Film Speed and Development Test (Excel spreadsheet supplied)

[Bill Burk]

Michael, now that you've achieved your goal. I'm going to show you why it's wrong. Not that you can't make quality prints with what you have, or that I'm suggesting changing anything you're doing. It's just that what you think is happening, isn't.

Michael Hoth,

I'll second what Stephen says. I'd be happy to print from the negative you achieved. The range would fit my paper, and the shadow detail gives plenty to work with. I've had similar results where I tested and pegged the shadows, yet they came up above the density I predicted.

I also like to understand what is going on, but I try not to let my (mis)understanding of why... get in the way of shooting. So keep doing, and let the theory discussions be the fireside chats that you mull over in spare time.

 

[Chuck_P]

Yeah, seriously...............I take "almost" nothing for granted in these forums....it doesn't pay. I'm sure Mark is not concerned about the post, if he is, he can let me know.

 

[markbarendt]

Yeah, seriously...............I take "almost" nothing for granted in these forums....it doesn't pay. I'm sure Mark is not concerned about the post, if he is, he can let me know.

Thank you Chuck. You are right I'm not concerned. In fact it is interesting understanding how others think.

 

[Stephen Benskin]

I must apologize. With all the running around this morning, I didn't take enough time to thoroughly read Chuck's post and I misinterpreted who the post was directed at and it's intention.

Mark, I looked through that chapter on Dunn and it was about metering techniques. I believe we are discussing two different subjects. I'm talking about how some believe Zone V has to be at a specific negative density. Curve shape makes that impossible. Or when someone interprets their film as overexposed just because it prints a little light using a just black proof. Simply put, that's bad theory. And I think it can be conceptually restrictive.

 

[Stephen Benskin]

I've added a few things to one of the two quad examples from post #201. This example has it's exposure based on the ISO. Zone V represents the metered exposure. As the example shows, the equation of metered exposure is 8 / ISO and the example uses a 125 speed film so the metered exposure is 0.064 lxs. Speed point falls Δ 1.0 log-H units below at 0.8/ISO or 0.8 / 125 = 0.0064 lxs. So in this example, the exposure was perfect for a film that has an ISO of 125. Zone I falls below the speed point at 0.0041 lxs.

 

[markbarendt]

I've added a few things to one of the two quad examples from post #201. This example has it's exposure based on the ISO. Zone V represents the metered exposure. As the example shows, the equation of metered exposure is 8 / ISO and the example uses a 125 speed film so the metered exposure is 0.064 lxs. Speed point falls Δ 1.0 log-H units below at 0.8/ISO or 0.8 / 125 = 0.0064 lxs. So in this example, the exposure was perfect for a film that has an ISO of 125. Zone I falls below the speed point at 0.0041 lxs.

View attachment 66741

For something that is impossible that was pretty easy.

 

[Stephen Benskin]

For something that is impossible that was pretty easy.

It's a specific example and not universally applicable.

 

[markbarendt]

It's a specific example and not universally applicable. View attachment 66743

View attachment 66747

I realize that its a special case but only because you are using ISO speed point as the reference point.

Your example provides an interesting problem for the ISO standard, "how do I get it to describe what my mid-tones will do in a print?" In a simplified sense, it can't, the question the ISO standard and other shadow point methods answer is just "what the reasonable lower limit?" We still have to figure out how the rest of the film behaves.

If the "print reference point" is the "metering point" and that was simply a density of .4 or .45, something appropriate, we might talk about film characteristics differently. TX might still get a 400 rating and TXP might get 200, so what, .4 may very well be a better predictor of print results.

 

[markbarendt]

Not exactly true.

I do realize that. Still the example provides a pretty stark difference. Wonder how Delta X would change that graph?

 

[Stephen Benskin]

I do realize that. Still the example provides a pretty stark difference. Wonder how Delta X would change that graph?

As the fractional gradient / Delta-X speeds don't change as quickly with development as the fixed density speeds (which aren't supposed to be used beyond the ISO parameters), the overall negative density will tend to increase and decrease in comparison to the fixed density negatives. This is one of the primary arguments against the idea of the just black printing approach for anything other than normally processed negatives.

How will Delta-X change the example? It wouldn't. The ISO standard uses Delta-X Criterion. That's why the US agreed to the change.

Apart from the greater tendency of what Jones calls "first choice prints" is more likely under certain printing conditions, I can't see a problem attempting to peg a certain density at a certain point on the curve. As long as the photographer has customized it to their materials and personal preference. A specific target negative density; however, shouldn't be considered universally applicable. Take the two quad example. What makes it a correct exposure for the ISO is not the negative density at the metered exposure point, but that the metered exposure was at 8/ISO and the exposure fell at the correct ratio from the speed point.

In the scientific photography papers, phrases like "greater tendency" and "more likely" are used a lot. Most methodologies will work adequately. The question is always about the one which has better results most often. This doesn't mean that in certain situations another method will work better. Just that in most situations, one method tends to have a higher consistancy. The question of fixed density vs fractional gradient is about what is more accurate over the greatest number of situations. It's all one big normal distribution curve. Advocating one approach over another is only about what is more likely.

 

[gmfotografie]

Hi Guys,

I have repeat the ISO Test with a Gray Card... Photographing with a 400 TX I have to setup the Lightmeter to ISO 200 for my personal setting ;-)
Everything is good

THX for your great constructive help!
It´s time to take pictures

 

[removedacct3]

Is there a prefered way how the development times should be changed? I would like to retest FP4+ in 510-pyro semi-stand developed. My current development time is 18 minutes. So I was thinking to use 5 developments of resp. 5.5, 8, 11, 19 and 22 minutes. Any ideas why this is a good or bad idea?

