ISO standard and Ilford emulsions

schyter · Dec 11, 2022

Hi guys.

The sensitivity of an emulsion must (should) be linked to the ISO standard which provides for:
ISO System (International Organization for Standardization)
The sensitivity is calculated on the basis of the minimum exposure E necessary to have a density of 0.1 above the veil, as in the DIN standards. However, the development, with a methol-hydroquinone bath, must be carried out in such a way that the density at the point Emax (such that LogEmax = LogEmin + 1.3) is 0.8 higher than the density corresponding to Emin. This ensures that the minimum density of the deepest shadow is well above the veil and that the density interval between the deepest shadow and the maximum light in a normal contrast subject is no greater than 0.8.

Because the producer Ilford in ALL film datasheets, writes this sentence ??? ""It should be noted that the exposure index (EI) range recommended for ... (all type film) is based on a practical evaluation of film speed and is not based on foot speed, as is the ISO standard.""

However, it writes on the packaging, for example, 100/21 ISO-DIN ... Isn't this an incongruity?

Many thanks.

Ian Grant · Dec 11, 2022

Kodak had the ASA portion of the ISO standard loosened to allow more realistic practical testing when they introduced Tmax films because they couldn't pass the existing standard. The ISO is a combination of the ASA/BS and DIN standards.

So like Kodak Ilford no longer use testing based on foot speed, however that didn't alter the effective emulsion speeds.

Ian

schyter · Dec 11, 2022

Ian Grant said:
Kodak had the ASA portion of the ISO standard loosened to allow more realistic practical testing when they introduced Tmax films because they couldn't pass the existing standard. The ISO is a combination of the ASA/BS and DIN standards.

So like Kodak Ilford no longer use testing based on foot speed, however that didn't alter the effective emulsion speeds.

Ian

thank you very much Jan.
Then I can behave normally and expose (reflected light) for the speed of the box; both for Ilford, Kodak etc. Taking into account that I will have an average gradient (G) of about 0.6 .

Ian Grant · Dec 11, 2022

It's best to test your film and developer combination, that also takes into account any slight variations in meters, shutter speeds etc. The manufacturers recommendations are good starting points, you can then fine tune if needed.

Ian

schyter · Dec 11, 2022

Ian Grant said:
It's best to test your film and developer combination, that also takes into account any slight variations in meters, shutter speeds etc. The manufacturers recommendations are good starting points, you can then fine tune if needed.

Ian

normally when I try a new film (or developer, paper, etc) I rely on the old ring-around system. It's always a great and easy system because my eyeballs will decide what I like and consequently the speed of the film.

RalphLambrecht · Dec 11, 2022

schyter said:
thank you very much Jan.
Then I can behave normally and expose (reflected light) for the speed of the box; both for Ilford, Kodak etc. Taking into account that I will have an average gradient (G) of about 0.6 .

That will certainly give you very decent results!

Stephen Benskin · Dec 11, 2022

schyter said:
Hi guys.

The sensitivity of an emulsion must (should) be linked to the ISO standard which provides for:
ISO System (International Organization for Standardization)
The sensitivity is calculated on the basis of the minimum exposure E necessary to have a density of 0.1 above the veil, as in the DIN standards. However, the development, with a methol-hydroquinone bath, must be carried out in such a way that the density at the point Emax (such that LogEmax = LogEmin + 1.3) is 0.8 higher than the density corresponding to Emin. This ensures that the minimum density of the deepest shadow is well above the veil and that the density interval between the deepest shadow and the maximum light in a normal contrast subject is no greater than 0.8.

View attachment 323864

Because the producer Ilford in ALL film datasheets, writes this sentence ??? ""It should be noted that the exposure index (EI) range recommended for ... (all type film) is based on a practical evaluation of film speed and is not based on foot speed, as is the ISO standard.""

However, it writes on the packaging, for example, 100/21 ISO-DIN ... Isn't this an incongruity?

Many thanks.

If you read it carefully, they are saying the film speed was tested under the ISO standard. When referring to the meter / camera settings, they use EI. It doesn't say the EI is the speed of the film. Just that the meter can be set to EIs different from the ISO setting. Ilford is pointing out there is a distinction between ISO and EI. One is the speed of the film and one is how the meter / camera is set. This way people aren't confused when they run across EI ratings in the datasheet. Notice the statement "Best results are obtained at EI 100". In other words it means the film has an ISO of 100 and the best results are when the meter / camera is set to EI of 100.

