Pirate
Guitar playing Fotografer
I know this requires shooting many complete rolls of film, and I'm not worried about that, I'm just looking for the process- how do you find the true ISO of a film?
How do you find the true ISO of a film?
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Vics
Veteran
Get a copy of Fred Picker's "Zone VI Workshop." It explains the whole thing really concisely.
sreed2006
Well-known
Appendix A of Ansel Adams "The Negative" gives a method for finding what speed to rate the film, and calibrating it with the camera, light meter, and developing technique. His method pretty much requires that you have access to a densitometer, though, since you need to measure the density of the negative. The good news is it takes less than one roll of film.
Juan Valdenebro
Truth is beauty
There's no such thing as the true ISO of a film.
There are different ways to use a B&W film... All equally correct, I mean... For x development time, giving y contrast on negative, and all that depending on z scene contrast, you can find the best possible ISO for wet printing by bracketing (metering at different ISOs) and by doing a contact print of that strip at the enlarger time base+fog reaches black on paper, then the best printed frame tells us the best ISO for that precise scene contrast, but then again, that's just for a certain paper or filter grade, and for a specific paper developer...
Any traditional B&W film has a really wide ability to be used (and very well used) at several ISOs... Tri-X is fine at ISO100 for direct sun if clean, detailed shadows are required (with short development), but it's fine also at 200 and 400 (with a bit longer development) for the same harsh light when the subject requires more difference in contrast between lights and shadows, and Tri-X is great for soft light at 200 when soft contrast is the goal (short development), and also great at 400, 800, 1600 and even 3200 (increasing development times) if the light is dull and we need a subject reaching higher contrast...
I know other people may disagree, but it's a fact ISO/metering, and development, just can't live apart...
So, the true ISO of a film is, in practice, very low compared to box speed if we need detail on what bride and groom wear in a scene with direct sun and shades, but very high compared to box speed when under gray overcast we photograph a scene without really high and really low values...
Some prefer saying "films have true ISO, and what you talk about is exposure index", etc., but I don't: if we change development time (and we need to do it depending on extreme scene contrast situations) not only the ISO we meter at varies, but also the way a single film reacts to a certain amount of light.
Cheers,
Juan
There are different ways to use a B&W film... All equally correct, I mean... For x development time, giving y contrast on negative, and all that depending on z scene contrast, you can find the best possible ISO for wet printing by bracketing (metering at different ISOs) and by doing a contact print of that strip at the enlarger time base+fog reaches black on paper, then the best printed frame tells us the best ISO for that precise scene contrast, but then again, that's just for a certain paper or filter grade, and for a specific paper developer...
Any traditional B&W film has a really wide ability to be used (and very well used) at several ISOs... Tri-X is fine at ISO100 for direct sun if clean, detailed shadows are required (with short development), but it's fine also at 200 and 400 (with a bit longer development) for the same harsh light when the subject requires more difference in contrast between lights and shadows, and Tri-X is great for soft light at 200 when soft contrast is the goal (short development), and also great at 400, 800, 1600 and even 3200 (increasing development times) if the light is dull and we need a subject reaching higher contrast...
I know other people may disagree, but it's a fact ISO/metering, and development, just can't live apart...
So, the true ISO of a film is, in practice, very low compared to box speed if we need detail on what bride and groom wear in a scene with direct sun and shades, but very high compared to box speed when under gray overcast we photograph a scene without really high and really low values...
Some prefer saying "films have true ISO, and what you talk about is exposure index", etc., but I don't: if we change development time (and we need to do it depending on extreme scene contrast situations) not only the ISO we meter at varies, but also the way a single film reacts to a certain amount of light.
Cheers,
Juan
paulfish4570
Veteran
i read the box ... 🙂
Freakscene
Obscure member
No.
No.
No.
Particularly no to the Picker/Adams suggestions - what they show you how to find is an EI for a given luminance range, which is only peripherally related to the ISO speed.
Yes, actually, that is the best way, certainly if you lack copious time and scientific equipment.
Yes, there is!
Go to the ISO web site and purchase the relevant standard, for B&W film it is:ISO6:1993
http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=3580
The method is very clear, but beyond most non-technical specialists to conduct. For example, many of the components (the thermometer, light source, the step wedge, the sensitometry etc) have their own standard, and much equipment and calibration is needed to obtain data to determine a film's ISO speed to standard.
But none of this matters much. Why? Just as Juan has explained . . .
