Why is Zone System EI often about half rated ISO/ASA?

[Stephen Benskin]

So although people with well-calibrated shutters are seeing half rated speed, it's a fallacy to conclude that the Zone System tests arrive at half rated speed. Because by definition, errors in shutter speeds are included in the personal exposure index.

Bill, I don't think that's the right conclusion to come to based on a broken shutter. It's more like the rationalizations of apologetics. From where I stand, this is another example of the problems with Zone System testing. I believe fixing the shutter or having the shutter calibrated would be preferable. What if the shutter is off only with the higher shutter speeds? What about large format that uses multiple lenses each having their own shutter? Should the photographer do a speed test at every f/stop and shutter speed combination for every lens? Wouldn't you think it might also be easier to identify problems like bad shutters if there is confidence in the value of the film speed?

Even if the shutter is working properly, it doesn't necessarily transmit the same amount of light at every shutter speed.

 

[Sirius Glass]

1. Their equipment is out of calibration.
2. They meter too much of the sky and they use half the film speed to compensate for their lack of skill and technique.
3. Very few want a denser negative.

 

[Bill Burk]

Bill, I don't think that's the right conclusion to come to based on a broken shutter. It's more like the rationalizations of apologetics. From where I stand, this is another example of the problems with Zone System testing. I believe fixing the shutter or having the shutter calibrated would be preferable. What if the shutter is off only with the higher shutter speeds? What about large format that uses multiple lenses each having their own shutter? Should the photographer do a speed test at every f/stop and shutter speed combination for every lens? Wouldn't you think it might also be easier to identify problems like bad shutters if there is confidence in the value of the film speed?

Even if the shutter is working properly, it doesn't necessarily transmit the same amount of light at every shutter speed.

View attachment 114819

I still think the relationship can be mathematically defined. But we have to clearly say that we assume correct shutter speeds or include shutter speed data in the definition. We cannot tell someone what their Zone System EI is given a film's ASA/ISO if their shutter speeds are incorrect. Exactly as you say, it's the problem with traditional Zone System Tests that multiple factors are tossed in.

Now I can see a valid argument in favor of traditional Zone System tests for a photography student facing an immediate assignment: Calibrate using traditional Zone System and then use the results to take a planned photograph. I think the traditional Zone System combined tests can give a student immediate results. The instructor can give grades based on the steps the student took and the results they obtained, and it may be different than expected but student can still get credit for doing the work properly, even if they come out with an EI that nobody else in the class got (except the other students who shared that camera).

But an amateur, who may want to make use of the results over a longer time frame, and with a variety of cameras, may be better served with separate film and equipment tests.

Other equipment must be assumed to be properly functioning too, for example RobC mentioned light meters. Generally light meters are the most reliable piece of a photographer's equipment, but what about my vintage Weston Master II whose emulsion speed scale is not ASA/ISO? What about the meters calibrated for mercury cells that are no longer available and photographers naturally are tempted to use whatever cell fits (Alkaline cells where the meter was meant for Mercury)?

So we must assume the equipment is properly functioning, or we need to test for the equipment separately.

I still hold the position that these tests are better broken out, but I enjoy the logic of the argument for a combined test to help a student achieve immediate success, even if those results glossed over a lot of variables.

Shutters are pretty awful.

We have already heard stories of malfunctioning shutters from David Allen and the photographer I was helping. I've got another story:

I used three factors once to test one of my shutters (a Retina I): Electronically-measured time, Angular time (rotation of a 78-RPM record player), Gray card density measurements. No one factor was useful across all shutter speeds. Electronic times were best at slow speeds. Gray card density measurements were best at high speeds.

At the airport in San Francisco on the way to Connecticut to take a photo of StoneNYC, I discovered the mainspring of that camera had broken. The end where it hooks onto the rotating ring had become wedged and then the next time I cocked the shutter, it sheared off. I was familiar with the assembly because I had done a CLA... So I took it apart with rudimentary tools (I think I had a sewing needle), bent another loop of spring material into a hook and reassembled the camera. It held together for that trip, I got the picture of StoneNYC.