The contrast parameters from the ISO standard is part of the Delta-X Criterion which is a mathematical method to determine the fractional gradient speed point using a 0.10 fixed density point. The paper should be available here:

http://beefalobill.com/benskin/content/Simple%20Methods%20for%20Approximating%20the%20Fractional%20Gradient%20Speeds.pdf

Most personalized testing will introduce known and unknown testing errors. Plus the majority of which have flawed methodology that guarantees inaccurate results even if the steps are carefully followed. The best best is to make sure the film is processed to the proper average gradient and field test the EI that suits your needs and approach.

ic-racer · Dec 11, 2022

Chuck_P · Dec 11, 2022

ic-racer said:
View attachment 323874

Can you show the associated figure or diagrams.

ic-racer said:
?

Chuck_P · Dec 11, 2022

Stephen Benskin said:
If you read it carefully, they are saying the film speed was tested under the ISO standard. When referring to the meter / camera settings, they use EI. It doesn't say the EI is the speed of the film. Just that the meter can be set to EIs different from the ISO setting. Ilford is pointing out there is a distinction between ISO and EI. One is the speed of the film and one is how the meter / camera is set. This way people aren't confused when they run across EI ratings in the datasheet. Notice the statement "Best results are obtained at EI 100". In other words it means the film has an ISO of 100 and the best results are when the meter / camera is set to EI of 100.

The contrast parameters from the ISO standard is part of the Delta-X Criterion which is a mathematical method to determine the fractional gradient speed point using a 0.10 fixed density point. The paper should be available here:

http://beefalobill.com/benskin/content/Simple%20Methods%20for%20Approximating%20the%20Fractional%20Gradient%20Speeds.pdf

Most personalized testing will introduce known and unknown testing errors. Plus the majority of which have flawed methodology that guarantees inaccurate results even if the steps are carefully followed. The best best is to make sure the film is processed to the proper average gradient and field test the EI that suits your needs and approach.

Just an FYI, for what it's worth.........my phone displayed a "malicious website" warning when I clicked on the link you provided in your post. I've no idea just sayin.

schyter · Dec 11, 2022

you guys are a really big well of knowledge here at Photrio. it's good to be here with all of you!

Now the question gets interesting ... If all manufacturers recommend exposing for IE recommended, why is the old axiom, expose for shadows and develop for highlights a dogma? Why should I expose a 100 ISO film to 25 ISO (and under develop).

schyter · Dec 11, 2022

Stephen Benskin said:
The paper should be available here:

http://beefalobill.com/benskin/content/Simple%20Methods%20for%20Approximating%20the%20Fractional%20Gradient%20Speeds.pdf

Most personalized testing will introduce known and unknown testing errors. Plus the majority of which have flawed methodology that guarantees inaccurate results even if the steps are carefully followed. The best best is to make sure the film is processed to the proper average gradient and field test the EI that suits your needs and approach.

superb link !!!

Stephen Benskin · Dec 11, 2022

Chuck_P said:
Just an FYI, for what it's worth.........my phone displayed a "malicious website" warning when I clicked on the link you provided in your post. I've no idea just sayin.

I'm a little surprised. Bill Burk set it up. It's safe as far as I know.

pentaxuser · Dec 11, 2022

Chuck_P said:
Just an FYI, for what it's worth.........my phone displayed a "malicious website" warning when I clicked on the link you provided in your post. I've no idea just sayin.

Under the details that any internet security package gives for this sort of thing, what does yours say? I get no warning with mine

pentaxuser

Vaughn · Dec 11, 2022

schyter said:
you guys are a really big well of knowledge here at Photrio. it's good to be here with all of you!

Now the question gets interesting ... If all manufacturers recommend exposing for IE recommended, why is the old axiom, expose for shadows and develop for highlights a dogma? Why should I expose a 100 ISO film to 25 ISO (and under develop).

You are confusing rating the film and using the film -- two different things.
One is how sensitive the film is to light and the other is how one uses the film's sensitivity to get what one wants on the film.

snusmumriken · Dec 11, 2022

schyter said:
normally when I try a new film (or developer, paper, etc) I rely on the old ring-around system. It's always a great and easy system because my eyeballs will decide what I like and consequently the speed of the film.

View attachment 323871

I'm really puzzled how you (or someone) managed to take the same stop-motion photo 9 times?

Bill Burk · Dec 11, 2022

Chuck_P said:
Just an FYI, for what it's worth.........my phone displayed a "malicious website" warning when I clicked on the link you provided in your post. I've no idea just sayin.

