Fstop timing

[monochromeFan]

Been reading on Bruce Tanners website again, stupid idea of f stop timing is actually starting to make sense. Perhaps its just the sleep deprivation.

At least the way bruce tanner describes the process makes it seem very simple.. do a test strip and instead of a linear 2-4,-6 or 5-10-15 second time differenctial sequence. You do it by a scientific "stops". And when you develop the test strip and let it dry you have a strip with far superior differences between each of the stops.

Then you can take your prefered stop number in the test strip and break it down by 1/4 and 1/3 and so forth to get a more accurate and enhanced accuracy versus the old "20 seconds is to dark, 10 is to light, but do i need to break down the 15 second section into 10-11-12-13-14-15 test strip sequence"


But then I hit a wee snag, in times past some of my convential test strips dictated I set the gralab 300 to 5 seconds, and using the dark room automation handy dandy fstop chart..


And doing some quick math, how the hell does a person deal with a 1 or 2 minute, or even 80 minute long expsure time without worring about heat buildup in the negtive itself causing defects?

[Pieter]

Been reading on Bruce Tanners website again, stupid idea of f stop timing is actually starting to make sense. Perhaps its just the sleep deprivation.

At least the way bruce tanner describes the process makes it seem very simple.. do a test strip and instead of a linear 2-4,-6 or 5-10-15 second time differenctial sequence. You do it by a scientific "stops". And when you develop the test strip and let it dry you have a strip with far superior differences between each of the stops.

Then you can take your prefered stop number in the test strip and break it down by 1/4 and 1/3 and so forth to get a more accurate and enhanced accuracy versus the old "20 seconds is to dark, 10 is to light, but do i need to break down the 15 second section into 10-11-12-13-14-15 test strip sequence"


But then I hit a wee snag, in times past some of my convential test strips dictated I set the gralab 300 to 5 seconds, and using the dark room automation handy dandy fstop chart..


And doing some quick math, how the hell does a person deal with a 1 or 2 minute, or even 80 minute long expsure time without worring about heat buildup in the negtive itself causing defects?

When would you need such an exposure time?

[monochromeFan]

Full Stop 5 10 20 40 80
+1/4 5.9 11.9 23.8 47.6 95.2
+1/2 7.1 14.1 28.3 56.6 113.2
+3/4 8.4 16.8 33.6 67.3 134.6
F-stop Timings with 1/4 stops

thats supposed to come from Nocons's book.. SO as a result if i start out making a f/8 @ 5 second print of an orange on 4x6 enlarging paper things can tend to get long and lenghty when you try to do an 8x10 or 11x14 print.

[esearing]

if heat from your enlarger is a problem you will want a different head. for 4x5 I also prefer the beseler glassed carriers to keep the negatives flat. Most of my 11x14 exposures on warmtone papers run near the 1 minute mark for exposure. But I also use the RHDesigns Analyzer which breaks down exposure into 1/6 or 1/12 stop increments and has an easel light meter to give me the starting times. Even if I could print in 5 seconds I would likely stop down my lens to slow it to 10 or 20 seconds for dodging/burning.

[jnantz]

im always amazed at how overly complicated people make a very simple process.
80 minute long exposures ?
they use a different light source
and modify their developing methodology so they don't need
a 1 hour 20 minute exposure ...

[notorius]

Well I dealt with longer times with no problem. 1 - 2 mintes exposure( Fomatone paper), 100W incandescent light bulb. There is an IR filtr between the light source and the film carrier. And I always use AN glass. I would definitely use LED technology these days.
How many prints have you done so far? And what are the real issues you need to solve in the process? It seems form the many posts you have started, that you are (over)prepared.

[paulbarden]

It looks to me like you're investigating theoretical problems that you will almost certainly never encounter in practice. The odds of you ever needing an 80 minute exposure to make a print is practically zero.

The only time in which I had to deal with a LONG exposure was one instance in my professional career as a darkroom-technician-for-hire, working for a well-known Canadian artist. We had to make 2.5 X 8 foot prints from 35mm negatives, using a Beseler 23C II enlarger. Exposures were between twenty and forty-five minutes long. There were no unusual technical challenges to the process - it was just a bit tedious. Yes, the lamp heated things up during the exposure, but that only meant that we had to pre-warm the enlarger for a couple of minutes to properly warm the negative, so that it didn't "pop" during the exposure (causing a focus shift). It was easy to avoid the problem.

You're fussing over scenarios you're unlikely to ever encounter. Just get on with it.

im always amazed at how overly complicated people make a very simple process.

Basically, yes. Some people love to throw obstacles in their path, so they have something to worry about. Some of us just get on with the work with as little fuss as possible.

[Doremus Scudder]

I think we're talking about an 80 second exposure here, not 80 minutes, which is not all that uncommon with larger prints (still long, though).