I used EI 250 which I determined sensitometrically as 400 and I shifted to 250 according to the relationship outlined in this thread so that I could use Zone System metering.

I used Zone System metering to read the light side of his face and placed it on Zone VI.

I used a modern meter (Sekonic TwinMate modified to support Zone System metering), which takes currently available batteries. After determining the required shutter speed, I selected a shutter speed (I think I selected 1/2 second) which I believe by sound was approximately one second.

The shot came out fine.

 

[Xmas]

Personally, I don't care how anyone rates their film. That is a question of personal taste. What the question should be is about the accuracy of a testing method and the precision of the resulting information. Technically, the Zone System can't be considered a film speed methodology. And what Bill is asking about is why it produces different test results than the ISO speed standard.

There are two variables the EI you set on the calculator and how you use the meter itself.

Reflective average
" spot
Incident to camera
Incident to source
Etc.

Which zone you pick

Eg I only use a spot zone1 but also allow for subject contrast Kentucky windage style

 

[Xmas]

I still think the relationship can be mathematically defined. But we have to clearly say that we assume correct shutter speeds or include shutter speed data in the definition. We cannot tell someone what their Zone System EI is given a film's ASA/ISO if their shutter speeds are incorrect. Exactly as you say, it's the problem with traditional Zone System Tests that multiple factors are tossed in.

Now I can see a valid argument in favor of traditional Zone System tests for a photography student facing an immediate assignment: Calibrate using traditional Zone System and then use the results to take a planned photograph. I think the traditional Zone System combined tests can give a student immediate results. The instructor can give grades based on the steps the student took and the results they obtained, and it may be different than expected but student can still get credit for doing the work properly, even if they come out with an EI that nobody else in the class got (except the other students who shared that camera).

But an amateur, who may want to make use of the results over a longer time frame, and with a variety of cameras, may be better served with separate film and equipment tests.

Other equipment must be assumed to be properly functioning too, for example RobC mentioned light meters. Generally light meters are the most reliable piece of a photographer's equipment, but what about my vintage Weston Master II whose emulsion speed scale is not ASA/ISO? What about the meters calibrated for mercury cells that are no longer available and photographers naturally are tempted to use whatever cell fits (Alkaline cells where the meter was meant for Mercury)?

So we must assume the equipment is properly functioning, or we need to test for the equipment separately.

I still hold the position that these tests are better broken out, but I enjoy the logic of the argument for a combined test to help a student achieve immediate success, even if those results glossed over a lot of variables.

Shutters are pretty awful.

We have already heard stories of malfunctioning shutters from David Allen and the photographer I was helping. I've got another story:

I used three factors once to test one of my shutters (a Retina I): Electronically-measured time, Angular time (rotation of a 78-RPM record player), Gray card density measurements. No one factor was useful across all shutter speeds. Electronic times were best at slow speeds. Gray card density measurements were best at high speeds.

At the airport in San Francisco on the way to Connecticut to take a photo of StoneNYC, I discovered the mainspring of that camera had broken. The end where it hooks onto the rotating ring had become wedged and then the next time I cocked the shutter, it sheared off. I was familiar with the assembly because I had done a CLA... So I took it apart with rudimentary tools (I think I had a sewing needle), bent another loop of spring material into a hook and reassembled the camera. It held together for that trip, I got the picture of StoneNYC.

I used EI 250 which I determined sensitometrically as 400 and I shifted to 250 according to the relationship outlined in this thread so that I could use Zone System metering.

I used Zone System metering to read the light side of his face and placed it on Zone VI.

I used a modern meter (Sekonic TwinMate modified to support Zone System metering), which takes currently available batteries. After determining the required shutter speed, I selected a shutter speed (I think I selected 1/2 second) which I believe by sound was approximately one second.

The shot came out fine.

I have an Avery label on my BTL shutter cameras for the aperture dependency adjustment and if the shutter were sticky you would get overexposure which is not normally catastrophic.

