finding film speed?

[Mark_3632]

To stop the smart asses among us I know the film speed is printed on the box.

Can someone please explain how to find the actual film speed. I thought I had a handle on it but as I read more I am definately not getting it. How can a developer increase a film's exposure speed? How can BPF 200 go from Ei200 to EI320(as I read in a post on photo.n#$)in rollo pyro? As I am finding out quickly with an increase in format the increase in cost is pretty much proportional.

This is what I understand. Posted film speed is a starting point and, like exposure, dictates the amount of lite needed to record the average light intensity. slower speed equals denser neg, higher speed equals thinner neg.

Anyone shoot BPF 200, and what speed do you use?

[Bruce Watson]

Two suggested readings:

Adams' The Negative

Anchell and Troop's The Film Development Cookbook.

The first one defines how to perform a film speed test. The second one tells you how various developers effect film speed, among other things.

The thing to understand is that film speed isn't a constant. It depends on lots of factors, including the developer you use and your processing method. That's why you have to "calibrate" your process, which is what finding your personal exposure index (EI) is all about.

[David A. Goldfarb]

The zone system approach is to test what exposure gives you a density value of 0.1 at Zone I and use that as your starting personal film speed.

Then (after establishing development times) you might evaluate the kind of shadow detail you are getting in your prints, and you might make further adjustments. If the film's characteristic curve has a long toe, for instance, you might decide that a little more exposure gives you better shadow detail without sacrificing highlight detail, so you might lower your EI from the tested speed with that film as a general practice.

If you don't have access to a densitometer, then you might just look at your negatives on a light table and see whether they have the detail that you want in the shadows. If not, try lowering the EI, and check your prints to see that the highlights aren't getting washed out. If your shadows are okay, but you want thinner negs with finer grain, try raising the EI and see if the shadows hold.

[John Cook]

Mark, you have just received two excellent brief summaries. If you require the lengthy step-by-step details, email me and I’ll send you complete instructions on testing from my old Kodak manuals. Not too difficult, but too lengthy to fit in a simple forum post.

[Tim Curry]

Get a copy of Fred Picker's "Zone VI Workshop." He gives simple, easy to understand directions for film testing with a minimum for fuss and confusing terminology. Here is the short answer to your question.

Basically, run a series of test exposures with a white wall as your subject. Place your shots on zone 1 as you would meter the wall (not zone 5). Vary the exposure with each shot (asa), but keep track of the film speed as you do. For example: Film is rated at 100 from the factory, but you may run from asa 25 up to asa 200. Develop all film for recommended time with your developer of choice.

Next, print all film. Use the unexposed film edge to print a maximum black for the minimum time necessary as your guide. Ignore the exposed portion of the film until you have a maximum black. This would represent film base plus fog, or true black. The film which shows the first hint of lightening above this film base plus fog is what you want with this print exposure. This would correspond to zone 1, which was your shot placement with the given asa rating for the film.

Repeat the test now using this asa rating to develop for zone 8. Place a white wall with some texture on zone 8 and develop until you have a true zone 8 value.

Different developers act with different characteristics. Pyrocat HD tends to give "normal" speeds. PMK pyro usually reduces film speed by one stop. ABC pyro tends to reduce film speed by 2 stops.

[Rob_3836]

To clarify, the Zone 1 density value shouldn't just be 0.1, but "0.1 above film base plus fog".

So first, you would need to use a densitometer to find out the film base plus fog on an unexposed negative. Assuming film base plus fog on the unexposed negative was .1, the proper EI (personal film speed) would be the one used to produce a Zone 1 exposure that resulted in a densitometer reading of 0.2

In addition to the books recommended above, I would recommend Picker's Zone VI workshop book, which I still consider to be the most concise explanation of the Zone System and its testing procedures.

[Bill_1856]

I rate BPF200 at EI=100 developed in Xtol. Just expose for the shadows and develop for the highlights, like they've said for 125 years. If your negatives don't have enough shadow detail, then increase exposure by 1/2 stop until they do have. If negative areas that should be totally clear are light gray, decrease exposure by 1/2 stop until the negative is virtually clear. Then adjust the development to print on #2 or #3 paper without blown-out light areas. Piece of cake. Have fun.

[Kevin Crisp]

Mark: I also think Picker's book is the place to start. Different meters and processing techniques give you different numbers, you have to find your speed by testing.