Monochromefan,

F-stop timing really works better with and f-stop timer, which has settings in stops and fractions of stops. Otherwise, you need to use the conversion charts.

If you want the logical spacing of f-stop timing without the timer or the conversion chart, just use percentages. That's what I do. Test strips are usually in 30% intervals (I don't think you'd get useful information from a test strip in full stops or 100% intervals; the spacing between exposures is just too great).

I like exposures in the 15-30+ second range. I time with a metronome and count seconds, so I make test strips by sequentially covering stripes of the test strip after an initial base exposure. My (approximate) 30% test has these final exposures: 10 sec., 13 sec., 17., sec., 22 sec., 29 sec., 38 sec. That means I start the exposure, count 10 seconds and cover the first stripe, count 3 seconds, cover the next, etc. The counting sequence is easy to remember after a time or two: 10 - 3 - 4 - 5 - 7 - 9.

If that's not enough exposure, then I'll open up a stop or adjust the light intensity and make another test strip. I'd only use base exposures longer than 40 seconds or so If the print were really large and needed longer exposures or if the negative were really dense and I didn't have enough light, even only closed down one stop. In that case, I simply double the strip timing to 20 - 26 - 34 - 44 - 58 - 76 (count: 20 - 6 - 8 - 10 - 14 - 18).

When printing, make exposure adjustments as you need and dodge and burn as needed, but think in percentages of the base exposure (e.g., dodge 10% here, burn 70% there, etc.). After a while, you get a pretty good idea of how much x% exposure change makes. Keep in mind, however, that all this is contrast-grade dependent (even with f-stop timing). A 2/3-stop increase in exposure is about that same as adding 70%, but that much extra exposure makes a smaller change in print density at grade/contrast setting #1 than at grade/contrast setting #4.

Keeping track of print manipulations in percentages is helpful when you make a different size print. Once you establish the base exposure for the new print size, you can then easily figure the timing of dodges and burns, which should get you in the ballpark (I find that different-size prints often need a bit different treatment, so those times are always just a starting point for me).

Hope this helps,

Doremus

[Peter Lewin]

A quick thank-you to Doremus, who is one of the most reliable and helpful members of this forum. I've been printing for around 50 years, so I'm not a novice, and I still learn new ideas from his posts, in this case about his test strips. I always made mine as I was taught by Fred Picker, setting my timer for 2 or 3 seconds, and making strips straight across, getting for example, 3,6,9,12,15 seconds, which were not always as easy to read as I would like. So yesterday I tried Doremus's approach. In Excel, I made a simple spread sheet. For the top section, I made rows from 4 seconds to 10 seconds, and going across, each column was 30% longer than the one to its left. Then below I changed the formula so that keeping the first column of seconds, each column now showed just the difference from the column to its left, so I had a number of sequences similar to the ones Doremus mentioned (for example I had one which I think - my cheat sheet is down in my darkroom - went something like 4 second base, then 2,2,3,3,4,6). Worked very nicely! And since I have an idea of final exposures for different format negatives and enlargement sizes, I can simply pick a row (sequence) which puts my "expected" exposure near the middle, and use the test strip to fine tune.

[Doremus Scudder]

A quick thank-you to Doremus, who is one of the most reliable and helpful members of this forum. ...

Thanks Peter!

Glad you found the percentage method helpful. FWIW, I've standardized on just one sequence at 30% intervals (25% works too, but I've found that 30% is not too wide to be able to interpolate intermediate values closely enough - I do quite a bit of exposure tweaking once I get to making full-size prints anyway). I've got my test-strip sequence taped to the wall by the enlarger, writ large in sharpie so I can refresh my memory if needed.

If I find I need longer or shorter than 10 seconds or longer than my usual 38 seconds, I'll just add a few intervals on either end. It's just a tiny bit harder to figure going down in time rather than up and keep the same interval. I just multiply by 0.77 (not the 0.7 that you'd think would work).

So, the intervals below 10 would be, in descending order: 10 - 8 - 6 - 5 - 4. Easy to remember. I have all these written in on my taped-up reminder too, so I can just start where I want in the sequence. Normally, I'll start at 10, but if there are special circumstances, I'll pick a lower number.

On the other end, it goes 38 - 50 - 65... that's enough! And, as I mentioned above, you can always pick a spot to start and just double the times and counting and get really long times if needed.

Just for clarity, my reminder sheet looks like this (bold type is the "core" sequence):

Time : 4 - 5 - 6 - 8 - 10 - 13 - 17 - 22 - 29 - 38 - 50 - 65
Count: 4 - 1 - 1 - 2 -- 2 -- 3 -- 4 -- 5 -- 7 --- 9 - 12 - 15

I can just start anywhere in the sequence and end anywhere too.

Best,

Doremus