Real world luminances are unlikely to always be the same, or even similar to the very strict ISO standard, and scanners and paper are very adaptable, so you can make a very nice print from a negative that is a lot different from that which the ISO standard gives you. Your camera meter will very rarely meet the ISO standard, though it will be close, and you have an ability to interpret and modify how you want the results to look - the standard gives you only ONE SET of outputs.
So why do we have a standard?
So you can compare films in a standardised way. In low light, for instance, TMX is much faster than Tri-X, because it has much better reciprocity failure characteristics, and Fuji Acros is faster again. But do you think it would be useful to have labels that state that Acros or TMX is faster than Tri-X? No. The results of the standard are a decent representation of a film's characteristics under fairly average circumstances. You can go to a store and know that you will get a negative of fairly well controlled CI under a given set of circumstances.
That's all it's for.
If you want to work out a personal EI, follow some of the guidelines, but they only tell you marginally more than the old 'ring test' explained here: http://theonlinephotographer.typepad.com/the_online_photographer/a_simple_system.html
And, in the end, unless you have a lot of time, determining an exact speed is a waste of effort. After 20 years of shooting B&W film I came to a similar set of controls to Mike J's described above: expose enough to get decent shadow detail and contrast but not so much as to make the film too grainy or lose sharpness, and then develop enough to get good highlight contrast but not so much as to make the negatives too contrasty or grainy. Adams described it as "expose carefully and give N-1 development" or something similar. With modern film you don't even need to be that careful.
There is a lot more flexibility in the system that people give credit for and really tight controls aren't always needed. The amusing thing about Adams' zone system is that with large format, to which it is best suited, you need those tight controls the least, because a larger film area keeps things higher quality whatever you do.
Marty
No.
No.
Particularly no to the Picker/Adams suggestions - what they show you how to find is an EI for a given luminance range, which is only peripherally related to the ISO speed.
Yes, actually, that is the best way, certainly if you lack copious time and scientific equipment.
Yes, there is!
Go to the ISO web site and purchase the relevant standard, for B&W film it is:ISO6:1993
http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=3580
The method is very clear, but beyond most non-technical specialists to conduct. For example, many of the components (the thermometer, light source, the step wedge, the sensitometry etc) have their own standard, and much equipment and calibration is needed to obtain data to determine a film's ISO speed to standard.
But none of this matters much. Why? Just as Juan has explained . . .
Real world luminances are unlikely to always be the same, or even similar to the very strict ISO standard, and scanners and paper are very adaptable, so you can make a very nice print from a negative that is a lot different from that which the ISO standard gives you. Your camera meter will very rarely meet the ISO standard, though it will be close, and you have an ability to interpret and modify how you want the results to look - the standard gives you only ONE SET of outputs.
So why do we have a standard?
So you can compare films in a standardised way. In low light, for instance, TMX is much faster than Tri-X, because it has much better reciprocity failure characteristics, and Fuji Acros is faster again. But do you think it would be useful to have labels that state that Acros or TMX is faster than Tri-X? No. The results of the standard are a decent representation of a film's characteristics under fairly average circumstances. You can go to a store and know that you will get a negative of fairly well controlled CI under a given set of circumstances.
That's all it's for.
If you want to work out a personal EI, follow some of the guidelines, but they only tell you marginally more than the old 'ring test' explained here: http://theonlinephotographer.typepad.com/the_online_photographer/a_simple_system.html
And, in the end, unless you have a lot of time, determining an exact speed is a waste of effort. After 20 years of shooting B&W film I came to a similar set of controls to Mike J's described above: expose enough to get decent shadow detail and contrast but not so much as to make the film too grainy or lose sharpness, and then develop enough to get good highlight contrast but not so much as to make the negatives too contrasty or grainy. Adams described it as "expose carefully and give N-1 development" or something similar. With modern film you don't even need to be that careful.
There is a lot more flexibility in the system that people give credit for and really tight controls aren't always needed. The amusing thing about Adams' zone system is that with large format, to which it is best suited, you need those tight controls the least, because a larger film area keeps things higher quality whatever you do.
Marty
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timor
Well-known
The simple approach :
http://www.ohio.edu/people/schneidw/vico222/222Handouts/expdev2.pdf
No need to shoot many rolls. This method will get you very close to your personal exposure index.
And also take under consideration, that what is on the box is not taken out of the blue sky (however it might be on the high end of film performance), so it is a good place to start if you not ready for experimentation yet.
Mind that if you are using more then one camera with built in light meter, you gonna have to run this simple test for each as light meters may differ by much.
