Sensitometry. Testing film. Help.

[jejes]

I wouldn’t bother calibrating the enlarger for white light. I’ve always set the color knobs to 0/0/0, or used a condenser that isn’t equipped with color.

I have a durst m670 only bw

 

[jejes]

Must? No. Should? Yes.

Easily you could get an 80B bluish filter to have a better chance of getting repeatable and comparable results. So you should get a filter. It can be old and scratched.

Which density to read? Honestly doesn’t matter. If you get step 21 to approach zero above base & fog then all the other steps will have a meaningful value.

But do you have a patch and a value you measure for?

 

[jejes]

Did all that reading include Richard Henry's "Controls in Black & White Photography"? He describes how to set up your own tests. You start with developing your paper. Exposing the film comes last.

Do you have a link or copy to send me?

 

[BCM]

Personally, I don't use a step wedge to determine a personal EI for any film. To my mind, it's better to create an exposure series in-camera, thereby removing variables such as lens flare, camera flare, shutter speed variance, etc. There are many ways to test film, but here's what I do:

1. On a cloudless day around noon, I setup a black card in open shade (not under a tree, for example, you want shade open to the sky)

2. For a film with box speed of 100, for example, I set my meter for ISO 25, meter the card, then chose a lens/aperture combo 4 stops less exposure. What you're doing here is moving a mid-gray Zone V exposure value down to Zone 1.

3. Make an exposure, close (edit: I incorrectly wrote open initially) the lens 1/2 stop, make another exposure, open 1/2 stop, expose, etc, until you've exposed for one stop over the box speed.

4. Process the film as you normal would and, when dry, you're looking for the frame that's at or close to 0.10 over fb+f (film base + fog). You should zero out the densitometer for the fb+f on a clear area of film.

This all sounds more complicated than it is to do.

Good luck.

P.S. Not clear if you're asking about sensitometry or densitometry, since you mention both terms in your post. These are two very different things.

In camera testing (after doing hundreds of them) is inherently flawed. Test your shutter speed first so that you can understand that variable. Flare and other factors vary over a very small amount between coated lenses. Getting partial stops on a standard LF shutter can be off by quite a bit. The proven and best way to test is to test your film and developer combination then introduce variables with shutter speed and other external factors. I've seen experienced photographers disagree with exposure values by +/- one stop in the field.

In the end, it all depends on how close you want to be in your final results. The testing in the BTZS book takes less than half a day then you can go out and shoot. IMHO

 

[Romanko]

Yes, I would like all the sensitometry. This is what I want to know.

There is a whole spectrum of techniques called "sensitometry" ranging from traceable measurements by an accredited laboratory to purely subjective determination of EI for a certain film. It would help if we could better understand your goals. If you are a photographer who wants to get most out of his materials and equipment your approach would be totally different from that of a calibration engineer aiming at producing traceable and reproducible measurements. As an example, using your camera to expose the film would introduce flare that affects your characteristic curve. This could be desirable as this is part of the setup that you are trying to characterise.

 

[Romanko]

Richard Henry's "Controls in Black & White Photography"

Available from archive.org (registration required):
https://archive.org/details/controlsinblackw0000henr/

 

[Bill Burk]

But do you have a patch and a value you measure for?

You place any exposure at all on the step wedge and after developing you read all the density values. The exact exposure that occurred doesn’t matter, it reveals itself through the curve you get when you graph the results.

You want the exposure to be consistent from test to test so you can compare tests to each other.

Adjust exposure to maximize the number of steps you can read. Give enough exposure to be able to see differences between the highest steps.

If you underexpose there will be several clear steps on your developed test negatives and you won’t be able to read as many high density steps of the shoulder.

If you overexpose, and you don’t have any steps beneath 0.1 above base+fog, you won’t find the speed.

You find the speed by interpolating where the curve crosses 0.1 above base+fog

And the best part… every other step is one stop of exposure. To figure out what the right exposure should be when you miss the first time… just count the steps between what you got and what you want… divide by two… and that’s how many f/stops you need to open (or close) before you try again.

 

[jejes]

There is a whole spectrum of techniques called "sensitometry" ranging from traceable measurements by an accredited laboratory to purely subjective determination of EI for a certain film. It would help if we could better understand your goals. If you are a photographer who wants to get most out of his materials and equipment your approach would be totally different from that of a calibration engineer aiming at producing traceable and reproducible measurements. As an example, using your camera to expose the film would introduce flare that affects your characteristic curve. This could be desirable as this is part of the setup that you are trying to characterise.

I’m a photographer but a tech guy too. I would like to have a good and traceable method and of course that can repeat over time.

Thank you

 

[Vetus]

How do you plot density readings on a graph?

 

[Romanko]

How do you plot density readings on a graph?

Phil Davis. Beyond the Zone System

 

[Stephen Benskin]

Kodak's Basic Photographic Sensitometry Workbook. Publication H-740.

 

[jejes]

How do you plot density readings on a graph?

Film curves plotting

 

[ic-racer]

Using Sensitometry for Process Control in the B&W Darkroom


The development time and exposure of a known film are obtained via trial and error, or years of experience.

The known film is exposed in a sensitometer (any kind that is consistent).

The results are plotted to obtain two numerical indicators. One would be a contrast, gamma or other indication of development activity and the other an indicator of the film’s sensitivity.

