Empirically Determining Film Speed

Reading 'The Negative' (A.A. 1981), Ansel describe metering for Zone I, shooting slight variations in exposure, then, using your standard developer, temperature, dilution, and agitation to develop the film. And, measuring density using a densitometer to find the one closest to 0.1 density, and that exposure determines the 'true' film speed.

I have no access to a densitometer, so here is another idea, and I wonder if it will work.

Meter a slightly texture surface at Zone V, and then shoot exposures for Zones 0 through X. Print the Zone V exposure to match a standard gray card in density (visual comparison), and then use that enlarger setting to print all 11 Zones. Look a the prints, particularly Zones I, II and VIII, IX, to see how the texture is rendered. Assuming its unbalanced (texture missing where it ought to be, or too much texture where it shouldn't be, then adjust exposure by changing the meter ISO setting to balance out the texture in the those extreme zones. And, when the texture becomes balanced, the ISO setting on the meter that worked is the true film speed.

Does this make sent, or an I nuts?

It’s not a reliable plan because Zone V varies a lot with development.

Fix a piece of film and wash and dry it. That will be your base. Then do Ansel Adams’ test.

We can help you see which of your results is 0.10 even without a densitometer.

For instance put your fixed film on a light box and aim a camera at it or a spot meter. Get the reading as precise as you can. Then put one of your Ansel Adams tests on the light box. The one that drops the reading by one film speed mark compared to the clear film is 0.10

0.1 log d is one-third of a stop. Like mentioned above you can compare a blank frame to your zone I frame over your meter to see the one-third of a stop drop. Why this is not mentioned in the book, I don't know.

For the equipment shortfall: any spot meter can be used with a strong diopter to stand in for a densitometer. For instance, with my (1970s vintage) Pentax 21/1 (yes, it calls for an obsolete mercury cell, but I have an adapter to give the correct voltage from an alkaline or silver oxide 76 size cell -- works fine, except the meter light won't run on the current the regulator will pass), I can mount any 46mm screw-in filter, so I got a +10 diopter in that mount. That lets the meter's internal telescope, which normally focuses "near infinity", focus instead at about 10 cm (close to four inches) and makes the 1 degree metering spot a mere 1.7 mm (about 5/64 inch) across, and the circle in the spotmeter's viewfinder tells me exactly where I'm reading.

This can be done either with the negative on a smooth light source (a tablet displaying a blank white image will work at this scale; the screen's pixel texture is still much smaller than the measured spot), or with the negative projected from an enlarger onto a piece of clean paper or board (best to start with projecting a piece of clear film to be able to correct for potential vignetting in the enlarger light).

Greg Davis, The Naked Photographer on YouTube, has information on how to convert the spotmeter's reading in EV to density in one of his videos on sensitometry.

Thank you both. So, I will be comparing a meter reading through film base plus fog (FB+F) to the several A.A. exposures, which are each one-stop away from the adjacent exposures, and 0.1 density (ideally) from one another. The one that is 1/3 stop darker then the FB+F is the Zone 1 Exposure. Yes?

@ic-racer : You stated that 0.1* log(d) is 1/3 stop exposure difference. I wish I understood that better? If density is 0.1 (as noted by A.A. for Zone I), then 0.1*log(0.1) equals -0.1. That looks like a 10% increase in density, so that makes sense, but, why is that 1/3 stop?

@Bill Burke : I understand that film development procedures affect exposure density. But, isn't that the point of A.A.'s test? To determine how your (my) procedures perform. FWIW, my standard procedure is 68ºF, XTOL 1:1 in a Paterson tank using twisting agitation for 30 seconds initially and then 5 seconds every 30 second thereafter. If I alway used this technique, won't the test be effective for my procedures? Also, FYI, I shoot HP5 and FP4, which have always been rated at box speed using Mfr.'s development times.

Again, thank you both. I will get this dialed in. My ultimate goal is to accurately exposure for the shadows (Zone III) and develop for the highlights (Zone VII). Hopefully.

@Donald Qualls : Thank you too. I am subscribed to the Naked Photographer (not in a creepy way), and thank you for that link. BTW, I have an Pentax Digital Spotmeter coming to me in a day or two, and a light box, so these test procedures are very doable for me.

Cheers to all...

I recommend a ring around shoot, I recommend Carson Graves The Zone System for 35mm Photographers, he provides simple instructions.

