BTZS Metering Question

[IanBarber]

I am reading the BTZS fourth edition book and have a question.

Phil states that after the exposure has been made, you consult the chart to arrive at the development time depending on the calculated SBR.

Am I right in thinking that you use these times instead of any previous times you may have used

[loonatic45414]

You're supposed to meter, which gives you zone 5 at the starting point speed. Close 4 stops to get your theoretical zone I. Ideally you want zone I to be at 0.1 above base+fog. But depending on the characteristics of your film (like if it has a long toe) you may want zone I to fall where the (somewhat) straight part of your film's curve begins.

Ultimately, however, the paper is calibrated first & the film exposure & development tailored to get what you want on the paper. In theory. But you could have an ideal speed to get the most out of highlight detail & an ideal speed when you want to bring out better shadow detail also. There's no absolute.

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[Bill Burk]

If you do the tests where you develop several sheets of film, (for example developing one sheet for 2 1/2 minutes, others for 4, 6, 9, 15 minutes)... And then if you created a chart of your own after reading the test negatives with a densitometer and plugging the numbers into the chart... Then yes. The chart would tell you how many minutes to develop your film for any particular SBR and you would use that time from the chart instead of any customary time you are used to.

[IanBarber]

If you do the tests where you develop several sheets of film, (for example developing one sheet for 2 1/2 minutes, others for 4, 6, 9, 15 minutes)... And then if you created a chart of your own after reading the test negatives with a densitometer and plugging the numbers into the chart... Then yes. The chart would tell you how many minutes to develop your film for any particular SBR and you would use that time from the chart instead of any customary time you are used to.

Thanks Bill. I need to go back a few chapters and re read this again until it starts to sink in, O the joys of been over 50 :)

[loonatic45414]

I'm sorry, I was answering the metering question. It's actually a development question. 😄

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[Pere Casals]

I am reading the BTZS fourth edition book and have a question.

Phil states that after the exposure has been made, you consult the chart to arrive at the development time depending on the calculated SBR.

Am I right in thinking that you use these times instead of any previous times you may have used


Well BTZS, IMHO, has two different sections. First half of the book explains the physics, second part explains a couple of practical recipes.

To me the important thing is to understand very, very well first half, it explains all.

Look, you have a family of curves, for different development times, from that you can take the reading of any spot of the scene and you will know what precise density will deliver in the negative.

I'd suggest that you do what I did to get practice. Just take a very contrasty scene, then use a spot photometer (SLR/DSLR) and the graphs of the family of curves. Then you can design how it will be your negative.

You will be able to place your shadows at a desired density, also your higlights. You will be able to determine what will be lost... what will be more or less printable in the darkroom... (if scan + PS its easier... )


You should be able to determine/predict what density will have every spot of the scene on the negative, then you can say that you understood very well the first part of BTZS. So you will need to correlate lux*second to photometer reading. (Saturated colors and filters add more complexity...)


Tools you need is an Stouffer density wedge, a cheap handheld luxometer ($25) and a way to measure densities. Scanner can be used as a densitometer, just disable any scanner image treatment (gamma, curves, adaptative contrast...) and scan the Stouffer wedge at the side of your negative to compare, linearly.


In this way you will know what will result from choices you make about exposure/development, next step will be using all that without thinking too much, with some practice in few seconds you will select N-1 or N+1, and the exposure.

[loonatic45414]

Pere, good point. I think the first half is fabulous in terms of presentation & I still get new ideas from re-reading it.

I get the feeling Ian has made an exposure (actual photograph as opposed to a gray card or Stouffer wedge test exposure) and needs a development time from someone else's (published?) chart versus one he himself has come up with by standardizing his materials.

To me, development is like wearing a tailored suit. Too many variables that a suit made for someone else just never seems to fit right.

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[Ken Lee]

I am reading the BTZS fourth edition book and have a question.

Phil states that after the exposure has been made, you consult the chart to arrive at the development time depending on the calculated SBR.

Am I right in thinking that you use these times instead of any previous times you may have used

Below is a graph generated for me by Fred Newman of the View Camera store, using the BTZS Plotter software. It shows recommended development times for different treatments according to the Zone System. (N is the development we would give for subjects of normal contrast range.)

The graph is specifically for Ilford HP5+, tray-developed by me in my darkroom in D-23 1:1 at 70 deg F.

http://www.kennethleegallery.com/images/forum/BTZS-ZoneSystem.jpg

You can see that the recommended time for N development is around 9 minutes and 20 seconds. For N-1, it's just over 7 minutes... etc.

This graph was made by Fred exposing sheets of film under an enlarger with a step-wedge, then me doing the development, then Fred measuring the results with a densitometer. Thus, it is independent of any camera, shutter or lens. Because I developed the film, it was custom tailored to my method of agitation, my water, my thermometer, etc.

I shared the Zone System graph here since you know that system, but the Plotter software delivers many graphs, such as how effective film speed changes with changes in development time, contrast, SBR, etc.

BTZS generates a lot of charts with great precision, but the results are not essentially different from what we get by following widely published time/temperature charts. If the differences were substantial, we'd have to wonder why.

[loonatic45414]

Hi Ken, do you use D-23 often? I have been wanting to try that out.

I don't doubt the accuracy of published charts, but where I do my tailoring is in modifying exposure, temperature, agitation, dilution, and development time to customize the look I get from a film.