[Mark_3632]

Thanks for the info but how does a developer increase or decrease film speed?

Maybe I am just panicking over the idea of a new learning curve for making Pd and kallitype ready negs.

[William Blunt]

Mark, You just threw in another variable, Pd and Kallitype negs. These negs will need a longer scale to fit the process so you will need to extend development to get there. When you do this you will need to give less exposure because when you extend dev. you will gain some density in the thin areas of the neg. which only makes for long exposure times. One way of giving less exposure is to use a higher film speed on your meter. Good luck, it makes more sense once you use it for awhile.

[David A. Goldfarb]

Not all developers develop thin areas and dense areas of the negative at the same rate. In addition, the rate at which dense areas are developed with respect to the rate at which thin areas are developed can be controlled by agitation. Think of the principle behind stand development (no agitation, long dev. time) to reduce contrast--the developer molecules that are adjacent to dense (highlight) areas are quickly exhausted, while the developer molecules in the thin (shadow) areas continue to act, bringing the shadows up and holding the highlights back to bring a neg of a contrasty scene into printable range. Now if a developer, by virtue of its chemical formula, can allow Zone I density reach 0.1 over base + fog density faster than another developer formula without letting the highlights getting out of hand, then it can produce a real film speed increase while maintaining normal contrast. Developers like Acufine, Diafine, and others act this way.



You don't really need to worry about this though, for what you're doing. You just need to know the film speed that results from your particular developer/film combination.

[Robert C. McColloch]

Picker is THE simple answer on how to determine personal film speed. A densitometer is NOT needed.

[Brian Ellis]

I second the suggestion to read Picker's book. A few quibbles with what's been posted so far. I wouldn't use a white wall, in theory it shouldn't matter but I think it's best to avoid the extremes when testing so I wouldn't use white or black. Also many walls are textured and you want whatever you're photographing to be smooth, not textured. I've used a gray card several times, also have used the smooth side of a cardboard box (with no writing on it of course). For your first exposure try to select a shutter speed that will allow you to stop down four stops at each of the film speeds you'll be trying without having to change the shutter speed in the middle of the tests. Also, you need to plan it all out ahead of time and do a few dry runs first because you usually have to move fast because the light has a tendency to change if you spend much time doing the tests and if that happens the test is no good, the light has to be exactly the same for all the different film speeds you try.

It isn't absolutely necessary to have a densitometer but it sure does help. If you don't have access to a densitometer I'd suggest letting The View Camera Store do the exposure and development times testing for you. I've used them several times and have been very pleased. You get much more information than you're likely to obtain on your own and the cost is only about $30, not much more than you'll likely spend on film by the time you finish with both the film speed and development times testing plus you'll have saved a lot of time and aggravation. The thing that finally drove me to stop doing it myself was when I kept getting a different base plus fog readings when doing my development tests than I was getting when doing the film speed tests. Between that and the changing light I think I went through a box of film trying to do the final series of tests that I did on my own and was never confident that I got it right.

[Jorge Gasteazoro]

:-) seems nobody is really answering your question so I will give it a shot.

A developer does not change the exposure index (EI) of the film. It mostly has to do with the way the film speed tests are done under ISO standards. For example Kodak, Ilford etc, have labs where all their instruments are calibrated under ISO, that is light intensity, metering, thermometers, timers, agitations times, agitation machines etc, etc. When they conduct a film speed test under these tight conditions they obtain a specific film speed.

Now then we come to you and your darkroom, you have a thermometer which I am sure is not calibrated, you have a meter which might, or might not be calibrated to ISO standards, etc. When you do your test all these factors add up to give you a different film speed, there is nothing wrong with this if the negatives you are getting are what you are looking for and you can consistently obtain these result. So this could be one reason for a different film speed.

OTOH perhaps you have heard of changing the EI when you do expansion (develop the film for longer time) or contraction (develop the film for shorter time) this has nothing to do with the developer being more or less energetic or changing the speed of the film, it simply has to do with the inherent contrast of the film. When you do a contraction, you have a scene which has a high contrast, and you are trying to "fit" all those tones in the film. Now when you develop, the developer has little effect on the shadows or "thin" parts of the film, no matter how much more you leave the film in the developer this parts of the negative will stay essentially the same, but do vary a little bit. So then when you are trying to fit a high contrast scene into the film if you develop for less time then those thin parts of the negative are more affected than the rest so you have to give them more exposure to counteract the lesser development time. In essence you are adjusting the contrast of the film.The easiest way to do this is to change the EI to a smaller number. The opposite also holds true for more development, since you are going to put the negative in the developer for longer time, you want the shadows not to overdevelop so give the film less exposure. This is done by changing the EI to a higher number.

