ISO standard and Ilford emulsions

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.

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That is just a warning that if you really get down into the weeds with the stuff that Stephen discusses, your day at least is shot for doing anything else!
And as for the meaning of "foot speed", I expect that references the toe or "foot" of the characteristic curve, and is one of those very UK English terms, equivalent to the ISO shadow speed.

MattKing said:

That is just a warning that if you really get down into the weeds with the stuff that Stephen discusses, your day at least is shot for doing anything else!
And as for the meaning of "foot speed", I expect that references the toe or "foot" of the characteristic curve, and is one of those very UK English terms, equivalent to the ISO shadow speed.

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So foot speed has nothing to do with foot-in-the-mouth but rather the characteristic curve at the toe? Well the websites runs on English so why don't we bloody well use it!

'bloody'

Vaughn said:

'bloody'

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Thank you. Corrected to be bloody correct.

Good on ya, mate...

When I spent 1975 at uni in New Zealand, it took a few weeks until people (and myself) stopped having to ask the other to repeat what was just said. Then add the identical words with different mothers, and communication can be bloody difficult and yet oddly entertaining.

Vaughn said:

Good on ya, mate...

When I spent 1975 at uni in New Zealand, it took a few weeks until people (and myself) stopped having to ask the other to repeat what was just said. Then add the identical words with different mothers, and communication can be bloody difficult and yet oddly entertaining.

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We were in a high end hotel in Paris and this man dressed in a suit, very proper, was in the lobby. He looked distressed and had an oral thermometer in his hand. In pains takingcarefully crafted French he asked "Is 39 degrees was high?" People answered in French; he did not understand. Someone asked in German; he did not understand. He was asked in Spanish; he did not understand. Someone tried Yiddish; he is did not understand. Someone tired Hebrew; he still did not understand. In not very good French he carefully put together the question, "What language do you speak?" I said English. He burst out, "Well, why don't we bloody well use it?" It turned out one of his children had a fever and so I told the desk clerk to get "an American" doctor for him.

Bill Burk said:

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

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Thank you Bill

MattKing said:

That is just a warning that if you really get down into the weeds with the stuff that Stephen discusses, your day at least is shot for doing anything else!

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Yes, it is quite weedy........and foot speed at the toe of the curve, hmmm, why not toe speed.

Chuck_P said:

Yes, it is quite weedy........and foot speed at the toe of the curve, hmmm, why not toe speed.

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Foot speed:

Chuck_P said:

Yes, it is quite weedy........and foot speed at the toe of the curve, hmmm, why not toe speed.

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Maybe some have to get their feet wet first.

Usain Bolt's foot speed is around E.I 1000, but near enough 1600 under ISO testing conditions.

Never ever click on an unknown link. (Or so we are told) to avoid unnecessary bugs

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).

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Ciao Schyter,

Exposing for the shadows has nothing to do with what film speed (ISO or E.I.) you are using, but rather with how you meter and set your exposure. You see, averaging meters will underexpose the shadows in scenes with a wide luminance (contrast) range, choosing a middle value between light and dark areas that ends up not being enough exposure for the shadows. Similarly, scenes with predominantly light tones (think snow scenes) can fool the meter into underexposing and leaving you with inadequate shadow detail.

So, "meter for the shadows" means base your exposure on a shadow value by metering it directly (spot meter or whatever) and then, since the meter wants to overexpose a shadow value, stopping down to get the proper shadow exposure (usually two stops). Alternatively, you can use an averaging meter or whatever and learn to recognize scenes that fool the meter into underexposing and then just use exposure compensation to compensate.

See? You're not exposing ISO 100 film as 25 or anything. It is a good idea to find your own working E.I., because it takes into account your particular metering style and your equipment. Many of us find that 1/3-2/3 stop slower than "box speed" is better for us; it gives us a little exposure buffer and works better with spot-metering techniques associated with the Zone System.

"Develop for the highlights" is less important today than it was decades ago, but still relevant to a certain extent. The idea is to meter the luminance (contrast) range of your scene and then use a development time that will give you a negative with the proper range of densities to print easily on a specific contrast grade of paper. If we only had paper with one contrast grade, everyone would still be doing this. However, we no have VC papers with a wide range of contrasts, so the range of contrasts in the negative is less important; we can compensate for a negative that won't print perfectly on grade 2 by using other grades. Note that contact printers who use Lodima, Lupex or Azo papers that only come in one or two grades still spend a lot of time figuring out the proper development schemes to get the contrast range on their negatives needed to print well.

Still, it's a good idea to come up with a standard ("normal") development time that allows you to print average scenes on a middle contrast setting. This gives you the maximum flexibility for dealing with the extremes. And, if you work with very flat or very contrasty scenes a lot, it's not a bad idea to adjust development à la Zone System for extreme situations.

Hope this helps,

Doremus

Doremus Scudder said:

....

Hope this helps,

Doremus

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thank you. Very informative advice that definitely helps.

schyter said:

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).

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You might be surprised to know that judging a print is the best way to determine the best exposure for a film (if it is done properly). So much so, that today's ISO standard is based on testing done by Loyd Jones in the early 1940s. It's called the First Excellent Print test and consisted of people judging prints and placing them in order from lowest to highest quality. What made this test unique for the time is it wasn't simply about the subjective or psychological response of the judges, but Jones had recorded all the technical information from the materials and process and was able to determine the common denominator that made for an excellent print. He then tested various sensitometric methods of determining film speed to see which would best agree with the print judgement speeds or exposures that made for the prints judged as first excellent. By making the process psychophysical, Jones was able to apply a time and labor saving sensitometric approach that would produce the type of quality results as obtained from the print judgement tests.

The current sensitometric method based on Jones' results is in the ISO film speed standard. When a manufacturer places the ISO prefix with a speed number to a film, it means the procedures listed in the standard were followed. The purpose of the film speed portion of the first excellent print test is to provide a consistent starting point that is applicable to films with different characteristics. The photographer can then make adjustments based on their own taste and style.

^^^ Excellent summary of thousands of posts on film speed analysis.

Stephen Benskin said:

You might be surprised to know that judging a print is the best way to determine the best exposure for a film (if it is done properly). So much so, that today's ISO standard is based on testing done by Loyd Jones in the early 1940s. It's called the First Excellent Print test and consisted of people judging prints and placing them in order from lowest to highest quality.

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Thanks a lot Sthepen.
So with the ring around method I'm replicating what Jones did 40 years ago? Wow.

schyter said:

Thanks a lot Sthepen.
So with the ring around method I'm replicating what Jones did 40 years ago? Wow.

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Yup, except for the thousands of prints and hundreds of judges… but that’s what made Jones’ study stand forever.


Make the best prints you can and show them to other people and ask them what’s best!

schyter said:

Thanks a lot Sthepen.
So with the ring around method I'm replicating what Jones did 40 years ago? Wow.

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Essentially, but since you're not starting from scratch and are probably using the ISO speed as a starting point, it's probably closer to making adjustments to match your personal taste, style, and technique.