Does changing film speed affect zone employment?

ChristopherCoy · Jan 28, 2021

If you rate a 400 speed film at 200, you're over exposing by 1 stop.

So if you meter a shadow area at say 1/250th @ f5.6, and place it in zone III by shooting 1/1000th @ f5.6, wouldn't that cancel out the one stop over exposure for the speed change, and leave you with a 1 stop under exposure for the entire negative?

Donald Qualls · Jan 28, 2021

The rating you give the film is based on your testing of that film in your development process.

It starts with establishing a "normal" contrast process for a given film (real hard core practitioners will redo this test and the next one for each new lot number even of the "same" emulsion). This may require exposing and densitometer reading multiple sheets (since Zone is aimed at sheet film for individual development). Once you have normal contrast, you do your speed test in that development to get your EI.

Once you've done those tests, you still need to compensate for speed changes when you apply expansions (+1, +2, etc.) and contractions (-1, -2, etc.) to fit a given scene contrast into the film's range -- but when you shoot for "normal" contrast, at your tested EI, your zones are already compensated for the personal EI for that film in your normal contrast process.

Andrew O'Neill · Jan 28, 2021

Not of you've tested to see if EI 200 places zone I where it should be.... 0.10 above film base... And your development time is correct. Remember, your metre thinks it's looking at roughly zone V. Shadow is darker, so you have to under expose. EI 200 might be too much. Testing is in order.

ChristopherCoy · Jan 28, 2021

Donald Qualls said:
The rating you give the film is based on your testing of that film in your development process.

It starts with establishing a "normal" contrast process for a given film (real hard core practitioners will redo this test and the next one for each new lot number even of the "same" emulsion). This may require exposing and densitometer reading multiple sheets (since Zone is aimed at sheet film for individual development). Once you have normal contrast, you do your speed test in that development to get your EI.

Once you've done those tests, you still need to compensate for speed changes when you apply expansions (+1, +2, etc.) and contractions (-1, -2, etc.) to fit a given scene contrast into the film's range -- but when you shoot for "normal" contrast, at your tested EI, your zones are already compensated for the personal EI for that film in your normal contrast process.

Since you mentioned expansion and contraction, which is the exact paragraph I just started reading in the book, I'm assuming that I'm probably asking questions that will be answered with continued reading. I'm famous for jumping ahead of myself.

Dali · Jan 28, 2021

If you rate a 400 ISO film as 200 ISO, I guess it is for good reasons. So you are not over-exposing.

As Don detailed above, ISO rating is personal, can depend on your tastes and your development process. What is written on the box is just that... what is written on the box.

ChristopherCoy · Jan 28, 2021

Donald Qualls said:
Once you've done those tests, you still need to compensate for speed changes when you apply expansions (+1, +2, etc.) and contractions (-1, -2, etc.) to fit a given scene contrast into the film's range -- but when you shoot for "normal" contrast, at your tested EI, your zones are already compensated for the personal EI for that film in your normal contrast process.

ah... see... just like that I get "appendix 1 on pg 239". I told you I was famous for getting ahead of myself.

Paul Howell · Jan 28, 2021

If you don't have access to a densitometry the first edition AA the negative and Carson Graves' Zone System for 35mm Photographers provide pretty good instruction's on how to test for personal E.I.

ChristopherCoy · Jan 28, 2021

Paul Howell said:
If you don't have access to a densitometry the first edition AA the negative and Carson Graves' Zone System for 35mm Photographers provide pretty good instruction's on how to test for personal E.I.

reading them now....

Sirius Glass · Jan 28, 2021

michael_r said:
I suggest not getting bogged down in testing. Aside from some rough +/- development to change contrast (which is mostly superfluous/not needed), the rest of it can be skipped. You don't need to run a "personal EI" test for the Zone System. The Zone System EI is 2/3 stop less than the ISO speed.

Dammit! Stop simplifying things! This is photography we are talking about. It is supposed to be confusing. What are you thinking??

Donald Qualls · Jan 28, 2021

michael_r said:
The Zone System EI is 2/3 stop less than the ISO speed.

Not even always that. If you master the concepts of correct metering and have a developing technique that gives good speed at relatively low contrast, you can produce good negatives at box speed with most films. The biggest single thing is getting enough light into the shadows, follwed by avoiding overdeveloping to keep control of the highlights. The latter is where speed is usually lost, but if you use dilute developer and reduced agitation you can get full box speed at low enough contrast to keep the highlights in check.

sterioma · Jan 28, 2021

Donald Qualls said:
The biggest single thing is getting enough light into the shadows, follwed by avoiding overdeveloping to keep control of the highlights.