When I was a kid with a single speed box and Verichrome pan all my exposures were good.

 

[removed account4]

bill

i always assumed ZS rated films at half box speed
( and others who bracket, develop and decide accordingly might as well )
because the ISO is determined in a lab setting, with a camera that has
been calibrated a certain way, and a developer, and automation ...
not the unwashed masses whose shutters are probably off, who don't use
the same developer (as the testers) and who probably aren't automated.

it makes me wonder if a ZS practitioners who use the same camera, developer+dilution as kodak/ilford &c
... and who use the same development "system" would come out with box speed .. and it is a "methodology" thing,
not a " the film is really half box speed because the real iso isn't what is printed on the box" thing..
(then again kodak and others have suggeted development times are a starting point and not set in stone, so maybe iso values are too )

 

[Stephen Benskin]

bill

i always assumed ZS rated films at half box speed
( and others who bracket, develop and decide accordingly might as well )
because the ISO is determined in a lab setting, with a camera that has
been calibrated a certain way, and a developer, and automation ...
not the unwashed masses whose shutters are probably off, who don't use
the same developer (as the testers) and who probably aren't automated.

it makes me wonder if a ZS practitioners who use the same camera, developer+dilution as kodak/ilford &c
... and who use the same development "system" would come out with box speed .. and it is a "methodology" thing,
not a " the film is really half box speed because the real iso isn't what is printed on the box" thing..

It's a methodology thing. The results from a test I did are in post #117 of Zone System - Find EI and Development Time... thread. Here are the results again.

 

[removed account4]

thanks stephen !

 

[RalphLambrecht]

If half box speed held good for all or nearly all films when in users' hands as opposed to the strict test under lab conditions for "true box" or is that "foot speed" then wouldn't it be in film makers interests to say that while true speed is say 400 they advise users to try 320/200 as that is the speed at which film X gives proper/full shadow detail.

Sounds like a bit of "Devil's Advocate" on my part but in reality I'd rather have instructions that rendered sufficient shadow detail at a lower speed than a "faster" film that sacrificed it.

Of course this gums up the works for all the automatic cameras that can only read the DX code and can't be overridden and maybe for the vast majority of users, speed is better than good shadow detail.

I wonder how many here rate their films at 2/3rds to 1/2 of box speed? If enough of we 45,000 APUGers responded under a poll of the say the three top films from each manufacturer this might give newcomers to analogue useful information.

If 44,900 rate say TMax at 400 but only 1000 rate D400 at 400 or vice versa for balance then that might say a lot about the respective film speeds

pentaxuser

It' was also a marketing thing as faster speeds were more desirable than slow speeds when not everyone could afford superfast glass

 

[RalphLambrecht]

Just a thought on my part which depending on the volume of pollers might produce useful information - for some. It might be useful to some newcomers to film. You are not in that category and nor is Bill Burk but just a bit of thinking "out of the box" on my part

However I'll get back into my box now and try not to darken this thread's door again

pentaxuser

averaging garbage is still garbage

 

[Xmas]

averaging garbage is still garbage

The standard deviation and skew would be interesting, but otherwise confirmed.

 

[Ian Grant]

bill

i always assumed ZS rated films at half box speed
( and others who bracket, develop and decide accordingly might as well )
because the ISO is determined in a lab setting, with a camera that has
been calibrated a certain way, and a developer, and automation ...
not the unwashed masses whose shutters are probably off, who don't use
the same developer (as the testers) and who probably aren't automated.

it makes me wonder if a ZS practitioners who use the same camera, developer+dilution as kodak/ilford &c
... and who use the same development "system" would come out with box speed .. and it is a "methodology" thing,
not a " the film is really half box speed because the real iso isn't what is printed on the box" thing..
(then again kodak and others have suggeted development times are a starting point and not set in stone, so maybe iso values are too )

When I first began using the Zone System it was with Tmax 100 and then Agfa AP100 & AP25, followed by APX100 & APX25, my testing showed the Tmax 100 needed to be shot at 50 EI but the AP & APX 100 at 100 EI in Rodinal, neither contradicting the manufacturers data but the Agfa data was spot on probably because it came from DIN testing rather than the ASA.

