Understanding EI???

As I look through the Gallery and see the the film used and the ISO rating I see that many time people shot film at rating different than the box speed.
Can some one explain the basic reasons that this technique is used? If you rate a film slower, say a 100 ISO box, shot at 80 what is the reason? Is it more tone, more contrast????

We usually down rate for greater tonality and improved shadow detail, but many of us have run tests to determine the effective EI of a film/developer combination with our equipment & processing technique to give the contrast/tonality we require in a print at a set mid contrast paper grade under certain lighting conditions.

Taking that a step further using the Zone System or BTZS we can then adjust our dev times and tweak the EI to get easily printable negatives under other even extreme lighting conditions.

Ian

hi barry

there are no real secrets in photography

http://www.amazon.com/Black-White-P...=sr_1_1?ie=UTF8&s=books&qid=1262531538&sr=1-1
this book shows a lot of things, in images not just words. the author is a teacher at risd ..
ansel adam's the negative says the same thing in a lot of ways ...

they say it better than i could ever say it ...

(and their books are inexpensive and used at amazon! )

john

Thanks for the book reference. I found it used for $3.99 US...

One other note - unless you understand a photographers metering technique it is really impossible to make any sense of their EI - people using the Zone system typically have similar methods of working/metering - using a spot meter to measure shadows values and highlight values and then choosing and EI at the same time they are choosing a development time/contrast at the same time as placing those tones.

Others may use a very different way of metering and exposing in the field to get to a similar place. Example I know a ton of photographers that choose an EI based on trial and error that do just fine as long as the way they meter in particular shooting circumstances stays the same. Like shooting at box speed but pointing their in-camera center weighted meter to the darkest area in the scene and just setting the camera to whatever the meter says. In effect this MAY end up being the same thing as a zone system guy choosing an EI of half of box speed and using a completely different technique to get to the same place.

I would say that choosing an EI has as much and probably more to do with the way you work/meter/choose exposure in the field then any technical variations on meter sensitivity, actual film speed in a developer, etc. Last but not least people sometimes choose an EI that compensates for other artifacts/shortcomings of equipment so they do not have to remember to add/subtract things based on a particular piece of equipment they use. Example - I have an old old old LF lens that consistently over exposes for various reasons (like the aperture scale being off and other things) I could choose to build that in to an EI choice on my meter - personally I just remember and take account for it when I use that lens.

RB

I just ran such test on Tmax400 and XTOL 1:1 combination. I shot the same scene with test objects using 0EV, -1EV, and +1EV, cut the roll of film into 1/4 and developed each on development time that is -15%, 0%, and +15%. Then print each so that gray card in the scene look identical. I pasted the resulting 9 prints in 3x3 matrix.

What I found from this test was surprising. It didn't make that much difference between prints if I compare shots that are arranged side-by-side in any direction on this 3x3 matrix. I saw difference if I compare shots that are more than one a part. I show definite difference if I compare shots that are diagonally located.

Perhaps the difference will benefit me when I become more advanced in handling exposures in difficult situations.....

stradibarrius said:

Thanks for the book reference. I found it used for $3.99 US...

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It's time to give up the book writing!

Ralph, Keep in mind it was used in "good" condition. Some creases in the page corners etc. For me this is ok because it will be a reference book and I may underline and make notes in the margins.
If it were a different type book I would probably buy new.

stradibarrius said:

As I look through the Gallery and see the the film used and the ISO rating I see that many time people shot film at rating different than the box speed.
Can some one explain the basic reasons that this technique is used? If you rate a film slower, say a 100 ISO box, shot at 80 what is the reason? Is it more tone, more contrast????

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********
An outstanding question, Strad. There shall be as many answers as there are answerers.
To keepit simple: I want as many negatives as I can get which print as easily as possible, with the tones I need for expressing my "vision" at the time I released the shutter; and which print on my "target" paper---a Nr. 2, using a diffusion light source.
Periodic tests with the lens/shutter combo, film/developer combo, tell me the Exposure Index I must use to achieve those kinds of negatives, the maximum number of times.

stradibarrius said:

Ralph, Keep in mind it was used in "good" condition. Some creases in the page corners etc. For me this is ok because it will be a reference book and I may underline and make notes in the margins.
If it were a different type book I would probably buy new.

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Nothing wrong with buying used books. Just wondered why some used book increase and others decrease in value.

rwboyer said:

One other note - unless you understand a photographers metering technique it is really impossible to make any sense of their EI. ... Example I know a ton of photographers that choose an EI based on trial and error that do just fine as long as the way they meter in particular shooting circumstances stays the same. ... I would say that choosing an EI has as much and probably more to do with the way you work/meter/choose exposure in the field then any technical variations on meter sensitivity, actual film speed in a developer, etc. Last but not least people sometimes choose an EI that compensates for other artifacts/shortcomings of equipment so they do not have to remember to add/subtract things based on a particular piece of equipment they use.

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Yes.

