Personal Exposure Speed Testing - Folks still doing this?

I speed test my shutters, but generally not my film. I take notes on film, and if I run into a consistent problem, I'll make the appropriate corrections. But most of the time I don't have a problem shooting film at box speeds.

I will, however, speed test expired film.

Sirius Glass said:

Just shoot box speed unless you really have a good reason to do otherwise. Then fix the way you use a light meter or get your equipment fixed and you will find out that you did not have a good reason, only an excuse.

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Andrew O'Neill said:

This doesn't make any sense.

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Yes it does. Sixty years of experience proves it.

Kawaiithulhu said:

Makes perfect sense. Films are rated against a set standard and if a film isn't working out for you personally it's nice to know why instead of just throwing a blanket statement out that everyone is lying and all films are really slow.

Like Ian said, chemistry has a great effect on speed. Light meters have different spectral sensitivities, metering technique, light flare, mechanical shutters vary, F-stops are close but not directly correlated with light transmission (which is T-stops), and so on with a laundry list of items that can be controlled for not related to the film itself.

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Eat your heart out Andrew.

i do whenever i start a new film/developer combo. Over the last 45 years of doing darkroom work, I have found that the rated film speed by the manufacturer is always pretty darn close to being on the money unless I have screwed something up.Im really not testing the film, as much I am testing my process.

weasel said:

i do whenever i start a new film/developer combo. Over the last 45 years of doing darkroom work, I have found that the rated film speed by the manufacturer is always pretty darn close to being on the money unless I have screwed something up.Im really not testing the film, as much I am testing my process.

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That is because the manufacture has done more and better film speed research than you could ever do.

I do it, but not to the pedantic nirvana described by some. I buy a 100' roll of film, shoot it in various cameras under various lighting, over-expose it, under-expose it, push it, pull it, and generally get a feel for where I want to be with that film. Then I buy 20 rolls of 120 and shoot it in various cameras, attempting to produce particular looks via exposure & development. Then I buy a 25-sheet box of 5x7 and feel like a complete beginner all over again. Then I try another 100' roll of film. The pedantic way is much faster and cheaper, but I get to shoot a lot of film.

Life is too short for so much fuss and bother. Photography is, has always been, should be about going out and shooting film.

To keep everything as simple and uncomplicated as possible, consider the following. I've used these with great success for the past 50 years.

If you must test a black-and-white film, load a camera with film, shoot off five exposures - normal exposure, - half stop, - one stop, + half stop, + one stop. Take the camera to your darkroom or put into a changing bag, cut the film, load the exposed part into a developing tank, process for NORMAL developing time at normal temperature. Check results. You will see everything you need to know about the film and exposure,and you still have most of the roll to shoot on subjects you want to record on film. Using ISO 100 film, you have just tested from ISO 50 to ISO 200. Easy. Simple.

Ditto testing a camera. Load with film (either black-and-white or color negative will do for this test), put it on a tripod, meter and expose for normal setting, then vary up/down, adjusting both the speed settings and f/stop (= 1 second at f/22,1/2 second at f/16, 1/4 setting at f/11,and so on). If your speeds are correctly set up, every negative on the roll when processed should be equally exposed. No variations at all.

Without a darkroom or a processing tank, well you are a bit up the creek and paddleless then, aren't you? nd sheet film, well. Running almost any test on eight by ten film is a sure road to the bankruptcy court.

End of story. KISS.

If you are not sure of your shutter speeds, there are a few ways to test them. I’ve tried all three of these on one camera: 1. Electronic timer 2. Shoot a spinning object and measure the degrees of rotation. 3. Shoot a gray target and measure the deviation (in densitometer measurements) from the expected.

The third way was best at estimating the highest shutter speeds. The high shutter speeds are where I run into the most “accidental overexposure” situations.

After I did that test the mainspring snapped. I haven’t tested since I fixed the spring because of the trouble (the wind knocked out of sails syndrome)

Shooting 400 speed film outdoors in daylight puts me in a bind sometimes, because I might need f/16 at 1/250 for my preferred exposure.

When I tested a roll of (known bad batch) 120 film the other day I aimed at the foggy sky and with a 2 stop ND filter, shot at a variety of f/stops at 1/100 and found the shutter was about 1/60 - the worst part was the density varied shot to shot, which means the spring was relaxing as I used it.