 

[Rafal Lukawiecki]

I'd make the longest time a bit longer, so if you wish to have 19 min, make the longer one, perhaps 35 min. The idea is not to hit the exact target time with a test, but to generate enough data to the "right" and "left" of your target times that let you safely interpolate the actual, correct duration. If you feel that you are good with 18 min, and you wish to re-test, then you need enough data on both sides of the 18 min to be sure that, for example, 25 would not be better.

In general, choosing 5 dev times that follow the sqrt(2), ie, 1.4142 sequence helps to cover enough range for typical N-2 to N+2 needs. If your 18 min seems to be your N time, then I'd suggest a sequence of: 9, 12, 18, 25, 36 min. The key to the test is the interpolation of the correct times in-between the tested ones, based on the curves/contrasts that you would get from those tests, and those that you would desire to get. Ralph's method will lead you there, or you could follow many others. I've published curve-plotting software (there was a url link here which no longer exists), too, which can also calculate the resulting times, based on your contrast requirements, but it can all be done, easily, by hand.

 

[foen]

Sorry if resurrected this thread . But you can use this file to determine xls development time corrected using a sensitometer ? And how ? I tried but I'm having mixed responses

 

[Bill Burk]

Hi foen,

It's OK to resurrect threads like this.

A Sensitometer exposes test film in steps of different exposure.

Then you develop the film for different times.

A Densitometer reads the density of each step.

Each reading is a single dot, x-axis (exposure) and y-axis (density). When you connect the dots for a strip or sheet of film, you get a curve that reveals how the film responds to light and developer. The steeper the graph curve, the higher the contrast of the negative.

Here is what such a graph looks like on paper.

Each "dot" is a reading. Each line is the set of readings from a particular strip of film. Lots of readings, lots of dots.

I call the dashed-line triangle the "ASA Triangle" and I draw it on my graphs because it shows me the important part of the curve measured and where the curve has to land, when measuring film speed the way ASA does. I don't know if other people give that triangle a nickname.

You can see when I develop this film for 13 minutes 30 seconds, I get very near the ASA Triangle.

Looking up from the tip of the ASA Triangle (where 0.1 density crosses the film curve) you can see I labeled film speeds and my result is almost 100 which is a good speed for TMAX 100. You can also see that if I reduce developing time to 8 minutes, the speed drops to 64.

So that is the graph on paper.

The spreadsheet that Ralph Lambrecht provided at the beginning of this thread is a wonderful gift to APUG members.

His spreadsheet draws this graph for you automatically and interprets the curves for you - Ralph's spreadsheet gives you suggested developing times.

 

[foen]

Thanks again for your time and contribution. Then my sensitometer is a XRITE 334. On a sheet I hit about 4 times for Ilford fp4. I gently post my spreadsheet to see if I understand well the results or there is something wrong. It seems that by 8 minutes then blocks everything.

 

[bnxvs]

It is unfortunate that I have not seen this topic before. I made a script for myself for building curves (R Shiny). I also posted his sources on github.
If anyone has an interest in developing such a program, I ask you to join to this project. I would be grateful for any advice and comments, since for me the R language is a rather new discovery and I have not mastered it quite well at the moment. But the prospect in my opinion is very good.
So, this is working script: https://bnxvs.shinyapps.io/cc_film_plot/
Github source: https://github.com/bnxvs/cc_film_plotter

 

[ic-racer]

Can you post a screen shot of a sample dataset. I don't have any sample data that fits the source template at this time to try it.

 

[bnxvs]

Fuji HR-U (x-ray film) in homemade "Rodinal"

 

[PeterB]

Thanks for the screenshot, could you also attach the raw data as the excel file ? One that will generate that curve you posted using your program. i.e. so we can save it, run your program , browse to the Excel file and get the same graph you just posted.

 

[bnxvs]

It's done! Please, see previous edited post ))

 

[PeterB]

It's done! Please, see previous edited post ))

Great, that worked well. I was able to upload the xlss file into your online program and get the same curve. Thanks for your efforts in programming that. I don't have time to critique it closely right now, but what you have put together looks very useful.

 

[bnxvs]

Thanks a lot.

 

[mohmad khatab]

Fuji HR-U (x-ray film) in homemade "Rodinal"

- I have a lot to say in this field, but I really do not want to look like someone who loves controversy only.
I feel very disappointed and disappointed. I ask for help.
Leave the talk of photography aside, I now have a dilemma for the health of Egyptian citizens.
A medical problem has recently emerged in Egypt for unknown reasons.
- The Egyptian government has tightened the screws on the import of acids that are used in the treatment of (X-ray) and allow only government hospitals and the government sector ,,, the reasons are really unknown, and this made the prices of X-ray services rise suddenly.
A large number of X-ray Film, Acid and Medical Supplies dealers contacted me yesterday and today. They asked me about black and white photographic acids, D-19, and I sent them, but it didn't work out tolerably.
- I looked a lot for a reliable formula that was specially designed for X-rays but I didn't find any reliable formula,
Mitol is present in Egypt, but it is somewhat expensive, but hydroquinone is available at an affordable price. I also have (CD2-CD3) I want a prescription based on hydroquinone and (CD2).
I do not know what to do ,,
- Respected colleague (Rudi) from Austria brought me a good formula,
Calbe A49:
I don't have (CD1) so I used it instead (CD2)
CD-1 - 5g
Hydroquinone - 3g
Sodium sulfite - 100g
Sodium tetraborate - 5g
Boric acid - 1,5g
Potassium bromide - 0,5g
But it is slow and takes a long time to process X-rays.
- I really feel a lot of sadness, fatigue and frustration.
- I have done many failed experiments and a lot of chemical raw materials have been wasted, and I feel I am on the cusp of a major failure.
I am very sad, bored and angry.