Film speed test in winter

AndreasT · Jan 16, 2013

I have enlarged hundreds of photo for people. Artists and Photographer. Most od them use box speed. The results are aweful. So much trying to get a decent print. I lot of people do not change their exposure or development with thought according to the lighting situations.
Basically I use a similar method used by Phil Davis in exposing film under an enlarger. Develop five or more testa at differnt times and plot them. I use a more contrasty "standard" to Phil Davis since I find his reults to soft to be practical.
My aim is to fit my negatives to a Paper contrast of 1.05. As mentioned I usually increase my devolpment because of the use of unsharp masks. If I desire I do change my exposure according to what I want or need.
Have to go dinner is being served. I will get back to this later.

Chuck_P · Jan 16, 2013

Michael R 1974 said:
Well, the first thing I'd recommend to anybody using any kind of Zone System testing methodology is to produce a full curve, not just target a Zone I and Zone VIII density. To me, everything is about contrast - ie the shape of the entire curve since I am ultimately concerned with printing.

As I've said, the speed point is a means to an end. I'm concerned with local contrast.

But even when contrast is considered in Zone System testing, there should be a lot more discussion about local contrast (ie not just CI or Gamma) and the paper curve. After all, how many people come away from Zone System contraction methods (including extreme contractions) thinking N-4 necessarily means Zone XII will print with good detail because it has a Zone VIII density in the negative?

But I'm getting ahead of the discussion there. We've sort of disagreed regarding the practical use of measures like CI in the past - mostly because I am typically dealing with significantly wider subject brightness ranges than average.

I agree that producing a full curve is essential, especially since in the ZS, knowing the CI is not a relevant consideration for anything ......the films response to development is relevant along the entirety of the curve, not just by points on the curve connected by a straight line. Not to diminish CI, only that the specific value of CI has no inherent significance in the primary function of the ZS, which, as stated in The Negative, is to support visualization.

I disagree on the extreme contractions statement, shadows can be given added exposure with the "placement", and compensation development used to support that added density in the low values while keeping good separation at the important higher values. I have only accomplished an N-3 contraction, but I have indeed accomplished it through highly dilute developer with hc-110 and reduced agitation, with TMX, albeit at a loss of film speed at EI 50. The preferred neg density range was effectively maintained. But perhaps I'm just misreading your intent on it.

Chuck_P · Jan 16, 2013

Michael R 1974 said:
My point regarding extreme contractions is that one must be aware of the shape of the full curve under these exposure/development conditions.

And I agree.

Only, I can tell you with certainty that when I expose for a particular scene's important high luminance value and then plan development for it, there are no assumptions involved.

AndreasT · Jan 17, 2013

Most negatives which I have gotten to enlarge from others were underexposed and over developed. For me underexposed means simply put, using the wrong ISO rating. Of course metering etc. comes into that. It also relates to how the manufacturer gets this ISO rating and what it means. As I understand it and I may be wrong here but the rating correlates to a contrast of 1,5 am i wrong here? or me that is an overcast day in winter. Not a sunny day when many people take their cameras and run on the streets.

I aggre to the comments of Michael about local contrast. That is too often ignored. One shouldn't just totally fit the development to fit to the paper contrast. If the scene is contrasty it should be kept that way. Here we come to dodging and burning.
I would say that if one tests his stuff one will realize after awhile and handle accordingly. It is a matter of feeling and grasping what to do and that takes time.
To go into the finer details of all this would take up so much space in a book so it isn't really mentioned.
Yes in the good old days when the matterials were not that good as today the control of the situation was more important than today. With the long contrast range of today we can just record the situation better, but we need to get that exposure right and bend it in the direction we want and need.

markbarendt · Jan 17, 2013

I have come to belive that true-underexposures are almost always caused by "us". It is caused by outright mistakes in setting the camera, poor metering technique, a lack of understanding of what the meter is saying, and or in trying to cheat to avoid camera support or flash when it is clearly needed.

"We" are the wild card, not the film. I think it is actually almost impossible to get an underexposure caused by the film ISO rating. Ilford, Kodak, and Fuji are very good at their jobs, their films are well made and consistent and as best I can tell work extremely well and deliver exactly what they advertise.