Interestingly I always used EFKE PL25 at 50EI as well, the box ISO was the Tungsten rather than the daylight speed. So the irony was I was shooting a 25 ISO film at the same 50 EI as a 100 ISO film with the same development time, speeds determined by the ZS.

Ian

 

[DREW WILEY]

Ho hum. I just spent another week in the mountains with the 4x5 under all kinds of lighting and atmospheric extremes, and never thought about the Zone System even once, or labeled a single shot. Yet not a single shot was a guess. Do proficiently learn the chords on your piano, then forget that you ever had to do that, and make music instead.

 

[Stephen Benskin]

I know this example was already posted on this thread, but that was two years ago, and I think this clearly illustrates the differences in the exposure of the Zone System and ISO speed methods.



Stopping down 4 stops from the metered exposure point clearly places Zone I 2/3rds of a stop below 0.10 over Fb+f. To have the 4 stops below the metered exposure point fall on 0.10, the exposure / EI needs to be adjusted by 2/3rds of a stop.

 

[Steve Smith]

Do proficiently learn the chords on your piano, then forget that you ever had to do that, and make music instead.

That's quite a good analogy. Sometimes I could be playing guitar and if you stopped me and asked "what is that chord?" I might not be able to tell you without working it out. Equally, I sometimes watch my fingers to see where they are going next as they are not always under my control!

So yes, if you are proficient at something, you should be able to just get on with it without thinking about it too much.


Steve.

 

[removed account4]

that is a great analogy for photography, and "doing" in general, i couldn't agree more !

[ i know this is going to be taken the wrong way, it isn't my intent ... ]
but how is one supposed to "let go" when
as far as i have understood ( mis-understood? )
all these years, if using the zone system you really can't let go.
from what i have MISunderstood? the zone system is a set of tools that almost have to be in the foreground
not playing softly in the background, unless they have been modified somehow
( maybe i am wrong ) ... i have read ZS threads on this and other sites and news groups
on the web since maybe 1992? ... after reading the negative book in 1988
it does not seem to be a stream of consciousness sort of methodology of making
exposures, it's not like ron popeil's counter top chicken roaster where you "set it and forget it" .. but it seems
to be the opposite. one has to meter ( and meter a handful of different places ) decipher the light and film
make the exposure and then the development.
every time i have read that this system can be done without thinking too much, it is followed by a whole bunch of posts
suggesting that person is a hack &c ...

i would love to hear about people who don't over think it &c ...
(not that there is a problem with over thinking, and making sure everyting is just right )

 

[dpurdy]

I went to photography school in the 1970s with not even a previous interest in photography. I was taught from the beginning to use the zone system. My teacher was the man who wrote the manual for the Pentax spot meter. I had it pretty ingrained in me as a way of considering what the exposure should be and how processing should be adjusted up or down. What it has become for me now is a way to check with my spot meter the difference between the darkest area I want tone in and the brightest areas. It is not at that time something in the creative process I need to let go of or hold on to. Especially with roll film it is for me mostly a way to make sure I am not totally wasting my film on something that will be impossible to print. The creative process, at least for me, and talking about non studio photography, is in how I am responding to whatever environment I am in. Am I in a mental state that allows me to be responsive to what I see. Letting go is important then. Letting go of bullshit in the head from all the various bombardments of life. Responding to what I see is as simple as liking the way something looks and seeing interesting physical arrangements of things. At that point it becomes wondering what happens to it if I put a camera on it. Will it be what I saw or will it be something else and will I respond to what it is when I look through the camera. With roll film I am willing to try most anything. It doesn't cost much to snap a photo and dwell on it later. With sheet film it is a bit more expensive so I try to be a bit more sure I like what I am seeing in the camera. After this creative process, with either roll film or sheet film, it is time to close the deal, snap the shutter and put the image on film. At that point there isn't much to hold on to or let go of. Mostly I don't want blank film where I want shadow detail.. so I take a meter reading. Then usually mostly out of curiosity I take readings of bright areas. My contrast control is mostly handled in printing.

