Testing film? Using a densitometer?

[Peter De Smidt]

Or it might have to do with the development system used by the ISO standard, but maybe that should be a different thread?

For the original poster, the options seem to be.

1. Guess and revise. Shoot some picture rating the film at 1/2 box speed. Develop and print your negative (or scan....) Do you have enough shadow detail? Does the tonality look right? If not, adjust.
2. If you have an incident meter. You can do Phil Davis's "Beyond the Zone System" tests, or Ken's simplified system. Doesn't the View Camera Store offer BTZS testing?
3. If you have a spot meter, and access to a densitometer, you can do traditional zone system testing.
4. ?

A good current book on all of this is Way Beyond Monochrome, 2nd Edition by Ralph Lambrecht and Chris Woodhouse.

[Tin Can]

Randy:

The Zone System speed point is based on the pre-1960 ANSI/ISO standard that included an extra 2/3 stop "safety factor". The safety factor in the standard at that time was larger because historically meters, shutters etc. were less precise. The safety factor was then revised downward by 2/3 stop to account for improvements in equipment, and the increased popularity of smaller film formats. The Zone System was never updated. It is important to note the safety factor is just that. It is not, in and of itself, based on an improvement in print quality.

Since the Zone System speed point includes the larger safety factor than current ISO ("box" speed), all you're doing when you do a Zone System EI test, is confirming the difference in the safety factor. This is important, because it means most people actually misunderstand the Zone System EI test, and therefore misinterpret the results. When you do a Zone System EI tests, you're not actually revealing new information. You're not finding a "better" speed in terms of tone reproduction quality, you're not finding a "truer" speed, and also importantly, you're not finding a speed based on your own equipment and working methods (which most Zone System books would have us believe).

There's some more theory on this, and flare is important too, but I'll stop there pending attacks (that's usually what happens).

All this to say, barring extreme procedures and special purpose developers, 9 times out of 10 people will find personal ZS EIs in the range of 1/2 to 1 stop slower than ISO speed. Now you know why.

Peter's example is good to show there can be exceptions, although his case does seem odd to me. When I ran ZS tests on TMY-2 I found I got exactly what the theory predicts.

Thanks for the reply. I see your point and a major reason I don't use Zone is the whole added personalization to a lens, aperture, and shutter error combo. i play with too many combos to do that. I do test my shutter speeds, but don't fix shutters, simply adjust to actual and I am often using flash, so...

All good!

[Ken Lee]

When you do a Zone System EI tests, you're not actually revealing new information. You're not finding a "better" speed in terms of tone reproduction quality, you're not finding a "truer" speed, and also importantly, you're not finding a speed based on your own equipment and working methods (which most Zone System books would have us believe)....

All this to say, barring extreme procedures and special purpose developers, 9 times out of 10 people will find personal ZS EIs in the range of 1/2 to 1 stop slower than ISO speed. Now you know why.

Peter's example is good to show there can be exceptions, although his case does seem odd to me. When I ran ZS tests on TMY-2 I found I got exactly what the theory predicts.

Amen

By way of confirmation: when I purchased the BTZS Plotter program I was stunned to see that for every given film tested, every developer tested could deliver the same basic effective film speed and contrast curves. The only real variations were the dilutions and times required to reach them. The most differences I recall amounted to no more than 1/2 f/stop, more like 1/3 of a stop: well within the margin of error in the field.

Eventually, I found it all reassuring and felt safe to pay more attention to aesthetics.

[Peter De Smidt]

Peter's example is good to show there can be exceptions, although his case does seem odd to me. When I ran ZS tests on TMY-2 I got exactly what the theory predicts.

It surprised me, too, although I was using Xtol, which is supposed to give a small speed bump. I ran the tests two more times, and I now have a couple of years of use under my belt. It works for me. Here are the results in my system for other films: Acros (80), Delta 100 (64), HP5+ (200), Tri-x (250).

TMY @ EI 500:

[Michael R]

Or it might have to do with the development system used by the ISO standard, but maybe that should be a different thread?

Possible, but unlikely. The ISO standard doesn't specify a developer formula. I typically use XTOL and D-76 for this sort of thing.

Factoring in the 2/3 stop measurement difference combined with the fact you're targeting a higher density than 0.1, I'd have expected an EI more than a stop below ISO, and yet you're at 500. Can't argue with whatever works though.

And in the end, in the field a working EI depends mostly on how we meter. But ZS tests (or other similar tests) don't factor that in .