RalphLambrecht · Jan 17, 2013

markbarendt said:
I think it is actually almost impossible to get an underexposure caused by the film ISO rating. Ilford, Kodak, and Fuji are very good at their jobs, their films are well made and consistent and as best I can tell work extremely well and deliver exactly what they advertise.

well, there is delta3200

markbarendt · Jan 17, 2013

RalphLambrecht said:
well, there is delta3200

So where does Delta 3200 fall short? Our expectations or Ilford's info?

Stephen Benskin · Jan 17, 2013

markbarendt said:
I have come to belive that true-underexposures are almost always caused by "us". It is caused by outright mistakes in setting the camera, poor metering technique, a lack of understanding of what the meter is saying, and or in trying to cheat to avoid camera support or flash when it is clearly needed.

"We" are the wild card, not the film. I think it is actually almost impossible to get an underexposure caused by the film ISO rating. Ilford, Kodak, and Fuji are very good at their jobs, their films are well made and consistent and as best I can tell work extremely well and deliver exactly what they advertise.

Mark, that is why I suggest using the ISO speed as a starting point to determine the photographer's personal EI. Most pop testing methods have too many questionable elements that any true accuracy is impossible. All that they can really offer is a way to determine a personal EI. This is what most photographers really need, which is fine if they understand this. What I find troubling is when photographers question the legitimacy of the ISO standards based only on an understanding of a questionable "pop" methodology.

Since obtaining a personal EI is the goal for most photographers, why then waste the time with a convoluted testing method. Shoot some negative as determine how you tend to exposure. But first, determine your processing.

Stephen Benskin · Jan 17, 2013

Michael R 1974 said:
Probably a little of both (concerns all "super-speed" films). My understanding is in the case of say Delta 3200 and TMax 3200 these are not ISO speeds.

Great example on how understanding theory is beneficial to understanding the process. Nowhere does it say ISO with these films, which means they haven't been tested according to the ISO standards. The "P" in P3200 stands for process.

AndreasT · Jan 17, 2013

Stephen Benskin said:
Great example on how understanding theory is beneficial to understanding the process. Nowhere does it say ISO with these films, which means they haven't been tested according to the ISO standards. The "P" in P3200 stands for process.

But most do not this.
Testing or taking photo with film and checking the negative surely comes down to the same thing at the end of the day.

markbarendt · Jan 17, 2013

Ilford's data on Delta 3200 shows an ISO if 1000.

http://www.ilfordphoto.com/Webfiles/201071394723115.pdf

For Kodak this was copied from tech pub f32

EXPOSURE
KODAK T-MAX P3200 Professional Film is specially designed to be used as a multi-speed film. The speed you use depends on your application; make tests to determine the appropriate speed.
The nominal speed is EI 1000 when the film is processed in KODAK T-MAX Developer or KODAK T-MAX RS Developer and Replenisher, or EI 800 when it is processed in other Kodak black-and-white developers. It was determined in a manner published in ISO standards. For ease in calculating exposure and for consistency with the commonly used scale of film-speed numbers, the nominal speed has been rounded to EI 800.

AndreasT · Jan 17, 2013

Everybody I know in my small world exposes these film at 3200. None of them have ever read the data sheets

markbarendt · Jan 17, 2013

AndreasT said:
Everybody I know in my small world exposes these film at 3200. None of them have ever read the data sheets

Sadly, I agree that ignorance of reality is the norm.

Stephen Benskin · Jan 17, 2013

markbarendt said:
Sadly, I agree that ignorance of reality is the norm.

And we should struggle to correct that, not make excuses for its continuation.

markbarendt · Jan 17, 2013

Stephen Benskin said:
And we should struggle to correct that, not make excuses for its continuation.

Absolutely!

Stephen Benskin · Jan 17, 2013

AndreasT said:
Basically I use a similar method used by Phil Davis in exposing film under an enlarger. Develop five or more testa at differnt times and plot them. I use a more contrasty "standard" to Phil Davis since I find his reults to soft to be practical.