So I am a long time user of the zone system, the only system I have ever used. It does not over bear my mind or creative process or use up any space in my creative thought process. It is a support system much like a tripod.

Dennis

 

[removed account4]

hi dennis

thanks for your post ...
maybe it is my own notion, and seeing others who i imagined used
the ZS or maybe it wasn't embedded within their working methods as well.
or they were "newbies" to the system still getting acquainted with it so it seemed
like a cumbersome sort of thing .. boatloads of metering, reading notes, jotting notes
metering again, comparing what they had 3 seconds before, it was almost as if
whatever he had seen originally to photograph might not have even been there by the time
he settled on an fstop+shutter speed.
it seems the way you use the zone system, you don't spend so much time deciding the placement of
whatever it is you are placing ( detail in the highlights/shadow ? ) that the fleeting moment fleeted ...
i know you make portraits, so your subject i am sure would not be able to deal if you were fumbling &c
for too long ...

- john

 

[Vaughn]

I found knowing about the Zone System to be a very good grounding for my trial-and-error method...it helped me to figure out what to try next.

 

[Bill Burk]

I know this example was already posted on this thread, but that was two years ago, and I think this clearly illustrates the differences in the exposure of the Zone System and ISO speed methods.

View attachment 114858

Stopping down 4 stops from the metered exposure point clearly places Zone I 2/3rds of a stop below 0.10 over Fb+f. To have the 4 stops below the metered exposure point fall on 0.10, the exposure / EI needs to be adjusted by 2/3rds of a stop.

I re-read this whole thread, and saw every point we discussed.

This diagram tells directly and clearly where 2/3 stop decrease in Exposure Index comes from.

"Everything Else" we may have discussed or might bring up later that makes up a difference in Exposure Index between ISO and Zone System... taken together... amounts to what I think is about 1/3 stop decrease in Exposure Index.

So if it isn't interesting, I would not object to anyone who says the remaining difference of a third-stop is not significant enough to discuss any further.

Just to put some perspective on this discussion.

But I thought about another interesting factor today that hasn't been mentioned in this thread. You might know about T-Stops. These are like f/stops but include transmission of the lens. Well, it occurs to me that Zone System tests "find" the transmission of the lens. At least transmission is one of the factors heaped into the testing.

At one point I thought it would be helpful to have lenses calibrated in T-stops. But now that I see... that it probably amounts to less than 1/3 stop of light loss... T-stops might not really be necessary for pictorial still black and white negative photography...

 

[Bill Burk]

The figure shows the subject luminance range of 2.10 which is 7 stops, Zone I to Zone VIII. This agrees with discussion "Finding the N-Numbers" in Phil Davis' Beyond the Zone System. In that passage, Phil Davis also says you can count Zone II to VIII for 6 stops, or count Zone I to VI to agree with Ansel Adams for 5 stops.

Sounds like RobC counts Zone 0 to X for 10 stops. RobC's range is extreme in comparison, but I think RobC prints these extremes as paper maximum black to paper white... If he were to count only his textural range, it might be he is working with 8 stops...

These choices of subject luminance range - are a greater source of variation than 1/3 stop. So choosing one of these variations can have a significant impact on the negatives that you make.

Choosing 7 stops makes your subject luminance range so close to the ISO standard, that for all intents and purposes it is the same.

 

[RobC]

I would just like to throw into the conversation the following.

Those that have been down the Ansel Adams path and sensitometry tend come out the other the end with it ingrained in their minds that its desirable to capture a 10 stop range from black to white on a negative which prints at grade 2. Well this is fine if your typical subject range is greater than the ISO standard of 7 1/3 stops. It should be remembered that Adams is famous for his landscape images which you can see from most of them were taken in bright sunshine with bright clouds and dark rock crevices. His zone system is well suited to those kind of high SBR subjects.