Please use https: to take advantage of the certificate that will ensure your safety. It’s my site and it’s secure. Many browsers flag any use of http as a security risk so the warning is generic.

Nicholas Lindan · Dec 11, 2022

schyter said:
If all manufacturers recommend exposing for IE recommended, why is the old axiom, expose for shadows and develop for highlights a dogma? Why should I expose a 100 ISO film to 25 ISO (and under develop).

Well, the dogma works for many people. Look at the 'ring-around' above - I prefer the lower left image which is (photoshopped to look like it was) exposed at 1/2 box speed and developed for 75%(?) of the datasheet recommended development time.

I look at box speed as 'the most underexposure you can give and still end up with a good (though not necessarily the best) print.'

For art photography it's all a matter of taste - and there is no accounting for taste. Expose and develop as thou wilt.

Sirius Glass · Dec 11, 2022

schyter said:
Hi guys.

The sensitivity of an emulsion must (should) be linked to the ISO standard which provides for:
ISO System (International Organization for Standardization)
The sensitivity is calculated on the basis of the minimum exposure E necessary to have a density of 0.1 above the veil, as in the DIN standards. However, the development, with a methol-hydroquinone bath, must be carried out in such a way that the density at the point Emax (such that LogEmax = LogEmin + 1.3) is 0.8 higher than the density corresponding to Emin. This ensures that the minimum density of the deepest shadow is well above the veil and that the density interval between the deepest shadow and the maximum light in a normal contrast subject is no greater than 0.8.

View attachment 323864

Because the producer Ilford in ALL film datasheets, writes this sentence ??? ""It should be noted that the exposure index (EI) range recommended for ... (all type film) is based on a practical evaluation of film speed and is not based on foot speed, as is the ISO standard.""

However, it writes on the packaging, for example, 100/21 ISO-DIN ... Isn't this an incongruity?

Many thanks.

Excuse me, but what is foot speed? I wear a size 7 1/2 to size 8 shoe, so is my foot speed faster or slower than someone wearing a size 10 shoe? What about someone who wears a size 12 shoe? I use the box speed and on occasion use the box speed with the Zone System, but have an EI or even an IE.

BMbikerider · Dec 11, 2022

To be perfectly honest I must bow to those who give technical information which is way above my head and understanding. I have always used what the manufacturer suggested and have managed quite well for very close on 60 years without a serious problem. I applied this in my own photography and that asked of me by my employer without any undue distress to my self or others.
Are these lists or tacit explanations of of foot speed or different ISO (or ASA) ratings whatever, really needed when I am sure the vast majority of us just want to take pictures and talk about the end product and ask simple questions of where they have gone wrong without inviting a PHD thesis as a reply. They really are quite boring!

schyter · Dec 11, 2022

snusmumriken said:
Sono davvero perplesso come tu (o qualcuno) sia riuscito a scattare la stessa foto in stop-motion 9 volte?

it was just a (digital) example to make understand what happens with over / under exposure
and over / under development ...

schyter · Dec 11, 2022

BMbikerider said:
To be perfectly honest I must bow to those who give technical information which is way above my head and understanding. I have always used what the manufacturer suggested and have managed quite well for very close on 60 years without a serious problem. I applied this in my own photography and that asked of my by my employer without an undue distress to my self or others.
Are these lists or tacit explanations of of foot speed or different ISO (or ASA) ratings whatever, really needed when I am sure the vast majority of us just want to take pictures and talk about the end product and ask simple questions of where they have gone wrong without inviting a PHD thesis as a reply. They really are quite boring!

agree !!!! I also use a simple method and I enjoy photography. I only check with a ring-around what I think is most suitable for my taste, when I change a film/developer/paper (never used before).

my curiosity was about the info contained in the Ilford datasheets which seemed misleading to me
with respect to the ISO standard

Chuck_P · Dec 11, 2022

pentaxuser said:
Under the details that any internet security package gives for this sort of thing, what does yours say? I get no warning with mine

pentaxuser

I backed out rather quickly, I didn't pause to read it all.

Sirius Glass · Dec 11, 2022

I have only been doing photography since 1956 and I have never needed foot speed nor shoe size to get proper exposures.

Bill Burk · Dec 11, 2022

Chuck_P said:
I backed out rather quickly, I didn't pause to read it

You weren’t exposed to any malicious content. http is generally disparaged and pdf files are considered hazardous until they can be scanned. That’s universally true.

Here is a link to directory level where you can download, scan and open if you like

Index of /benskin/content

ISO standard and Ilford emulsions

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