Film Speed and Developing Time

[Flexnib]

Hello All,
I am trying to use the article in View Camera magazine by Steve Simmons to help find my personal EI. I understand the closing down 4 stops, but am having trouble with the next steps.
What would be "at a film speed of 75%" Would this mean changing the asa on my spot meter from 320 to 240asa then metering the wall again and close down lens again 4 stops?
50% asa 160
125% asa 400
150% asa 480
please help!
Arthur, NYC

[IanG]

Once you've determined your speed as 75%, assuming your shooting the Tri-X 320 you just set your meter to 240 EI. It's a simple as that, then use your meter as normal.

Ian

[Ken Lee]

Developing times may vary from person to person, but after all the testing has come and gone, most people shoot most b&w films at 1/2 the stated ISO.

This is more than a coincidence. It's probably due to the way that manufacturers determine their ISO or market their products.

[Bruce Barlow]

Sorry, Ken, but while "most people" use 1/2, that doesn't mean it's best. My tested Tri-X speed for LF and 35mm is 400, and I choose to goose it a little and use 320. That's good: I want as much speed in LF as I can get for the subject matter I typically hunt.

They're simple tests, whose psychological value (confidence in the materials) is well worth the effort. Exposure and development are mechanical, and should occupy as little of our brains as possible while guaranteeing good results.

[Flexnib]

Thanks, but will someone please answer the question asked?? I am trying to find out what my speed will be.

[IanG]

Once you've determined your speed as 75%, assuming your shooting the Tri-X 320 you just set your meter to 240 EI.
Ian

I thought that was the answer :D

240 EI - ASA

Ian

[Flexnib]

This may be the answer but since I do not know my EI. I am asking in the question above if this is how I should be doing the test to figure my EI out.

[IanG]

OK, sorry I thought Steve's article was quite good and explained it well, it's roughly how I did my Zone system speed tests about 20 years ago.

Maybe someone can post a link to a better explanation. Unfortunately it's not clear quite what you've done so far, so where your stuck.

Ian

[Steve Barber]

If I understand your question, you are trying to find a film speed for a Zone I density based on meter reading which gives a Zone V density. That is the reason for the four stop reduction. So, using the film's rated ASA, reduce the aperture 4 full stops. This gives you your initial setting for the first exposure. Then, open the aperture 1/3 stop for each exposure thereafter. This will start you with what would be a Zone I exposure at the rated ASA for the first one and an increase in the exposure for each succeeding one that will correspond to a decrease in the film rating of 1/3 stop for each one. A total of six will take you from an ASA of 400 to an ASA of 100, which should be enough. Start with a large enough aperture so you don't have to worry about reciprocity and remember to keep the camera focused at infinity so you don't have a bellows factor multiple to contend with. When developed, one negative should give the density you are looking for and that will indicate the film speed to use for that combination of film and equipment you used to make the exposure.

[Steve Barber]

Yes, I forgot you were starting with 320 not 400 film. If you are using 320 (TXP), use 400 anyway. It does not hurt to start a little high and it might help. Just ignore where I said "using the film's rated ASA" and use 400. If I am wrong and you are using something else, the idea is the same, just adjust the rating accordingly.

[Flexnib]

Thanks Steve,
So if i have it correct. Set meter ast 320 which gives me 1/30 at f/8 close down 4 stops to 1/30 at f/32 and then open up the aperture by thirds and take a shot each time. For a total of 6 shots. I am a little fuzzy on how this gives me shots from asa 400-100 but will take your word for it.
Thanks
Arthur

[Flexnib]

Steve,
First thanks and I will start at 400. So if my meter gives a reading of 1/30 af f/8 i would take the fist shot at 1/30 at f/32 then take the rest of the 5 shots each a 1/3 of a stop more open than the one before. I got this part but am fuzzy on how this goes from 400-100asa.
Arthur

[Steve Barber]

Steve,
First thanks and I will start at 400. So if my meter gives a reading of 1/30 af f/8 i would take the fist shot at 1/30 at f/32 then take the rest of the 5 shots each a 1/3 of a stop more open than the one before. I got this part but am fuzzy on how this goes from 400-100asa.
Arthur

Glad you asked. I forgot to count the first exposure and six will only get you to ASA 120, not ASA 100, if I remember the series correctly.

If you set your meter to ASA 400 and get 1/30 at f8, yes, reducing the aperture 4 full stops would give you the first exposure of 1/30 at f32. This will convert the meter reading that would have resulted in a negative density equivalent to Zone V to an exposure that will result in a negative density that should be the equivalent of Zone I, if the film rating is ASA 400. Opening the aperture by a third of a stop increases the exposure by the same amount as you would if you changed the film speed from ASA 400 to ASA 320. Another 1/3 of a stop takes you from 320 to 250 and the next to ASA 200 or one full stop from ASA 400. In other words, opening the aperture gives a greater exposure and is the equivalent of having used a slower ASA film speed when setting the meter. Six exposures would only get you to ASA 120, if I remember the series correctly--400, 320, 250, 200, 160, 120 and then, ASA 100 would be seven exposures. Since the probability that the film would rate at ASA 400 is not great, I would stay with six exposures and start with the film's rated speed at ASA 320. That way, six exposures will have you ending at the equivalent of ASA 100.