[Bill Burk]

This is the easiest way I can recommend: Take half the rated speed as a given (you are using fresh standard film and standard developer so this is trustworthy - people shooting X-Ray film or homemade emulsions have to do speed tests).

Now go out and shoot something, anything at all using that speed.

Pretend you are bracketing but this is special. Expose a second sheet with exposure increased by 2 f/stops.

Develop both sheets the same.

Print the thinner negative to your satisfaction. Mark the back of the print in pencil so you know it's the first one.

Double the time on your exposure timer and print and develop from the denser negative.

If you can't tell the prints apart, then your film development time is correct.

[Tin Can]

This is the easiest way I can recommend: Take half the rated speed as a given (you are using fresh standard film and standard developer so this is trustworthy - people shooting X-Ray film or homemade emulsions have to do speed tests).

Now go out and shoot something, anything at all using that speed.

Pretend you are bracketing but this is special. Expose a second sheet with exposure increased by 2 f/stops.

Develop both sheets the same.

Print the thinner negative to your satisfaction. Mark the back of the print in pencil so you know it's the first one.

Double the time on your exposure timer and print and develop from the denser negative.

If you can't tell the prints apart, then your film development time is correct.

I like that and will try it with HP5 actual contact prints, not scans.

Then I am off to X-Ray Land.

[Drew Wiley]

No need to get complicated and buy a densitometer. Besides, unless you understand the basics of film first, you're not going to understand film plotting either, using a densitometer. First, for any given film and developer combination you need to establish your threshold shadow value. Bracket a series of exposures starting
at about half "box speed". Look at your developed negative below a task lamp against a deep black background, holding it under the light. Often you can see a
reflected POSITIVE image which reveals how much shadow detail you've really got. ... Another simple trick is to make your own "visual densitometer". Buy a
calibrated step wedge, then take two pieces of black cardboard and punch a little hole in the middle of each. Put these side by side on the same light box.
Slide around your negative under one hole, you step wedge under the other, to find which step density matches. The human eye is surprisingly good at comparing density under such circumstances. Good enough, at least, for getting started in black and white work if you need to measure density at all.

[Tin Can]

No need to get complicated and buy a densitometer. Besides, unless you understand the basics of film first, you're not going to understand film plotting either, using a densitometer. First, for any given film and developer combination you need to establish your threshold shadow value. Bracket a series of exposures starting
at about half "box speed". Look at your developed negative below a task lamp against a deep black background, holding it under the light. Often you can see a
reflected POSITIVE image which reveals how much shadow detail you've really got. ... Another simple trick is to make your own "visual densitometer". Buy a
calibrated step wedge, then take two pieces of black cardboard and punch a little hole in the middle of each. Put these side by side on the same light box.
Slide around your negative under one hole, you step wedge under the other, to find which step density matches. The human eye is surprisingly good at comparing density under such circumstances. Good enough, at least, for getting started in black and white work if you need to measure density at all.

Drew, i like your idea of "visual densitometer" which has been something I want. I used to compare metal surface RA (roughness) with a stainless steel plate my factory used to sell to machinist. It had a variety of values to compare.

I find step wedges pretty expensive and some won't sell without buying the whole shebang.

Then I read a kidding? comment here about Stouffer running out of Tech Pan. Bingo!

What's a good plan to DIY a 35 mm film strip step wedge with my Nikon F5 which seems to expose everything perfectly?

I would appreciate any ideas. Thanks!

[Michael R]

DIY-ing a sensitometric wedge would be very difficult, time consuming, and require more $$ in film than it costs to buy a wedge from Stouffer ($7.50 - you don't need a calibrated wedge). For a DIY, you'd need a film/developer combo that is perfectly linear over a long density range, a gamma of 1.0, and a way to evaluate that, so the problem becomes somewhat circular. You have to start with something known, so you'd need a densitometer to make the DIY step wedge.

The best way to "calibrate" a system (and the way it should ultimately be done even if you do have a densitometer) is to make test prints. Negatives and paper are a system. Densitometry/target density ranges should only be considered starting points. One can easily end up with surprises in printing, after calibrating negatives to specific density ranges as measured with a densitometer.

Regarding ZS-type calibrations, also realize the negative density range you have on the test negatives is not necessarily the density range you end up with in the field due to flare, which changes where shadow placements fall on the curve.

(by the way Stouffer doesn't use Tech Pan).