Do you test your film for true ISO?

cluttered · Oct 12, 2015

I've never tested my "personal EI" before, but this thread sparked my interest so I've now finally tested it after many years For what it's worth, my tests (using a densitometer) show that I need to meter about half a stop slower than box speed but keep development time the same. For me, this gives Zone I density of 0.11 above FB+F, Zone VIII about 1.29.

That's for 120 roll film, I suppose I should do a similar test for sheet film for completeness. But once that's done, I don't know if I'd bother doing it ever again.

Ken Nadvornick · Oct 12, 2015

cluttered said:
I've never tested my "personal EI" before, but this thread sparked my interest so I've now finally tested it after many years For what it's worth, my tests (using a densitometer) show that I need to meter about half a stop slower than box speed but keep development time the same. For me, this gives Zone I density of 0.11 above FB+F, Zone VIII about 1.29.

That's for 120 roll film, I suppose I should do a similar test for sheet film for completeness. But once that's done, I don't know if I'd bother doing it ever again.

And if nothing changes significantly, you shouldn't need to. You have quickly and easily discovered your working sweet spot. Which appears to closely align with the generic advice regarding Zone System calibrations of down-rating film speed by about a half stop or so, when using a reasonably accurate shutter. When I did it my results were about two-thirds of a stop in the same direction. Essentially identical. Now just go out and use that information to make meaningful-to-you photographs.

There's really no real need to consult the Periodic Table of the Elements if all one is attempting is to cook a nice dinner. No need to research molecular bonding, electron energy states, or elemental isotopes of sodium and chlorine. Just add a couple of shakes of salt to the soup and it will taste marvelous.

Ken

Stephen Benskin · Oct 12, 2015

haziz · Oct 12, 2015

Yes.

I usually test for true speed using a Zone I test following the methodology described by Fred Picker in his Zone VI Workshop, which is itself based on the work of many other photographers. I never do a Zone VIII film developing test for developing time. As I test many of my cameras and lenses, however, I am coming to the realization that while my Pentax DIgital Spotmeter, that I use with large format and some medium format work, is consistent, and my technique of metering is fairly predictable, my other 35 mm cameras and MF cameras are all over the place with metering, and heaven knows about the shutters on some of these 20-50 year old cameras.

Makes me wonder.

frank · Oct 12, 2015

Stephen Benskin said:
View attachment 118212

Explain?

Ken Nadvornick · Oct 12, 2015

frank said:
Explain?

It's OK, Frank... Condescension is also a valid form of communication. Although the message received is not always the message intended.

Ken

Stephen Benskin · Oct 12, 2015

Ken Nadvornick said:
It's OK, Frank... Condescension is also a valid form of communication. Although the message received is not always the message intended.

Ken

Sorry, it's not condescension. Just tired.

frank · Oct 12, 2015

Stephen Benskin said:
Sorry, it's not condescension. Just tiered.

As in multi-layered?

MattKing · Oct 12, 2015

Stephen has been trying mightily to drive home the distinction between the usability of a personal EI and the objective reliability of a correct ISO speed rating.

The fact that your personal favourite EI is different from a published ISO does not lead to the conclusion that the ISO rating is somehow invalid (i.e. not "true").

Nor does it lead to a conclusion that a published ISO rating is an incorrect one to use for metering. It just might not be the rating that a particular photographer would choose as his/her preference.

One thing that this thread has driven home for me: any roll of film that I use where I intend to have a lab process it and make machine prints will be metered by me using the ISO rating.

Ken Nadvornick · Oct 13, 2015

MattKing said:
Stephen has been trying mightily to drive home the distinction between the usability of a personal EI and the objective reliability of a correct ISO speed rating.

Gently put, I believe most of us are already there on this point. And have been for a long while. Many since we were teenagers. Although back then on the street the term ASA was used to refer to both ISO and EI. "Hey... Kodak sez' 400, but what ASA do you shoot your Tri-X at?"

