will this effect the testing results? Without potential problems being described in the procedures, the uninitiated would never be the wiser and would confidently accept any results.

Go for it Stephen.

I think being "right in limited conditions" is a big trap when that info is passed on because we each have differing sensibilities about the expected result. It is surely a trap that I fell into.

AndreasT · Jan 14, 2013

If I may.
I test all my materials, film, paper ,developer.It has helped me in getting better results. Some people shun away from doing this just the way like the way I hate, hate doing my taxes. Blimey some people enjoy doing their taxes, some do it as a living for others.
How bonkers can you be doing taxes out of pleasure.
What I like about doing this is I also learn something, it is interesting seeing the results. As long as one one doesn't test a "new" film and a "new" developer every 2 months it is fine. I use two film, two developers when it comes to film and I know how they work. I have tested a few more in the past. It takes up about one or two days a year, no more. For me it is worth it.
I have decided to make my own developer. Some people ask me why do you want to do that. You can buy developer. But there is a sort of pride involved, and I know I will learn something doing it.
There is always something to learn, and if it is fun, do it, if not leave it.
As long as it doesn't keep you from taking photos it is fine.

AndreasT · Jan 14, 2013

Yes I agree what you are saying. That is why I test. If people want my results I give them them but I always tell them not to believe them.
Because there is so much hearsay and myths and legends I prefer to test my stuff. As far as I am concerned too much is passed on from one generation to the next with out anybody checking.
I really do agree but I want to know for myself, with my equipment etc.

markbarendt · Jan 14, 2013

Michael R 1974 said:
As Richard Henry noted (his work pointed in the right direction), myths abound when it comes to the behaviour of photographic materials, tone reproduction, flare etc. Too many methods and instructions published by people who may or may not have done proper testing, and present no data. Many of the books are written by fine photographers and printers. If their information is wrong, with experience they have learnt to work around it without realizing it.

Even Adams, whom I have learned much from and whom I would suggest that people might study, is out of date. Modern VC papers have changed the reality we live in and films have improved. Adams' concepts are right but the world changed.

Similarly Dunn & Wakefield Exposure manual. The concepts stand well but modern meters are better at their jobs.

In both cases it is prudent to modify some specifics to adapt to the new world when it makes sense.

To Andreas,

For me "finally" finding out what normal was and getting good at normal allowed me to get much better at everything, it gave me a baseline where things worked well and a way to judge what changes improved things and which didn't.

I have tested to find the limits of "normal", the range I can shoot in to get a good print, but my intent isn't to find a personal EI, it is to figure out where to stop when I have to move away from normal/box speed.

AndreasT · Jan 14, 2013

Well I have my personal EI, I have them upstairs. And I don't really care about them anymore. I check my materials once and that's it.
What this all brought me was finding the limits of the materials. To get a feeling what should or can be done.
I think at the end of the day we basically do get to do the same thing.
Adams and all the gurus are a help in getting started going down the path if one wants to test.
I agree only in part that VC paper has changed the reality we live in. A badly exposed film can't always be saved with VC paper.
Sure it makes life easier but I have often enough had negatives from people which I could not get a really good print from.

markbarendt · Jan 14, 2013

Yes Andreas we are on the same page I think.

The thought of finding the limits of the materials though, the range rather than an absolute EI to peg things to, is a sea change from much of the discussion around testing and the traditional wisdom of the community.

AndreasT · Jan 14, 2013

I expose a step wedge onto film in the darkroom and develope. According to my results I exposure another in the camera (at least for large format ). Then after real exposures I will see if I need to do any ajustments, they are usually seldom and slight.

kbrede · Jan 14, 2013

OK, I've been reading about all these different testing methods, and I realized I wasn't exactly sure what the purpose was. I was hoping to follow a testing method, and during the process all would become clear. So I thought about it last night. Please let me know if I'm on track, or where I'm going astray.

1. Testing for personal film speed is essentially learning how to accurately record dark parts of a scene, on film, with your personal equipment. Usually people pick zone III to calibrate to, but zone II could also be used if a person prefers that.

2. Finding your personal film development time, teaches you how long to develop, in order to print both darks and highlights in the range that you desire. Usually people pick zone VII as the upper highlight range to capture, but you could use zone VIII if you so desired.

3. Paper-black density test. Unexposed, developed film has some density, film base + fog. This test determines how many seconds it takes for a particular aperture/magnification to print near maximum black, or zone 0, on the paper you're using. These exposure settings allow us to standardize our print testing.

