I have a durst m670 only bw
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.
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.
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.
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.
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.Yes, I would like all the sensitometry. This is what I want to know.
Richard Henry's "Controls in Black & White Photography"
But do you have a patch and a value you measure for?
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.
How do you plot density readings on a graph?
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’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.
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.
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.
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