Film test results

[macandal]

I know film testing is very personal, but I want to compare notes with any of you who may have been used the same film/developer combination. In the past I've screwed up this test so badly, so I want to make sure I've done it right.

• I am testing Delta 100 (4x5) with Ilfotec DD-X.
• I kept the temperature at 68F.
• I used the development times suggested by the Ilford tech sheet for this film which was 12 minutes intermittent agitation.
• I used the nikor tanks to develop the sheets.
• I used the Ansel Adams method as it appears on The Negative (using third stops--my lens indicates these third stops)
• I left the shutter speed constant and changed the f stops.

My results showed that my personal EI for this combination is 160.

Are my results comparable with those some of you may have had?

Thanks.

[Leigh]

Hi Mario,

I expect your results are correct for you, assuming the tests were done correctly.

Film speed will vary from one batch to the next. It's affected by shutter speed errors and other factors.

That being the case, the results are quite personal indeed.

- Leigh

[Bill Burk]

Hi Mario,

The speed you found is higher than I would expect when testing for Zone System speed. But at this point you haven't determined developing times. You might have developed longer than "N".

So take it for now, use the speed you found to go on to the next phase of testing, finding the development times.

You might find your "N" time is less than 12 minutes, and if so, the fact this test set was developed longer than "N" could explain your "atypical" speed result.

[Leigh]

The shutter speeds have not been tested, nor has the aperture.

Given that shutter speeds can vary ±30% from nominal, that error could account for
over 50% of the difference between expected and calculated film speed.

Aperture error and differences in processing methodology could easily eat up the other half.

The bottom line is that we can't obtain any definitive information from the data presented.

Personal film speeds are exactly that... personal. There are myriad factors that affect those numbers.

If you want to do highly-controlled testing with thousands of sheets of film, you'll come up with the manufacturer's number. That's true because that's exactly how they got the number in the first place.

The concept of "personal ASA" is simply shorthand for the corrections required to your processes and
equipment that are needed to produce negatives with the same characteristics as the manufacturer.

- Leigh

[Bill Burk]

Let me clarify...

Normally people who rate film using the methods in Ansel Adam's "The Negative", find a personal exposure index that is less than the manufacturer's ISO speed.

I would have said there was something wrong for Mario to get 2/3 stops above manufacturer's ISO rating for the film.

But I noticed Mario developed according to manufacturer's instructions. The development to manufacturer's specification probably helped Mario achieve manufacturer's close to ISO speed.

So the fact Mario's "system" results in a plus 2/3 stop difference is not a surprise. For amateur purposes, plus or minus 2/3 stop could be considered "in control".

Like you say, Leigh, we don't have enough information to conclude anything. A shutter speed alone could cause this.

But if Mario still gets 160 as an end result of Zone System, I'd be concerned it's off a whole stop from what I expect.

Let's see how much the speed falls when Mario develops for "N".

[Leigh]

Let's see how much the speed falls when Mario develops for "N".

Realize that the exercises required to determine "N" are in fact compensating for errors in the personal system.

- Leigh

[Bill Burk]

Mario,

Getting back to your original request: I haven't tested that combination. I'm testing 35mm 100TMAX in D-76 tonight, soon as the water hits 68*F. I'm using sensitometry (exposed film using flash, EG&G at 10^-2) instead of camera tests and will develop in D-76 straight for 12, 24 minutes... and in D-76 1:1 for another series of times. The film and D-76 are fresh.

I expect I will get slightly less than rated speed because my techniques are not fully ISO-compliant.

[macandal]

I read somewhere (of course now that I want it I can't find it) that this film/developer combination should give me a personal EI below the stated ISO (80 or so) so when I got 160 I worried a bit. The lens I used has been calibrated so I trust my shutter speeds. I developed according to manufacturers instructions because ... well, because that's where one starts right? What else was I supposed to do? Guess? You start according to what the manufacturer tells you with your film/developer combo. I don't understand what else was I supposed to do? The only thing I may have done "wrong" is that I was going over my film development instructions and it said to agitate constantly for the first minute and then for 10 seconds every minute thereafter. Could one minute of constant agitation could have affected my final result?

Seriously? No one has ever done a film speed test using the film/developer combo I used? I would love to compare notes with you elusive guys.

Thanks.

(I don't want to retest if I don't have to because this is expensive film, but I will do it if I have to.)

[Leigh]

The only thing I may have done "wrong" is that I was going over my film development instructions and it said to agitate constantly for the first minute and then for 10 seconds every minute thereafter.

Disregarding technical issues like shutter speed accuracy, the major difference between manufacturer's speed and
personal speed lies in the development, both the choice of developer and the actual processing technique used.

The lower ASA that's commonly found supports the idea of "expose for the shadows, develop for the highlights" by
slightly increasing the exposure.

If you have reasonable shadow detail in your images (light grays rather than completely clear negative areas) at
your higher ASA, they your negs should print fine.

The most important test of any technique is whether you can easily make good prints from the negatives.

- Leigh

[macandal]

If you have reasonable shadow detail in your images (light grays rather than completely clear negative areas) at
your higher ASA, they your negs should print fine.

The most important test of any technique is whether you can easily make good prints from the negatives.

- Leigh

I'm not there yet, so I won't know that yet. I was trying to avoid further testing before I knew that my film speed test had been done right. At this point I'm not moving forward until I am certain I have done it right. I understand that this type of testing will yield a personal result (i.e., that it will vary from person to person), I cannot be that far off from someone using the same film/developer combination I have used and a similar agitation method. That's why I would love to compare results with other folks who have tested this in a similar way.

I do appreciate everyone's input, though.

Thank you Leigh and all.