These two are the reasons why YOUR film speed and the manufacturer's film speed are different.

If you really want to learn how to do testing correctly buy and read the BTZS book. It is a hard read, but the methodology once you get the hang of it is far simpler than the zone system.

As to the Picker book I am in the opposite camp, easier is not always better and in the case of the "minimum time for maximum black" test I find this a flawed test which does not really offer good information. If you want to learn how to make black prints, then use it, otherwise use a better method.

[Rob_3836]

"As to the Picker book I am in the opposite camp, easier is not always better and in the case of the "minimum time for maximum black" test I find this a flawed test which does not really offer good information."

I would like to hear some elaboration on this point.

Why is the minimum time for maximum black test flawed?

[Jorge Gasteazoro]

I would like to hear some elaboration on this point.

Why is the minimum time for maximum black test flawed?



IMO Rob it is a matter of percentages. Regardless of how careful you are when developing there are always small variations that take place. So for example, sometimes your b+f can be 0.08, sometimes it can be 0.11, a difference of 0.03 is no big deal unless you are doing your printing test based on a density of 0.1 over b+f. Then a difference of 0.03 is about 30% of the exposure. To me this is unacceptable. I have always said that a "standard" printing time should be based on a Zone V negative. You take a Zone V neg and make a print that has the same tone of the gray card. This has a few advantages:



1. Most manufacturers have grades 1, 2 and 3 with pretty close speeds, if you make your standard printing time based on Zone V then this printing time will apply to all these grades, or at least it will be so close that for all practical purposes you have an accurate first reference. Not so for the max black test, you have to test printing time for each grade. BTW I have verified this and done it as well as plot the curves, it is not something I am speculating about.



2. As stated before a difference in b+f of 0.03 can be as much as 30% of the exposure when using 0.1, the same difference when using a negative that has a density of 0.65 is about 0.5%, for all practical purposes this difference is insignificant.



3. A standard printing time based on a Zone V neg will apply with the same paper to most developer film combinations you might wish to try, thus giving you useful information. Again this is due to the percentage error, even if you have a variation in b+f as high as .05 or .08, this is still a small percentage of error that can easily be adjusted, not so with the max black test, if you change film or developer you have to do the test all over again, even if you are using the same paper.



So as you see, making the standard printing time based on a zone V negative gives you plenty of useful information. You can see how your print varies if you change contrast, you can easily adjust the time to a different film/developer combination and you avoid or minimize processing variations, these qualities are not present in the max black test, and of course all this without a densitometer.



Personally I hate testing, this is why I strived to learn how to do it right from the beginning, so I just have to do it once with repeatable, accurate results. IMO recommending Picker's method to a beginner is leading them down the wrong path.

[Mark_3632]

Brian

In terms of time available to me, and cost of materials, plus I do not have a densitometer 30$ sounds very affordable. I looked at the View Camera Store web site and cannot find the information. Of course I will contact them about it but I want a bit more info from you if you do not mind. What all did you need to send them and what was the turn around like.

William Great, one more variable to figure out. Hmmm... ---------------------------------- Damn it. I just want to go shooting. all of this thinking hurts. Anyone know of an autoeverything 5x7:)

[phil sweeney]

Mark, I think you should read the negative. But you do not need to do all that and I would not recommend doing all that stuff through the view camera store. I have used the zone system with good results. 0.1 over fb+f works for most films and developers but as Jorge points out there are problems. I have used a zone board for HC110, PMK, ABC and pyrocatHD (its just one method!). Those tests, result in a good speed for each except pyrocat. The zone board indicates at 0.1 over fb+f a speed 1/2 needed for pyrocat (i.e., overexposed). All photographers should be able to figure a "normal" speed with 3 negatives (and proof) and a developing time with 3 more. Most important one should be able to visually analyze a negative and see if the shadow densities are correct as others have stated! I have not used bergger film but if you are going to do pt/pd etc maybe you plan on using pyrocat. Great developer, good speed and probably for the bergger would rate at 200. I recently proved a speed for photowarehouse film in pyrocat with 1 negative. Its rated 125 and having experience with pyrocat I knew it should do well at the rating. I cheated using development by inspection.