I think with your Bronica you could expect more reliable shutter speeds, but it may help to get it checked out. Don’t need a darkroom for that, your Scanner-as-densitometer might be useful to check the negs you get back from the lab

I test... a lot... too much probably, but it likely comes from the fact that I come from a scientific background.

And speaking of film testing, ASA, ISO, film speed, zone system, and the like, I wonder if a little about the history of film speed might help explain the differences that many people see between box speed and film test results. It is my understanding that many decades ago film speed ratings had a one stop "safety factor" built in. Eventually the manufacturers decided to eliminate the safety factor, and magically film speeds doubled, though the films themselves did not actually change.

If we make the hypothesis that film testing by the zone system more or less matched the old film speed standard then voila, we see that film speeds determined by zone system testing will be about one stop slower than box speed. Does this sound plausible?

By the way, here is how I determine film speed. Once I have found the development time that gives the "right" slope on the log(exposure) vs. density curve I pick the point on the curve corresponding to 0.1 density units above base plus fog, which, by the way, isn't always easy to do, given the noise in the measurements. Then I count four stops over, and that is the exposure corresponding to the personal film speed.

Actually, what I described above is a kind of sanitized version of what I do which is to meter a blank wall using different iso settings on the meter. Then, instead of using different log(exposure) values for the x-axis I use the negative of log(iso) values for the x-axis. That way, when I count over four stops on the x-axis (i.e. ~0.3 units per stop). The corresponding point on the x-axis comes out directly as my personal speed. It's equivalent to what is described in the first paragraph, but it's a little easier to understand.

Is that how the rest of you do it?

A related question, since there are several ways of determining slope, and several opinions of what is the "correct" value for the slope, what slope on the curve to you specify as the "correct" slope, and exactly how do you determine the slope to use? For example, do you use contrast index as defined by Kodak for the slope, or perhaps Gbar as defined by Ilford?

alanrockwood said:

And speaking of film testing, ASA, ISO, film speed, zone system, and the like, I wonder if a little about the history of film speed might help explain the differences that many people see between box speed and film test results. It is my understanding that many decades ago film speed ratings had a one stop "safety factor" built in. Eventually the manufacturers decided to eliminate the safety factor, and magically film speeds doubled, though the films themselves did not actually change.

If we make the hypothesis that film testing by the zone system more or less matched the old film speed standard then voila, we see that film speeds determined by zone system testing will be about one stop slower than box speed. Does this sound plausible?

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It's a hypotheses worth exploring.

I don't know if there are a lot of opinions about what people found for their film speed when they did Zone System tests during the time when ASA had a higher safety factor. I don't think people used to say "hey I'm getting the same speed either way so why bother testing"...

I think it's plausible that Zone System film speeds didn't change from whatever they were.

And only more recently discussions about the "hey I'm getting half box speed" came to light.

alanrockwood said:

Is that how the rest of you do it?

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With my scientific and engineering background I leave the one exposure margin as margin, I leave latitude of exposure to capture the detail, I shoot box speed, and spend my life enjoying life rather than waste it on endless testing that the manufacturer already thoroughly conducted.

ISO speed calculations are based on work founded on "best print" observations. Those prints are/were un-manipulated, straight prints that a commercial lab might make using a machine printer.
The subjective appreciation of prints tends to be strongly related to how mid-tones and highlights are rendered.
Zone System speed calculations are based on shadow densities primarily. Many who use the Zone System are open to burning and dodging.
IIRC, the actual technical requirements of the two different standards include an inherent 2/3 of a stop difference.

Sirius Glass said:

Yes it does. Sixty years of experience proves it.



Eat your heart out Andrew.

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MattKing said:

ISO speed calculations are based on work founded on "best print" observations. Those prints are/were un-manipulated, straight prints that a commercial lab might make using a machine printer.
The subjective appreciation of prints tends to be strongly related to how mid-tones and highlights are rendered.
Zone System speed calculations are based on shadow densities primarily. Many who use the Zone System are open to burning and dodging.
IIRC, the actual technical requirements of the two different standards include an inherent 2/3 of a stop difference.