My point is that just because that same most-of-us aren't equipped to replicate the current standardized ISO test protocols in our home darkrooms does not mean that our far less rigorous personal EI tests are therefore useless. Or meaningless. To the contrary, it really is possible to conduct a few simple home-brew tests and end up in a better place knowledge- and technique-wise than we were before testing.

The truth is, I don't need to conduct research at CERN into how the Higgs boson confers mass in the universe to know when I'm carrying too much of it. All I need is the bathroom scale to know when I'm overweight. The existence of the former is certainly not being called into question. Only its applicability to the problem at hand is being questioned. Its fitness to purpose, when that purpose is simply dropping five or ten pounds after the holidays.

When every simplified attempt at home film testing is met with a dismissive attitude that we are all stupidly wasting our time because any test we might engage in is never going to be rigorous enough to satisfy certain poster's definitions of perfection, then it's time for someone to raise their hand and gently disagree.

I gently disagree...

Ken

Xmas · Oct 13, 2015

Yes but the ASA for Trix was 200 when I first had a camera.

MattKing · Oct 13, 2015

You have it backwards Ken.

Stephen Benskin · Oct 13, 2015

Ken Nadvornick said:
Gently put, I believe most of us are already there on this point. And have been for a long while. Many since we were teenagers. Although back then on the street the term ASA was used to refer to both ISO and EI. "Hey... Kodak sez' 400, but what ASA do you shoot your Tri-X at?"

My point is that just because that same most-of-us aren't equipped to replicate the current standardized ISO test protocols in our home darkrooms does not mean that our far less rigorous personal EI tests are therefore useless. Or meaningless. To the contrary, it really is possible to conduct a few simple home-brew tests and end up in a better place knowledge- and technique-wise than we were before testing.

The truth is, I don't need to conduct research at CERN into how the Higgs boson confers mass in the universe to know when I'm carrying too much of it. All I need is the bathroom scale to know when I'm overweight. The existence of the former is certainly not being called into question. Only its applicability to the problem at hand is being questioned. Its fitness to purpose, when that purpose is simply dropping five or ten pounds after the holidays.

When every simplified attempt at home film testing is met with a dismissive attitude that we are all stupidly wasting our time because any test we might engage in is never going to be rigorous enough to satisfy certain poster's definitions of perfection, then it's time for someone to raise their hand and gently disagree.

I gently disagree...

Ken

All I've been saying is that the level of precision with ISO speed testing is far greater than what any photographer can do. It also takes into consideration variables that I'm pretty certain most people don't. What's wrong with using the ISO speed as a knowable starting point. I believe this approach can yield a good working EI fairly quickly.

I'm not advocating ultra-precise testing methods or criticizing people who do their own testing. Although there are good tests and bad tests. Just because someone comes up with a result doesn't automatically make it a good test. How many times has someone claimed that their picture test showed film A was contrastier than film B in a certain developer, yet they never actually determined the contrast / gradient of either film. The obvious answer is that film A was developed to a higher contrast, but unaware our intrepid tester confidently walks away with his new hard earned knowledge. I try to make people aware of the strengths and weaknesses of different methods so they can make an informed decision.

How about Clutter's personal EI test. He didn't indicated his testing method, which is rather important for interpreting results, but my money is on the Zone System (the ISO prefix indicates that the standard was followed so we know how ISO speeds were determined). I've explained and shown multiple times that the Zone System methodology is different from the ISO methodology and the ZS testing will usually result in EIs around 2/3 of a stop slower +/- 1/3 stop. Which appears to be the case in this instance.

(This example is for informational purposes only. It's presence in no way endorses the use of curves in testing.)

Has the personal testing actually determine that the film speed is different from the ISO, or does their test simply use different testing parameters? So what does Zone System testing really tell you that simply opening up 1/2 to 1 stop from the ISO doesn't? How much is a test worth that doesn't produce results that can be trusted or aren't properly evaluated. If they were why are there so many claims about a "true speed" or conspiracy theories about the ISO speed?