The mathematics of exposure and development
suggest a precision but it is based on far too many
variables to be precise. How do you meter? What
type of meter do you use? Is it properly calibrated?
Is your shutter accurate? How about the thermometer
you use to prepare your developer? Trial and error
gets you to an EI that works for you, given the variables
idiosyncratic to your equipment and techniques.

Over time, I've found that if I want to guarantee shadow
detail, I should use an EI a stop slower than box speed.
It seems to me that the films I use will tolerate a good
deal of overexposure, so, if I err on the side of too much
light, I will always get enough light for the shadows, and
the negative will not suffer.

RalphLambrecht said:

It's time to give up the book writing!

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Is your book (currently unavailable) available at public libraries?

It is an across-the-board compensation for SOMETHING. Exactly what, nobody can say for all situations, as there are too many possible answers......though Sanders McNew above has a good general explanation of why in his first paragraph.

Personally, I trust the International Standards Organization and the film manufacturers more than anyone else on the matter to find a good mean point that should work for us all, and I generally prefer to do case-by-case manual exposure compensation instead of across-the-board exposure compensation by changing EIs.

I would never blindly downrate just in pursuit of the shadow density and tonality that everyone tells me I should have. That is totally subjective. ISO ratings are not. The ISO knows better than these people, IMO, and tells us everything we need to know to start learning our materials as much or as little as we want to.

In other words, I learn how my films behave at box speed with various types of altered or unaltered exposure and development. This gives you a "tool box" full of "curves" from which to pull in any given situation. Then, I simply choose a curve from the tool box that will be able to capture what I want from the composition. In this method, film "rating" is nothing but a fixed number that you plug into an exposure calculation. What speed the film "actually" is makes no difference whatsoever. It is irrelevant. It is like choosing which drawing pencil to use. Do you really need to know exactly how hard each level of pencil is on a scientific level? No. You just need to know how each one will act in your hand when you do certain things with it, and how the different levels will act relative to each other.

In any case, box speed can almost always give total satisfaction if you actually take the time to delve into the characteristics of your film when you "treat it" (expose, develop, or otherwise manipulate it) different ways. Some use EI to apply their manipulation. Some, like me, do not generally do so, but manually alter exposure shot to shot instead.

IMHO, the constant problems with "lack of shadow detail" that plague so many photographers are mostly caused by inadequate understanding of metering, and barring that (or perhaps in addition to it), an undeveloped eye for subject brightness range, and likely lighting in general. Beginners learn far too much about cameras and lenses and how to use them, and far too little (as in almost nothing) about light and light meters and how to use them. Instead of having someone take the time to teach them how to meter, most beginners are simply told "half rate your film" to combat lack of shadow detail. This drives me absolutely crazy.....

fotch said:

Is your book (currently unavailable) available at public libraries?

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An internet library search reveal a few, but please post all questions about our book in the 'Sponsors' area. Thanks.

ISO is the speed a film achieves when it is developed to a standard contrast using a standard developer like D76. If all is done correctly, this film speed should be achieved by anyone in the world if they follow the same developpment procedures with calibrated equipment.

Speed is defined as .1 denity over film base +fog at a certain level of exposure, commonly known as shadow detail.

EI is a homemade speed someone believes they should use because their conditions do not match those of the testing lab either knowingly or unknowingly, ie shutters are off, they use a push developer instead of a standard, meters are off, thermometer is incorrect, clock is slow or fast, film was purposly under or over exposed, etc.

I usually use box speed with D76 and never have a problem.

Some tab grain films do not strictly match the ISO requirements, but that exposure works best under usual conditions.

2F/2F said:

It is an across-the-board compensation for SOMETHING. Exactly what, nobody can say for all situations, as there are too many possible answers......though Sanders McNew above has a good general explanation of why in his first paragraph.

Personally, I trust the International Standards Organization and the film manufacturers more than anyone else on the matter to find a good mean starting point for us all, and I generally prefer to do case-by-case manual exposure compensation instead of across-the-board exposure compensation by changing EIs.

I would never blindly downrate just in pursuit of the shadow density and tonality that everyone tells me I should have. That is totally subjective. ISO ratings are not. The ISO knows better than these people, IMO, and tells us everything we need to know to start learning our materials as much or as little as we want to.

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You are correct that ISO ratings are not subjective
in the way the standards are tested. But the ISO
standard is itself an arbitrary, or subjective,
benchmark. The test does not tell you the "optimal"
exposure for a film. In fact, no test can tell anyone
that, because what is "optimal" is in the eye of the
person shooting, and what best produces the sort
of image he or she is trying to create.

All the ISO can do is to set (an arbitrary) benchmark
and then tell you how the various films measure up
to it. That is one piece of information, to be used
along with shutter speed, aperture setting, developer
choice, and so on in getting to a negative that is
exposed the way you want it to look. There is
nothing magical or normative about the box speed,
and nothing to be gained or lost by adhering to it.
It is just a datum, nothing more.