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Yes. It would be 2/3 of a stop if both were developed to the same contrast, but Zone System develops slightly less for N (normal) than ASA/ISO so that increases the difference. I haven’t figured whether it’s 5/6 of a stop or a full stop.

MattKing said:

ISO speed calculations are based on work founded on "best print" observations. Those prints are/were un-manipulated, straight prints that a commercial lab might make using a machine printer.
The subjective appreciation of prints tends to be strongly related to how mid-tones and highlights are rendered.
Zone System speed calculations are based on shadow densities primarily. Many who use the Zone System are open to burning and dodging.
IIRC, the actual technical requirements of the two different standards include an inherent 2/3 of a stop difference.

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When film had a narrower latitude the Zone System helped as stated. However now that modern negative films have a much greater latitude one can use burning and dodging without the rigorous testing and experimentation needed in the past.

I am no saying that the Zone System does not have uses in the present day. The Zone System can be used to determine the best exposure when the lighting situations are difficult to get optimal or near optical readings. Example, see the thread on determining the exposure for Hawaiian lava flows at night from a boat.

I worked directly from the film curves and my metering today. Then I picked a developing time that would give me the density I wanted for the spot I metered.

It's all still relevant and it all still works.

My purpose in contrasting the two (Zone and ISO) speed approaches was in essence to respond to those who seem to think that ASA/ISO speeds are somehow "inflated". They are not and were not in the past.
They just measured the film's response in relation to different criteria than the criteria used by many Zone system practitioners. Both (all three?) sets of criteria are very useful, and lead to excellent results. One set of results may be preferred in some circumstances, while other sets may very well be preferred in other circumstances.

MattKing said:

My purpose in contrasting the two (Zone and ISO) speed approaches was in essence to respond to those who seem to think that ASA/ISO speeds are somehow "inflated". They are not and were not in the past.
They just measured the film's response in relation to different criteria than the criteria used by many Zone system practitioners. Both (all three?) sets of criteria are very useful, and lead to excellent results. One set of results may be preferred in some circumstances, while other sets may very well be preferred in other circumstances.

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Matt, the original ASA criteria added an extra safety margin of exposure actually a stop, this was removed in the early 1960's. The current ISO system is a combination of the ASA/BS and DIN systems technically the films can be tested by either of the two methods. The US ASA system and corresponding British BS system used testing that was laboratory based and had little relation to practical use, the DIN testing was far more practical.

With the introduction of Tmax films and their inability to reach the box speeds (in the then ASA tests) Kodak lobbied to have the ASA testing criteria changed to a more practical system. These days both Kodak and Ilford do more practical film tests they don't tell us exactly how though.

Sirius Glass said:

When film had a narrower latitude the Zone System helped as stated. However now that modern negative films have a much greater latitude one can use burning and dodging without the rigorous testing and experimentation needed in the past.

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Older films like Verichrome Pan and Selochrome Pan had a much wider latitude which was why they were the amateur films of choice in a range of relatively simple cameras with little exposure control.

There's a myth that current B&W films have more latitude than they used to, in the years I've been using Ilford films (about 50 years) there;s been no changes in that respect. I cut my teeth on ex British Government (military) surplus FP3 and HP3 and use Ilford films today. Tmax films and to some extent Delta have slightly less latitude compared to conventional grain films.

Sirius Glass said:

I am no saying that the Zone System does not have uses in the present day. The Zone System can be used to determine the best exposure when the lighting situations are difficult to get optimal or near optical readings. Example, see the thread on determining the exposure for Hawaiian lava flows at night from a boat.

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Some testing Zone or other is beneficial to obtain the optimal balance of Film speed and Development time regardless of whether the lighting is difficult, this is particularly important with 35mm and 120 films where there maybe differing lighting situations and contrast.. This a fundamental principle of the Zone system, but is not exclusive to it and there are other ways of obtaining a personal EI and dev time for different film/developer combinations.

Bill Burk said:

I worked directly from the film curves and my metering today. Then I picked a developing time that would give me the density I wanted for the spot I metered.

It's all still relevant and it all still works.

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Bill, I think what's not understood is why we use our control systems and not necessarily the manufacturers recommended ISO/Dev times. It's just fine tuning to get the best results, something that can help lift above the mediocre. It's craft learning to use controls prperly.

Ian