I uploaded an exposure vs quality curve earlier and indicated on the curve what could be considered a Goldilocks area. How precise does the exposure have to be if +/- 1/2 stop doesn't make any difference in quality?

What about the results of Clutter's contrast test? This is a separate topic, but in my opinion, determining development is the more essential of the two tests and the test people should be most concerned with. It's also a test that is easily done in any darkroom.

____________________________________________________________________

"This new learning is amazing. Explain to me again how sheep's bladders can be use to prevent earthquakes." - Monty Python and the Holy Grail

cluttered · Oct 13, 2015

Stephen Benskin said:
How about Clutter's personal EI test. He didn't indicated his testing method, which is rather important for interpreting results

My basic approach was modelled on that described on a web page I can't find just now. I shot one roll of 120, shooting a plain Zone I exposure at box speed and then a plain Zone VIII exposure at box speed. Repeat the pair but changing the metering to a slightly slower speed. eg meter first pair at 400, next pair at 320, next pair at 250, etc. Develop film as per normal, and then measure density of each negative, aiming to get a Zone I at 0.10 and Zone VIII at 1.30. For me, this happened at roughly half a stop slower than box speed but with the standard development.

I'm definitely not claiming that this is an exhaustive and fully correct approach; rather than going around in circles in this thread is there a web page somewhere out there that describes a process which is better? I'm keen to learn more and to get better results. And it's nice to have an excuse to play with my densitometer.

For what it's worth, my negatives have seemed a bit low contrast of late (even in bright sunny scenes) so I was keen to measure if it was just my imagination or if my process does actually need tweaking, which is why I started doing this. Always keen to learn more! And it's something to do while I'm waiting for more suitable weather for the series I'm working on...

Sirius Glass · Oct 14, 2015

Ken Nadvornick said:
Gently put, I believe most of us are already there on this point. And have been for a long while. Many since we were teenagers. Although back then on the street the term ASA was used to refer to both ISO and EI. "Hey... Kodak sez' 400, but what ASA do you shoot your Tri-X at?"

My point is that just because that same most-of-us aren't equipped to replicate the current standardized ISO test protocols in our home darkrooms does not mean that our far less rigorous personal EI tests are therefore useless. Or meaningless. To the contrary, it really is possible to conduct a few simple home-brew tests and end up in a better place knowledge- and technique-wise than we were before testing.

The truth is, I don't need to conduct research at CERN into how the Higgs boson confers mass in the universe to know when I'm carrying too much of it. All I need is the bathroom scale to know when I'm overweight. The existence of the former is certainly not being called into question. Only its applicability to the problem at hand is being questioned. Its fitness to purpose, when that purpose is simply dropping five or ten pounds after the holidays.

When every simplified attempt at home film testing is met with a dismissive attitude that we are all stupidly wasting our time because any test we might engage in is never going to be rigorous enough to satisfy certain poster's definitions of perfection, then it's time for someone to raise their hand and gently disagree.

I gently disagree...

Ken

I am with Ken on this. One does not need to be a testinesta to be a successful photographer who can get details in the shadows. Film testing is highly overrated.

Old-N-Feeble · Oct 14, 2015

I agree with Ken too, Sirius. When I was a kid I thought photography needed to be so scientific and ultraprecise. Eventually, I learned that getting exposure close is fine provided I didn't underexpose at all or overexpose much. These days with today's whiz-bang films, extreme precision is fine but very unnecessary. At any rate, my cognitive plasticity, memory and patience are nearly nil so I'll be doing well to get anything done at all.

Bill Burk · Oct 14, 2015

cluttered said:
I've never tested my "personal EI" before, but this thread sparked my interest so I've now finally tested it after many years For what it's worth, my tests (using a densitometer) show that I need to meter about half a stop slower than box speed but keep development time the same. For me, this gives Zone I density of 0.11 above FB+F, Zone VIII about 1.29.