4. After discovering your EI for shadows and developing time for highlights, you should be able to efficiently record on film, and print, a normal contrast scene containing zone III through zone VII.

markbarendt · Jan 14, 2013

Michael R 1974 said:
How did you establish your lower limit (ie highest EI)?

I guess you are asking me.

The minimum film exposure level that can get me a decent print of my main subject matter, say a face. It is not based off an exact amount of shadow detail.

AndreasT · Jan 14, 2013

kbrede said:
OK, I've been reading about all these different testing methods, and I realized I wasn't exactly sure what the purpose was. I was hoping to follow a testing method, and during the process all would become clear. So I thought about it last night. Please let me know if I'm on track, or where I'm going astray.

1. Testing for personal film speed is essentially learning how to accurately record dark parts of a scene, on film, with your personal equipment. Usually people pick zone III to calibrate to, but zone II could also be used if a person prefers that.

2. Finding your personal film development time, teaches you how long to develop, in order to print both darks and highlights in the range that you desire. Usually people pick zone VII as the upper highlight range to capture, but you could use zone VIII if you so desired.

3. Paper-black density test. Unexposed, developed film has some density, film base + fog. This test determines how many seconds it takes for a particular aperture/magnification to print near maximum black, or zone 0, on the paper you're using. These exposure settings allow us to standardize our print testing.

4. After discovering your EI for shadows and developing time for highlights, you should be able to efficiently record on film, and print, a normal contrast scene containing zone III through zone VII.

Yes I would say you about summed it up. If you want to delve deeper into this subject check out Adams, Phil Davis or Ralph Lambrecht. Ralph post here a lot.
Just don't end up testing too much just remember that.

Stephen Benskin · Jan 14, 2013

Michael R 1974 said:
Andreas - the point Stephen is making, further to Mark's earlier post, is that we should ask some questions about testing methodologies, sources of error/distortion etc. Otherwise we may not know how to interpret the results, or apply them in a meaningful way to different situations, in which case we can't be sure we're better or worse off than simply using the manufacturer's instructions.

For example, flare is a significant factor which is often overlooked in typical zone system testing methods.

That's the basic idea. Important elements can get lost when the necessary simplification occurs when creating a methodology and accompanying step-by-step approach. Ever notice how no method concerns itself with hold time? Now, I'm not just talking about how Simmons' shooting a wall example has no mention of the color temperature of the light, or color of the wall, or the choice of the material of the wall and how they reflect various wavelengths like infrared. Not only can this have differing effects on the film, but can influence the exposure meter which is the principle instrument toward measuring the testing conditions. The vague instruction of "take a meter ready of the wall" doesn't address whether the wall should be in specular or diffuse light, or the angle of the meter in relation to the camera potentially causing results very different from what is intended.

While scrutinizing each element of testing is an important part of any evaluation of a methodology, let's not overlook the more fundamental question of theory, and how the methodology addresses it. Like what is the difference between the metered exposure and the speed point, or what is the metered exposure, or even what is film speed?

Simmons' use of the just black printing method is a good example the need to question the theory behind the approach. What are the assumptions about proper exposure and film speed that the use of this method suggest and are those assumptions correct?

Another example which is a personal favorite of mine is about metering the object and stop down four stops. Ever wonder where's the theory to support this assumption? What if this assumption is wrong, how will using this approach influence the results?

Personally, I find it kind of peculiar that people are determined to put all that effort to come up with their own testing method when one already exists that has been standardized. All the fiddling around introduces too many potential errors, but as they will persist in doing so, we need to approach each methodology with the proper level of skepticism.

Stephen Benskin · Jan 15, 2013

Where does it say 0.10 over Fb+f is the target shadow density, or the minimum useful density? Where does it say it is a universal speed point?

RalphLambrecht · Jan 15, 2013

michael,please read ssteven's multiple and highly-educational postings concerningspeed points and systems to measure film speed. most of themworkwith a toe densityor shadow contrastto determine film speed.at the end of the day, you have to pick a method that works for you.snsel's assumption about zone Ihaving a target density of 0.1works very well in my opinion.what assumption do you work with?

Stephen Benskin · Jan 15, 2013

Michael R 1974 said:
I don't know where/if anyone called it a universal speed point. As you know it is simply a common targetted net negative density called "Zone I" in most Zone System books/methods, used to determine a working EI that presmubaly will lead to "full" local contrast around the "Zone III" density.