I am currently reading "The Art of Photography" from Bruce Barnbaum, who basically says "don't worry much about the hightlights becasue with modern films you have good separation well beyond Zone X and you can always print it down in the darkroom". This seems to go against many other books that I have read, that insist on keeping the hightlights of interest around Zone VIII at the most. I do see the point of what Barnbaum is saying, so I wonder if anyone else other than him shares the same approach.

ChristopherCoy · Jan 28, 2021

michael_r said:
I suggest not getting bogged down in testing. Aside from some rough +/- development to change contrast (which is mostly superfluous/not needed), the rest of it can be skipped. You don't need to run a "personal EI" test for the Zone System. The Zone System EI is 2/3 stop less than the ISO speed.

After reading the film speed test instructions that AA gives in the back of "The Negative" I'm inclined to go with your advice, simply because the technicality needed to produce his tests are about 17 levels above where I am in knowledge right now.

But doesn't shooting 400 speed film at 200 change things at least somewhat when it comes to using the zone system, and development?

138S · Jan 28, 2021

ChristopherCoy said:
If you rate a 400 speed film at 200, you're over exposing by 1 stop.
So if you meter a shadow area at say 1/250th @ f5.6, and place it in zone III by shooting 1/1000th @ f5.6, wouldn't that cancel out the one stop over exposure for the speed change, and leave you with a 1 stop under exposure for the entire negative?

If you make that kind of question then you should practice with spot metering a bit, later you may use what metering way you want, but let me suggest you shot some rolls with spot metering mode.

ISO speed is calculated in a way that spots underexposed by 3.33 (3 and a thrid) stops are recorded almost totally black, with no shadow detail. "Speed point" (the exposure at what we start recording detail) is at -3.33, remember that number. At -3.33 normalized density is 0.1D more than the density of not exposed areas, so more than base+fog density (density is a way to say opacity). Some factors may modify the real Speed, some developers loss or boost speed slightly.

Do next exercise: decide a manual exposure and then check your scene wth spot meter (of a cheap SLR), take notes about what under/over exposure results in each interesting scene spot. Then also bracket and expose a fram ar (say) +1 and aonther one at -1. If clouds were at +2 then the bracketed +1 shot will be at +3...

So you will learn how spots in the image get depicted at different under-over exposure. From then when you decide a manual exposure you can check how different spots in the scene are under/over exposed, so you'll be able to make a good prediction of the result.

Let me recommend you the book bellow, it can be found used very cheap. First part is about practical sensitometry, it contains some math, this is the basic knowledge that allows a full understanding of the process, so it's important to master it well. Second part speaks about metering ways.

You would learn to calibrate film, and you will understand what you are doing when you use a certain E.I. With this book you'll master practical sensitometry, involved math requirs you use logarithms, a bit painful for some, but this will allow you to understand the graphs in the film datasheets which can be great for those liking a technical approach. This book has been used in many antique Photo schools, if you make the effort you'll master the exposure techniques, and this will alllow you to use the best metering way for any situation.

Donald Qualls · Jan 28, 2021

sterioma said:
I am currently reading "The Art of Photography" from Bruce Barnbaum, who basically says "don't worry much about the hightlights becasue with modern films you have good separation well beyond Zone X and you can always print it down in the darkroom". This seems to go against many other books that I have read, that insist on keeping the hightlights of interest around Zone VIII at the most. I do see the point of what Barnbaum is saying, so I wonder if anyone else other than him shares the same approach.

While this is largely true, when Adams last edited The Negative T-Max (the first film with this characteristic) had only been out a couple years. Kodak's other B&W films of the day were starting to gain this "no shoulder" quality, but it was still in its infancy. When Adams originally wrote that book, there was no film with that capability.

MattKing · Jan 28, 2021

The other reason to do film speed tests is that they compensate for peculiarities in your shutters and your meter and your metering technique and your choice of developer.
Mostly though, if you are using roll film, experiment with a few speeds close to the ISO speed, and pick the speed that gives you the prints you like.
If you were using a lab to develop and machine print your photography, most likely you would get the nicest prints from box speed.

ChristopherCoy · Jan 28, 2021

MattKing said:
The other reason to do film speed tests is that they compensate for peculiarities in your shutters and your meter and your metering technique and your choice of developer.
Mostly though, if you are using roll film, experiment with a few speeds close to the ISO speed, and pick the speed that gives you the prints you like.
If you were using a lab to develop and machine print your photography, most likely you would get the nicest prints from box speed.

So essentially I just need to do another roll like I did for this thread, and rate half the roll at 200, half the roll at 400 and see what I like best.

Donald Qualls · Jan 28, 2021

michael_r said:
What I'm saying is that by definition the Zone System EI is 2/3 stop below ISO speed.