That's for 120 roll film, I suppose I should do a similar test for sheet film for completeness. But once that's done, I don't know if I'd bother doing it ever again.

Well since you have a densitometer... You could do a "one extra shot" test every once in a while for contrast control purposes. That is, take one shot normally of "anything" and then take another copy of the same shot with "two stops" more exposure. This will waste one shot (assuming you took a good picture for the first shot - and it might not even be a waste). When you look at the two negatives under the densitometer, measure a few middle tones from corresponding parts of each negative and find their differences. Average the sample differences. To find a reasonably useful measure of your contrast, calculate "run over rise"... (0.60 exposure difference / average density difference).

Stephen Benskin · Oct 14, 2015

Doesn't anyone read my posts? Maybe they're too long. So here's a short version of what I've been saying over and over and over again.

For general purpose developers, I recommend not testing for film speed. Use the ISO speed as a starting point. On the other hand, I believe a lot can be learned from doing film testing for development considerations. Now, if someone wants to test, it's important how the test is done. Otherwise it's garbage in, garbage out.

Sirius Glass · Oct 14, 2015

I do not test film therefore I have a life. If I really did not have a life I would get a PC instead of a Mac.

cluttered · Oct 14, 2015

Bill Burk said:
Well since you have a densitometer... You could do a "one extra shot" test every once in a while for contrast control purposes. That is, take one shot normally of "anything" and then take another copy of the same shot with "two stops" more exposure. This will waste one shot (assuming you took a good picture for the first shot - and it might not even be a waste). When you look at the two negatives under the densitometer, measure a few middle tones from corresponding parts of each negative and find their differences. Average the sample differences. To find a reasonably useful measure of your contrast, calculate "run over rise"... (0.60 exposure difference / average density difference).

Sounds like a nice simple way to measure contrast. But just to make sure I've properly understood, you measure the densities of the same mid-tone in two negatives (exposed with 2 stops difference), and allow for sampling errors. So what is the number range I should be looking for? (I've probably missed that info somewhere in this long thread!).

As others have pointed out, the film speed isn't so much of an issue, but I'm keen to make sure my development process (and hence my contrast) is where it should be.

Maybe I should go back and re-read this thread in full more carefully

[LATER]

I've taken my own advice and trawled the thread again and found the info in one of Bill's earlier posts, in (there was a url link here which no longer exists)

Thanks for the tips.

Bill Burk · Oct 14, 2015

cluttered said:
Sounds like a nice simple way to measure contrast. But just to make sure I've properly understood, you measure the densities of the same mid-tone in two negatives (exposed with 2 stops difference), and allow for sampling errors. So what is the number range I should be looking for? (I've probably missed that info somewhere in this long thread!).

As others have pointed out, the film speed isn't so much of an issue, but I'm keen to make sure my development process (and hence my contrast) is where it should be.

Maybe I should go back and re-read this thread in full more carefully

[LATER]

I've taken my own advice and trawled the thread again and found the info in one of Bill's earlier posts, in (there was a url link here which no longer exists)

Thanks for the tips.

It's rise over run by the way, my mistake... but what you are looking for is very similar to what you are looking for in the first place. Your more complete test is aiming for 0.57

So you might as well aim for 0.57

Yes, I found that I had varying densities in casual test pictures. For example I took two pictures aiming down at the sand pit at my sister-in-law's ranch. I found that a picture of sand isn't evenly illuminated, so I looked for pockets of shadow and light next to pebbles that I could see in both pictures, and averaged to minimize sample errors.

Also to clarify, your main test is good for speed and contrast tests when you are establishing your standard exposure and development... Then this one extra shot plan gets tossed in when ever you think about it. So you don't have to do a full test with every film run.

Bill Burk · Oct 14, 2015

Michael R 1974 said:
You might even discover there is no need to carry out the test.