: You stated that 0.1* log(d) is 1/3 stop exposure difference. I wish I understood that better? If density is 0.1 (as noted by A.A. for Zone I), then 0.1*log(0.1) equals -0.1. That looks like a 10% increase in density, so that makes sense, but, why is that 1/3 stop?

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0.1 is already a log. To get the actual intensity of light in lumens one would take the anti-log.
The factor 2 is common in photography (one stop) and its log (0.3) is also common. So 0.3 = one stop and 0.1 = one-third stop.

This should be required reading before attempting to read anything on Zone Systems:
https://www.kodak.com/content/products-brochures/Film/Basic-Photographic-Sensitometry-Workbook.pdf

OK, got it, thank you.

By the way you’re right about FB+F . Fixing will give FB which is nice to know but you want 0.1 above FB+F

Zone V isn’t a good place to check for speed because a small variation in developing can cause a great variation in the Zone V density. It is useful to check Zone VII or Zone VIII density for development time, but for speed you look at the toe where light is just starting to have an effect on film

If you don't have access to a densitometer, you can use a visual method, like I do.

Get yourself a copy of "The New Zone System Manual" by Minor White et al. and use their instructions.

The method is based on the "proper proof," i.e. printing the negative on the paper you use most at the minimum exposure that renders the clear portion of the negative (fb-fog) at maximum black. This latter is determined by printing the negative next to a stripe of the paper that is exposed to the printing light source without the negative in the middle. Think contact printing with a border or enlarging with the negative offset in the carrier somewhat to let unimpeded light strike the paper.

You do a test strip and compare the blacks under "ideal gallery lighting" (i.e., not too bright or too dim) and find the minimum printing time that renders the two blacks indistinguishable. That's your proper proofing time.

Now take your test negatives, i.e., the ones with Zone I, II, III etc. on them and make proper proofs from them. It's helpful to have a stripe of pure paper white and maximum black on them, so expose a stripe to the bare light and cover up a stripe with a ruler or something.

After processing and drying them, evaluate. If you've got your film speed correct, Zone I will be just distinguishable from maximum black and Zone III will be the first black with some texture. If your development is correct, Zone VIII will be the first white with some texture and Zone IX will be almost indistinguishable from unexposed paper white.

This method works just fine to get you started.

Some caveats:
Don't evaluate the proper proofs in too-bright light or you'll end up rating your film too fast and vice-versa. The perfect lighting is the one you think is ideal for print viewing.
Evaluate everything dry. Drydown changes things a lot.
If you change your film developing time much for a subsequent test, you need to find a new proper-proofing time, since fb+fog will change a little.
Remember that shooting test negatives of test targets is only an approximation of real-life situations, so keep careful notes and adjust your personal E.I. and film-developing times as necessary.

Or, if you want to go "down-and-dirty," just rate your film at 2/3 stop lower than box speed and shave 15% off the manufacturer's recommended development time as a starting point. Go out and shoot, keep notes, adjust as needed. Really, this works a lot better than people are willing to admit, since it puts you well into the ballpark with the errors on overexposing a bit and underdeveloping a bit, both of which are the easiest to compensate for when printing. Then, if your negatives are consistently flat, increase your developing time a bit and vice-versa, and if your shadow detail is not enough, rate your film a bit slower, and vice-versa.

Keep in mind that the most important thing is to expose your film well enough so that you have shadow detail where you want it, and develop it well enough so that you can get the print you want. There's a rather large bandwidth of possibilities of different E.I.s and development times that will get that job done.

Best,

Doremus

I wish there was a LIKE button. You'd all get a LIKE.

My testing has begun, shot a test roll, have test bits inbound. I'm gonna keep my textures in the correct Zones. Development processes will be as consistent as possible.

michael_r said:

Without a densitometer I suggest OP take the opportunity to not do the silly EI test, which is little more than a densitometry exercise in the first place.

The practical way to determine if you need an EI that differs from ISO is by making negatives and printing them. If you consistently find yourself struggling with thin shadows, decrease EI. If you consistently find yourself printing down, increase EI.

It should be a determination from tone reproduction rather than an arbitrary criterion.

EDIT: TYPOS

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+1! Determining a satisfactory EI for an individual's equipment/processes is very much a practical matter and definitely doesn't necessarily require the hair splitting precision of a densitometry lesson.