But how legitimate is that? You are referring to a system/method and what it states. Does the theory support the premise and if so where is it? And the reason I used universal is that it is the speed point only in a specific situation and cannot be applied to all situations.

One of the questions I propose is what is film speed. And one of the conclusions is that there is a difference between film speed and exposure. This is a distinction not frequently made.

Stephen Benskin · Jan 15, 2013

Michael R 1974 said:
Further, even if 0.1 above Fb+f is "correct", depending on how you test for the exposure that produces that density, you can get all sorts of exposure index values.

Exactly my point. Stuff everyone needs to be aware of when considering testing.

I'm not sure I'm following the dichotomy of film speed and exposure. Why wouldn't they be different?

Many systems, including Zone System, considers the fix density speed point of 0.10 the same as the minimum exposure / shadow exposure point of exposure. In fact, the just black printing method is predicated on this concept. Film speed is a standardization for comparison between films and a guide for exposure. According to the standard model and not factoring in personal exposure preference, shadow exposure isn't intended to fall on the speed point.

Stephen Benskin · Jan 15, 2013

Michael R 1974 said:
Ultimately for me the speed point is a means to an end, not a target in and of itself, the end being maximized local contrast.

Another important point of theory generally missing in most methodologies. Film speed is about the shadow gradient and not a point of density. That's why the ISO standard has the contrast parameters. How many methods incorporate this concept?

markbarendt · Jan 15, 2013

Michael R 1974 said:
I'm not sure I'm following the dichotomy of film speed and exposure. Why wouldn't they be different?

Having a well defined speed point is important when exposure placement needs to have a very specific relationship to the films toe.

For me its more about "am I on the straight line somewhere?".

I'm not suggesting shooting wild or without thought where important detail might be lost, just that an exact correlation between placement of print tones and the placement of tones on the negative is not that important to most of my work. I'd even suggest that that is true for many, many people.

RalphLambrecht · Jan 15, 2013

true but this so,because a point of density is much essier to measure than a gradient(contrst).besides being effective any method also needs to be practical.

Stephen Benskin · Jan 15, 2013

Michael R 1974 said:
Perhaps I'm accidentally inventing the ISO standard for myself, or at least confirming it, albeit probably with the safety factor.

Film speed as a target net density versus a reference point is an interesting issue when it comes to flare as well. I'm always told flare increases film speed. Well, in a way yes, but if the toe is flattened by flare, I haven't gained anything. In fact I've effectively lost "speed" because local contrast has been flattened in the shadows.

Like with film speed calculation, what is considered the minimum useful gradient, while determined using a flare free test, has been adjusted to reflect the affects of flare.

In my opinion most of the testing methods are more about producing a range of EIs that reflects the author's personal taste, whether it's about having enough of a safety factor, or producing enough shadow contrast, or producing a negative that works in conjunction of the just black printing test. For all but specialty developers, speed testing isn't really all that necessary and with specialty developers a simple comparison is between the two developers is all that is really required. It's more important to personalize the way the photographer likes to expose (personal EI) and that can be determined using the ISO speed as a foundation.

I believe one of the reasons why there's such a fixation on speed determination is that with simplified Zone System method of sensitometric testing, you don't produce a curve, but only two points of density. In order to determine the contrast, you first need to find the base point. This is backwards from general sensitometric testing. There the film is exposed and developed to differing degrees. The contrast is then determined along with the effective film speed for that contrast. Has the simplification involved in such methods as the Zone System unintentionally overemphasized the importance of speed and a speed point and under emphasized of the importance of contrast determination? There seem to be far more discussions on speed and how to test for it then there are about contrast.

markbarendt · Jan 15, 2013

Stephen Benskin said:
There seem to be far more discussions on speed and how to test for it then there are about contrast.

And when contrast is talked about it seems tied to speed point rather than SBR or preferred print contrast.

Bill Burk · Jan 16, 2013

From a recent family of tests I contact printed a negative image of a step wedge which fit the whole 21 steps on paper. (An original step wedge wouldn't do this - but a negative step wedge developed Normal would).

I cut chips from the contact print to make a Zone System sticker for my Weston Master II meter last night.

I wanted to include one stop of flare in my Zone System sticker, so I picked the next step above blackest black for my Zone 0 chip.

Stephen Benskin · Jan 16, 2013

Michael R 1974 said:
As I've said, the speed point is a means to an end. I'm concerned with local contrast.

It is a means to an end, but that doesn't mean it's arbitrary. If done according to the ISO Standard, the speed point can yield useful information. It defines the relationship between the meter exposure and the shadow exposure, it defines the local contrast as well as determining the point of useful minimum exposure (0.29 log-H units to the left where the gradient is 0.3x the average gradient).