Suddenly I was struck by a vision of my high school print shop teacher, Mr. Ford, looking down over the top of his half frame glasses calling me a pinhead.

My inclination to test frequently comes from my pre-press experience, where I would run control strips every day and would check test patches on every sheet. Maybe I skipped one or two sheets here and there. But when things start to drift you know it's time to clean the lenses in something.

It's never a big problem if you check frequently and spot a problem. But boy would people get upset if you didn't test... things got out of control... you got caught... and a couple days worth of work has to be thrown away...

Stephen Benskin · Oct 14, 2015

Michael R 1974 said:
But Ken tested his film. I don't think he was arguing against testing. He was arguing for the validity of EI tests. However this seems to have been based on a misreading of Stephen's posts. Stephen is not saying home testing is inherently stupid, or that tests are useless unless you have standardized calibrated equipment. He's just trying to get us to understand what we're doing. What are these EI tests telling us? Why are we doing them? Nobody seems to be able to answer those questions.

With respect to being a successful photographer without testing, everyone knows this, and it's pretty much the whole point. You can make great prints without knowing what's going on. However if you're going to bother with testing, you should understand the nature of the test(s), what you're testing for, what the results mean or don't mean. Perhaps counterintuitively, that knowledge can often simplify things. You might even discover there is no need to carry out the test.

Thanks Michael. You are always able to succinctly sum things up. Considering the concept of what the results mean. I'd like to try something. This might not work.

cluttered said:
Develop film as per normal, and then measure density of each negative, aiming t.o get a Zone I at 0.10 and Zone VIII at 1.30.

Could you please define in quantifiable terms the purpose of the above test and how the results are applicable?

cluttered · Oct 15, 2015

Stephen Benskin said:
Could you please define in quantifiable terms the purpose of the above test and how the results are applicable?

Sigh. I think I'll decline and bow out of this thread at this point, it seems to be going around in circles somewhat.

Stephen Benskin · Oct 15, 2015

Here is an evaluation of the 1.30 test result for normal development.

Why a 1.20 negative density range? The idea is to find the negative density range that will fit onto the paper's log exposure range (LER). As this is a test for normal development, that usually means a paper grade 2, which has an average LER of 1.05. Obviously, the numbers don't match. Is this an example of a bad test or is there something else occurring here. Determining the film gradient (Rise / Run) might produce some answers. Why a film curve? Because the two values from ZS testing don't offer very much information. Zone I - Zone VIII is 7 stops.

1.20 / 2.1 = 0.57

This is just about what Kodak uses for Normal development. But the resulting negative density range is supposed to fit the paper LER. It should be 1.05 and not 1.20. Why is the gradient fit but the tested variable doesn't? Simple, there's a missing variable. While Rise / Run defines the gradient of the curve, it doesn't account for flare. Flare will effectively reduce the subject luminance range at the film plane. Instead of the film seeing 2.10 for one stop flare conditions, it only sees 1.90. That makes the equation:

1.20 / (2.10 - 0.30) = 0.667

That isn't the gradient for normal. We know ~0.57 is the gradient for normal in order for a normal subject luminance range to fit onto a grade 2 paper with an LER 1.05. Yet the tested negative density range is 1.20.

The answer is the 1.20 negative density range is a misinterpretation. Instead of counting to the right 2.10 log units from 0.10 on the film's characteristic curve, then searching for the density at that point. Subtract 0.30 for flare from 2.10 and count only 1.90 log units. Now find the density at that point. Chances it will be around 1.15. 1.15 minus 0.10 = 1.05 which is the aim we are looking for. These values for the variables reflect reality. An aim negative density range of 1.05, and a log-H range of 2.10 - 0.30 = 1.90.

1.05 / 2.10 - 0.30 = 0.58

In short, flare conditions needed to be applied to a non-flare test. So how do we know the test that produced the 1.30 value is a non-flare test? Wasn't it shot in a camera?

Do you test your film for true ISO?