Film Testing with Step Wedge for Dummies

bascom49 · Apr 22, 2019

I've always been curious about film testing with a step wedge, densitometer and plots.
I do have a working understanding of the Zone system and do use an abbreviated method to determine film speed
and development times like so:
For film speed, spot meter a grey target for Zone V, close down four stops to Zone I.
Bracket in 1/3 stops below film speed to above film speed.
Find film speed that is 0.11 density above b+F.

For Development time spot meter a grey target for Zone V, open up three stops for Zone VIII.
If density above b+F is below 1.25 for diffusion enlarger increase development, if above decrease development.

But now I would like to make a chart, just to be in the sensitometry film club.

I have read and searched the forum, especially posts by Bill Burke and PE.
How is it DONE ? There does not seem to be a step by step thread from start to finish. It looks like
everyone in the discussions assume that everyone is familiar with the process.
Where do you get the charts and graph paper to make the plots?
What is a step by step procedure from start to finish to generate a curve plot, PLEASE?
So, here is what I know:
1) Get a 21 step Stouffer step wedge. Check, have one.
2) Insert step wedge in 4x5 film holder over film. Check
3) Set bellows at infinity. Check
4) Use white foam board for target. Check
5) Spot meter target, open up five stops for Zone X. Check
6) Release shutter. Check
7) Develop film. Check
8) Turn on Densitometer. Check, in my case an X-rite 810 recently calibrated with factory calibration thingys.
Now What ?

ic-racer · Apr 22, 2019

Now What ?

You expose your 'comparison' film to the exact same conditions. Depending on your target, immediately afterwards. If you ever make or obtain a sensitometer, it would be the same thing as you are doing now, but the target light source would be consistent from day to day.

silveror0 · Apr 22, 2019

bascom49 said:
...Where do you get the charts and graph paper to make the plots?...

My step-by-step is almost identical to your method. But I don't make plots on graph paper by hand. I've learned how to make plots using MS Excel. The result would look like the attachment. But if you prefer to hand plot on graph paper, you can print paper customized to your liking with this link:
http://customgraph.com/pi.php?cat=1
This link may also be helpful:
https://www.kodak.com/uploadedfiles...en_motion_education_sensitometry_workbook.pdf

Mr Bill · Apr 22, 2019

bascom49 said:
8) Turn on Densitometer. Check, in my case an X-rite 810 recently calibrated with factory calibration thingys.
Now What ?

Well, basically what you're gonna do is to compare how the film responds to different amounts of exposure. A convenient way to do this is to make a graph comparing amount of exposing light vs the resulting film density. Now, you won't know the actual exposure in terms of light energy ('cuz you don't have a calibrated light source, aka sensitometer. But you DO HAVE a way to get reliable RELATIVE amounts of light - by contact printing your step tablet. The step tablet is a reliable way to "subtract" light in predictable steps. (You just pick some arbitrary number for the base amount of light, say 1, or perhaps 10, whatever you want, and then subtract the step wedge's density.) Then you make a graph of the exposing light vs the resulting processed film density. Since density is a log value you will now have a graph of log exposure vs film density. If you keep both axes on the same size increment it should look like the graphs published by the film makers.

bascom49 said:
Where do you get the charts and graph paper to make the plots?

Kodak used to sell curve plotting graph paper (I did probably thousands of those in my younger days), but I doubt it's available anymore. It was somewhat translucent, so you could overlay 2 or 3 separate plots on a light table for comparison.

Today I would just put the data into an Excel spreadsheet and let Excel draw the graph. If you don't already have something like this, and know how to use it, it can be a big learning curve. In this case, any graph paper you can find will probably work; you just have to decide the scale you want to use.

Kodak used to have something called the "Sensitometry Workbook," or something to that effect available online. It was a pretty good primer, as I recall.

MattKing · Apr 22, 2019

Mr Bill said:
Kodak used to have something called the "Sensitometry Workbook," or something to that effect available online. It was a pretty good primer, as I recall.

Let's see if this will upload:

MattKing · Apr 22, 2019

Mr Bill said:
Kodak used to sell curve plotting graph paper (I did probably thousands of those in my younger days), but I doubt it's available anymore. It was somewhat translucent, so you could overlay 2 or 3 separate plots on a light table for comparison.