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Moriturii
Well-known
What everybody else has said, and also you might enjoy these two articles,
http://www.halfhill.com/speed1.html
http://www.halfhill.com/speed2.html
http://www.halfhill.com/speed1.html
http://www.halfhill.com/speed2.html
rogerzilla
Well-known
These days it also depends on your scanner, if you have a hybrid film/digital setup. If you expose for the shadows in bright sunlight, the scanner may not be able to show any highlight detail even if it's there, because it can't penetrate the dense areas of the negative. IME scanners are better at bringing out faint shadow detail than they are at keeping the highlights. Therefore I just expose for the highlights to avoid whited-out cheeks on people.
YMMV or, more accurately, your scanner's Dmax may vary.
YMMV or, more accurately, your scanner's Dmax may vary.
Turtle
Veteran
It depends on usage. I would not recommend the zonie approach unless you intend to work this way. If you are going to shoot rolls of film and do regular documentary/street type shooting, I would recommend a much simpler approach.
Put film in the camera and shoot everything in multiples of three: Box speed -1/3 stop as the middle exposure, then box speed and Box speed -2/3 stops. Alternately use half stops if your equipment is geared up for that. Makes notes of the lighting and meter in your normal way. try to shoot a variety of contrast levels on that one roll then go and develop it for either your normal time, or a good starting point.
Either print the negs or examine them (if you have the experience to do so) and determine whether you need to make changes to your development time. Most people in most developers rate the film a little below box speed, hence recommending this is the 'zero' about which you bracket. Even looking at your first roll you should be getting an impression; however, repeat the process with a second roll that is developed for your adjusted time.
What you are looking for is shadow detail. its critical that you learn to meter consistently, or at least remember what you are doing. Find the negs with what you consider to be the right amount of shadow detail for the look you are after. Highlights are largely a product of development time; however, significant increased win dev time will increase shadow detail a touch and vica versa.
Note the differences that arise from changing scene contrast. You will notice, if using any sort of area metering system, that the more contrast in a scene, the worse the shadows fare. Looking at your strips you may conclude:
In dead flat lighting, shooting at box speed makes sense.
In moderate contrast... box speed -1/3 (or 1/2) stop looks good.
In high contrast... box speed -2/3 (or 1 stop - or even more) might look best.
At the end of the day it is all up to you and what you like.
I set a very different film speed for shooting in really high contrast light compared to flat light, but this is because I know that for what I do there is little opportunity to find a mid tone or find a good shadow upon which to base my exposure. however, if shooting in bright contrasty light, if I DO find a good shadow upon which to calculate my exposure, I use my 'flat light' speed rating to do so, because in essence, the reduced speeds used in contrasty light are merely a way of compensating for the fact that the 'average' a meter will calculate is influenced by the highlights as much as the shadows. For B&W film at least, we generally want to weight what we do towards the shadows to ensure that where the brightness range is very high, the average does not represent an exposure in which the shadows are going to fall below the necessary recording levels on the film.
A lot of this is fairly simple once you have understood it the first time, but its quite hard to explain concisely. I'd recommend reading Barry Thornton's Edge of Sharpness, or something similar. Note that B&W film, digital and slide film can have quite different metering approaches. Some of Roger Hick's books might be just what you need. I think he did one called B&W photography (which I have somewhere in storage) whichI recall covers this nicely.
FWIW I did read and learn lots about the zone system and knowing it is useful, but not essential. Regardless, the methods I use now are much simpler because with the advent of VC papers, I have a lot more leeway than he did. I use much simpler rules of thumb and generally do not worry about highlights much, only getting the necessary level of shadow exposure on the fim for B&W.
Put film in the camera and shoot everything in multiples of three: Box speed -1/3 stop as the middle exposure, then box speed and Box speed -2/3 stops. Alternately use half stops if your equipment is geared up for that. Makes notes of the lighting and meter in your normal way. try to shoot a variety of contrast levels on that one roll then go and develop it for either your normal time, or a good starting point.
Either print the negs or examine them (if you have the experience to do so) and determine whether you need to make changes to your development time. Most people in most developers rate the film a little below box speed, hence recommending this is the 'zero' about which you bracket. Even looking at your first roll you should be getting an impression; however, repeat the process with a second roll that is developed for your adjusted time.
What you are looking for is shadow detail. its critical that you learn to meter consistently, or at least remember what you are doing. Find the negs with what you consider to be the right amount of shadow detail for the look you are after. Highlights are largely a product of development time; however, significant increased win dev time will increase shadow detail a touch and vica versa.
Note the differences that arise from changing scene contrast. You will notice, if using any sort of area metering system, that the more contrast in a scene, the worse the shadows fare. Looking at your strips you may conclude:
In dead flat lighting, shooting at box speed makes sense.