In other words, opening the aperture gives a greater exposure and is the equivalent of having used a slower ASA film speed when setting the meter.

Hope this helps.

[Flexnib]

Steve,
First thanks for all the help.
After reading your explanation I was able to use the Steve Simmons artical. It was almost exactly like the way you explained.
I started witha meter reading of- asa 400
100%-1/60 f/8 = 1/60 f/32 - asa400
75%-1/60 f/22 bet. 1/3 and 2/3 asa300
50%-1/60 f/22- asa 200
125%-1/60 f/32 1/3- asa 500
150%=1/60 f322/3- asa 600
Somewhat different than yours but if it works great if not I will do it exactly like your sugesstion. Right off the bat it looks like not enough of a spread.

Arthur

[Steve Barber]

Arthur,

I would suggest that using smaller increments for the ASA values in a range that is more probably where the answer lies and f stop settings that are a usable minimum (1/3 of a stop) will get you an answer quicker than using large increments for changes in the ASA rating and aperture settings that are so fine (<1/3 of a stop) as to be unusable. I think your rating will be somewhere, as someone else has already mentioned, near &#189; of Kodak’s ASA rating for the film.

I am not saying that what Mr. Simmons suggested is wrong, but he was presenting a more universal approach that will work without having to know what film a reader might be using. Since the parameters of what you are using are reasonably well known, you can cast a finer net and get a usable answer with less trials if you restrict the range of possible ratings to something from 320 to 100. If you use the schedule you have indicated, based on using even hundreds for the possible ratings, the three higher ratings, 400, 500 and 600 are probably a waste of film. The remaining two, 300 and 200, are within the probable range, but exclude the more probable result of something less than 200 and, in any event, are too far apart to give a usable result. In other words, using your schedule, I think you will end up with only two useful exposures and they will only give you an indication of what to try next, but not a rating that you can actually use.

Steve

[Flexnib]

Yes and thanks again

[Stephen Benskin]

Just to add some general information to the discussion. ISO speed point is only 3 1/3 stops below meter calibration point and not 4 as indicated by the Zone System. This is why most people find their film speeds to be approximately 1/2 stop slower when doing Zone System testing.

The 0.10 speed point in the ISO standard does not represent the desired aim point for shadow density. It is the speed point which means it is the point from which speed is calculated. The place where shadow exposure falls is actually in a different spot(s).

Has anyone ever wondered why ANSI changed their ASA method in 1960, where speed basically doubled, but the Zone System method has never changed? Before 1960, Zone System testing results would generally be close to the ASA film speed. After, not so much. One of the changes in the 1960 ASA standard eliminated a safety factor. They did this for a number of reasons which include the increased accuracy of meters, the increased use of meters, and the growing number of lenses that used anti-flare coatings. The other is to use a fixed density method to calculate film speed as opposed to the fractional gradient method. In the early 1940s, Loyd Jones at Kodak found the fractional gradient method was the most accurate method for the determination of film speed. While the most accurate method, it created some problems in the practice of testing film speeds. Jones, however, didn't compromise. The fractional gradient method was still more accurate than any fixed density method. What he did was to find a calculation that when used in conjunction with a fixed density method under certain contrast conditions closely approximates the results produced from the fractional gradient method. This is known as the Delta D Criterion. The scientific paper that was released concurrently with the ANSI standard states that as the Delta D method is really just a different way of calculating the fractional gradient method, it is only valid when testing under the parameters stated in the standard. Any testing for extended or contracted development couldn't rely on the fixed density point of 0.10 to determine film speed. It would require the application of an additional mathematical formula. The interesting thing is that if you use the fractional gradient method / Delta D method, film speed almost doesn't change with anything but extreme developmental changes. (Apug has an upload of the paper I've written on the Delta D Criterion.)

What does all of this say about Zone System speed testing? Well, the method is flawed. I've attached a jpg file of the camera image curve and film curve that illustrates the flaw. Still, by using the Zone System method for normal development speed determination, you are really just obtaining the pre-1960 speeds. So, it really doesn't hurt anything.

Two other things to consider. Flare plays a major roll in film speed. The statistical average flare is 1 1/3 stops. Flare affects the shadows at a greater rate that the highlights and consequently increases film speed by approximately one stop. This is calculated into the ISO standard. Changes in flare will change the EFS of the film. If the scene you are shooting has low flare, than the film speed will be slightly lower and conversely if the scene has high flare, the film speed will be slightly higher. Therefore, actual shooting conditions have to be taken into consideration when judging the "precision" of you testing results. Second and finally, any method of speed determination will yield acceptable results under most conditions. That's why a disposable cameras will produce good images even though there is a fixed shutter and f/stop. It's the extreme conditions that separates the best methods from the pack.

Just some fun facts.

Steve

[Stephen Benskin]

Correction:

Where it reads "Delta D", it should read "Delta X". Sorry for the typos.