I don't know if this is relevant...
https://125px.com/docs/techpubs/kodak/y30.pdf

RalphLambrecht · Apr 23, 2019

bascom49 said:
I've always been curious about film testing with a step wedge, densitometer and plots.
I do have a working understanding of the Zone system and do use an abbreviated method to determine film speed
and development times like so:
For film speed, spot meter a grey target for Zone V, close down four stops to Zone I.
Bracket in 1/3 stops below film speed to above film speed.
Find film speed that is 0.11 density above b+F.

For Development time spot meter a grey target for Zone V, open up three stops for Zone VIII.
If density above b+F is below 1.25 for diffusion enlarger increase development, if above decrease development.

But now I would like to make a chart, just to be in the sensitometry film club.

I have read and searched the forum, especially posts by Bill Burke and PE.
How is it DONE ? There does not seem to be a step by step thread from start to finish. It looks like
everyone in the discussions assume that everyone is familiar with the process.
Where do you get the charts and graph paper to make the plots?
What is a step by step procedure from start to finish to generate a curve plot, PLEASE?
So, here is what I know:
1) Get a 21 step Stouffer step wedge. Check, have one.
2) Insert step wedge in 4x5 film holder over film. Check
3) Set bellows at infinity. Check
4) Use white foam board for target. Check
5) Spot meter target, open up five stops for Zone X. Check
6) Release shutter. Check
7) Develop film. Check
8) Turn on Densitometer. Check, in my case an X-rite 810 recently calibrated with factory calibration thingys.
Now What ?

the ones who know how make photographs do; the others plot graphs!

Bill Burk · Apr 23, 2019

I'm certainly guilty of wasting time on this stuff instead of taking pictures. I almost started the water running last night then other things happened...

It occasionally helps for example, I fished through my Panatomic-X graphs last night to confirm 10 minutes is my dev time to hit ASA parameters.

Here's some graph paper. Take readings of your original Stouffer scale and make tick marks at the bottom where the scale runs 0.00 on the right to 3.00 on the left. (The nominal steps are marked)

Then read your film result. I like to zero on Base + Fog but that's not important.

Plot the density of each step on the vertical scale that goes 0.0 to 2.4, with the horizontal scale being the corresponding step wedge original density. Connect the dots.

Try to interpolate where the curve crosses 0.10 over Base + Fog and mark that as the 0.10 speed point.

Here's some graph paper

http://beefalobill.com/imgs/sensitometry.pdf

And a write-up (I see now I left out step by step instructions)...

http://beefalobill.com/imgs/20150812 CallingYourShot-DividedAttention.pdf

Cheers,

Bill

silveror0 · Apr 23, 2019

RalphLambrecht said:
the ones who know how make photographs do; the others plot graphs!

With all due respect, Ralph, I'm astounded at your comment, given that your book "Way Beyond Monochrome Ed.2" is chocked full of how-to links that promote testing film and graphing the results. I've always preferred to do the testing before using a film in the field to minimize poor negatives.

tih · Apr 23, 2019

RalphLambrecht said:
the ones who know how make photographs do; the others plot graphs!

...which is why the OP certainly shouldn't buy Ralph Lambrecht's excellent book, "Way Beyond Monochrome", and most emphatically not use his documented test process and the spreadsheet he made for evaluating the results, both downloadable at https://www.waybeyondmonochrome.com/WBM/Library.html.

Mr Bill · Apr 23, 2019

MattKing said:
I don't know if this is relevant...
https://125px.com/docs/techpubs/kodak/y30.pdf

Matt, that's a form used in routine "process control," where the lab tech periodically records the "condition" of the process. It's sort of a chronological record of the condition of the process.

I dug up some old "CURVE PLOTTING GRAPH PAPER." It came in a package called publication "E-64," but now seems forgotten on the internet. Even the cat # doesn't show up.

I'm sure that Bill Burk's version is a worthy substitute for those who want to do it by hand.

bernard_L · Apr 23, 2019

bascom49 said:
I do have a working understanding of the Zone system and do use an abbreviated method to determine film speed
and development times like so:

That is fine and sufficient. Spend your time shooting and in the darkroom. The club is no fun: members spend their time arguing.

baachitraka · Apr 23, 2019

RalphLambrecht said:
the ones who know how make photographs do; the others plot graphs!

Or others give 1 stop safety factor...

bascom49 · Apr 23, 2019

tih said:
...which is why the OP certainly shouldn't buy Ralph Lambrecht's excellent book, "Way Beyond Monochrome", and most emphatically not use his documented test process and the spreadsheet he made for evaluating the results, both downloadable at https://www.waybeyondmonochrome.com/WBM/Library.html.

