Find dev time without enlarger

[Bill Burk]

Here’s a graph of EDU 100 in PMK Pyro.

I subtracted B+F and drew green vertical lines to match densities of the Stouffer scale.

Your 10 minutes is just a tad high but meets ASA.

I sketched a quick Time / CI chart from the two data points.

Now all you have to do to find development time is decide what CI (Kodak Contrast Index) you want to develop the film to.

[Pere Casals]

Now all you have to do to find development time is decide what CI (Kodak Contrast Index) you want to develop the film to.

This is !!

[younghoon Kil]

To be honest, I'd like to ask you more about why 10 minutes meet the ASA, how did you get two data points, and which CI should I choose.
But I think that's a shameless question.
I think I should learn from the basics.
Thank you once again for everything you’ve done.

[Bill Burk]

The dashed triangle I drew are the ASA parameters. Your 10 minute curve is the one closest to meeting the tip of the triangle on the right. It just touches the top bar of tolerance. So 10 minutes is almost too much time.

The two points are the time vs contrast for 10 and 12 minutes. If you want a contrast in between you can pick it off the chart. For example if you want 0.65 (say N+1) you might develop for 10:45 in PMK Pyro.

If you do more tests at different development times you can get more points for the time - contrast chart and it will be more accurate.

For which CI you should choose, you will need to buy my book ( just kidding it’s free).... look at the charts on pages 10 and 11


http://beefalobill.com/imgs/20150812...dAttention.pdf

[Bill Burk]

Here are your other two curves. I can’t say much except they are relatively underdeveloped.
But 0.5 is a “fine choice” if you consider printing with grade 3 as a target for normal subject luminance range. (It’s approximately N-1 in Zone System terms where the traditional aim is grade 2.)

I know you aren’t “printing” in the traditional sense but I consider the traditional aims to be still relevant (just in case someone wants to print your negatives one day) and the jargon helps to describe where you are and where you want to be.

Development to 0.6 contrast is a test standard for ASA speed, but in practice practically everyone “dials it back a notch” when doing their own development.

[younghoon Kil]

I have just started developing black and white film, but I'm getting a bit better negatives by little by little.
But I wanted to get a uniform and predictable result, so I was asked a few questions.

Thanks again for taking the time to explain.
Thank you very much!!


[20190309: Arista EDU Ultra 100 4x5 @ ISO 64, PMK Pyro, 21C, 9 min]
0.1
0.11
0.11
0.12
0.14
0.16
0.19
0.23
0.27
0.33
0.38
0.46
0.53
0.59
0.63
0.67
0.79
0.89
0.97
1.08
1.15
1.22
1.29
1.33
1.39
1.44
1.48
1.53
1.56
1.58
1.62

[Bill Burk]

Your new curve falls between the first two. Either it is an outlier, or a new point for the time/CI chart.

I mark my own time-CI charts with these “scatter points”. Eventually a pattern will emerge and you will see the times you made a mistake and when it was right. Nothing ever really goes perfectly by plan, but it’s aiming and checking where you hit that helps you make “constant quality negatives”.

[Chuck Pere]

Something fundamental I don't understand. If you're scanning the film wouldn't you just develop the film to match the scanner density range? The density range should be part of the scanner specifications.

[Bill Burk]

Even if you do produce film for scanning, you will want to produce a negative with characteristics of quality.

Scanners have high Dmax in order to handle slides.

But most excellent negatives have relatively low density range. (Compared to slides I mean).

A contrast index (CI) 0.62 is on the high side of what most people do these days.

I don’t know the ideal for scanning, you would have to ask someone who does this, but I imagine it’s between CI 0.62 and CI 0.50

That holds down grain, maintains resolution and holds a host of other good qualities.

[younghoon Kil]

Thank you again for your sincere explanation.
I decided to start with the basics.
For example, I will look for the proper EI number again, and I will try to find a suitable development time by creating a contact proof.
I hope to learn more from these experiences.
Thank you.

p.s. So I am making a DIY contact printing box.(thicker board, multigrade filter, vc paper, contact print frame..) I think I might use the "Aputure Amaran AL-F7 On-Camera Variable Color LED Light" as a light source.

https://www.bhphotovideo.com/c/produ...amera_led.html