By definition, the Zone System EI is whatever you determined by testing to be the true film speed in your normal process. With most cubic grain films, if your processing is very conventional (agitation every 30 or 60 seconds in developer similar in operation to D-76 1+1), your tested EI is likely to come out lower than box speed, and probably close to 2/3 stop lower. But if your preferred process isn't the conventional, or you use a speed-enhancing developer (or both) your EI might test to be another stop slower, full box speed, or even 1/3 to 2/3 stop above box speed. Your process at the correct Zone C.I. determines the EI.

MattKing · Jan 28, 2021

ChristopherCoy said:
So essentially I just need to do another roll like I did for this thread, and rate half the roll at 200, half the roll at 400 and see what I like best.

One roll is probably not enough.
And tests like that aren't as useful as real photography.
For a while, do a bit of bracketing - exposures metered at, for example, 250, 400 and 640 - and taken in a variety of situations. Keep good notes - things like descriptions of how you metered, what the light conditions were, what camera and lens was involved. Then try to print those negatives. Take good notes there too, and connect your printing notes to your taking notes. You will build a feedback loop that will lead to conclusions like: "When the light is harsh and contrasty, I should meter at 250 and either pull back on development a bit or I can print using grade 1.5. When light is slightly diffused but still directional (say with high overcast), I should meter at 400 and I can print at grade 2, and when light is very flat and grey and without direction) I can either increase development a bit and/or print at grade 3."
You can then look back at AA's books, and see the parallels between your experiences and what he says the Zone System tools can do for you. That will aid in your understanding of WHY.
You may find that this feedback loop will lead to consistently low contrast or consistently high contrast results. If that is the case, it makes sense for you to adjust your standard developing times.
When you analyze this, it is important to pay attention to the gamma or contrast index or slope of the curve (whatever resonates with you), not just how dark the print shadows are.

Donald Qualls · Jan 28, 2021

michael_r said:
What you are describing is the EI "tradition", where somehow testing a film for one's individual EI is supposed to somehow account for all sorts of variables - meters, developers, technique, equipment inaccuracies, slop etc. etc. It doesn't really do that.

Okay. You do your negatives, I'll do mine. My process today isn't the same as what it was when I consistently got a speed increase; instead of Parodinal 1:50 at "Push +2" dev chart times, but with agitation only every five minutes to keep contrast down (which routinely got me 2/3 stop above box speed at normal contrast) I'm now processing in Xtol replenished (at least, if I can get Xtol that has my confidence before my current batch of replenisher runs out). I now get full box speed -- on Fomapan 400, which everyone else claims is 2/3 to 1 stop slow even without "Zone EI". Or maybe I don't, but until I have trouble printing those negatives, I'll believe what I'm doing is working.

MattKing · Jan 28, 2021

Donald Qualls said:
QUOTE="michael_r, post: 2375703, member: 38467"What I'm saying is that by definition the Zone System EI is 2/3 stop below ISO speed.

By definition, the Zone System EI is whatever you determined by testing to be the true film speed in your normal process.[/QUOTE]
Yes and no.
The Zone System method of measuring speed is different than the ISO method of measuring speed. Given an existing characteristic curve, when you are determining speed, you do it by looking in slightly different ways at slightly different parts of that curve.
The net result of those differences is that a film with an ISO speed of 400 has a Zone system speed 2/3 of a stop different - 250.
The EI you choose to use is the one affected by your testing.

Andrew O'Neill · Jan 28, 2021

ChristopherCoy said:
So essentially I just need to do another roll like I did for this thread, and rate half the roll at 200, half the roll at 400 and see what I like best.

Or you could just shoot the whole roll at EI 200, and bracket around the exposure. Of course it would be more ideal if your camera lens can do 1/3rd stop adjustments, but half stops will still give you a good idea. At any rate, keep good notes!

BradS · Jan 28, 2021

ChristopherCoy said:
If you rate a 400 speed film at 200, you're over exposing by 1 stop....

No. Its not "over exposure" if your testing indicates that is the optimal EI for your process & equipment.

MattKing · Jan 28, 2021

BradS said:
No. Its not "over exposure" if your testing indicates that is the optimal EI for your process & equipmeny.

+1
To "over-expose" means to give too much exposure
If you rate a 400 ISO film at an EI of 200, you are merely increasing exposure.

MattKing · Jan 28, 2021

michael_r said:
If it works, it works Ultimately what matters is the print (or scan or whatever) and if the way you do it ain't broke don't fix it.

I agree.
But I also find it frustrating when I see posts from people who claim with great certainty that manufacturers aren't telling the truth when they report an obviously incorrect and exaggerated ISO speed that is a clear 2/3 of a stop higher than their true measurement of a Zone System speed!

ChristopherCoy · Jan 28, 2021

........iiiiiiiiii'm just gonna go click the shutter a few times and see what develops.

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