[Rob_3836]

Jorge-

You do have some valid and interesting points regarding printing time being based on a zone V negative.

However, I do question your contention regarding the variances in fb+f readings. It appears that you are basing this on the allegation that "Regardless of how careful you are when developing there are always small variations that take place". While I have no doubt that small differences can take place, I would certainly think that these variances would be insignificant if you are careful to use the exact same temp., developer dilution, development time and agitation regime.

If this is done, I would be VERY surprised to see any significant differences in the fb+f readings. If there are, there is a problem with consistency in the development method somewhere in the chain.

When I did my testing, I did it with two unexposed sheets of film, each developed seperately (but consistenly). They both had the same fb+f reading.

Was this not the case for you?

[Jorge Gasteazoro]

If this is done, I would be VERY surprised to see any significant differences in the fb+f readings

This is exactly my point, what is significant?, and in relation to what?



I use a staining developer with many different times to adjust the CI, or G bar as we call it, and with this a variation in b+f is normal. Before I used Tmx RS and there was little if any change, but as I said, a .01 change is 10% of the exposure in your test. Also, two sheets do not a make a comprehensive sample, are you sure every time you make a neg this is your result? A proper testing procedure should always provide you with repeatable information and minimize the possibility of error where they can occur. Also, if you do contraction or expansion of the film to fit your paper you will get a different b+f regardless of how careful you are it is just the behavior of film, if you develop you film for 5 more min to increase your contrast, you will increase your b+f and once again the max black test is prone to a high degree of error.
Look, lets say you are correct and every time you develop a sheet of film you obtain 0.08 b+f regardless of development time etc, I am willing to accept this. Tell me then, what other information can you gather from your test? Can you change paper contrast and get useful information about the negative? Can you change film/developer combo and obtain useful information about the behavior of the film without a densitometer? You cannot with the max black test, but you can with the way I propose you do it.
I always thought that a test is designed to provide you with useful information under a wide range of circumstances. I find amusing that those who propose the max black test they do so because they "hate testing" yet they find themselves repeating this test more often than those who do it right from the start. If you have settled in a film/developer combo (which BTW is what I recommend to people who are starting until they have mastered it) then this is not a problem, you do your test and move on, but if you ever want to try anything new...well then as Reagan used to say "there you go again". :-))



Look, in the end I am not trying to prove that Picker is wrong and I am right, if you like the max black test then stick with it, some people with many years of experience like Steve Simmons swear by this test. IMO it is not a good test but that is only my opinion.

[Mark_3632]

You folks have given me a lot to think about. Thanks.

In the tests mentioned it sounds like I need a densitometer. Something that is not in the future for me.

Phil:

"I have used a zone board for HC110, PMK, ABC and pyrocatHD (its just one method!)"

I do not understand this. Do you mean that the Zone Board is one method of testing?

[Rob_3836]

""This is exactly my point, what is significant?, and in relation to what?""

Well, perhaps I should have stated it differently. I would be surprised to see ANY change in the fb+f readings if care is taken to duplicate the development regime.

As far as what is significant, the fact that Picker says a reading ".08 to .10 above film base plus fog" is the proper film speed for a zone 1 negative tells me that a difference as high as .02 is fairly insignificant.

I still don't really see the problem, as you stated yourself that when you were using Tmx RS developer you saw little or no change in the readings.

That being said, your points regarding the changing of film etc. requiring a new slew of tests is a valid one. But wouldn't this still be the case with your method?

Enjoying the discussion....

[Jorge Gasteazoro]

As far as what is significant, the fact that Picker says a reading ".08 to .10 above film base plus fog" is the proper film speed for a zone 1 negative tells me that a difference as high as .02 is fairly insignificant



I disagree with this Rob, .02 might be insignificant if you have a density of .65, if you have a total density of .2 it is still 10% error. But remember since you are trying to match the Zone I (.1) to the clear part of the film your exposure is based only on .1 not .18 or .2 , so then .02 is 20% of your exposure. I have no idea how to express it better without showing you pictures, I hope this is clear.