In moderate contrast... box speed -1/3 (or 1/2) stop looks good.
In high contrast... box speed -2/3 (or 1 stop - or even more) might look best.
At the end of the day it is all up to you and what you like.
I set a very different film speed for shooting in really high contrast light compared to flat light, but this is because I know that for what I do there is little opportunity to find a mid tone or find a good shadow upon which to base my exposure. however, if shooting in bright contrasty light, if I DO find a good shadow upon which to calculate my exposure, I use my 'flat light' speed rating to do so, because in essence, the reduced speeds used in contrasty light are merely a way of compensating for the fact that the 'average' a meter will calculate is influenced by the highlights as much as the shadows. For B&W film at least, we generally want to weight what we do towards the shadows to ensure that where the brightness range is very high, the average does not represent an exposure in which the shadows are going to fall below the necessary recording levels on the film.
A lot of this is fairly simple once you have understood it the first time, but its quite hard to explain concisely. I'd recommend reading Barry Thornton's Edge of Sharpness, or something similar. Note that B&W film, digital and slide film can have quite different metering approaches. Some of Roger Hick's books might be just what you need. I think he did one called B&W photography (which I have somewhere in storage) whichI recall covers this nicely.
FWIW I did read and learn lots about the zone system and knowing it is useful, but not essential. Regardless, the methods I use now are much simpler because with the advent of VC papers, I have a lot more leeway than he did. I use much simpler rules of thumb and generally do not worry about highlights much, only getting the necessary level of shadow exposure on the fim for B&W.
JohnTF
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Read a lot of books, did a lot of gray scale photography, took some advanced classes, -- but I agree, Picker was worth the read, as is Adams.
ISO lets you know how much exposure is necessary to achieve .1 density, or above, above base fog, and it is measurable.
If you do not have sufficient exposure, you cannot make an image appear by over developing, which does tell you there is an ISO for each film. The exposure, especially relative to the ISO, determines your shadow detail.
You can do what else you wish to get what results you want, hopefully they will become predictable.
The folks with all that equipment who make the films do a lot of tests. If you choose to disbelieve them, by all means, test yourself.
Keep in mind, many opinions of photographers are anecdotal and it is not always simple to keep the variables controlled during exposure and in home lab conditions.
Tests outlined by Picker yield interesting data. I used the densitometer at my local lab to check base and gray scale densities. Calibrated gray scales are a help as well. I used to include one with proof sheets.
I feel much confusion arises from mixing the terms "film speed" or "ISO" settings with your "Exposure Index" (EI), which reflects how you choose to expose the emulsion. Films do not become "faster" when you change the setting on your meter, nor really, when you push them, nor do they become slower when you pull them.
Regards, John
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bulevardi
Well-known
Same here.
I could doubt everything else too:
- what is the true shutter speed of my camera if is set it on 1/500 ?
- what is the true aperture of my camera if it put it on f16 ?
- what is the true iso when I put a roll of 100 iso in my camera ?
- what's the actual focal length at 50mm ?
I don't know everything in depth of photography, and I don't want to. There is a limit to my interest.
Even if I knew what differences in iso there are in same iso films, one can come along with a theory that you have to count all the atoms and molecules on 1mm² of film to be really sure what you are talking about.
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JohnTF
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Good nuts and bolts approach, very similar to Picker -- if you wish to know more, you can investigate and research.
I prefer a film that gives a lot of tones in between, and then you get all the subjective evaluations. This approach explains "expose for the shadows, develop for the highlights", even if you do not get it the first time around. 🙂
I had friends who spent a complete year working with a densitometer, working out many variables, which is what the folks who print the ISO on the box have done.
Regards, John
George Bonanno
Well-known
You don't...
You don't...
It seems to me you need to use a Canon Snappy LX camera, load it with your favorite B&W filum and take pictures. A trip to Garden Place in Brooklyn Heights NYC will make you a world famous photographer. I kid you not...
George
PS: There is no useful information whatsoever in the shadows of a B&W picture except for tire tread on a 1937 Buick 6.
You don't...
It seems to me you need to use a Canon Snappy LX camera, load it with your favorite B&W filum and take pictures. A trip to Garden Place in Brooklyn Heights NYC will make you a world famous photographer. I kid you not...
George
PS: There is no useful information whatsoever in the shadows of a B&W picture except for tire tread on a 1937 Buick 6.
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AndySig
Established
I asked a similar question a while ago on another forum and got a lot of answers:
http://www.apug.org/forums/forum37/85762-real-iso-values-sheet-film.html
http://www.apug.org/forums/forum37/85762-real-iso-values-sheet-film.html
Roger Hicks
Veteran
Marty (Freakscene) says pretty much all that needs to be said.