When one is presented with an unknown film, it can be exposed on the same sensitometer and the results compared to the known film with respect to developer activity and speed.

This provides a starting point for exposure and development for the new film.

 

[greg zinselmeier]

Personally, I don't use a step wedge to determine a personal EI for any film. To my mind, it's better to create an exposure series in-camera, thereby removing variables such as lens flare, camera flare, shutter speed variance, etc. There are many ways to test film, but here's what I do:

1. On a cloudless day around noon, I setup a black card in open shade (not under a tree, for example, you want shade open to the sky)

2. For a film with box speed of 100, for example, I set my meter for ISO 25, meter the card, then chose a lens/aperture combo 4 stops less exposure. What you're doing here is moving a mid-gray Zone V exposure value down to Zone 1.

3. Make an exposure, close (edit: I incorrectly wrote open initially) the lens 1/2 stop, make another exposure, open 1/2 stop, expose, etc, until you've exposed for one stop over the box speed.

4. Process the film as you normal would and, when dry, you're looking for the frame that's at or close to 0.10 over fb+f (film base + fog). You should zero out the densitometer for the fb+f on a clear area of film.

This all sounds more complicated than it is to do.

Good luck.

P.S. Not clear if you're asking about sensitometry or densitometry, since you mention both terms in your post. These are two very different things.

I slightly vary from this :

cloudless day, In open shade, tripod and camera, a white sheet of paper taped to a wall. expose 1/1000@ f22 all the way down to 1sec@f/2, and all stops inbetween. spot meter you paper and note zone V. after processing did zone I start at .1 above base + fog? if not, identify the correct film speed, where zone I is .1 above B+F. where did zone VIII fall? in regards to the numbers on densimeter? was 1.25 -1.35 above B+F etc. .. . ??? add/subtract-or adjust time, temp, or aggitation, to get the required contrast index.

now that you have that. take your neg. that has no exposure, BUT DEVELOPED, (this is B+F) stick it in the enlarger. make a test print on a paper. keep adding time on test strip till you cannot see the difference in black when developed. take the shorter of the two times. for this height of lens to paper and at this F stop. "this time" will be your starting point for printing, anything above B+F will show as "a Grey".

go out and shoot! use the same ISO, and developement technique of film. from tests. when you print and use the same f stop and time, and paper, and devloper!!! does the contrast look good? is there enough or too much shadow detail? is there too little detail in highlights? if so adjust film speed for shadows, adjust time.temp. aggitation for highlights. Keep tweeking till perfection. A densimeter is really a quick way to use a tool to find your personal ISO for any given film, to find your personal development style ( developer + technique). to find a paper and a paper developer. to make fairly descent images on a regular base

 

[greg zinselmeier]

I forgot to mention to use your densitometer to measure the plain white paper.

 

[L Gebhardt]

I’m a photographer but a tech guy too. I would like to have a good and traceable method and of course that can repeat over time.

Thank you

You could use a flash. They are daylight balanced with short duration, so no reciprocity failure. Plus very repeatable. You could calibrate it with a flash meter.

 

[Bill Burk]

You could use a flash. They are daylight balanced with short duration, so no reciprocity failure. Plus very repeatable. You could calibrate it with a flash meter.

Yes! A Vivitar 283 with Vari-Power module would be great in a box aimed at a sheet of glass you can tape the step wedge to and put a lid on with a little foam for pressure.

 

[jejes]

And another question that I don’t find answer in Xrite 331 densitometer. Emulsion down or up?

thank you

 

[Bill Burk]

https://www.xrite.com/-/media/xrite/files/manuals_and_userguides/3/331-10_331_operators_manual_en.pdf

Emulsion side up.

 

[Stephen Benskin]

And another question that I don’t find answer in Xrite 331 densitometer. Emulsion down or up?

thank you

The best thing to do is to get a couple of good, comprehensive books on the subject. Beyond the Zone System is a good how to and Photographic Materials and Processes is excellent for the theory.

 

[Bill Burk]

The best thing to do is to get a couple of good, comprehensive books on the subject. Beyond the Zone System is a good how to and Photographic Materials and Processes is excellent for the theory.

Agree. Sensitometry is best learned by book.

Photographic Sensitometry the Study of Tone Reproduction

I discovered this book in high school at the Brand Library in Glendale. It was a great art library with walls of photography books. I thought all libraries were like that until I moved away and visit libraries now. There’s nothing like that library.

And there’s nothing like this book. Closest corrolary (but different discipline) are books by Donald Knuth or Kernighan and Ritchie. I renewed it a bunch of times and soaked in what I could, but I never put it in practice until joining this site.

I refer to it all the time, there’s nothing incorrect in it.

 

[Stephen Benskin]

Agree. Sensitometry is best learned by book.

Photographic Sensitometry the Study of Tone Reproduction

I discovered this book in high school at the Brand Library in Glendale. It was a great art library with walls of photography books. I thought all libraries were like that until I moved away and visit libraries now. There’s nothing like that library.

And there’s nothing like this book. Closest corrolary (but different discipline) are books by Donald Knuth or Kernighan and Ritchie. I renewed it a bunch of times and soaked in what I could, but I never put it in practice until joining this site.

I refer to it all the time, there’s nothing incorrect in it.

+1. Also an excellent book.