This is what I mean about questioning the steps in any methodology. Most methods are just variations of the basic Zone System approach where the speed point is unconnected with the three elements list above. While the 0.10 density may have come from the ISO speed standard (the ZS use of 0.10 probably was derived from DIN or the early British standard), it has been misinterpreted or simply impoperly applied.

Using the ISO speed standard we know the speed point is 1.0 log-H units to the left of the metered exposure point. According to many popular methods, the speed point is four stops down or 1.20 log-H units below the metered exposure point. Obviously the two methods will produce film speeds typically differing by two-thirds of a stop. This is why Zone System testing consistently produces EIs 1/2 to 1 stop slower than the ISO speed. While the 1.20 log-H method will produce quality negatives and will create perfectly acceptable EIs, it shouldn't be regarded as a reliable way to determine film speed. Of course, if the additional exposure from the lower EI matches your style, why not save the time and just use the ISO speed and make the 2/3 stop adjustment. Afterall, what's the point of doing the test if it's not going to produce a reliable number.

Most of the authors won't explain this difference (mostly because they aren't aware of it), so when shopping around for a non-ISO testing method, understanding the theory is important. Just because someone wrote it down doesn't mean it's true. This doesn't mean you shouldn't use a non-ISO method. I'm just suggesting to use it knowingly.

AndreasT · Jan 16, 2013

To tell the truth I am bit lost here.
Reading all this.
All I can say is that I use the 0.1 speed point as my first reference. I plot my curves to see how the shape is. This is important for me. When I use my adopted method (a bit of this a bit of that) I can usually make my print at about Grade 2 (to simplify this using Grades), I increase the development times slightly because I like to use unsharp masks and the funny thing is I land at a contrast of about 0.62 which is what most published time use as a standard. However my actuall development times are always less than published and I always have to overexpose.
I am always amazed and wondering when people say they use box speed. It doesn't make sense to me.

Sirius Glass · Jan 16, 2013

Stephen Benskin said:
This is why Zone System testing consistently produces EIs 1/2 to 1 stop slower than the ISO speed. While the 1.20 log-H method will produce quality negatives and will create perfectly acceptable EIs, it shouldn't be regarded as a reliable way to determine film speed. Of course, if the additional exposure from the lower EI matches your style, why not save the time and just use the ISO speed and make the 2/3 stop adjustment. Afterall, what's the point of doing the test if it's not going to produce a reliable number.

So the bottom line of the endless Zonistas testing [This is not an attack on Stephen, I am just using his data to make a point] is a difference of less than a stop based on poor assumptions and uncalibrated equipment, sloppy testing and developing that the Zonistas are basing their work on. << Duh>> with the present dynamic range of both black & white and color C41 film of 12 to 14 f/stops depending on the choice of film, developer, developer dilution, and whom you choose to believe, less than one stop change will not produce any signifacant advantage or disadvantage. That being the case, why was time, money, film and chemicals to do all this testing when one will end up with essentally the same results using the box speed? Testing was useful when cameras and light meters were not that accurate, the results from the variation developers' result was wider ranging for all the dilution recommendation at that time1 and the film quality and dynamic sensitivity range was narrower.

1Since then Kodak and others recommend a narrower range of dilution, staying closer to 1:1 and 2:1 than the 4:1 then.

Stephen Benskin · Jan 16, 2013

AndreasT said:
To tell the truth I am bit lost here.
Reading all this.
All I can say is that I use the 0.1 speed point as my first reference. I plot my curves to see how the shape is. This is important for me. When I use my adopted method (a bit of this a bit of that) I can usually make my print at about Grade 2 (to simplify this using Grades), I increase the development times slightly because I like to use unsharp masks and the funny thing is I land at a contrast of about 0.62 which is what most published time use as a standard. However my actuall development times are always less than published and I always have to overexpose.
I am always amazed and wondering when people say they use box speed. It doesn't make sense to me.

My point is that it is good practice to critically question the details / theory of testing method they use or are considering using. I believe the testing results most people produce create a false sense of accuracy. They basically aren't getting what they think they are getting.

Would you mind breaking down your testing process? You say you use 0.10 speed point. How do you test for this? Do you have a reference for the CI 0.62 that you say most published sources use this standard? Are you determining it yourself or have you chosen it based on a source?

Why are you amazed people use box speed?

Film speed test in winter

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