Cheers,
R.
Cheers,
R.
sreed2006
Well-known
What a truly fascinating range of responses.
I've followed most of the links in the posts so far, and even links from there.
What has become clear to me about this is the following:
Your end goal has to be defined. Are you going for "good enough" or for prints that would stand scrutiny at an art gallery?
How will the negatives be processed, and by whom?
Also, the precise definition of what it is that you are looking for needs to be worked out. There is Box Speed, ISO, Exposure Index, and some other measurements that apparently are useful.
I won't retract my recommendation for Appendix A of "The Negative" though, simply because apparently that is a central theme in the controversy surrounding all this, and thus it would be worthwhile to at least become familiar with what Ansel Adams suggested, since knowing that will help in understanding a lot of these other discussions, objections, shortcuts, and "it's too hard so it doesn't matter" postings.
I've followed most of the links in the posts so far, and even links from there.
What has become clear to me about this is the following:
Your end goal has to be defined. Are you going for "good enough" or for prints that would stand scrutiny at an art gallery?
How will the negatives be processed, and by whom?
Also, the precise definition of what it is that you are looking for needs to be worked out. There is Box Speed, ISO, Exposure Index, and some other measurements that apparently are useful.
I won't retract my recommendation for Appendix A of "The Negative" though, simply because apparently that is a central theme in the controversy surrounding all this, and thus it would be worthwhile to at least become familiar with what Ansel Adams suggested, since knowing that will help in understanding a lot of these other discussions, objections, shortcuts, and "it's too hard so it doesn't matter" postings.
Roger Hicks
Veteran
Dear Sid,
If you can stand his long-winded and jargon-laden prose. It is, after all, merely a summary of basic sensitometry dating back to 1890. The naming of Zones is a work of genius: the rest put me off learning about sensitometry for years.
Cheers,
R.
JohnTF
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Minor White is a much shorter read, but I thought Picker a quick read and insightful, not that he was so "original" but well stated, practical, and thought out. You are risking $10 and a few hours here.
Adams was written in an earlier time frame and for folks who wanted all the information they could get in one place from a master.
Reading more may not turn you in to "one with the art", but generally it is not a waste of time, -- wait, I have to go watch Judge Judy and effectively use my time today. ;-)
I grew up with a paucity of information and a lot of trial and error, well, a lot of error.
You do recall Roger, when folks thought you could not take photos in doors without a flash bulb? ;-) I shot a lot with a 2.8 lens, Tri X, D76 at about 1/30 and scale focus, enough to help fill the paper and year book, not much I would hang on a wall. I also figured out +1 processing times, yep, thought I was on to something new.
The paucity may well been because I did not access sufficient resources, but it was a long time ago when I got my first "adjustable" camera in an age when people would not buy them because they had to be adjusted? Photo books seemed to be the ones that came with the camera, or "How to make good pictures".
People asked for a copy of the photo, if it came out.
At the camera shop, we used to offer to set the cameras at 1/60 sec, f8 and 15 feet for them and toss in a roll of Verichrome Pan, Plus X for the big deals, mostly we hoped they read the instructions, loading the film was way up there in the skills areas.
I used to recommend to students they buy "The Golden Book of Photography", I wore out a couple of copies.
Regards, John
Adams was written in an earlier time frame and for folks who wanted all the information they could get in one place from a master.
Reading more may not turn you in to "one with the art", but generally it is not a waste of time, -- wait, I have to go watch Judge Judy and effectively use my time today. ;-)
I grew up with a paucity of information and a lot of trial and error, well, a lot of error.
You do recall Roger, when folks thought you could not take photos in doors without a flash bulb? ;-) I shot a lot with a 2.8 lens, Tri X, D76 at about 1/30 and scale focus, enough to help fill the paper and year book, not much I would hang on a wall. I also figured out +1 processing times, yep, thought I was on to something new.
The paucity may well been because I did not access sufficient resources, but it was a long time ago when I got my first "adjustable" camera in an age when people would not buy them because they had to be adjusted? Photo books seemed to be the ones that came with the camera, or "How to make good pictures".
People asked for a copy of the photo, if it came out.
At the camera shop, we used to offer to set the cameras at 1/60 sec, f8 and 15 feet for them and toss in a roll of Verichrome Pan, Plus X for the big deals, mostly we hoped they read the instructions, loading the film was way up there in the skills areas.
I used to recommend to students they buy "The Golden Book of Photography", I wore out a couple of copies.
Regards, John
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