[Flexnib]

Steve Barber,
I have completed the first 2 parts of the test the film shots and dev. plus finding my proof time for max black. When I plcaed the negs in the enlarger and made a print with my max black time and the one that come closest to the way Steve Simmons has explained is more like asa 500-600 Can this be possible? It seems from everything I have read it is most common to find that your personal EI is about half the rated film speed. I think I will test again and see if i get the same results. This time I will do a wider range and be more careful.
I will test in 1/3 from 320 down to 100 then 400 and 500 which will give me 8 sheets plus one blank I will fire with the lens hood on. I will use the blank sheet to find my proof max black time again.
Thanks again for the help.
Stephen B. thank you also for your time and help.

[Steve Barber]

Arthur,

Maybe, before you make more negatives, we need to think about the ones you have. When you printed the negatives; the prints would have been one half completely black (where the negative was covered by the dark slide) and the other half (where the film was uncovered during exposure), would have been less black. So, what you are saying is that, using an exposure that was the equivalent of what it would have been using a film speed of 500 or 600 ASA, you still got an exposure that printed less black than the unexposed half? This would mean that none of your prints would have had the same maximum black all the way across. Does that describe the prints you got?

Steve

[Ken Lee]

"In 1955 Tri-X had an ASA (ISO's predecessor) of 200. In 1965 it was 400. The film hadn't changed, just the official judgement of what the best exposure was." - Ctein, A Proposal to Redefine Digital ISO (http://theonlinephotographer.com/the_online_photographer/blog_index.html)

"They're simple tests, whose psychological value (confidence in the materials) is well worth the effort. Exposure and development are mechanical, and should occupy as little of our brains as possible while guaranteeing good results". - Bruce Barlow

I have always tested my film speed and developer times. It's comforting when the numbers agree with the manufacturers' (original) numbers, and with the the results of other testers. It gives confidence that the process is basically sound, that the water, thermometer, light meter, agitation, shutter, etc. are all... "normal".

[Steve Barber]

Ken,

I would appreciate you editing your post. I did not say what you are attributing to me.

Steve

[Ken Lee]

Hi Steve - Oops, I must have misunderstood. I certainly appreciate your contributions, and tried to quote you directly, as I did with Bruce's posting.

Please accept my sincere apology. I removed the reference entirely.

[Steve Barber]

Ken,

What bothered me was not that you might have misunderstood the comment or that you quoted the comment inaccurately. It was just the simple fact that I am not the one who posted the comment you were quoting.

Thank you for removing it.

Steve

[Ken Lee]

Oh ! It was Steve Benskin. :rolleyes: Oops !

Still, by using the Zone System method for normal development speed determination, you are really just obtaining the pre-1960 speeds. So, it really doesn't hurt anything. - Steve Benskin

[Flexnib]

Steve,
Yes one side of PRINT is completely black where the film slide covered the negative. And yes the exposed side of the film gives me different depths of black in the PRINT. So I have 5 prints each with a black side and a side which is "less" black. The PRINTS which were exposed in camera at 400asa and less, down to 200asa have one complete black side and one side a bit lighter than max black. The prints where the exposure was 500 and 600asa have one side comp. black and one side just bearly a little lighter. That what leads me to believe that my EI would be anywhere from 400asa to 600asa. Am I correct?
Arthur

[Steve Barber]

Arthur

Have you been using this film and equipment combination at the film's rated speed of 320 and getting what appeared to be normal exposures?

From what you are saying, your EI would be 600 or more. That is not a reasonable result. It indicates a full stop or more reduction in exposure from Kodak’s rating of 320, when you would expect to get something like a full stop increase in exposure. I wonder if there was some error in the settings for the exposures in the test series or if there is a problem with the equipment used to make them and, because of that, I suggest you try to be sure there is not some problem with the shutter and/or the meter before you re-shoot the series.

Steve

[Stephen Benskin]

Developing times may vary from person to person, but after all the testing has come and gone, most people shoot most b&w films at 1/2 the stated ISO.

This is more than a coincidence. It's probably due to the way that manufacturers determine their ISO or market their products.

It isn't a coincidence. It's because there are two different methods at work here - one is the ISO standard and the other is a common method used or inspired from basic Zone System testing.

I always find it arrogant when people claim the latter method as the way to find the "real" film speed or even "your personal" film speed especially since most of these people are unaware of reasons for the difference in the results. (not talking about anyone in particular here)

[Stephen Benskin]

Arthur,

I haven't read the article you are using, but it appears that you are using a just black approach. As a side note, according to the Fractional Gradient Method / Delta X Method, this approach won't give you very accurate results. Still, it will give you something that you can begin to work with.

Anyway, first did you include exposures for the 640 EI range? Second, how are you determining your contrast / processing? If you are over processing, the shadow density will be higher which will result in a suggested higher EI. Third, I assume you didn't change the shutter speed setting, and in any case it shouldn't result in a one stop variation. The best bet for any inconsistency is in either your note taking or interpreting the initial exposure.

Steve