Davis' BTZS is the closest method to good sensitometry, but it's still a method and while I've never found anything in Davis' book to be inaccurate, he has a tendency to short hand the explanations of some point especially theory. It's been awhile since I've read BTZS, but I believe he mentions how testing with an enlarge doesn't produce an accurate film speed. The color temperature of the lightsource, the lack of precision of most timers, and the difficulty in determining the illuminance of the light source are all contributing factors. The enlarger is a compromise. Isn't it better to know that than to think the results can be as accurate as with a sensitometer?

It also relates to how the manufacturer gets this ISO rating and what it means. As I understand it and I may be wrong here but the rating correlates to a contrast of 1,5 am i wrong here? or me that is an overcast day in winter. Not a sunny day when many people take their cameras and run on the streets.

The 1.5 you are thinking about is the log-H range used to determine the average gradient when doing fractional gradient testing. How it relates to how the manufacturer gets the ISO rating is what I'm talking about. By knowing how the details, parameters, and theory on a test, the photographer can better utilize the testing data. There will be a slight difference in the film's responce when testing under an overcast day and sunny day. the ISO speed standard uses daylight color temperature for exposure. When the speed standard changed the color temperature for the film exposure from sunlight to daylight they had to adjust the speed constant from 1.0 to 0.80. But if the photographer is testing using natural light, they are probably using a camera. All the variables associated with camera exposures will tend to obscure and speed change caused by different color temperatures.

The value of 0.62 for contrast index that you said was standard in most books, I believe came from the contrast parameters defined in the ISO speed standard. The delta 1.30 log-H by delta 0.80 density has a gradient between 0.61 and 0.62; however, it can't be referred to as a contrast index because the use of that term implies a testing methodology. The 1.30 log-H range is intended to define the shadow portion of the curve and not the average gradient.

Now, a CI 0.62 is perfectly acceptable as a normal. It's just a little high to be considered the results from the statistical average conditions. Most books have aims more around 0.56 and 0.58 depending on the average flare factor - whether it's for a large format lens or medium and 35 mm lens.

My basic premise is that there is good testing and bad testing. The best possible decissions come from a position of knowledge.

AndreasT · Jan 17, 2013

I see what you are getting at Stephen, or most of it. I use a enlarger to expose my film but I put in a lens with a shutter so that the times I would suppose is relativly accurate. While there is a strong talk about accuracy here I believe if one is pretty close the parameters should cancel each other out on average.
Though there may be problems here and there or even false results, by seeing the collected data one does get a knowledge or feeling how ones methods work. This will get us what we want.
I feel comfortable when I test my materials.

Bill Burk · Jan 18, 2013

AndreasT,

I think you don't have misconceptions.

When you expose a test strip, even if you set aside the whole concept of speed, you can always get a measure of the contrast.

Photographers could work from box speed, if they used appropriate metering technique (like incident metering). But people meter badly at times. I remember times when I got underexposed shots using the camera on automatic because I included too much sky or backlit situations.

AndreasT · Jan 18, 2013

All I know now is that I have become confused. I am going to have read up on all this. I feel like I am in a dark forest at night.

Stephen Benskin · Jan 18, 2013

AndreasT said:
I see what you are getting at Stephen, or most of it. I use a enlarger to expose my film but I put in a lens with a shutter so that the times I would suppose is relativly accurate. While there is a strong talk about accuracy here I believe if one is pretty close the parameters should cancel each other out on average.
Though there may be problems here and there or even false results, by seeing the collected data one does get a knowledge or feeling how ones methods work. This will get us what we want.
I feel comfortable when I test my materials.

Andreas, I have no doubt about the quality of your results, or most people's for that matter. The manufacturers have strived to make the photographic process as fool proof as possible. Gone are the days of needing to be a chemist in order to make your own emulsion. When I talk about accuracy in testing, I'm not suggesting everyone has to adhere to the strictest testing standards. This is obviously not necessary for what most people require. What I do feel is important is that we should approach testing from a position of knowledge, to be aware of the strengths and weaknesses of a methodology, and have a reasonable understanding and expectation of the results. Knowledge is a good BS gauge.