Danner said:

Reading 'The Negative' (A.A. 1981), Ansel describe metering for Zone I, shooting slight variations in exposure, then, using your standard developer, temperature, dilution, and agitation to develop the film. And, measuring density using a densitometer to find the one closest to 0.1 density, and that exposure determines the 'true' film speed.

I have no access to a densitometer, so here is another idea, and I wonder if it will work.

Meter a slightly texture surface at Zone V, and then shoot exposures for Zones 0 through X. Print the Zone V exposure to match a standard gray card in density (visual comparison), and then use that enlarger setting to print all 11 Zones. Look a the prints, particularly Zones I, II and VIII, IX, to see how the texture is rendered. Assuming its unbalanced (texture missing where it ought to be, or too much texture where it shouldn't be, then adjust exposure by changing the meter ISO setting to balance out the texture in the those extreme zones. And, when the texture becomes balanced, the ISO setting on the meter that worked is the true film speed.

Does this make sent, or an I nuts?

Click to expand...

no need;film speed is printed on the box the film came with;the rest is personal taste.

Bill Burk said:

By the way you’re right about FB+F . Fixing will give FB which is nice to know but you want 0.1 above FB+F

Zone V isn’t a good place to check for speed because a small variation in developing can cause a great variation in the Zone V density. It is useful to check Zone VII or Zone VIII density for development time, but for speed you look at the toe where light is just starting to have an effect on film

Click to expand...

+1

Here are photographs of my first test prints (5"x8" MGIV with 2.5 filter). This is the test I outlined in my original post to this thread. The original exposures are all based the Zone V exposure (using a Gossen Luna Pro meter), with the shutter speed then adjusted one-stop at a time to achieve the Zone 0 through Zone X exposures. The prints are all at the same enlarger/development settings, based on the Zone V print matched to a gray card. Film was Neopan 400, developed in XTOL (stock). Subject was a large cabinet with a low-contrast grain pattern printed on it, the vertical bars are silver handles.

IMHO, the contrast of the grain pattern is too low for this test, probably less than 1/2 stop, and my next test will use a higher contrast pattern, maybe some fabric.

At any rate, here they are...

Zone II


Zone III


Zone IV



Zone V


Zone VI


Zone VII


Zone VIII


Zone IX

That’s perfect! The grain pattern is fine for this test. You can see what is important to note about this series, for example Black and White prints drop to black faster than you might have thought before. It’s supposed to do that, now you know - and not from someone just telling you so.

Doremus Scudder said:

The method is based on the "proper proof," i.e. printing the negative on the paper you use most at the minimum exposure that renders the clear portion of the negative (fb-fog) at maximum black. This latter is determined by printing the negative next to a stripe of the paper that is exposed to the printing light source without the negative in the middle. Think contact printing with a border or enlarging with the negative offset in the carrier somewhat to let unimpeded light strike the paper.

Click to expand...

This guarantees that deep shadows will be (a) at the low end of the toe of the negative; (b) at the high end (density-wise) of the shoulder of the paper. Not good for separation.

What I might do, for grins, is try to print more of the negatives to a Zone V (looking) print. Because, examining the negatives, there is quite a bit more detail in them as compared to the foregoing 'fixed' print settings. So that would be a test for what can be achieved with over-exposed and under-exposed negatives.

But yes, this is a rather enlightening test.

bernard_L said:

This guarantees that deep shadows will be (a) at the low end of the toe of the negative; (b) at the high end (density-wise) of the shoulder of the paper. Not good for separation.

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Bernard,

As far as I have experienced, using the proper-proof visual method as outlined in "The New Zone System Manual" by White, et al. gets you visually to about the same Zone System speed point as using a densitometer, erring on the side of overexposure if anything. The result should have Zone III on the same point in the film's characteristic curve as other methods. This one, however, takes the curve of the paper (the shoulder) into account too, so should really optimize separation in the shadows. Plus, one can always rate the film a bit slower and print down a bit if one is not happy with the shadow separation (a refinement that I didn't mention earlier). Still, the object is to get the maximum effective film speed and still get the shadows we like. The visual method of achieving this works just fine, maybe better than just blindly following the density requirements for the Zones one sees published.

Best,

Doremus

Bill Burk said:

That’s perfect! The grain pattern is fine for this test. You can see what is important to note about this series, for example Black and White prints drop to black faster than you might have thought before. It’s supposed to do that, now you know - and not from someone just telling you so.

Click to expand...

Right! But it must be emphasized that what the OP wanted to do, find film speed, can't be done like this.

