Finding developing time. Question please

[coops]

I made 6 exposures of a white textured surface, over exposing them all 3 stops over what my meter read. That is, placing the value on zone 8. I developed the 4x5 sheets 30 secs apart, starting at 6.5 mins and the last one at 9 mins. After determining my printing time, I printed each negative, covering up half the paper with cardboard so one half of the paper was totally white. The negative developed for 8.5 mins printed as totally white. The neg. developed at 8 mins left a feint but noticable grey tone. So somewhere between 8 and 8.5 mins that tone disapeared. Would most of you use 8 mins 15 secs as your developing time? Or do you re-test and develop/print a negative for 8.15?
I used Kodak stop and it gave me a blinding headache. I figured if I use water next time and developed for 8 mins, by the time the development stopped in water it may have had 8.15 of development time.

[Bill Burk]

This sounds a little like the Minor White dev time test except instead of four squares you're exposing one. He recommended a two-tone target where your meter reads the tones 1 stop apart. He'd pull the darkslide halfway out and expose for Zones 0 and I then pull it all the way out and expose for two high zones (figuring that the 0 and I on top of it wouldn't matter much at all).

Assuming you don't want to scrap your work and start over, one of the four squares was supposed to come out where Zone VIII is a faint white. So your simplified test kind of did that. And if you know your black is OK you might have the information you need.

You might call 8 minutes = N.

Now expose 3 sheets placed at VII and process more than 8 min. The dev time where this print looks the same as your N print will be your N+1.

Do 3 sheets placed at IX and process less than 8 min. The dev time where that print looks the same as your N print will be your N-1.

If you want to take it further, I suppose there are plenty of better ways to test. But you're on the right track.

[coops]

Thanks Bill. I used this as a guide:

http://www.viewcamera.com/pdf/2006/V...%20Started.pdf

[Bruce Barlow]

8:15.

[Bill Burk]

OK you got your black from earlier steps in that pdf.

I'll align with Bruce and your own instinct, choose 8:15 for N.

[Jim Noel]

If you want to determine your effective film speed (EI) you need to think about the other end of the curve. Film speed is determined by the amount of exposure needed to establish Zone I. HL density is determined by development.
Expose one sheet of film with the dark slide 1/2 out, at the assigned ISO, one twice as long (1/2 the ISO), and one half of that (1/4 the ISO). The third one is rarely necessary.
Develop for the suggested time. Lacking a densitometer, look for the one which just barely has an increase in tonality from the unexposed portion. This can actually be done with a single sheet of film.
If you want to determine both EI and development time quickly and easily, use the Nine Negative Test.
Remember that the final proof is in the printing so whatever method is used the negatives need to be printed on the paper of your choice using the least time necessary to get a full black on the portion under the clear portion of the film.

[ki6mf]

A good step by step guide can be found at Jerry Orabona web site. The step by step instructions will walk you through film speed tests development time tests etc.

http://www.jerryo.com/teaching.htm

[coops]

ThisYou might call 8 minutes = N.

Now expose 3 sheets placed at VII and process more than 8 min. The dev time where this print looks the same as your N print will be your N+1.

Do 3 sheets placed at IX and process less than 8 min. The dev time where that print looks the same as your N print will be your N-1.

If you want to take it further, I suppose there are plenty of better ways to test. But you're on the right track.

Thanks Bill. How far apart do you suggest I develop the N+1 and N-1? So far I developed 30 secs apart, but I have a feeling I should extend that a little, particularly for N+

[Bill Burk]

One of my old graphs suggests you might be looking around 7 minutes for N-1 and 10 minutes for N+1

So your idea is good to develop minute by minute on the plus side.

[ic-racer]

Your test is perfectly fine. As Bruce points out 8:15 is your time. Timing to the second like that you may want a proper stop bath. Did you dilute the acetic acid bath correctly?