For an example of the opposite result, you need not go any further than the many posts claiming that a given in camera testing method proves the ISO standard is inaccurate, yet the poster has no idea what the standard contains. Another example is the conspiracy theory over the K-factor in exposure meters. What's worse, unquestioning confidence in knowledge that is wrong or no knowledge at all?

AndreasT · Jan 18, 2013

Yes I know what about the story of a grey card reflecting 18%, a lightmeter is actually calibrated for 12% reflection and if one measures a 50-50 surface of black and white we get a, I think it was 9%. (the last I do not remember) there are so many confusing things stated.
I feel secure about my own method, always learning something new.
It was certainly fun reading all this.

Stephen Benskin · Jan 18, 2013

AndreasT said:
Yes I know what about the story of a grey card reflecting 18%, a lightmeter is actually calibrated for 12% reflection and if one measures a 50-50 surface of black and white we get a, I think it was 9%. (the last I do not remember) there are so many confusing things stated.
I feel secure about my own method, always learning something new.
It was certainly fun reading all this.

So many sources claim that exposure meters are calibrated to 18% (putting aside the fact that meters aren't calibrated to reflectance). Other sources say it's 12%. This discrepancy can make a difference with certain testing methodologies. Too many simply accept the calibration percentage their chosen method uses or adopt the percentage supported by an authority figure, but I think the smart idea is to do some research on their own?

Bill Burk · Jan 19, 2013

AndreasT,

To illustrate how you can gain confidence by acquiring knowledge, while at first feeling confused. Here's a thought that is confusing me lately.

You probably have no trouble thinking of filter factors as simple as 1 stop for yellow, 2 stops for green, 3 stops for red. But lately I've been reading a chapter from LP Clerc which explains the common sense that the factor you use depends on the effect you want.

If you want to make a gray card gray those factors may be correct.

But a green filter can be used to lighten greens and darken reds. Really brighten the greens while leaving the reds natural. Or really darkening the reds while leaving the greens natural. You would want to use three different settings for the three different effects.

I had to think through those last few sentences, because the idea's still sinking in. But it's pretty obvious.

In sensitometry there is plenty talk of making sure that you use the correct illumination. What if the light source of your enlarger is tungsten and you shoot daylight? Does it invalidate your tests? My opinion is that it matters, but not much. Suppose you develop your film to 0.6 Contrast Index (you think) but in reality you truly obtain 0.5 Contrast Index. You will still get great negatives. So long as you are consistent, you will make adjustments as needed.

Stephen Benskin · Jan 19, 2013

Bill, this is not about how much one factor or another has on the results or determining what you can get away with. I'm simply advocating a little critical thinking to better understand the process. It's more about the philosophy of testing. I'm tired of reading "I've heard that", or "this famous photographer says", or seeing uncritical and uncommented on links. I brought up the question of the validity of the just black printing method in my first post. This technique is part of a testing method that was linked to in this thread and the OP was considering using. I believe evaluating the strengths and weakness of this method would make for a worthy discussion. Beginners tend not to be aware that there are variances, tolerances, and nuances involved, and few absolutes.

If one camp claims exposure meters "read" 18% and another 12%, shouldn't a person have the intellectual curiosity to investigate? How many of the people who do Zone System type testing ask themselves why their EIs are almost universally 1/2 to one stop slower than the ISO speed? This would be my second question after wondering if I did the test correctly. I guess it comes down to asking the right questions. Most ask "how to" and not "why."

AndreasT · Jan 19, 2013

Yes Steven you are right. But...
Not everybody has the will or discipline to find the "why". Starting out one doesn't have a clue where to start so one has to rely on information coming from others. Some find it damn boring trying to find the why.
It takes time and money to find all this. I have little of both.
I do believe we may get blinded from all the information out there, while looking for that magic potion.
How often have I told people to read the Technical Pages published by manufacturers. Either they don't have the nerve or don't know they excist.
Yes to Bill with the filters, thank goodness I don't use filters that mush, lazy me. But when one has a sound idea how the film react I think not that much can go wrong. Besides when in doubt I just take two photos the second one with a half or full stop more and according to the first film change the processing of the second one as needed.
We still have multigrade to save us.

Film speed test in winter

Privacy & Transparency

Privacy & Transparency