Rolleiflexible said:

You are correct that ISO ratings are not subjective
in the way the standards are tested. But the ISO
standard is itself an arbitrary, or subjective,
benchmark. The test does not tell you the "optimal"
exposure for a film. In fact, no test can tell anyone
that, because what is "optimal" is in the eye of the
person shooting, and what best produces the sort
of image he or she is trying to create.

All the ISO can do is to set (an arbitrary) benchmark
and then tell you how the various films measure up
to it. That is one piece of information, to be used
along with shutter speed, aperture setting, developer
choice, and so on in getting to a negative that is
exposed the way you want it to look. There is
nothing magical about the box speed, and nothing
to be gained or lost by adhering to it. It is just a
datum, nothing more.

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EXACTLY. Just a piece of data. My point exactly. Since it really doesn't matter anyhow, I choose to leave it alone, and fiddle with exposure and exposure compensation is other ways. Far less confusing, IMO, especially to a beginner. Changing EI introduces the disturbing idea into "fresh photographic minds" that you can actually change the speed of your film, or that the ISO and the film manufacturers are "just wrong". The most important thing about EI the way I see it is that it never changes. It is arbitrary the way it is determined, so it is most important to lend its arbitrariness some constancy. Take something arbitrary, make it a constant, and it is now a "reference". To me, there is nothing more useful than the information in your statement: "All the ISO can do is to set (an arbitrary) benchmark and then tell you how the various films measure up to it." That is the most useful thing they can do. It is EXACTLY what I need to figure out my materials and how to use them.

Rolleiflexible said:

Over time, I've found that if I want to guarantee shadow detail, I should use an EI a stop slower than box speed.

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When I first read about finding a personal EI, I found lots of articles suggesting various complex test procedures involving grey cards at various exposures and developing times and measurements with densitometers.

I also noticed that the conclusion of most of them was to halve the box speed and decrease the development by 25%

I tried this and liked it and HP5+ at EI 200 became my standard for outside shots in good light. In overcast conditions with lower contrast, I revert back to ISO 400 and normal exposure.



Steve.

RalphLambrecht said:

Nothing wrong with buying used books. Just wondered why some used book increase and others decrease in value.

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Limited supply maybe?
Amazon has only 1 of your 'Way Beyond Monochrome' listed at $999.99.

The late Barry Thornton's Edge of Darkness is found very cheaply but his Elements book is hard to find and is several hundred dollars.

mwdake said:

Limited supply maybe?
Amazon has only 1 of your 'Way Beyond Monochrome' listed at $999.99...

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I hope that nonsense stops when the new edition is out in a few weeks!

RalphLambrecht said:

I hope that nonsense stops when the new edition is out in a few weeks!

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A new edition coming out, that is great.

I have had your book on my want list for some time now.
Seeing as my birthday us coming up soon I will move it to the front of the list and drop a few hints to my family.

Like most things supply and demand.

ISO ratings apply to film testing by manufacturers following a protocol that is designed to test films. It has nothing to do with taking pictures.

A photographer MIGHT get the the right negative following the ISO protocol,
but it is like going to a shoe store and finding the display shoe fits you. It's nice, but it wasn't meant to, and it would be dangerous to assume any significance from such an accident.

EI is simply the number we each assign the film, based on our own work. TRI-X can have an EI the ranges from 50 to 3200, depending on how the photographer uses it.

The box rating (ISO rating) is just the EI that works for the way Kodak, Fuji, Ilford, etc... read their meters, set their cameras, and process a given film.

It is fully dependent on controlling absolutely every variable in the whole process.

The problem is that you don't read your meters, set your cameras, or agitate your film exactly like Kodak or me or anybody else might so your personal EI is probably different than mine.

If you find that you are constantly getting under-exposed shots (not enough detail in the shadows) when you follow the directions then shooting 100 ISO film at an EI of 80 will get you 1/3 stop extra exposure on every frame, at an EI of 50 it's a full stop extra.

Set your camera EI wherever you get the best shots for a given film, that is your personal EI.

While I agree with most of what has been said, I have to disagree with the use of the term "arbitrary" when it comes to ISO film speed. In fact the current method, which dates back to the forties, is the first method that doesn't determine speed based on an almost entirely arbitrary property of the characteristic curve. As Berg states in Exposure Theory and Practice, "the whole of the exposure problem is treated from the point of view of obtaining a satisfactory picture; it has been stressed over and over again that the quality of the picture is the factor which decides what exposure should be given. This consideration outweighs all others when it comes to choosing the speed criterion, since on its choice, together with the conditions of the subject, will depend the camera exposure to be given.

Thus all those speed criteria must be rejected which are based merely on a property of the negative material alone; unless and until it can be shown that this property is intimately liked with the quality of the print. Nevertheless, speed criteria are in practice invariably determined from the behaviors of the negative material alone. Where progress has been made in recent years in fixing a sensible criterion, it has been in the direction of linking print quality with the characteristics of the negative material."

I believe what they meant to say is "the speed of a photographic material is not a fundamental concept, but provides an index number useful for calculating camera settings" (from Todd and Zakia, A review of Speed Materials.)