Good information. What I, the OP, really want, is to be able to is spot meter a scene and decide where the negative's Zone III should fall, and then set exposure to make that happen. My personal calibration could be to ISO rating, development time, agitation, or ???. Assuming I am very consistent with temperature and agitation, adjusting ISO seems the logical independent variable. I don't think I have achieved that yet, I am still working on it. Looking at the prints, above, the Zone III print doesn't show detail to my eye, so, setting the ISO to a somewhat slower speed would increase exposure and shadow detail, and might get me there.

Another queer thing, I thought the camera (Nikon N80) had HP5 in it, but it turned out to be an old roll of Neopan 400 (my very last one), so I am going to have to re-do this with HP5, and ultimately FP4 as well. I do have a spot meter coming soon, so I'll wait for it to arrive before further testing.

I may be doing this incorrectly, but at least I'm learning something, even if it's the 'hard' way.

Cheers...

Doremus Scudder said:

As far as I have experienced, using the proper-proof visual method as outlined in "The New Zone System Manual" by White, et al. gets you visually to about the same Zone System speed point as using a densitometer, erring on the side of overexposure if anything.

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Point taken. Thank you for your detailed response.
On the other hand, I am annoyed by this dogma advocated by some ZS enthusiasts: determine enlarger f-stop and exposure time for exactly max black on B+F, and freeze those values.

• The New Zone System Manual, p. 61 (1978 edition)
• Zone VI workshop, p. 35 (1978 edition)

I much prefer the pragmatic approach of David Vestal, who demonstrates near-perfect prints with Tri-X exposed 400, 200... 25ASA, and acceptable prints down to maybe 0.6ASA (too lazy to go and check); Not with the same enlarger f-stop and time of course.
Point being not that I'm going out and proudly expose my 400TX at 0.3 ISO (like the kids proudly announcing they have "pushed" three stops and then asking for a suitable developer), but rather that tonality is (to me) more important than speed or grain, and I'd rather err by one stop over than one stop under. And adjust print times accordingly.

BTW, if anyone reading this wants to have The New Zone System Manual, it's yours for the cost of postage (I live in EU). Not sure it's really a gift, rather a rabbit hole.

Bernard,

The whole "proper proof" thing has little to do with the final exposure for making a fine print. It's just a way of seeing where your film starts to register exposure and how developing time is affecting the highlights. I fine tune my E.I. and development times after that to get a Zone III where I want it if it isn't right where the Zone I exposure shows up with the max. black exposure; a bit of a fudge to get the shadows up off the toe if needed, and to make sure Zone VIII or IX is where I want it with whatever E.I. I'm using. Nevertheless, making proper proofs can give you lots of information about where to start with a print and it's a good control on one's processing. If I consistently start getting flat negatives, I'll adjust my development time, etc.

The largest hindrance to making excellent prints is underexposure of the film. Making sure your negative delivers a maximum black from clear areas when you print a Zone III value where it should be ensures that you are exposing adequately.

Really, getting from Zone III to VIII on the straight-line portion of the film is most important, so that should be our goal (but real film speed isn't determined that way either...). With film with long straight-line portions, overexposing makes little difference in this regard. Some films (notably 320TX) have a long toe that can deliver different shadow renderings depending on exposure (one reason I like it - more exposure = more separation in the shadows, "regular" exposure gets me shadow detail, but emphasizes the mid tones more).

With bigger film, overexposure is much less of a problem, still it's good to try for that sweet spot - minimum exposure to get a negative you can make an excellent print from - for a number of reasons; grain (still an issue for me with 4x5), shutter speed/aperture combination when taking, etc.

Best,

Doremus

Doremus,

Thank you again for that detailed response. I agree to most of what you wrote. Indeed, B+F (clear film) and first exposure that is visibly above is probably as good as a densitometer for practical purposes. In the end, the metering method (e.g., ZIII placement, as you write) of an actual scene is probably just as important as the initial film calibration. Then, as you point out, there are short toes and long toes...

Two arguments against indiscriminately generous exposure (i.e. caveats to my previous post). (1) consistent exposure makes contact sheets more usable. (2) Some films are mildly compensating, by virtue of their emulsion rather than special development; this helps tame vigorous highlights without neutering them. Examples are the defunct films Fuji Neopan 400 (just right, stash in fridge) and Agfa APX 100 (the real one, stronger compensation). Making the most of that feature requires a proper placement of the exposure.

Best,
Bernard