However, a 10 stop range is not ideally suited to studio photography or family photography in the back garden with a hedge behind your subjects and SBR is only 5 stops or other situations where SBR may only be 4 to 7 stops.

Also there is no law which says 1 zone is 1 stop range. You can use 1 zone is 0.7 of stop range if you want, which means if you are using box ISO box speed and manufacturers recommended dev for that then you can apply the zone system with zero testing by saying zone 3 will be metered and close down 2 x 0.7 which is 1.4 or 1 1/3 stops which is close enough. Or if you want to place exposure on zone 8 you can meter and open up 3 X 0.7 which is 2.1 or 2 stops which is close enough.

There you have it the zone system for ISO speed and dev with zero testing. It really couldn't be any easier.

The range you calibrate your film dev to should be aimed at YOUR typical SBR and not necessarily Adams or anyone elses typical SBR. The ISO standard as we know is around 7 1/3 stop range and not 10.

And if you calibrate to an 8 stop range then 1 zone is 0.8 of a stop or 6 stop range then 1 zone is 0.6 of a stop. So you can still use the zone system using zone III or Zone VIII or whichever to place your exposure on by just using a different range for each zone. It only requires the ability to do the most elementary mathematics when setting your exposure.

So when you're discussing this stuff bear that in mind becasue if you don't you may get led down a path which really isn't suited to YOUR typical subjects.

 

[RalphLambrecht]

The trouble is, my typical subjects are all over theplace.

 

[RobC]

The trouble is, my typical subjects are all over theplace.

thats why I calibrate for 10 stops and expose for the highlights. But there are situations where you know a whole roll of film exposed in one location will have SBR of 8 stops or less or 7 stops or less and you can use calibration for that. But calibrating for 10 stops and exposing for highlights will handle that too, you can correct at the printing stage.

 

[Stephen Benskin]

The figure shows the subject luminance range of 2.10 which is 7 stops, Zone I to Zone VIII. This agrees with discussion "Finding the N-Numbers" in Phil Davis' Beyond the Zone System. In that passage, Phil Davis also says you can count Zone II to VIII for 6 stops, or count Zone I to VI to agree with Ansel Adams for 5 stops.

Sounds like RobC counts Zone 0 to X for 10 stops. RobC's range is extreme in comparison, but I think RobC prints these extremes as paper maximum black to paper white... If he were to count only his textural range, it might be he is working with 8 stops...

These choices of subject luminance range - are a greater source of variation than 1/3 stop. So choosing one of these variations can have a significant impact on the negatives that you make.

Choosing 7 stops makes your subject luminance range so close to the ISO standard, that for all intents and purposes it is the same.

Bill, that's one of the problems with many of the "systems" out there. They are long on how and very short of why (with the possible exception of Davis). I just got the Kodak publication, Advanced Black-and-White Photography. In the testing section, the author has decided to base everything on a Zone System approach, but not exactly as outlined in The Negative. In the film development section, he says to measure the density at Zone VII (not Zone VIII) and the NDR - Fb+f should be 1.05. I thought, that's one stop shorter than it should be. But if you break it down, under no flare testing conditions, a 1.05 density range is reached at Zone VII at a CI of 0.58 or Normal development. But the author doesn't point that out, thus more potential for general confusion. One of the key aspects of sensitometry (science) is that it uses agree upon terms. If a film speed has an ISO prefix, it means the film was tested using the procedures stated in the ISO standards. I plan on addressing this further later today.

And for those Thornton followers and his reference to the Kodak publication. Well, the Kodak publication uses Zone System speed methodology which means EIs will be lower than the ISO (this thread). Thornton basically did a little quote mining to imply that Kodak acknowledged "true film speed" is lower than the ISO.

Bill, t/stops are used in the motion picture industry where they require consistency between different shots. And yes, the difference between f and t can make a difference in exposure, but like I have pointed out before, f/stops are not consistently off by the same amount per stop or within a set of lenses. ZS testing will not compensate for this. Like in the motion picture industry, if a higher degree of accuracy is desired, get the lenses calibrated. The t/stops are scratched into the f/stop ring on the lens.