I do have Ralph's book, and have read it. It is an invaluable resource for my darkroom and replaced several shelf feet of books that I used to use as a reference. "Way Beyond Monochrome" along with Ansel's three take care of anything that I may need.
What is not in Ralph's book is how to actually expose a step wedge, with step by step instructions, for the inexperienced. There are several posts on this forum dealing with lens flare as to his suggestion to tape the wedge on a north facing window and shoot it. It did not give me a properly exposed negative using the 31 step wedge (8 x10 in size from Stouffers) that his spread sheet would like in terms of data points. Alas, if it were that simple live would be great. There does seem to be some technique and process to use his suggested method, but I have no idea what that may be. Which is why I am reaching out to others to fill in the gaps so to speak.

bascom49 · Apr 23, 2019

bernard_L said:
That is fine and sufficient. Spend your time shooting and in the darkroom. The club is no fun: members spend their time arguing.

I agree whole heartedly, and I am guilty of making cynical comments in those threads in regards to incessantly arguing and discussing charts, lens flare, testing etc.
My goal with this thread is to establish an easily followed, step by step process to create a film curve, and establish two parameters - EI and development time with a better understanding of film and exposure along the way.

bascom49 · Apr 23, 2019

Bill Burk said:
I'm certainly guilty of wasting time on this stuff instead of taking pictures. I almost started the water running last night then other things happened...

It occasionally helps for example, I fished through my Panatomic-X graphs last night to confirm 10 minutes is my dev time to hit ASA parameters.

Here's some graph paper. Take readings of your original Stouffer scale and make tick marks at the bottom where the scale runs 0.00 on the right to 3.00 on the left. (The nominal steps are marked)

Then read your film result. I like to zero on Base + Fog but that's not important.

Plot the density of each step on the vertical scale that goes 0.0 to 2.4, with the horizontal scale being the corresponding step wedge original density. Connect the dots.

Try to interpolate where the curve crosses 0.10 over Base + Fog and mark that as the 0.10 speed point.

Here's some graph paper

http://beefalobill.com/imgs/sensitometry.pdf

And a write-up (I see now I left out step by step instructions)...

http://beefalobill.com/imgs/20150812 CallingYourShot-DividedAttention.pdf

Cheers,

Bill

Thank you very much Bill, this fills in many gaps. It may seem simplistic to you guys way more familiar with this degree of film testing, but just looking at your graph paper and being able to relate the scale numbers on the bottom with the steps on the 21 step tablet
is a huge help in understanding.
I think that there are many here who would like to follow the discussions had by you and others in film testing and sensitometry but simply lack the familiarity to do so.
Thanks for your attention to my post.

bascom49 · Apr 23, 2019

silveror0 said:
My step-by-step is almost identical to your method. But I don't make plots on graph paper by hand. I've learned how to make plots using MS Excel. The result would look like the attachment. But if you prefer to hand plot on graph paper, you can print paper customized to your liking with this link:
http://customgraph.com/pi.php?cat=1
This link may also be helpful:
https://www.kodak.com/uploadedfiles...en_motion_education_sensitometry_workbook.pdf

View attachment 222063

I would love to make plots using Excel, but again, I spend my time making pictures, not learning MS Excel and programming spread sheets. Could you post one of yours that I could plug my data into ?
I have tried using Ralph's spread sheet in "Way Beyond Monochrome" but it seems to need more experience with Excel to implement than I have.
That would be greatly appreciated.

bascom49 · Apr 23, 2019

MattKing said:
Let's see if this will upload:

Matt, thanks and thanks and thanks. And thanks.
Many questions have been answered.
And thanks again.

bascom49 · Apr 23, 2019

silveror0 said:
My step-by-step is almost identical to your method. But I don't make plots on graph paper by hand. I've learned how to make plots using MS Excel. The result would look like the attachment. But if you prefer to hand plot on graph paper, you can print paper customized to your liking with this link:
http://customgraph.com/pi.php?cat=1
This link may also be helpful:
https://www.kodak.com/uploadedfiles...en_motion_education_sensitometry_workbook.pdf

View attachment 222063

Thanks, and Thanks and Thanks.
Matt also posted the work book, along with Bill Burk you guys have really helped me understand the discussions.
Thanks

MattKing · Apr 23, 2019

I'm glad we could be helpful, but I think the nature of my contribution was to know and remember where a fair number of old Kodak documents can be found - including in some cases my own computer!

silveror0 · Apr 23, 2019

bascom49 said:
I would love to make plots using Excel, but again, I spend my time making pictures, not learning MS Excel and programming spread sheets. Could you post one of yours that I could plug my data into ?