To me, it's not about just making a good negative by the book. It's about using recipes that bring out shadow detail, high/low contrast, emphasize apparent sharpness or to bring out texture in highlights. I look at the film as a canvas and to just develop by the book can be quite limiting. I don't begrudge someone for being satisfied just reproducing what's there, but we have to be true to our inner artist also.

D-23 has been on my list of developers to try for a long time. It can be very striking.

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[Ken Lee]

We need to know what normal is before we can depart from it :)

I've been using D-23 for a number of years. See http://www.kennethleegallery.com/html/tech/D-23.php

[Ken Lee]

Sorry Ian, I missed that you asked about development times with respect to SBR, not the Zone System.

Below is a chart for the same film/developer combination. Note that for SBR 7 - which corresponds to a scene of normal contrast - the recommended development time is the same as previously given for N development.

http://www.kennethleegallery.com/images/forum/BTZS-SBR.jpg

[Ken Lee]

Here is another graph which shows how effective film speed changes as we modify development time. This chart uses Zone System notation.

Again, this chart is only for HP5+ in D-23 1:1 at 70 degrees F, but the principles are fairly universal.

http://www.kennethleegallery.com/images/forum/BTZS - EFS.jpg

Note that film speed is around 250+ for N development, goes down 200+ for N-1 development, etc.

Each film/developer combination will have its own characteristics, but this is nothing new: back in the 1970's Minor White suggested that we modify film speed by 10-15% with each level of expansion and contraction. He wasn't the first to discover it either. Note that since one f/stop equates to 50%, 10 or 15% amounts to a fairly modest adjustment in film speed: a fraction of an f/stop.

With a scanning workflow, contrast can be increased ad infinitum. This eliminates the need for over-development which increases grain. If in addition we avoid scenes which require dramatic contraction, life becomes much easier. In photojournalism we have to bring back the photo whatever it takes. With Fine Art photography we can pre-select scenes which match the tonal scale of our medium.

If we shoot this film at ISO 200 and rely on the scanner's wide dynamic range which gives us an automatic N-1 contraction, we can easily accommodate scenes of 1 more f/stop than usual. If we use an Infra Red viewing device and develop by inspection, each negative gets its own treatment, correcting any mistakes made in the field, which do happen, in spite of all this BTZS and Zone System... stuff.

[loonatic45414]

Develop by inspection? No problem, we'll fix it on the scan?

I guess we just pour powder chemistry into the water "until it looks good more or less."

Yikes.

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[loonatic45414]

You're consulting charts on exposure versus development but you have no idea of the development time until after the exposure.

Sounds more like Before The Zone System.

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[Pere Casals]

Here is another graph which shows how effective film speed changes as we modify development time. This chart uses Zone System notation.

Again, this chart is only for HP5+ in D-23 1:1 at 70 degrees F, but the principles are fairly universal.

Note that film speed is around 250+ for N development, goes down 200+ for N-1 development, etc.

Each film/developer combination will have its own characteristics, but this is nothing new: back in the 1970's Minor White suggested that we modify film speed by 10-15% with each level of expansion and contraction. He wasn't the first to discover it either. Note that since one f/stop equates to 50%, 10 or 15% amounts to a fairly modest adjustment in film speed: a fraction of an f/stop.

With a scanning workflow, contrast can be increased ad infinitum. This eliminates the need for over-development which increases grain. If in addition we avoid scenes which require dramatic contraction, life becomes much easier. In photojournalism we have to bring back the photo whatever it takes. With Fine Art photography we can pre-select scenes which match the tonal scale of our medium.

If we shoot this film at ISO 200 and rely on the scanner's wide dynamic range which gives us an automatic N-1 contraction, we can easily accommodate scenes of 1 more f/stop than usual. If we use an Infra Red viewing device and develop by inspection, each negative gets its own treatment, correcting any mistakes made in the field, which do happen, in spite of all this BTZS and Zone System... stuff.


I find this explanation containing a lot of knowledge. Of course, a too contrasty illumination can be an unnecessary complication to generate an art we visualize. Anyway I feel attracted by the challenge from very contrasty scenes like night photography. Then the N+/- comes short, as you point, using compensating development techniques to get sound results is another war :)

[Kirk Gittings]

Below is a graph generated for me by Fred Newman of the View Camera store, using the BTZS Plotter software. It shows recommended development times for different treatments according to the Zone System. (N is the development we would give for subjects of normal contrast range.)

The graph is specifically for Ilford HP5+, tray-developed by me in my darkroom in D-23 1:1 at 70 deg F.

http://www.kennethleegallery.com/images/forum/BTZS-ZoneSystem.jpg

You can see that the recommended time for N development is around 9 minutes and 20 seconds. For N-1, it's just over 7 minutes... etc.

This graph was made by Fred exposing sheets of film under an enlarger with a step-wedge, then me doing the development, then Fred measuring the results with a densitometer. Thus, it is independent of any camera, shutter or lens. Because I developed the film, it was custom tailored to my method of agitation, my water, my thermometer, etc.

I shared the Zone System graph here since you know that system, but the Plotter software delivers many graphs, such as how effective film speed changes with changes in development time, contrast, SBR, etc.

BTZS generates a lot of charts with great precision, but the results are not essentially different from what we get by following widely published time/temperature charts. If the differences were substantial, we'd have to wonder why.

Did you pre-soak for this test?

[Ken Lee]

Did you pre-soak for this test?

Hi Kirk -

Yes, as I remove the sheets from their holders, I place them into a water bath and pre-soak for 3-5 minutes.