With Tmx RS I saw no changes for "normal" development, but I did see great changes for expanded developing, b+f went from .09 to as much as .14
if I was using the max black test I would have an error of 50%.



As to my film testing, since it does not rely on the paper to make a judgement you are correct, I have to make a test for every film/developer combo, but the difference is that since I know the exposure scale of my paper I fit all my film developing to fit the paper's curve which results in not having to make any more paper tests. For example I know that if I have a negative that has a density range of 1.28 that it will print well using developer solution #2 exposed at 500 units of light in my Nu arc ( I am talking about pt/pd here, since it has been years since I have done silver printing) I dont have to do test strip, etc. I just put the paper under the light, dial 500 and I have a print that has all the useful information I need, from there I concentrate on contrast changes etc, but there have been times when I expose the print and it comes out perfect on the first try, and this is the goal of appropriate testing, to get as close as you can to a perfect exposure without much waste, this is specially relevant with pt/pd, which is not cheap, a failing I find enlarging paper has, if you had to pay $3 per sheet of paper, I bet you would have learned how to control your materials better by now.



But I digress, look my point is, that if you plan to use the paper as a tool to judge the negative development, then the paper should be a fixed constant that is capable of "absorbing" small variations, and the max black test does not do this.



I hesitated to write this down in the previous response in fear of sounding condescending, but lets "walk" through an example.



Suppose you try a new film/developer combo, and you have made your standard printing time based on a Zone V neg. From experience I know that grades 1, 2 and 3 will have very close exposures, and this is important to be able to judge film development. So then you develop your film, you put in the enlarger and you make your test print with paper grade 2 at the Zone V printing time. The resulting print is too contrasty, at this moment you have already gathered two important pieces of information. You now know you either developed the film too much, or that your negative density range fits better a paper of lower grade. You then change the paper to grade 1 and expose for the same Zone V time, your print comes out better, with good highlights and still nice dark tones. At this point you have two choices, you can keep the same development time and just print on paper grade 1 or reduce the development time to print on grade two. Notice however that I said this is a new film/developer combo, yet you still are using the paper printing times of your old combo, you dont need to make a new Zone V test for the new combination since small variations wont make a difference when exposing the paper. Furthermore, depending on how light was the print on the first exposure you can guesstime how much time to reduce the film development.



All of this is not available in the max black test, if you expose your new combo to a new max black test, (the old one does not work anymore because of the b+f thing). you still dont know if the information given on the print is due to too much development, what happens if your film has a short toe and zone I is fine but then the following zones jump up?



I am almost sure that this has happened to you, you make your max black test and your print does not look right, you then change paper contrast (make a new max black test) and still it does not look right, you then wonder if all that was required in the first test was more/less exposure, or if the second test needs more/less exposure and you still have no information about the negative development itself. You then proceed to make test strip on the paper, I wonder, why make the max black test if you still have to make test strips?



To compound on all these objections, what if your Zone I is .15 or .19 over b+f? Rarely have I seen a film test where the film comes at exactly .1 over b+f, So far we have assumed that you are getting a perfect result, but this is not the case in real life, at least not in my expereince.



IMO this is no way to work, or at least I could not work like this. I just cant see how the max black test can give any useful information other than how to make a nice black print.

[David A. Goldfarb]

Mark: For a description of the Zone board, see Gordon Hutchings' _The Book of Pyro_.

It's a simple and ingenious concept. The idea is that you have a light colored board, maybe 6 or 8 feet long, with a lamp at the top aimed downward. There are labels from I to X with arrows running along the long side. Place Zone I somewhere at the greatest distance from the lamp, and then use a spot meter to find where the other zones are, and label them as such (II, III, etc.). Photograph it, take notes on exposure, and you can use it for speed and development tests and to plot film curves.

You don't even need to build anything to use it. If you've got a light stand or a convenient way of mounting a lamp in this manner, you could use a light-colored wall and Post-It notes with the zone values written in thick marker as a Zone board.

Things to be careful of with this approach--don't use a wide lens for the test, or your results will be confused by falloff of illumination at the edge of the image circle. The camera should be far enough away so that bellows factor doesn't enter in if possible. Also use a bright enough lamp so that reciprocity isn't a factor for the test.