I was sufficiently up on the Excel learning curve from my day job prior to retiring that it was easy to set up my film testing files, which would not be useful to you as something you could just plug your data into. They were set up prior to getting Ralph's book and were based on the step-by-step procedure gleaned from Book 2 in this link:
https://www.amazon.com/Ansel-Adams-Guide-Techniques-Photography/dp/0821219561/ref=sr_1_4?crid=DJKB7D0M8SWE&keywords=basic+techniques+of+photography&qid=1556037629&s=gateway&sprefix=basic+techniques+,aps,431&sr=8-4

I also have Book 1 in the series, which I found useful for tray processing of sheet film, except for his suggestion to have film face DOWN in the tray; I choose to follow AA's face UP suggestion. I set up my white target indoors and illuminate it evenly with a pair of blue 5000K floods to approximate daylight. The camera is a 5x7 Sinar Norma and is easy to use a bellows shade to minimize flare. I also tape a .25" x .25" piece of aluminum foil to the film that insures a spot on the negative to read fb+fog (a tip from one of Howard Bond's articles).

BTW, the target net density for Zone VIII of 1.30 is per AA's recommendation for a diffusion enlarger.

bascom49 · Apr 23, 2019

silveror0 said:
I was sufficiently up on the Excel learning curve from my day job prior to retiring that it was easy to set up my film testing files, which would not be useful to you as something you could just plug your data into. They were set up prior to getting Ralph's book and were based on the step-by-step procedure gleaned from Book 2 in this link:
https://www.amazon.com/Ansel-Adams-Guide-Techniques-Photography/dp/0821219561/ref=sr_1_4?crid=DJKB7D0M8SWE&keywords=basic+techniques+of+photography&qid=1556037629&s=gateway&sprefix=basic+techniques+,aps,431&sr=8-4

I also have Book 1 in the series, which I found useful for tray processing of sheet film, except for his suggestion to have film face DOWN in the tray; I choose to follow AA's face UP suggestion. I set up my white target indoors and illuminate it evenly with a pair of blue 5000K floods to approximate daylight. The camera is a 5x7 Sinar Norma and is easy to use a bellows shade to minimize flare. I also tape a .25" x .25" piece of aluminum foil to the film that insures a spot on the negative to read fb+fog (a tip from one of Howard Bond's articles).

BTW, the target net density for Zone VIII of 1.30 is per AA's recommendation for a diffusion enlarger.

Thanks for the reply. I had similar thoughts as to the white target. I have modern flash strobes with adjustable and stable color temperature. I'm planning on using a large 84 inch umbrella to light up my target.
Thanks for the reminder that the density values differ between contrast and diffusion.

silveror0 · Apr 23, 2019

bascom49 said:
Thanks for the reply. I had similar thoughts as to the white target. I have modern flash strobes with adjustable and stable color temperature. I'm planning on using a large 84 inch umbrella to light up my target.
Thanks for the reminder that the density values differ between contrast and diffusion.

I'd be skeptical of using flash (very brief duration) for test exposures unless you're looking for data applicable to use under studio conditions; Reciprocity occurs with both very short exposures as well as very long exposures. AA suggested a shutter speed around 1/25 sec, as it's usually most accurate around that speed. I used 1/25 but checked it to be certain it's spot on.

The target density for VIII is 1.30 above fb+fog for diffusion enlargers like mine; it's 1.20 above fb+fog for condenser enlargers (which inherently produce higher contrast).

RalphLambrecht · Apr 23, 2019

silveror0 said:
With all due respect, Ralph, I'm astounded at your comment, given that your book "Way Beyond Monochrome Ed.2" is chocked full of how-to links that promote testing film and graphing the results. I've always preferred to do the testing before using a film in the field to minimize poor negatives.

Well, I know what I'm talking about but ,I admit,for some the graphing and plotting are a necessary step to understand their materials and then, it's well worth it.

RalphLambrecht · Apr 23, 2019

tih said:
...which is why the OP certainly shouldn't buy Ralph Lambrecht's excellent book, "Way Beyond Monochrome", and most emphatically not use his documented test process and the spreadsheet he made for evaluating the results, both downloadable at https://www.waybeyondmonochrome.com/WBM/Library.html.

knowledgable photographer can chose his tools and methods more wisely.

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